vetiver system for slope stabilization

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i

iiiii

Thi

s ha

ndbo

ok is

ded

icat

ed to

the

mem

ory

of

Dit

i Hen

gcha

ovan

ich

Geo

tech

nica

l Eng

inee

r

of

Tha

iland

.

He

pion

eere

d th

e us

e of

vet

iver

on

a la

rge

scal

e fo

r h

ighw

ay

stab

iliza

tion,

and

for

man

y ye

ars

was

a v

ery

valu

able

con

trib

utor

to

The

Vet

iver

Net

wor

k In

tern

atio

nal.

Diti

will

be

rem

embe

red

with

gr

atef

ulne

ss b

y m

any.

1st E

diti

on 2

008

Pub

lish

ed b

y T

he V

etiv

er N

etw

ork

Inte

rnat

iona

l

Cov

er b

y L

ily

Gri

msh

aw

ivi

PR

EF

AC

E

TH

E V

ET

IVE

R S

YST

EM

F

OR

SL

OP

E S

TAB

ILIZ

AT

ION

AN

EN

GIN

EE

R'S

HA

ND

BO

OK

The

Vet

iver

Sys

tem

(V

S) i

s de

pend

ent

on t

he u

se o

f a

very

uni

que

trop

ical

pl

ant,

vetiv

er

gras

s,

Veti

veri

a zi

zani

oide

s –

rece

ntly

re

clas

sifie

d as

Chr

ysop

ogon

ziz

anio

ides

. T

he p

lant

can

be

grow

n ov

er a

ver

y w

ide

rang

e of

clim

atic

and

soi

l con

ditio

ns, a

nd if

pla

nted

co

rrec

tly c

an b

e us

ed v

irtu

ally

any

whe

re u

nder

trop

ical

, sem

i-tr

opic

al,

and

Med

iterr

anea

n cl

imat

es.

It h

as c

hara

cter

istic

s th

at i

n to

talit

y ar

e un

ique

to a

sin

gle

spec

ies.

Whe

n ve

tiver

gra

ss is

gro

wn

in th

e fo

rm o

f a

narr

ow s

elf-

sust

aini

ng h

edge

row

it

exhi

bits

spe

cial

cha

ract

eris

tics

that

are

ess

entia

l to

man

y of

the

dif

fere

nt a

pplic

atio

ns t

hat

com

pris

e th

e V

etiv

er S

yste

m.

Vet

iver

gra

ss c

an b

e us

ed f

or a

pplic

atio

ns th

at w

ill p

rote

ct r

iver

bas

ins

and

wat

ersh

eds

agai

nst e

nvir

onm

enta

l dam

age,

par

ticul

arly

from

poi

nt

sour

ce f

acto

rs r

elat

ing

to:

1. s

edim

ent

flow

s (o

ften

ass

ocia

ted

with

ag

ricu

lture

and

inf

rast

ruct

ure)

, an

d 2.

tox

ic c

hem

ical

flow

s re

sulti

ng

from

exc

ess

nutr

ient

s, h

eavy

met

als

and

pest

icid

es i

n le

acha

te f

rom

ag

ricu

lture

and

oth

er in

dust

ries

. Bot

h ar

e cl

osel

y lin

ked.

Thi

s ha

ndbo

ok

is

a m

odifi

ed

extr

actio

n fr

om

Vetiv

er

Syst

ems

App

licat

ions

- A

Tec

hnic

al R

efer

ence

Man

ual (

2008

) by

Paul

Tru

ong,

T

ran

Tan

Van

, an

d E

lise

Pinn

ers,

and

foc

uses

on

the

prot

ectio

n of

in

fras

truc

ture

and

for

dis

aste

r m

itiga

tion

by a

pply

ing

the

Vet

iver

Sy

stem

to

slop

e st

abili

zatio

n. I

t dr

aws

on o

ngoi

ng v

etiv

er w

ork

in

Vie

tnam

and

els

ewhe

re i

n th

e w

orld

. It

s te

chni

cal

reco

mm

enda

tions

an

d ob

serv

atio

ns a

re b

ased

on

real

lif

e si

tuat

ions

, pr

oble

ms

and

solu

tions

. The

han

dboo

k is

pri

mar

ily f

or e

ngin

eers

and

oth

ers

with

res

po

nsib

ility

for

the

cons

truc

tion

and

prot

ectio

n of

infr

astr

uctu

re.

Dic

k G

rim

shaw

Fou

nder

and

Cha

irm

an o

f T

he V

etiv

er N

etw

ork

Inte

rnat

iona

l.

ii

FO

RW

AR

D

Bas

ed o

n th

e re

view

of

the

huge

vol

ume

of V

etiv

er S

yste

m r

esea

rch

and

appl

icat

ion,

the

aut

hors

con

side

red

that

it

was

tim

e to

com

pile

a

new

pub

licat

ion

to r

epla

ce t

he fi

rst

Wor

ld B

ank

publ

ishe

d ha

ndbo

ok

(198

7), V

etiv

er G

rass

- A

Hed

ge A

gain

st E

rosi

on (c

omm

only

kno

wn

as

the

Gre

en B

ook)

, pre

pare

d by

Joh

n G

reen

field

. Thi

s ha

ndbo

ok is

one

of

thre

e, a

nd fo

cuse

s on

the

use

of th

e V

etiv

er S

yste

m fo

r inf

rast

ruct

ure

prot

ectio

n th

roug

h its

app

licat

ion

for

slop

e st

abili

zatio

n.

The

han

dboo

k in

clud

es th

e m

ost u

p to

dat

e R

&D

resu

lts a

nd n

umer

ous

exam

ples

of

high

ly s

ucce

ssfu

l re

sults

fro

m a

roun

d th

e w

orld

and

pa

rtic

ular

ly f

rom

Vie

tnam

, w

here

an

inte

nsiv

e co

untr

y w

ide

vetiv

er

prog

ram

has

bee

n in

trod

uced

sin

ce 2

000.

The

mai

n ai

m o

f th

is

hand

book

is

to i

ntro

duce

VS

to p

lann

ers,

des

ign

and

cons

truc

tion

engi

neer

s an

d ot

her

pote

ntia

l us

ers

invo

lved

with

inf

rast

ruct

ure

at

all

leve

ls,

who

oft

en a

re u

naw

are

of t

he e

ffec

tiven

ess

of t

he V

etiv

er

Syst

em f

or b

io-e

ngin

eeri

ng a

pplic

atio

ns.

In a

dditi

on to

the

info

rmat

ion

in th

is h

andb

ook

ther

e ar

e m

any

artic

les

and

rese

arch

pap

ers

rela

ting

to th

e us

e of

the

Vet

iver

Sys

tem

for

slo

pe

stab

iliza

tion

on th

e V

etiv

er N

etw

ork'

s w

ebsi

te a

t: w

ww

.vet

iver

.org

.

Det

ails

ab

out

the

auth

ors,

an

d ac

know

ledg

men

ts

of

thos

e w

ho

cont

ribu

ted

to th

is h

andb

ook

can

be fo

und

in th

e m

aste

r man

ual V

etiv

er

Syst

ems

App

licat

ions

- A

Tec

hnic

al R

efer

ence

Man

ual

(200

8). I

t is

su

ffice

to

say

that

we

deep

ly a

ckno

wle

dge

and

appr

ecia

te a

ll th

ose

invo

lved

in th

is h

andb

ook

prod

uctio

n.

The

pri

ncip

le a

utho

r of

this

han

dboo

k is

Tra

n Ta

n V

an, V

ice-

Dir

ecto

r of

the

Vie

tnam

Ins

titut

e of

Geo

scie

nces

and

Min

eral

Res

ourc

es i

n V

ietn

am a

nd C

oord

inat

or o

f T

he V

ietn

am V

etiv

er N

etw

ork.

Pau

l Tru

ong,

Tra

n Ta

n Va

n an

d E

lise

Pin

ners

.T

he a

utho

rs.

iii

TH

E V

ET

IVE

R S

YST

EM

F

OR

SL

OP

E S

TAB

ILIZ

AT

ION

AN

EN

GIN

EE

R'S

HA

ND

BO

OK

PAR

T 1

- V

ET

IVE

R G

RA

SS -

TH

E P

LA

NT

1

PAR

T 2

- V

ET

IVE

R S

YST

EM

FO

R S

LO

PE

STA

BIL

IZA

TIO

N

16IN

DE

X -

87

iv1

PAR

T 1

V

ET

IVE

R G

RA

SS -

TH

E P

LA

NT

CO

NT

EN

TS

1.

INT

RO

DU

CT

ION

1

2.

SPE

CIA

L C

HA

RA

CT

ER

IST

ICS

OF

VE

TIV

ER

GR

ASS

2

2.1

Mor

phol

ogic

al c

hara

cter

istic

s 2

2.2

Phys

iolo

gica

l cha

ract

eris

tics

32.

3 E

colo

gica

l cha

ract

eris

tics

42.

4 C

old

wea

ther

tole

ranc

e of

vet

iver

gra

ss

62.

5 Su

mm

ary

adap

tabi

lity

rang

e 7

2.6

Gen

etic

cha

ract

eris

tics

92.

7 W

eed

pote

ntia

l 14

3.

CO

NC

LU

SIO

N

154.

R

EFE

RE

NC

ES

15

1. I

NT

RO

DU

CT

ION

The

Vet

iver

Sys

tem

(V

S), w

hich

is b

ased

on

the

appl

icat

ion

of v

etiv

er

gras

s (V

etiv

eria

ziz

anio

ides

L N

ash,

now

rec

lass

ified

as

Chr

ysop

ogon

zi

zani

oide

s L

Rob

erty

), w

as fi

rst

intr

oduc

ed b

y th

e W

orld

Ban

k fo

r so

il an

d w

ater

con

serv

atio

n in

Ind

ia i

n th

e m

id 1

980s

. W

hile

thi

s ap

plic

atio

n st

ill p

lays

a v

ital

role

in

agri

cultu

ral

land

man

agem

ent,

R&

D c

ondu

cted

in th

e la

st 2

0 ye

ars

has

clea

rly

dem

onst

rate

d th

at, d

ue

to v

etiv

er g

rass

’ ex

trao

rdin

ary

char

acte

rist

ics,

VS

also

has

im

port

ant

appl

icat

ion

as a

bio

engi

neer

ing

tech

niqu

e fo

r ste

ep s

lope

sta

biliz

atio

n,

was

tew

ater

dis

posa

l, ph

yto-

rem

edia

tion

of c

onta

min

ated

lan

d an

d w

ater

, and

oth

er e

nvir

onm

enta

l pro

tect

ion

purp

oses

.

Wha

t doe

s th

e Ve

tiver

Sys

tem

do

and

how

doe

s it

wor

k?

VS

is a

ver

y si

mpl

e, p

ract

ical

, in

expe

nsiv

e, l

ow m

aint

enan

ce a

nd

very

eff

ectiv

e m

eans

of s

oil a

nd w

ater

con

serv

atio

n, s

edim

ent c

ontr

ol,

land

sta

biliz

atio

ns a

nd r

ehab

ilita

tion,

and

phy

to-r

emed

iatio

n. B

eing

ve

geta

tive

it is

als

o en

viro

nmen

tal

frie

ndly

. W

hen

plan

ted

in s

ingl

e

2

row

s ve

tiver

pla

nts

will

form

a h

edge

whi

ch is

ver

y ef

fect

ive

in s

low

ing

and

spre

adin

g ru

n of

f w

ater

, re

duci

ng s

oil

eros

ion,

con

serv

ing

soil

moi

stur

e an

d tr

appi

ng s

edim

ent a

nd f

arm

che

mic

als

on s

ite. A

lthou

gh

man

y he

dges

can

do

this

, ve

tiver

gra

ss,

due

to i

ts e

xtra

ordi

nary

and

un

ique

m

orph

olog

ical

an

d ph

ysio

logi

cal

char

acte

rist

ics

desc

ribe

d be

low

can

do

it be

tter

than

all

othe

r sy

stem

s te

sted

. In

add

ition

, th

e ex

trem

ely

deep

and

mas

sive

ly t

hick

roo

t sy

stem

of

vetiv

er b

inds

the

so

il an

d at

the

sam

e tim

e m

akes

it v

ery

diffi

cult

for

it to

be

disl

odge

d un

der

high

vel

ocity

wat

er fl

ows.

Thi

s ve

ry d

eep

and

fast

gro

win

g ro

ot

syst

em a

lso

mak

es v

etiv

er v

ery

drou

ght

tole

rant

and

hig

hly

suita

ble

for

stee

p sl

ope

stab

iliza

tion.

The

Ext

ensi

on W

orke

rs M

anua

l, or

the

Lit

tle

Gre

en B

ook

Com

plem

entin

g th

is h

andb

ook

is t

he s

lim g

reen

ext

ensi

on w

orke

rs

pock

et b

ook

first

pub

lishe

d be

the

Wor

ld B

ank

in 1

987

and

refe

rred

to

on

page

ii

as V

etiv

er G

rass

- A

Hed

ge A

gain

st E

rosi

on,

or m

ore

com

mon

ly k

now

n th

e “l

ittle

gre

en b

ook”

by

John

Gre

enfie

ld.

Thi

s ha

ndbo

ok is

far m

ore

tech

nica

l in

its d

escr

iptio

n of

the

Vet

iver

Sys

tem

an

d is

aim

ed a

t en

gine

ers,

tec

hnic

ians

, ac

adem

ics,

pla

nner

s an

d G

over

nmen

t offi

cial

s an

d la

nd d

evel

oper

s.

2. S

PE

CIA

L C

HA

RA

CT

ER

IST

ICS

OF

VE

TIV

ER

GR

ASS

2.1

Mor

phol

ogic

al c

hara

cter

istic

s:•

Vet

iver

gra

ss d

oes

not

have

sto

lons

or

rhiz

omes

. It

s m

assi

ve

finel

y st

ruct

ured

roo

t sys

tem

that

can

gro

w v

ery

fast

, in

som

e ap

plic

atio

ns r

ootin

g de

pth

can

reac

h 3-

4m i

n th

e fir

st y

ear.

Thi

s de

ep r

oot s

yste

m m

akes

vet

iver

pla

nt e

xtre

mel

y dr

ough

t to

lera

nt a

nd d

iffic

ult t

o di

slod

ge b

y st

rong

cur

rent

. •

Stif

f an

d er

ect

stem

s, w

hich

can

sta

nd u

p to

rel

ativ

ely

deep

w

ater

flow

- p

hoto

1.

• H

ighl

y re

sist

ance

to p

ests

, dis

ease

s an

d fir

e -

phot

o 2.

• A

den

se h

edge

is fo

rmed

whe

n pl

ante

d cl

ose

toge

ther

act

ing

as

a ve

ry e

ffec

tive

sedi

men

t filte

r an

d w

ater

spr

eade

r. •

New

sho

ots

deve

lop

from

the

und

ergr

ound

cro

wn

mak

ing

vetiv

er

resi

stan

t to

fir

e,

fros

ts,

traf

fic

and

heav

y gr

azin

g pr

essu

re.

• N

ew

root

s gr

ow

from

no

des

whe

n bu

ried

by

tr

appe

d

3

sedi

men

t. V

etiv

er w

ill c

ontin

ue to

gro

w u

p w

ith th

e de

posi

ted

silt

even

tual

ly f

orm

ing

terr

aces

, if

tra

pped

sed

imen

t is

not

re

mov

ed.

Ph

oto

1:

Ere

ct a

nd

sti

ff s

tem

s fo

rm a

den

se h

edg

e w

hen

pla

nte

d c

lose

to

get

her

.

2.2

Phy

siol

ogic

al c

hara

cter

istic

s •

Tole

ranc

e to

ext

rem

e cl

imat

ic v

aria

tion

such

as

prol

onge

d dr

ough

t, flo

od,

subm

erge

nce

and

extr

eme

tem

pera

ture

fro

m

-15º

C to

+55

ºC.

• A

bilit

y to

regr

ow v

ery

quic

kly

afte

r bei

ng a

ffec

ted

by d

roug

ht,

fros

ts,

salin

ity

and

adve

rse

cond

ition

s af

ter

the

wea

ther

im

prov

es o

r so

il am

elio

rant

s ad

ded.

Tole

ranc

e to

wid

e ra

nge

of s

oil

pH f

rom

3.3

to

12.5

with

out

soil

amen

dmen

t. •

Hig

h le

vel o

f to

lera

nce

to h

erbi

cide

s an

d pe

stic

ides

. •

Hig

hly

effic

ient

in

abso

rbin

g di

ssol

ved

nutr

ient

s su

ch a

s N

an

d P

and

heav

y m

etal

s in

pol

lute

d w

ater

. •

Hig

hly

tole

rant

to g

row

ing

med

ium

hig

h in

aci

dity

, alk

alin

ity,

salin

ity, s

odic

ity a

nd m

agne

sium

. •

Hig

hly

tole

rant

to

Al,

Mn

and

heav

y m

etal

s su

ch a

s A

s, C

d,

Cr,

Ni,

Pb, H

g, S

e an

d Z

n in

the

soils

.

4

2.3

Eco

logi

cal c

hara

cter

istic

s A

lthou

gh v

etiv

er i

s ve

ry t

oler

ant

to s

ome

extr

eme

soil

and

clim

atic

co

nditi

ons

men

tione

d ab

ove,

as

typi

cal

trop

ical

gra

ss,

it is

int

oler

ant

to s

hadi

ng. S

hadi

ng w

ill r

educ

e its

gro

wth

and

in e

xtre

me

case

s, m

ay

even

elim

inat

e ve

tiver

in th

e lo

ng te

rm. T

here

fore

vet

iver

gro

ws

best

Ph

oto

2: U

pp

er: V

etiv

er g

rass

su

rviv

ing

fore

st fi

re;

low

er: t

wo

mo

nth

s af

ter

the

fire

.

in t

he o

pen

and

wee

d fr

ee e

nvir

onm

ent,

wee

d co

ntro

l m

ay b

e ne

eded

du

ring

est

ablis

hmen

t ph

ase.

On

erod

ible

or

unst

able

gro

und

vetiv

er

first

red

uces

ero

sion

, sta

biliz

es th

e er

odib

le g

roun

d (p

artic

ular

ly s

teep

sl

opes

), th

en b

ecau

se o

f nu

trie

nt a

nd m

oist

ure

cons

erva

tion,

impr

oves

its

mic

ro-e

nvir

onm

ent s

o ot

her v

olun

teer

ed o

r sow

n pl

ants

can

est

ablis

h la

ter.

Bec

ause

of

thes

e ch

arac

teri

stic

s ve

tiver

can

be

cons

ider

ed a

s a

nurs

e pl

ant o

n di

stur

bed

land

s.

5

Ph

oto

3: O

n c

oas

tal s

and

du

nes

in Q

uan

g B

ình

(u

pp

er)

and

sal

ine

soil

in G

ò C

ôn

g P

rovi

nce

(lo

wer

).

6

Ph

oto

4: O

n e

xtre

me

acid

su

lfat

e so

il in

Tân

An

(u

pp

er)

and

alk

alin

e an

d s

od

ic s

oil

in N

inh

Th

un

(lo

wer

).

2.4

Col

d w

eath

er to

lera

nce

of v

etiv

er g

rass

A

lthou

gh v

etiv

er i

s a

trop

ical

gra

ss,

it ca

n su

rviv

e an

d th

rive

und

er

extr

emel

y co

ld c

ondi

tions

. U

nder

fro

sty

wea

ther

its

top

gro

wth

die

s ba

ck o

r bec

omes

dor

man

t and

‘pur

ple’

in c

olou

r und

er fr

ost c

ondi

tions

bu

t its

und

ergr

ound

gro

win

g po

ints

sur

vive

d. I

n A

ustr

alia

, ve

tiver

gr

owth

was

not

aff

ecte

d by

sev

ere

fros

t at

–14

ºC a

nd i

t su

rviv

ed f

or

a sh

ort

peri

od a

t –2

2ºC

(-8

ºF)

in n

orth

ern

Chi

na.

In G

eorg

ia (

USA

),

vetiv

er s

urvi

ved

in s

oil t

empe

ratu

re o

f -1

0ºC

but

not

at –

15ºC

. Rec

ent

rese

arch

show

ed th

at 2

5ºC

was

opt

imal

soil

tem

pera

ture

for r

oot g

row

th,

but v

etiv

er r

oots

con

tinue

d to

gro

w a

t 13º

C. A

lthou

gh v

ery

little

sho

ot

grow

th o

ccur

red

at th

e so

il te

mpe

ratu

re r

ange

of

15ºC

(da

y) a

nd 1

3ºC

ro

ot g

row

th c

ontin

ued

at th

e ra

te o

f 12.

6cm

/day

, ind

icat

ing

that

vet

iver

gr

ass

was

not

dor

man

t at t

his

tem

pera

ture

and

ext

rapo

latio

n su

gges

ted

7

that

roo

t dor

man

cy o

ccur

red

at a

bout

5ºC

(Fi

g.1)

.

Fig

ure

1: T

he e

ffec

t of s

oil t

empe

ratu

re o

n th

e ro

ot g

row

th o

f vet

iver

.

2.5

Sum

mar

y ad

apta

bilit

y ra

nge

Tabl

e 1:

Ada

ptab

ility

ran

ge o

f ve

tive

r gr

ass

in A

ustr

alia

and

ot

her

coun

trie

s.

cont

inue

d on

nex

t pag

e ...

.

Con

diti

on

char

acte

rist

icA

ustr

alia

Oth

er C

ount

ries

Adv

erse

Soi

l C

ondi

tion

s

Aci

dity

(pH

)3.

3-9.

54.

2-12

.5 (

high

leve

l so

lubl

e A

l)

Salin

ity (

50%

yie

ld

redu

ctio

n)17

.5 m

Scm

-1

Salin

ity (

surv

ived

)47

.5 m

Scm

-1

Alu

min

ium

leve

l (A

l Sa

t. %

)B

etw

een

68%

- 8

7%

Man

gane

se le

vel

> 5

78 m

gkg-1

Sodi

city

48%

(ex

chan

ge N

a)

Mag

nesi

city

2400

mgk

g-1 (

Mg)

8

Con

diti

on

char

acte

rist

icA

ustr

alia

Oth

er C

ount

ries

Fer

tiliz

er

vetiv

er c

an b

e es

tabl

ishe

d on

ver

y in

fert

ile s

oil d

ue to

its

str

ong

asso

ciat

ion

with

myc

orrh

iza

N a

nd P

(3

00 k

g/ha

DA

P)N

and

P, f

arm

man

ure

Hea

vy M

etal

s

Ars

enic

(A

s)

100

- 25

0 m

gkg-1

Cad

miu

m (

Cd)

20 m

gkg-1

Cop

per

(Cu)

35 -

50

mgk

g-1

Chr

omiu

m (

Cr)

200

- 60

0 m

gkg-1

Nic

kel

(Ni)

50 -

100

mgk

g-1

Mer

cury

(H

g)>

6 m

gkg-1

Lea

d (P

b)>

150

0 m

gkg-1

Sel

eniu

m (

Se)

> 7

4 m

gkg-1

Zin

c (Z

n)>

750

mgk

g-1

Loc

atio

n15

0 S to

370 S

410 N

- 3

80 S

Clim

ate

Ann

ual R

ainf

all (

mm

)45

0 -

4000

250

- 50

00

Fro

st (

grou

nd te

mp.

)-1

10 C-2

20 C

Hea

t wav

e45

0 C55

0 C

Dro

ught

(no

eff

ectiv

e

rain

)15

mon

ths

Pal

atab

ility

Dai

ry c

ows,

cat

tle, h

orse

, ra

bbits

, she

ep, k

anga

roo

Cow

s, c

attle

, goa

ts,

shee

p, p

igs,

car

p

Nut

riti

onal

Val

ueN

= 1

.1 %

Cru

de p

rote

in 3

.3%

P =

0.1

7%C

rude

fat

0.4

%

K =

2.2

%

Cru

de fi

bre

7.1%

Gen

otyp

es:

VV

Z00

8-18

, Ohi

to, a

nd T

aiw

an, t

he l

atte

r tw

o ar

e ba

sica

lly t

he

sam

e as

Sun

shin

e. T

empe

ratu

re t

reat

men

ts:

day

15ºC

/ni

ght

13ºC

(PC

: YW

W

ang)

.

9

2.6

Gen

etic

cha

ract

eris

tics

Thr

ee v

etiv

er s

peci

es a

re u

sed

for

envi

ronm

enta

l pro

tect

ion

purp

oses

.

2.6.

1 Ve

tiver

ia z

izan

ioid

es r

ecla

ssifi

ed a

s C

hrys

opog

on z

izan

ioid

es

The

re a

re tw

o sp

ecie

s of

vet

iver

ori

gina

ting

in th

e In

dian

sub

cont

inen

t: C

hrys

opog

on z

izan

ioid

es a

nd C

hrys

opog

on l

awso

nii.

Chr

ysop

ogon

zi

zani

oide

s ha

s m

any

diff

eren

t acc

essi

ons.

Gen

eral

ly th

ose

from

sou

th

Indi

a ha

ve b

een

culti

vate

d an

d ha

ve l

arge

and

str

ong

root

sys

tem

s.

The

se a

cces

sion

s te

nd t

owar

ds p

olyp

loid

y an

d sh

ow h

igh

leve

ls o

f st

erili

ty a

nd a

re n

ot c

onsi

dere

d in

vasi

ve. T

he n

orth

Ind

ian

acce

ssio

ns,

com

mon

to th

e G

ange

tic a

nd I

ndus

bas

ins,

are

wild

and

hav

e w

eake

r ro

ot sy

stem

s. T

hese

acc

essi

ons a

re d

iplo

ids a

nd a

re k

now

n to

be

wee

dy,

thou

gh n

ot n

eces

sari

ly i

nvas

ive.

The

se n

orth

Ind

ian

acce

ssio

ns a

re

NO

T r

ecom

men

ded

unde

r th

e V

etiv

er S

yste

m. I

t sho

uld

also

be

note

d th

at m

ost

of t

he r

esea

rch

into

dif

fere

nt v

etiv

er a

pplic

atio

ns a

nd fi

eld

expe

rien

ce h

ave

invo

lved

the

sou

th I

ndia

n cu

ltiva

rs t

hat

are

clos

ely

rela

ted

(sam

e ge

noty

pe) a

s M

onto

and

Sun

shin

e. D

NA

stu

dies

con

firm

th

at a

bout

60%

of

Chr

ysop

ogon

ziz

anio

ides

use

d fo

r bi

o-en

gine

erin

g an

d ph

ytor

emed

iatio

n in

tro

pica

l an

d su

btro

pica

l co

untr

ies

are

of t

he

Mon

to/S

unsh

ine

geno

type

.

2.6.

2 C

hrys

opog

on n

emor

alis

T

his n

ativ

e ve

tiver

spec

ies a

re w

ide

spre

ad in

the

high

land

s of T

haila

nd,

Lao

s, a

nd V

ietn

am a

nd m

ost

likel

y in

Cam

bodi

a an

d M

yanm

ar a

s w

ell.

It i

s be

ing

wid

ely

used

in

Tha

iland

for

tha

tchi

ng p

urpo

se. T

his

spec

ies

is n

ot s

teri

le, t

he m

ain

diff

eren

ces

betw

een

C. n

emor

alis

and

C

. ziz

anio

ides

, are

that

the

latte

r is

muc

h ta

ller a

nd h

as th

icke

r and

stif

f st

ems,

C. z

izan

ioid

es h

as a

muc

h th

icke

r an

d de

eper

roo

t sy

stem

and

its

leav

es a

re b

road

er a

nd h

as a

ligh

t gre

en a

rea

alon

g th

e m

id r

ibs,

as

show

n on

the

phot

os b

elow

- p

hoto

s 5-

8.

10

Ph

oto

5: V

etiv

er le

aves

, up

per

: C. z

izan

ioid

es, l

ow

er: C

. nem

ora

lis.

Ph

oto

6:

Dif

fere

nce

bet

wee

n C

. zi

zan

ioid

es (

up

per

) an

d C

. n

emo

ralis

ro

ots

(lo

wer

).

11

Ph

oto

7: V

etiv

er s

ho

ots

: up

per

- C

. nem

ora

lis, l

ow

er -

C. z

izan

ioid

es.

12

Ph

oto

8: V

etiv

er r

oo

ts a

fter

bei

ng

gro

wn

in

so

il (t

op

lef

t an

d r

igh

t), a

nd

af

ter

bei

ng

gro

wn

su

spen

ded

in w

ater

(lo

wer

).

13

Alth

ough

C. n

emor

alis

is n

ot a

s eff

ectiv

e as

C. z

izan

ioid

es, f

arm

ers h

ave

also

rec

ogni

zed

the

usef

ulne

ss o

f C

. ne

mor

alis

in

soil

cons

erva

tion;

th

ey h

ave

used

it i

n th

e C

entr

al H

ighl

ands

as

wel

l as

in s

ome

coas

tal

prov

ince

s of

Cen

tral

Vie

tnam

suc

h as

Qua

ng N

gai t

o st

abili

ze d

ikes

in

rice

fiel

ds, -

pho

to 9

.

Ph

oto

9:

C.

nem

ora

lis o

n a

ric

e fi

eld

bu

nd

in

Qu

ang

Ng

ai (

up

per

), an

d

wild

in C

entr

al H

igh

lan

ds

(lo

wer

).

2.6.

3 C

hrys

opog

on n

igri

tana

Thi

s sp

ecie

s is

nat

ive

to S

outh

ern

and

Wes

t Afr

ica,

its

app

licat

ion

is

mai

nly

rest

rict

ed to

the

sub

con

tinen

t, an

d as

it p

rodu

ces

viab

le s

eeds

its

app

licat

ion

shou

ld b

e re

stri

cted

to th

eir

hom

e la

nds

- ph

oto

10.

14

2.7

Wee

d po

tent

ial

Vet

iver

gra

ss c

ultiv

ars

deri

ved

from

sou

th I

ndia

n ac

cess

ions

are

non

-ag

gres

sive

; the

y pr

oduc

e ne

ither

sto

lons

nor

rhi

zom

es a

nd h

ave

to b

e es

tabl

ishe

d ve

geta

tivel

y by

roo

t (cr

own)

sub

divi

sion

s. I

t is

impe

rativ

e th

at a

ny p

lant

s us

ed f

or b

ioen

gine

erin

g pu

rpos

es w

ill n

ot b

ecom

e a

wee

d in

the

loca

l env

iron

men

t; th

eref

ore

ster

ile v

etiv

er c

ultiv

ars

Ph

oto

10:

Ch

ryso

po

go

n n

igri

tan

a in

Mal

i, W

est

Afr

ica.

(suc

h as

Mon

to, S

unsh

ine,

Kar

nata

ka, F

iji a

nd M

adup

atty

) fro

m s

outh

In

dian

acc

essi

ons

are

idea

l fo

r th

is a

pplic

atio

n. I

n Fi

ji, w

here

vet

iver

gr

ass

was

int

rodu

ced

for

that

chin

g m

ore

than

100

yea

rs a

go,

it ha

s be

en w

idel

y us

ed fo

r soi

l and

wat

er c

onse

rvat

ion

purp

oses

in th

e su

gar

indu

stry

for

ove

r 50

yea

rs w

ithou

t sho

win

g an

y si

gns

of in

vasi

vene

ss.

Vet

iver

gra

ss c

an b

e de

stro

yed

easi

ly e

ither

by

spra

ying

with

gly

phos

ate

15

(Rou

ndup

) or

by

cutti

ng o

ff th

e pl

ant b

elow

the

crow

n.

3. C

ON

CL

USI

ON

Due

to

C.

nem

oral

is l

ow g

row

th f

orm

s an

d m

ost

impo

rtan

tly v

ery

shor

t roo

t sys

tem

it is

not

sui

tabl

e fo

r st

eep

slop

e st

abili

zatio

n w

orks

. In

add

ition

, no

rese

arch

has

bee

n co

nduc

ted

on it

s w

aste

wat

er d

ispo

sal

and

trea

tmen

t, an

d ph

yto-

rem

edia

tion

capa

citie

s, i

t is

rec

omm

ende

d th

at o

nly

non

fert

ile c

ultiv

ars

of C

. ziz

anio

ides

be

used

for a

pplic

atio

ns

liste

d in

this

man

ual.

4. R

EF

ER

EN

CE

S

Ada

ms,

R.P

., D

affo

rn,

M.R

. (1

997)

. D

NA

fing

erpr

ints

(R

APD

s) o

f th

e pa

ntro

pica

l gr

ass,

Vet

iver

ia z

izan

ioid

es L

, re

veal

a s

ingl

e cl

one,

“Su

nshi

ne,”

is

wid

ely

utili

sed

for

eros

ion

cont

rol.

Spec

ial P

aper

, The

Vet

iver

Net

wor

k, L

eesb

urg

Va,

USA

.A

dam

s,

R.P

., M

. Z

hong

, Y

. T

urus

peko

v,

M.R

. D

affo

rn,

and

J.F.

Vel

dkam

p. 1

998.

DN

A fi

nger

prin

ting

reve

als

clon

al n

atur

e of

Vet

iver

ia z

izan

ioid

es (

L.)

Nas

h, G

ram

inea

e an

d so

urce

s of

po

tent

ial n

ew g

erm

plas

m. M

olec

ular

Eco

logy

7:8

13-8

18.

Gre

enfie

ld, J

.C. (

1989

). V

etiv

er G

rass

: T

he id

eal p

lant

for

veg

etat

ive

soil

and

moi

stur

e co

nser

vatio

n.

AST

AG

- T

he W

orld

Ban

k,

Was

hing

ton

DC

, USA

.N

atio

nal

Res

earc

h C

ounc

il. 1

993.

Vet

iver

Gra

ss: A

Thi

n G

reen

Lin

e A

gain

st E

rosi

on. W

ashi

ngto

n, D

.C.:

Nat

iona

l Aca

dem

y Pr

ess.

17

1 pp

.Pu

rseg

love

, J.

W.

1972

. T

ropi

cal

Cro

ps:

Mon

ocot

yled

ons

1. ,

New

Y

ork:

Joh

n W

iley

& S

ons.

Tru

ong,

P.N

. (19

99).

Vet

iver

Gra

ss T

echn

olog

y fo

r la

nd s

tabi

lisat

ion,

er

osio

n an

d se

dim

ent

cont

rol

in

the

Asi

a Pa

cific

re

gion

. Pr

oc.

Firs

t A

sia

Paci

fic C

onfe

renc

e on

Gro

und

and

Wat

er

Bio

engi

neer

ing

for

Ero

sion

Con

trol

and

Slo

pe S

tabi

lisat

ion.

M

anila

, Phi

lippi

nes,

Apr

il 19

99.

Vel

dkam

p. J

.F.

199

9. A

rev

isio

n of

Chr

ysop

ogon

Tri

n. i

nclu

ding

Ve

tive

ria

Bor

y (P

oace

ae)

in T

haila

nd a

nd M

elan

esia

with

no

tes

on

som

e ot

her

spec

ies

from

Afr

ica

and

Aus

tral

ia.

Aus

trob

aile

ya 5

: 503

-533

.

16

PAR

T -

2

TH

E V

ET

IVE

R S

YST

EM

F

OR

SL

OP

E S

TA

BIL

IZA

TIO

N

CO

NT

EN

TS

1. T

YPE

S O

F N

AT

UR

AL

DIS

AST

ER

S T

HA

T C

AN

BE

RE

DU

CE

D B

Y U

SIN

G T

HE

VE

TIV

ER

SY

STE

M (

VS)

17

2. G

EN

ER

AL

PR

INC

IPL

ES

OF

SLO

PE S

TAB

ILIT

Y A

ND

SLO

PE S

TAB

ILIS

AT

ION

19

2.1

Slop

e pr

ofile

19

2.2

Slop

e st

abili

ty

192.

3 Ty

pes

of s

lope

fai

lure

22

2.4

Hum

an im

pact

on

slop

e fa

ilure

22

2.5

Miti

gatio

n of

slo

pe f

ailu

re

252.

6 V

eget

ativ

e sl

ope

stab

ilisa

tion

263.

SL

OPE

STA

BIL

ISA

TIO

N U

SIN

G V

ET

IVE

R S

YST

EM

29

3.

1 C

hara

cter

istic

s of

vet

iver

sui

tabl

e fo

r sl

ope

stab

ilisa

tion

29

3.2

Spec

ial c

hara

cter

istic

s of

vet

iver

sui

tabl

e fo

r

w

ater

dis

aste

r m

itiga

tion

32

3.3

Tens

ile a

nd s

hear

str

engt

h of

vet

iver

roo

ts

33

3.4

Hyd

raul

ic c

hara

cter

istic

s 36

3.

5 Po

re w

ater

pre

ssur

e 37

3.

6 A

pplic

atio

ns o

f V

S in

nat

ural

dis

aste

r

m

itiga

tion

an in

fras

truc

ture

pro

tect

ion

37

3.7

Adv

anta

ges

and

disa

dvan

tage

s of

Vet

iver

Sys

tem

38

3.

8 C

ombi

natio

ns w

ith o

ther

type

s of

rem

edy

40

3.9

Com

pute

r m

odel

ling

404.

APP

RO

PRIA

TE

DE

SIG

NS

AN

D T

EC

HN

IQU

ES

41

4.1

Prec

autio

ns

41

4.2

Plan

ting

time

43

4.3

Nur

sery

44

4.

4 Pr

epar

atio

n fo

r ve

tiver

pla

ntin

g 45

17

4.

5 L

ayou

t spe

cific

atio

ns

45

4.6

Plan

ting

spec

ifica

tions

47

4.

7 M

aint

enan

ce

475.

VS

APP

LIC

AT

ION

S FO

R S

LO

PE S

TAB

ILIZ

AT

ION

RE

LA

STE

D T

O N

AT

UR

AL

DIS

AST

ER

RE

DU

CT

ION

A

ND

IN

FRA

-ST

RU

CT

UR

E P

RO

TE

CT

ION

IN

VIE

TN

AM

49

5.1

VS

appl

icat

ion

for

sand

dun

e pr

otec

tion

in

C

entr

al V

ietn

am

495.

2 V

S ap

plic

atio

n to

con

trol

riv

er b

ank

eros

ion

565.

3 V

S A

pplic

atio

n fo

r co

asta

l ero

sion

con

trol

73

5.4

VS

appl

icat

ion

to s

tabi

lize

road

bat

ters

80

6. C

ON

CL

USI

ON

S 84

7. R

EFE

RE

NC

ES

85

1. T

YP

ES

OF

NA

TU

RA

L D

ISA

STE

RS

TH

AT

CA

N B

E

RE

DU

CE

D B

Y U

SIN

G T

HE

VE

TIV

ER

SY

STE

M (

VS)

Bes

ides

soi

l er

osio

n, t

he V

etiv

er S

yste

m (

VS)

can

red

uce

or e

ven

elim

inat

e m

any

type

s of

na

tura

l di

sast

ers,

in

clud

ing

land

slid

es,

mud

slid

es,

road

bat

ter

inst

abili

ty,

and

eros

ion

(riv

er b

anks

, ca

nals

, co

astli

nes,

dik

es, a

nd e

arth

-dam

bat

ters

).

Whe

n he

avy

rain

s sa

tura

te ro

cks

and

soils

, lan

dslid

es a

nd d

ebri

s-flo

ws

occu

r in

man

y m

ount

aino

us a

reas

of V

ietn

am. R

epre

sent

ativ

e ex

ampl

es

are

the

cata

stro

phic

lan

dslid

es, d

ebri

s flo

ws

and

flash

floo

ding

in

the

Muo

ng L

ay d

istr

ict,

Die

n B

ien

prov

ince

(19

96),

and

the

lan

dslid

e on

th

e H

ai V

an P

ass (

1999

) tha

t dis

rupt

ed N

orth

-Sou

th tr

affic

for m

ore

than

tw

o w

eeks

and

cos

t mor

e th

an $

1 m

illio

n U

SD to

rem

edy.

Vie

tnam

’s

larg

est

land

slid

es, t

hose

lar

ger

than

one

mill

ion

cubi

c m

eter

s (a

mon

g th

em T

hiet

Din

h L

ake,

Hoa

i N

hon

dist

rict

, B

inh

Din

h pr

ovin

ce,

in

An

Ngh

iêp

and

An

Lin

h co

mm

unes

, T

uy A

n di

stri

ct,

and

Phu

Yen

pr

ovin

ce),

cau

sed

loss

of

life

as w

ell a

s pr

oper

ty d

amag

e.

Riv

er b

ank

and

coas

tal

eros

ion,

and

dik

e fa

ilure

s ha

ppen

con

tinua

lly

thro

ugho

ut V

ietn

am. T

ypic

al e

xam

ples

inc

lude

: ri

ver

bank

ero

sion

in

Phu

Tho

, Han

oi, a

nd i

n se

vera

l ce

ntra

l Vie

tnam

pro

vinc

es (

incl

udin

g T

hua

Thi

en H

ue,

Qua

ng N

am,

Qua

ng N

gai

and

Bin

h D

inh)

; co

asta

l

18

eros

ion

in H

ai H

au d

istr

ict,

Nam

Din

h pr

ovin

ce,

and;

riv

erba

nk

and

coas

tal

eros

ion

in t

he M

ekon

g D

elta

. A

lthou

gh t

hese

eve

nts

and

flood

ing/

stor

m d

isas

ters

usu

ally

occ

ur d

urin

g th

e ra

iny

seas

on,

som

etim

es r

iver

bank

ero

sion

take

s pl

ace

duri

ng th

e dr

y se

ason

, whe

n w

ater

dro

ps t

o its

low

est

leve

l. T

his

happ

ened

in

Hau

Vie

n vi

llage

, C

am L

o di

stri

ct, i

n Q

uang

Tri

pro

vinc

e.

Lan

dslid

es a

re m

ore

com

mon

in

area

s w

here

hum

an a

ctiv

ities

pla

y a

deci

sive

rol

e. A

lmos

t 20

perc

ent o

r 20

0 km

(12

4 m

iles)

of

mor

e th

an

1000

km

(62

1 m

iles)

of

the

Ha

Tin

h -

Kon

Tum

sec

tion

of th

e H

o C

hi

Min

h H

ighw

ay i

s hi

ghly

sus

cept

ible

to

land

slid

e or

slo

pe i

nsta

bilit

y,

mai

nly

beca

use

of p

oor

road

con

stru

ctio

n pr

actic

es a

nd a

n un

derl

ying

fa

ilure

to u

nder

stan

d th

e un

favo

urab

le g

eolo

gica

l con

ditio

ns.

Rec

ent

land

slid

es i

n th

e to

wns

of

Yen

Bai

, L

ao C

ai,

and

Bac

Kan

fol

low

ed

mun

icip

al d

ecis

ions

to e

xpan

d ho

usin

g by

allo

win

g cu

tting

at i

ncre

ased

sl

ope

grad

ient

s.

Maj

or e

arth

quak

es h

ave

also

gen

erat

ed la

ndsl

ides

in V

ietn

am, i

nclu

ding

th

e 19

83 s

lide

in T

uan

Gia

o di

stri

ct, a

nd th

e 20

01 s

lide

alon

g th

e ro

ute

from

Die

n B

ien

tow

n to

Lai

Cha

u di

stri

ct.

From

a s

tric

tly e

cono

mic

poi

nt o

f vi

ew, t

he c

ost o

f re

med

iatin

g th

ese

prob

lem

s is h

igh

and

the

Stat

e bu

dget

for s

uch

wor

ks is

nev

er su

ffici

ent.

For e

xam

ple,

rive

r ban

k re

vetm

ent u

sual

ly c

osts

bet

wee

n U

S $2

00,0

00-

300,

000

/km

, som

etim

es r

unni

ng a

s hi

gh a

s U

S $7

00,0

00-$

1 m

illio

n /k

m. T

he T

an C

hau

emba

nkm

ent

in t

he M

ekon

g D

elta

is

an e

xtre

me

case

tha

t co

st n

earl

y U

S $7

mill

ion

/km

. R

iver

ban

k pr

otec

tion

in

Qua

ng B

inh

prov

ince

alo

ne i

s es

timat

ed t

o re

quir

e an

exp

endi

ture

of

mor

e th

an U

S $2

0 m

illio

n ; t

he a

nnua

l bud

get i

s on

ly U

S $3

00,0

00 .

Con

stru

ctio

n of

sea

dik

es u

sual

ly c

osts

bet

wee

n U

S $7

00,0

00-$

1 m

illio

n /k

m, b

ut m

ore

expe

nsiv

e se

ctio

ns c

an c

ost u

pwar

ds o

f US

$2.5

m

illio

n /k

m, a

nd a

re n

ot u

ncom

mon

. Aft

er s

torm

No.

7 in

Sep

tem

ber

2005

was

hed

away

man

y im

prov

ed d

ike

sect

ions

, som

e di

ke m

anag

ers

conc

lude

d th

at e

ven

sect

ions

eng

inee

red

to w

ithst

and

stor

ms

up to

the

9th

leve

l ar

e to

o w

eak,

and

beg

an t

o se

riou

sly

cons

ider

con

stru

ctin

g se

a di

kes

capa

ble

of w

ithst

andi

ng s

torm

s of

up

to t

he 1

2th

leve

l th

at

wou

ld c

ost b

etw

een

US

$7-$

10 m

illio

n /k

m.

19

Bud

get

cons

trai

nts

alw

ays

exis

t, w

hich

co

nfine

s ri

gid

stru

ctur

al

prot

ectio

n m

easu

res

to th

e m

ost a

cute

sec

tions

, nev

er to

the

full

leng

th

of th

e ri

ver

bank

or

coas

tline

. T

his

band

aid

app

roac

h co

mpo

unds

the

prob

lem

s.

Eac

h of

thes

e ev

ents

repr

esen

ts a

type

of s

lope

failu

re o

r mas

s w

astin

g,

refle

ctin

g th

e do

wn

slop

e m

ovem

ent o

f roc

k de

bris

and

soi

l in

resp

onse

to

gra

vita

tiona

l st

ress

es.

Thi

s m

ovem

ent

can

be v

ery

slow

, al

mos

t im

perc

eptib

le,

or d

evas

tatin

gly

rapi

d an

d ap

pare

nt w

ithin

min

utes

. Si

nce

man

y fa

ctor

s in

fluen

ce w

heth

er n

atur

al d

isas

ters

will

occ

ur, w

e sh

ould

und

erst

and

the

caus

es a

s w

ell a

s so

me

basi

c pr

inci

ples

of

slop

e st

abili

satio

n. T

his

info

rmat

ion

will

allo

w u

s to

eff

ectiv

ely

empl

oy V

S bi

oeng

inee

ring

met

hods

to r

educ

e th

eir

impa

ct.

2. G

EN

ER

AL

PR

INC

IPL

ES

OF

SLO

PE

ST

AB

ILIT

Y A

ND

SL

OP

E S

TA

BIL

ISA

TIO

N

2.1

Slop

e pr

ofile

Som

e sl

opes

are

gra

dual

ly c

urve

d, a

nd o

ther

s ar

e ex

trem

ely

stee

p.

The

pro

file

of a

nat

ural

ly-e

rode

d sl

ope

depe

nds

prim

arily

on

its r

ock/

soil

type

, the

soi

l’s n

atur

al a

ngle

of

repo

se, a

nd t

he c

limat

e.

For

slip

re

sist

ant

rock

/soi

l, es

peci

ally

in

arid

reg

ions

, ch

emic

al w

eath

erin

g is

slo

w c

ompa

red

to p

hysi

cal

wea

ther

ing.

The

cre

st o

f th

e sl

ope

is

slig

htly

con

vex

to a

ngul

ar, t

he c

liff f

ace

is n

earl

y ve

rtic

al, a

nd a

deb

ris

slop

e is

pre

sent

at

a 30

-35°

ang

le o

f re

pose

, th

e m

axim

um a

ngle

at

whi

ch lo

ose

mat

eria

l of

a sp

ecifi

c so

il ty

pe is

sta

ble.

Non

-res

ista

nt r

ock/

soil,

esp

ecia

lly in

hum

id r

egio

ns, w

eath

ers

rapi

dly

and

erod

es e

asily

. The

res

ultin

g sl

ope

cont

ains

a t

hick

soi

l co

ver.

Its

cres

t is

conv

ex, a

nd it

s ba

se is

con

cave

.

2.2

Slop

e st

abili

ty2.

2.1

Upl

and

natu

ral s

lope

, cut

slo

pe, r

oad

batte

r et

c.T

he s

tabi

lity

of s

uch

slop

es i

s ba

sed

on t

he i

nter

play

bet

wee

n tw

o ty

pes

of f

orce

s, d

rivi

ng f

orce

s an

d re

sist

ing

forc

es.

Dri

ving

for

ces

prom

ote

dow

n sl

ope

mov

emen

t of

mat

eria

l, w

hile

res

istin

g fo

rces

de

ter m

ovem

ent.

Whe

n dr

ivin

g fo

rces

ove

rcom

e re

sist

ing

forc

es, t

hese

sl

opes

bec

ome

unst

able

.

20

2.2.

2 R

iver

ban

k, c

oast

al e

rosi

on a

nd in

stab

ility

of w

ater

reta

inin

g st

ruct

ures

Som

e hy

drau

lic e

ngin

eers

may

arg

ue th

at b

ank

eros

ion

and

unst

able

w

ater

ret

aini

ng s

truc

ture

s sh

ould

be

trea

ted

sepa

rate

ly f

rom

oth

er

type

s of

slo

pe f

ailu

re b

ecau

se t

heir

res

pect

ive

load

s ar

e di

ffer

ent.

In o

ur o

pini

on, h

owev

er, b

oth

are

subj

ect

to t

he s

ame

inte

ract

ion

betw

een

“dri

ving

for

ces”

and

“re

sist

ing

forc

es”.

Fai

lure

res

ults

w

hen

the

form

er o

verc

omes

the

latte

r.

How

ever

, er

osio

n of

ban

ks a

nd t

he i

nsta

bilit

y of

wat

er r

etai

ning

st

ruct

ures

ar

e sl

ight

ly

mor

e co

mpl

icat

ed;

they

re

sult

from

in

tera

ctio

ns b

etw

een

hydr

aulic

for

ces

actin

g at

the

bed

and

toe

an

d gr

avita

tiona

l for

ces

affe

ctin

g th

e in

-situ

ban

k m

ater

ial.

Failu

re

occu

rs w

hen

eros

ion

of th

e ba

nk to

e an

d th

e ch

anne

l bed

adj

acen

t to

the

ban

k ha

ve i

ncre

ased

the

hei

ght

and

angl

e of

the

ban

k to

th

e po

int t

hat g

ravi

tatio

nal f

orce

s ex

ceed

the

shea

r st

reng

th o

f th

e ba

nk m

ater

ial.

Aft

er fa

ilure

, fai

led

bank

mat

eria

l may

be

deliv

ered

di

rect

ly t

o th

e flo

w a

nd d

epos

ited

as b

ed m

ater

ial,

disp

erse

d as

w

ash

load

, or

depo

site

d al

ong

the

toe

of t

he b

ank

eith

er a

s in

tact

bl

ock,

or

as s

mal

ler,

disp

erse

d ag

greg

ates

.

Fluv

ial c

ontr

olle

d pr

oces

ses

of b

ank

retr

eat a

re e

ssen

tially

twof

old.

Fl

uvia

l sh

ear

eros

ion

of b

ank

mat

eria

ls r

esul

ts i

n pr

ogre

ssiv

e in

crem

enta

l ba

nk r

etre

at. A

dditi

onal

ly,

a ri

se i

n ba

nk h

eigh

t du

e to

nea

r-ba

nk b

ed d

egra

datio

n or

an

incr

ease

in

bank

ste

epne

ss

due

to fl

uvia

l ero

sion

of

the

low

er b

ank

may

act

alo

ne o

r to

geth

er

to d

ecre

ase

the

stab

ility

of

the

bank

with

res

pect

to

mas

s fa

ilure

. D

epen

ding

on

the

cons

trai

nts

of i

ts m

ater

ial

prop

ertie

s an

d th

e ge

omet

ry o

f its

pro

file,

a b

ank

may

fai

l as

the

res

ult

of a

ny o

ne

of s

ever

al p

ossi

ble

mec

hani

sms,

inc

ludi

ng p

lana

r, ro

tatio

nal,

and

cant

ileve

r ty

pe f

ailu

res.

Non

-fluv

ial

cont

rolle

d m

echa

nism

s of

ban

k re

trea

t in

clud

e th

e ef

fect

s of

wav

e w

ash,

tra

mpl

ing,

and

pip

ing

- an

d sa

ppin

g-ty

pe

failu

res,

ass

ocia

ted

with

str

atifi

ed b

anks

and

adv

erse

gro

undw

ater

co

nditi

ons.

21

2.2.

3 D

rivi

ng f

orce

sA

lthou

gh g

ravi

ty i

s th

e m

ain

driv

ing

forc

e, i

t ca

nnot

act

alo

ne.

Slop

e an

gle,

ang

le o

f re

pose

of

spec

ific

soil,

clim

ate,

slo

pe

mat

eria

l, an

d es

peci

ally

wat

er, c

ontr

ibut

e to

its

effe

ct:

• Fa

ilure

occ

urs

far m

ore

freq

uent

ly o

n st

eep

slop

es th

an o

n ge

ntle

slo

pes.

Wat

er p

lays

a k

ey ro

le in

pro

duci

ng s

lope

failu

re e

spec

ially

at

the

toe

of th

e sl

ope:

- In

the

for

m o

f ri

vers

and

wav

e ac

tion,

wat

er e

rode

s th

e ba

se o

f slo

pes,

rem

ovin

g su

ppor

t, w

hich

incr

ease

s dr

ivin

g fo

rces

.-

Wat

er a

lso

incr

ease

s th

e dr

ivin

g fo

rce

by lo

adin

g, th

at

is, fi

lling

pre

viou

sly

empt

y po

re s

pace

s an

d fr

actu

res,

w

hich

add

s to

the

tota

l mas

s su

bjec

ted

to g

ravi

tatio

nal

forc

e.-

The

pre

senc

e of

wat

er r

esul

ts i

n po

re w

ater

pre

ssur

e th

at r

educ

es t

he s

hear

str

engt

h of

the

slo

pe m

ater

ial.

Impo

rtan

tly,

abru

pt

chan

ges

(dra

mat

ic

incr

ease

s an

d de

crea

ses)

in

pore

wat

er p

ress

ure

may

pla

y th

e de

cisi

ve r

ole

in s

lope

fai

lure

.-

Wat

er’s

inte

ract

ion

with

surf

ace r

ock

and

soil

(che

mic

al

wea

ther

ing)

sl

owly

w

eake

ns

slop

e m

ater

ial,

and

redu

ces

its s

hear

str

engt

h.

Thi

s in

tera

ctio

n re

duce

s re

sist

ing

forc

es.

2.2.

4 R

esis

ting

forc

esT

he m

ain

resi

stin

g fo

rce

is th

e m

ater

ial's

she

ar s

tren

gth,

a fu

nctio

n of

coh

esio

n (t

he a

bilit

y of

par

ticle

s to

attr

act a

nd h

old

each

oth

er

toge

ther

) an

d in

tern

al f

rict

ion

(fri

ctio

n be

twee

n gr

ains

with

in a

m

ater

ial)

that

opp

oses

dri

ving

for

ces.

The

rat

io o

f re

sist

ing

forc

es

to d

rivi

ng f

orce

s is

the

saf

ety

fact

or (

SF).

If

SF >

1 th

e sl

ope

is s

tabl

e. O

ther

wis

e, i

t is

uns

tabl

e. U

sual

ly a

SF

of 1

.2-1

.3 i

s m

argi

nally

acc

epta

ble.

Dep

endi

ng o

n th

e im

port

ance

of

the

slop

e an

d th

e po

tent

ial

loss

es a

ssoc

iate

d w

ith i

ts f

ailu

re,

a hi

gher

SF

shou

ld b

e en

sure

d. I

n sh

ort,

slop

e st

abili

ty is

a f

unct

ion

of: r

ock/

soil

type

and

its

stre

ngth

, slo

pe g

eom

etry

(he

ight

, ang

le),

clim

ate,

ve

geta

tion

and

time.

Eac

h of

the

se f

acto

rs m

ay p

lay

a si

gnifi

cant

ro

le in

con

trol

ling

driv

ing

or r

esis

ting

forc

es.

22

2.3

Typ

es o

f sl

ope

failu

reD

epen

ding

on

the

type

of

mov

emen

t an

d th

e na

ture

of

the

mat

eria

l in

volv

ed, d

iffe

rent

type

s of

slo

pe f

ailu

re m

ay r

esul

t:

Tabl

e 1:

Typ

es o

f sl

ope

failu

re

In r

ock,

usu

ally

fal

ls a

nd t

rans

latio

nal

slid

es (

invo

lvin

g on

e or

mor

e pl

anes

of

wea

knes

s) w

ill o

ccur

. Si

nce

soil

is m

ore

hom

ogen

ous

and

lack

s a

visi

ble

plan

e of

wea

knes

s, r

otat

iona

l sl

ides

or

flow

s oc

cur.

In

gene

ral,

mas

s w

astin

g in

volv

es m

ore

than

one

type

of

mov

emen

t, fo

r ex

ampl

e, u

pper

slu

mp

and

low

er fl

ow,

or u

pper

soi

l sl

ide

and

low

er

rock

slid

e.

2.4

Hum

an im

pact

on

slop

e fa

ilure

Lan

dslid

es a

re n

atur

al o

ccur

ring

phe

nom

ena

know

n as

geo

logi

cal

eros

ion.

Lan

dslid

es o

r sl

ope

failu

res

occu

r w

heth

er p

eopl

e ar

e th

ere

or n

ot!

How

ever

, hu

man

lan

d us

e pr

actic

es p

lay

a m

ajor

rol

e in

sl

ope

proc

esse

s. T

he c

ombi

natio

n of

unc

ontr

olla

ble

natu

ral

even

ts

Typ

e of

mov

emen

tM

ater

ial i

nvol

ved

Roc

kSo

il

Fal

lsR

ock

fall

Soil

fall

Slid

esR

otat

iona

lR

ock

slum

p bl

ock

Soil

slum

p bl

ocks

Tra

nsla

tiona

lR

ock

slid

ede

bris

slid

e

Flo

ws

Slow

Roc

k cr

eep

Soil

cree

p

satu

rate

d &

un

cons

olid

ated

m

ater

ial

eart

h flo

w

mud

flow

(up

to

30%

wat

er)

Fast

debr

is fl

ow

debr

is a

vala

nche

Com

plex

Com

bina

tion

of tw

o or

mor

e ty

pes

of m

ovem

ent

23

(ear

thqu

akes

, hea

vy ra

inst

orm

s, e

tc.)

and

art

ifici

ally

alte

red

land

(slo

pe

exca

vatio

n, d

efor

esta

tion,

urb

anis

atio

n, e

tc.)

can

cre

ate

disa

stro

us

slop

e fa

ilure

s.

2.5

Miti

gatio

n of

slo

pe f

ailu

reM

inim

izin

g sl

ope

failu

re

requ

ires

th

ree

step

s:

iden

tifica

tion

of

pote

ntia

lly

unst

able

ar

eas;

pr

even

tion

of

slop

e fa

ilure

, an

d;

impl

emen

tatio

n of

cor

rect

ive

mea

sure

s fo

llow

ing

slop

e fa

ilure

. A

th

orou

gh u

nder

stan

ding

of g

eolo

gica

l con

ditio

ns is

cri

tical

ly im

port

ant

to d

ecid

e th

e be

st m

itiga

tion

prac

tice.

2.5.

1 Id

entifi

catio

nT

rain

ed t

echn

icia

ns i

dent

ify

pros

pect

ive

slop

e fa

ilure

by

stud

ying

ae

rial

pho

togr

aphs

to

loca

te p

revi

ous

land

slid

e or

slo

pe f

ailu

re s

ites,

an

d co

nduc

ting

field

inv

estig

atio

ns o

f po

tent

ially

uns

tabl

e sl

opes

. Po

tent

ial

mas

s-w

astin

g ar

eas

can

be

iden

tified

by

st

eep

slop

es,

bedd

ing

plan

es i

nclin

ed t

owar

d va

lley

floor

s, h

umm

ocky

top

ogra

phy

(irr

egul

ar,

lum

py-l

ooki

ng s

urfa

ces

cove

red

by y

oung

er t

rees

), w

ater

se

epag

e, a

nd a

reas

whe

re l

ands

lides

hav

e pr

evio

usly

occ

urre

d. T

his

info

rmat

ion

is u

sed

to g

ener

ate

a ha

zard

map

sho

win

g th

e la

ndsl

ide-

pron

e un

stab

le a

reas

.

2.5.

2 P

reve

ntio

nPr

even

ting

land

slid

es a

nd s

lope

inst

abili

ty is

muc

h m

ore

cost

eff

ectiv

e th

an c

orre

ctio

n. P

reve

ntio

n m

etho

ds i

nclu

de c

ontr

ollin

g dr

aina

ge,

redu

cing

slo

pe a

ngle

and

slo

pe h

eigh

t, an

d in

stal

ling

vege

tativ

e co

ver,

reta

inin

g w

all,

rock

bol

t, or

sho

tcre

te (fi

nely

-agg

rega

ted

conc

rete

, with

ad

mix

ture

for

fas

t so

lidif

ying

, ap

plie

d by

a p

ower

ful

pum

p).

The

se

supp

ortiv

e m

etho

ds m

ust

be c

orre

ctly

and

app

ropr

iate

ly a

pplie

d by

fir

st e

nsur

ing

that

the

slo

pe i

s in

tern

ally

and

str

uctu

rally

sta

ble.

Thi

s re

quir

es a

goo

d un

ders

tand

ing

of lo

cal g

eolo

gica

l con

ditio

ns.

2.5.

3 C

orre

ctio

nSo

me

land

slid

es c

an b

e co

rrec

ted

by i

nsta

lling

a d

rain

age

syst

em t

o re

duce

wat

er p

ress

ure

in t

he s

lope

, an

d pr

even

t fu

rthe

r m

ovem

ent.

Slop

e in

stab

ility

pro

blem

s bo

rder

ing

road

s or

oth

er i

mpo

rtan

t pl

aces

ty

pica

lly r

equi

re c

ostly

tre

atm

ent.

Don

e tim

ely

and

prop

erly

, sur

face

an

d su

bsur

face

dra

inag

e w

ould

be

very

eff

ectiv

e.

How

ever

, si

nce

24

such

mai

nten

ance

is u

sual

ly d

efer

red

or n

egle

cted

ent

irel

y, m

uch

mor

e ri

goro

us a

nd e

xpen

sive

cor

rect

ive

mea

sure

s be

com

e ne

cess

ary.

In V

ietn

am,

rigi

d st

ruct

ural

pro

tect

ion

met

hods

(co

ncre

te o

r ro

ck

ripr

ap b

ank

reve

tmen

t, gr

oins

, re

tain

ing

wal

ls,

etc.

) ar

e co

mm

only

us

ed to

sta

biliz

e sl

opes

and

riv

erba

nks

and

to c

ontr

ol c

oast

al e

rosi

on.

Nev

erth

eles

s, d

espi

te th

eir c

ontin

uous

use

for d

ecad

es, s

lope

s co

ntin

ue

to f

ail,

eros

ion

wor

sens

, mai

nten

ance

cos

ts i

ncre

ase.

So

wha

t ar

e th

e m

ain

wea

knes

ses

of th

ese

mea

sure

s? F

rom

a s

tric

tly e

cono

mic

poi

nt o

f vi

ew, r

igid

mea

sure

s are

ver

y ex

pens

ive,

and

stat

e or

mun

icip

al b

udge

ts

for

such

pro

ject

s ar

e ne

ver

suffi

cien

t. A

tec

hnic

al a

nd e

nvir

onm

enta

l an

alys

is r

aise

s th

e fo

llow

ing

conc

erns

: •

Min

ing

of

the

rock

/con

cret

e oc

curs

el

sew

here

, w

here

it

undo

ubte

dly

wre

aks

envi

ronm

enta

l hav

oc.

• L

ocal

ized

rig

id s

truc

tura

l de

vice

s do

not

abs

orb

flow

/wav

e en

ergy

. Sin

ce ri

gid

stru

ctur

es c

anno

t fol

low

the

loca

l set

tlem

ent,

they

ca

use

stro

ng

grad

ient

s.

Stro

ng

grad

ient

s ge

nera

te

addi

tiona

l tur

bule

nce,

whi

ch c

reat

es m

ore

eros

ion.

Mor

eove

r, si

nce

the

devi

ces

are

loca

lized

, the

y fr

eque

ntly

end

abr

uptly

; th

ey d

o no

t tra

nsit

grad

ually

and

sm

ooth

ly to

the

natu

ral b

ank.

T

hus,

the

y si

mpl

y tr

ansf

er e

rosi

on t

o an

othe

r pl

ace,

to

the

oppo

site

sid

e or

dow

nstr

eam

, w

hich

agg

rava

tes

the

disa

ster

, ra

ther

tha

n re

duci

ng i

t fo

r th

e ri

ver

as a

who

le.

Exa

mpl

es o

f th

ese

abou

nd in

sev

eral

Cen

tral

Vie

tnam

pro

vinc

es.

• St

ruct

ural

, ri

gid

mea

sure

s in

trod

uce

cons

ider

able

am

ount

s of

sto

ne,

sand

, ce

men

t in

to t

he r

iver

sys

tem

, di

spla

cing

and

di

spos

ing

larg

e vo

lum

es o

f ba

nk s

oil

into

the

riv

er.

As

the

rive

r be

com

es s

ilted

up,

its

dyn

amic

s ch

ange

, its

bed

ris

es,

and

flood

and

ban

k er

osio

n pr

oble

ms

incr

ease

. Thi

s pr

oble

m

is p

artic

ular

ly g

rave

in

Vie

tnam

whe

re w

orke

rs t

hrow

was

te

soil

dire

ctly

int

o th

e ri

ver

as t

hey

re-s

hape

the

ban

k. O

ften

th

ey d

ump

ston

e di

rect

ly i

nto

the

rive

r to

sta

biliz

e th

e to

e of

uns

tabl

e ba

nk,

or t

ry t

o la

y ro

ck p

iece

s on

the

riv

erbe

d,

whi

ch r

educ

es t

he fl

ow d

epth

(ch

anne

l) c

onsi

dera

bly.

W

hen

the

emba

nkm

ents

ul

timat

ely

fail,

sc

raps

of

ro

ck

bask

ets,

gr

oins

, et

c. r

emai

n sc

atte

red

in t

he w

ater

cau

sing

man

-mad

e ag

grad

atio

n of

the

rive

r be

d.•

Rig

id s

truc

ture

s ar

e un

natu

ral

and

are

inco

mpa

tible

with

25

the

soft

gro

und

of e

rodi

ng o

r er

odib

le s

oils

. A

s th

e gr

ound

is

con

solid

ated

and

/or

erod

ed a

nd w

ashe

d aw

ay, i

t un

derc

uts

and

unde

rmin

es t

he u

pper

rig

id l

ayer

. E

xam

ples

inc

lude

the

ri

ght b

ank

imm

edia

tely

dow

nstr

eam

of

the

Tha

ch N

ham

Wei

r (Q

uang

Nga

i pro

vinc

e) th

at c

rack

ed a

nd c

olla

psed

. Eng

inee

rs

who

rep

lace

con

cret

e pl

ates

with

roc

k ri

prap

with

or

with

out

conc

rete

fra

mes

lea

ve u

nsol

ved

the

prob

lem

of

subs

urfa

ce

eros

ion.

Alo

ng th

e H

ai H

au s

ea d

ike,

the

who

le s

ectio

n of

rock

ri

prap

col

laps

ed a

s th

e fo

unda

tion

soil

unde

rnea

th w

as w

ashe

d aw

ay.

• R

igid

str

uctu

res

only

tem

pora

rily

redu

ce e

rosi

on.

The

y ca

nnot

he

lp s

tabi

lize

the

bank

whe

n bi

g la

ndsl

ides

with

dee

p fa

ilure

su

rfac

e.

• C

oncr

ete

or ro

ck re

tain

ing

wal

ls a

re p

roba

bly

the

mos

t com

mon

en

gine

erin

g m

etho

d em

ploy

ed t

o st

abili

ze r

oad

batte

rs i

n V

ietn

am. M

ost

of t

hese

wal

ls a

re p

assi

ve, s

impl

y w

aitin

g fo

r th

e sl

opes

to f

ail.

Whe

n th

e sl

opes

do

fail,

the

wal

ls a

lso

fail,

as

see

n in

man

y ar

eas

alon

g th

e H

o C

hi M

inh

Hig

hway

. The

se

stru

ctur

es a

re a

lso

dest

roye

d by

ear

thqu

akes

.

Alth

ough

ri

gid

stru

ctur

es

like

rock

em

bank

men

ts

are

obvi

ousl

y un

suita

ble

for

cert

ain

appl

icat

ions

, su

ch a

s sa

nd d

une

stab

ilisa

tion,

th

ey a

re s

till

bein

g bu

ilt,

as c

an b

e ob

serv

ed a

long

the

new

roa

d in

ce

ntra

l Vie

tnam

.

2.6

Vege

tativ

e sl

ope

stab

ilisa

tion

Veg

etat

ion

has

been

us

ed

as

a na

tura

l bi

oeng

inee

ring

to

ol

to

recl

aim

lan

d, c

ontr

ol e

rosi

on a

nd s

tabi

lize

slop

es f

or c

entu

ries

, an

d its

pop

ular

ity h

as i

ncre

ased

mar

kedl

y in

the

las

t de

cade

s. T

his

is

part

ly d

ue t

o th

e fa

ct t

hat

mor

e in

form

atio

n ab

out

vege

tatio

n is

now

av

aila

ble

to e

ngin

eers

, an

d al

so p

artly

due

to

the

cost

-eff

ectiv

enes

s an

d en

viro

nmen

t-fr

iend

lines

s of

this

“so

ft”

engi

neer

ing

appr

oach

.

Und

er t

he i

mpa

ct o

f th

e se

vera

l fa

ctor

s pr

esen

ted

abov

e a

slop

e w

ill

beco

me

unst

able

due

to:

(a)

sur

face

ero

sion

or

‘she

et e

rosi

on’;

and

(b

) in

tern

al s

truc

tura

l wea

knes

ses.

She

et e

rosi

on w

hen

not c

ontr

olle

d of

ten

lead

s to

rill

and

gul

ly e

rosi

on th

at, o

ver

time,

will

des

tabi

lize

the

slop

e; s

truc

tura

l w

eakn

ess

will

ulti

mat

ely

caus

e m

ass

mov

emen

t or

26

land

slip

. Sin

ce s

heet

ero

sion

can

als

o ca

use

slop

e fa

ilure

, slo

pe su

rfac

e pr

otec

tion

shou

ld b

e co

nsid

ered

as i

mpo

rtan

t as o

ther

stru

ctur

al

rein

forc

emen

ts b

ut it

s im

port

ance

is o

ften

ove

r lo

oked

. Pro

tect

ing

the

slop

e su

rfac

e is

an

effe

ctiv

e, e

cono

mic

al,

and

esse

ntia

l pr

even

tive

mea

sure

. I

n m

any

case

s, a

pply

ing

som

e pr

even

tive

mea

sure

s w

ill

ensu

re c

ontin

ued

slop

e st

abili

ty,

and

alw

ays

cost

muc

h le

ss t

han

corr

ectiv

e m

easu

res.

The

veg

etat

ive

cove

r pr

ovid

ed b

y gr

ass

seed

ing,

hyd

ro-s

eedi

ng o

r hy

dro-

mul

chin

g no

rmal

ly i

s qu

ite e

ffec

tive

agai

nst

shee

t er

osio

n an

d sm

all

rill

eros

ion,

and

dee

p-ro

oted

pla

nts

such

as

tree

s an

d sh

rubs

ca

n pr

ovid

e so

me

stru

ctur

al r

einf

orce

men

t fo

r th

e gr

ound

. H

owev

er,

on n

ewly

-con

stru

cted

slo

pes,

the

sur

face

lay

er i

s of

ten

not

wel

l co

nsol

idat

ed,

so e

ven

wel

l-ve

geta

ted

slop

es c

anno

t pr

even

t ri

ll an

d gu

lly e

rosi

on. D

eep-

root

ed tr

ees

grow

slo

wly

and

are

oft

en d

iffic

ult t

o es

tabl

ish

in su

ch h

ostil

e te

rrito

ry.

In th

ese

case

s, e

ngin

eers

oft

en ru

e th

e in

effic

ienc

y of

the

vege

tativ

e co

ver a

nd in

stal

l str

uctu

ral r

einf

orce

men

t so

on a

fter

con

stru

ctio

n. I

n sh

ort,

trad

ition

al s

lope

sur

face

pro

tect

ion

prov

ided

by

loca

l gra

sses

and

tree

s ca

nnot

, in

man

y ca

ses,

ens

ure

the

need

ed s

tabi

lity.

2.6.

1 P

ros,

con

s an

d lim

itatio

ns o

f pl

antin

g ve

geta

tion

on s

lope

.Ta

ble

2: G

ener

al p

hysi

cal e

ffec

ts o

f ve

geta

tion

on

slop

e st

abili

zati

on.

Eff

ect

Phy

sica

l Cha

ract

eris

tics

Ben

efici

al

Roo

t rei

nfor

cem

ent,

soil

arch

ing,

bu

ttres

sing

, anc

hora

ge, a

rres

ting

the

roll

of lo

ose

boul

ders

by

tree

s

Roo

t aer

atio

n, d

istr

ibut

ion

and

mor

phol

ogy;

Ten

sile

st

reng

th o

f ro

ots;

Spa

cing

, di

amet

er a

nd e

mbe

dmen

t of

tree

s, th

ickn

ess

and

incl

inat

ion

of y

ield

ing

stra

ta;

Shea

r st

reng

th p

rope

rtie

s of

so

ils

Dep

letio

n of

soi

l moi

stur

e an

d

incr

ease

of

soil

suct

ion

by r

oot

upta

ke a

nd tr

ansp

irat

ion

Moi

stur

e co

nten

t of

soil;

L

evel

of

grou

nd w

ater

; Por

e pr

essu

re/s

oil s

uctio

n

27

Tabl

e 3:

Slo

pe a

ngle

lim

itat

ions

on

esta

blis

hmen

t of

veg

etat

ion.

Slop

e an

gle

(deg

rees

)V

eget

atio

n ty

peG

rass

Shru

bs/T

rees

0 -

30

Low

in d

iffic

ulty

; ro

utin

e pl

antin

g te

chni

ques

may

be

used

Low

in d

iffic

ulty

; rou

tine

plan

ting

tech

niqu

es m

ay b

e us

ed

30 -

45

Incr

easi

ngly

dif

ficul

t fo

r sp

rigg

ing

or

turfi

ng; r

outin

e ap

plic

atio

n fo

r hy

dro

seed

ing

Incr

easi

ngly

dif

ficul

t to

plan

t

> 45

Spec

ial c

onsi

dera

tion

requ

ired

Plan

ting

mus

t gen

eral

ly b

e on

be

nche

s

Inte

rcep

tion

of r

ainf

all b

y fo

liage

, in

clud

ing

evap

orat

ive

loss

es.

Net

rai

nfal

l on

slop

e

Incr

ease

in th

e hy

drau

lic r

esis

tanc

e in

irri

gatio

n an

d dr

aina

ge c

anal

s.M

anni

ng’s

coe

ffici

ent

Adv

erse

Roo

t wed

ging

of

near

-sur

face

roc

ks

and

boul

ders

and

upr

ootin

g in

ty

phoo

ns.

Roo

t are

a ra

tion,

dis

trib

utio

n an

d m

orph

olog

y

Surc

harg

ing

the

slop

e by

larg

e(h

eavy

) tr

ees

(som

etim

es b

enefi

cial

de

pend

ing

on a

ctua

l situ

atio

ns).

Mea

n w

eigh

t of

vege

tatio

n

Win

d lo

adin

g.D

esig

n w

ind

spee

d fo

r re

quir

ed r

etur

n pe

riod

; m

ean

mat

ure

tree

hei

ght f

or

grou

ps o

f tr

ees

Mai

ntai

ning

infil

trat

ion

capa

city

Var

iatio

n of

moi

stur

e co

nten

t of

soil

with

dep

th

28

2.6.

2 Ve

geta

tive

slop

e st

abili

satio

n in

Vie

tnam

To

a le

sser

ex

tent

, so

fter

, ve

geta

tive

solu

tions

ha

ve

also

be

en

empl

oyed

in

Vie

tnam

. T

he m

ost

popu

lar

bioe

ngin

eeri

ng m

etho

d to

co

ntro

l ri

verb

ank

eros

ion

is p

roba

bly

the

plan

ting

of b

ambo

o (w

hich

is

the

wor

st m

easu

re y

ou c

an ta

ke.

Onc

e ba

mbo

o cl

umps

was

hout

in a

flo

od a

nd g

o do

wn

rive

r th

ey c

an ta

ke o

ut b

ridg

es o

r an

ythi

ng th

ey g

et

caug

ht u

p in

. The

y ha

ve s

uch

high

ten

sile

str

engt

h th

ey d

o no

t br

eak

up).

To

cont

rol c

oast

al e

rosi

on, m

angr

ove,

cas

uari

nas,

wild

pin

eapp

le,

and

nipa

pal

m a

re a

lso

empl

oyed

. H

owev

er,

thes

e pl

ants

hav

e so

me

maj

or d

efici

enci

es, f

or e

xam

ple:

Gro

win

g in

clu

mps

, bam

boo

whi

ch is

sha

llow

roo

ted

does

not

cl

ose

as a

hed

gero

w. T

here

fore

floo

dwat

er c

once

ntra

tes

at th

e ga

ps b

etw

een

clum

ps,

whi

ch i

ncre

ases

its

des

truc

tive

pow

er

and

caus

es m

ore

eros

ion.

Bam

boo

is t

op h

eavy

. It

s sh

allo

w (

1-1.

5 m

dee

p) b

unch

roo

t sy

stem

doe

s no

t bal

ance

the

high

, hea

vy c

anop

y. T

here

fore

,

clum

ps

of

bam

boo

add

stre

ss

to

a ri

ver

bank

, w

ithou

t co

ntri

butin

g to

its

stab

ility

.•

Freq

uent

ly t

he b

unch

roo

t sy

stem

of

bam

boo

dest

abili

zes

the

soil

bene

ath

it, e

ncou

ragi

ng e

rosi

on a

nd c

reat

ing

the

cond

ition

s fo

r la

rger

la

ndsl

ides

. Se

vera

l C

entr

al

Vie

tnam

pr

ovin

ces

disp

lay

exam

ples

of

bank

fai

lure

fol

low

ing

inst

alla

tion

of

exte

nsiv

e ba

mbo

o st

rips

.•

Man

grov

e tr

ees,

whe

re th

ey c

an g

row

, for

m a

sol

id b

uffe

r th

at

redu

ces

wav

e po

wer

, w

hich

, in

tur

n, r

educ

es c

oast

al e

rosi

on.

How

ever

, est

ablis

hing

man

grov

e is

dif

ficul

t and

slo

w a

s m

ice

eat i

ts s

eedl

ing.

Typ

ical

ly, o

f the

hun

dred

s of

hec

tare

s pl

ante

d,

only

a s

mal

l pe

rcen

tage

sur

vive

s to

bec

ome

fore

st.

Thi

s ha

s be

en r

epor

ted

rece

ntly

in H

a T

inh

prov

ince

.•

Cas

uari

nas

tree

s ha

ve l

ong

been

pla

nted

on

thou

sand

s of

he

ctar

es o

f sa

nd d

unes

in

Cen

tral

Vie

tnam

. Wild

pin

eapp

le i

s al

so p

lant

ed a

long

ban

ks o

f riv

ers,

str

eam

s an

d ot

her c

hann

els,

an

d al

ong

the

cont

our

lines

of

dune

slo

pes.

Alth

ough

the

y re

duce

win

d po

wer

and

min

imiz

e sa

nd s

torm

, th

ese

plan

ts

cann

ot

stem

sa

nd

flow

be

caus

e th

ey

have

sh

allo

w

root

sy

stem

s an

d do

not

for

m c

lose

d he

dger

ows.

Des

pite

pla

ntin

g ca

suar

inas

and

wild

pin

eapp

le tr

ees

atop

the

sand

dik

es a

long

29

flow

cha

nnel

s in

Qua

ng B

inh

prov

ince

, san

d fin

gers

con

tinue

to

inv

ade

arab

le l

and.

Mor

eove

r, bo

th p

lant

s ar

e se

nsiti

ve

to c

limat

e; c

asua

rina

s se

edlin

gs b

arel

y su

rviv

e sp

orad

ic b

ut

extr

eme

cold

win

ters

(les

s th

an -1

5ºC

/5ºF

), a

nd w

ild p

inea

pple

ca

nnot

sur

vive

Nor

th V

ietn

am’s

blis

teri

ng s

umm

ers.

Fort

unat

ely,

vet

iver

gro

ws

quic

kly,

bec

omes

est

ablis

hed

unde

r ho

stile

co

nditi

ons,

and

its

ver

y de

ep a

nd e

xten

sive

roo

t sy

stem

pro

vide

s st

ruct

ural

str

engt

h in

a r

elat

ivel

y sh

ort

peri

od o

f tim

e. T

hus,

vet

iver

ca

n be

a s

uita

ble

alte

rnat

ive

to tr

aditi

onal

veg

etat

ion,

pro

vide

d th

at th

e fo

llow

ing

appl

icat

ion

tech

niqu

es a

re le

arne

d an

d fo

llow

ed c

aref

ully

.

3. S

LO

PE

ST

AB

ILIS

AT

ION

USI

NG

VE

TIV

ER

SY

STE

M

3.1

Cha

ract

eris

tics

of v

etiv

er s

uita

ble

for

slop

e st

abili

satio

nV

etiv

er’s

uni

que

attr

ibut

es h

ave

been

rese

arch

ed, t

este

d, a

nd d

evel

oped

th

roug

hout

the

tro

pica

l w

orld

, th

us e

nsur

ing

that

vet

iver

is

real

ly a

ve

ry e

ffec

tive

bioe

ngin

eeri

ng to

ol:

• A

lthou

gh t

echn

ical

ly a

gra

ss,

vetiv

er p

lant

s us

ed i

n la

nd

stab

ilisa

tion

appl

icat

ions

beh

ave

mor

e lik

e fa

st-g

row

ing

tree

s or

shr

ubs.

Vet

iver

roo

ts a

re, p

er u

nit a

rea,

str

onge

r an

d de

eper

th

an tr

ee r

oots

.•

Vet

iver

’s e

xtre

mel

y de

ep a

nd m

assi

ve fi

nely

str

uctu

red

root

sy

stem

can

ext

end

dow

n to

tw

o to

thr

ee m

eter

s (s

ix t

o ni

ne

feet

) in

the

firs

t ye

ar.

On

fill

slop

e, m

any

expe

rim

ents

sho

w

that

thi

s gr

ass

can

reac

h 3.

6m (

12 f

eet)

in

12 m

onth

s. (

Not

e th

at

vetiv

er

cert

ainl

y do

es

not

pene

trat

e de

eply

in

to

the

grou

ndw

ater

tabl

e. T

here

fore

at s

ites

with

a h

igh

grou

ndw

ater

le

vel,

its r

oot s

yste

m m

ay n

ot e

xten

d as

long

as

in d

rier

soi

l).

Vet

iver

’s e

xten

sive

, and

thic

k ro

ot s

yste

m b

inds

the

soil

whi

ch

mak

es i

t ve

ry d

iffic

ult

to d

islo

dge,

and

ext

rem

ely

tole

rant

to

drou

ght.

• A

s st

rong

or

stro

nger

tha

n th

ose

of m

any

hard

woo

d sp

ecie

s,

vetiv

er r

oots

hav

e ve

ry h

igh

tens

ile s

tren

gth

that

has

bee

n pr

oven

pos

itive

for

roo

t rei

nfor

cem

ent i

n st

eep

slop

es.

• T

hese

roo

ts h

ave

a m

ean

test

ed t

ensi

le s

tren

gth

of a

bout

75

Meg

a Pa

scal

(M

Pa),

whi

ch i

s eq

uiva

lent

to

1/6

of m

ild s

teel

re

info

rcem

ent

and

a sh

ear

stre

ngth

inc

rem

ent

of 3

9% a

t a

30

dept

h of

0.5

m (

1.5

feet

).•

Vet

iver

roo

ts c

an p

enet

rate

a c

ompa

cted

soi

l pr

ofile

suc

h as

har

dpan

and

blo

cky

clay

pan

com

mon

in

trop

ical

soi

ls,

prov

idin

g a

good

anc

hor

for

fill a

nd to

psoi

l.•

Whe

n pl

ante

d cl

osel

y to

geth

er,

vetiv

er p

lant

s fo

rm d

ense

he

dges

tha

t re

duce

flow

vel

ocity

, sp

read

and

div

ert

runo

ff

wat

er,

and

crea

te a

ver

y ef

fect

ive

filte

r th

at c

ontr

ols

eros

ion.

T

he h

edge

s sl

ow d

own

the

flow

and

spr

eads

it

out,

allo

win

g m

ore

time

for

wat

er to

soa

k in

to th

e gr

ound

.•

Act

ing

as a

ver

y ef

fect

ive

filte

r, ve

tiver

hed

ges

help

red

uce

the

turb

idity

of

surf

ace

run-

off.

Sin

ce n

ew r

oots

dev

elop

fro

m

node

s w

hen

buri

ed b

y tr

appe

d se

dim

ent,

vetiv

er c

ontin

ues

to

rise

with

the

new

gro

und

leve

l. Te

rrac

es f

orm

at t

he f

ace

of

Ph

oto

1: V

etiv

er fo

rms

a th

ick

and

eff

ecti

ve b

io-fi

lter

bo

th a

bov

e (u

pp

er)

and

bel

ow

gro

un

d (

low

er).

31

the

hedg

es,

this

sed

imen

t sh

ould

nev

er b

e re

mov

ed.

The

fe

rtile

sed

imen

t typ

ical

ly c

onta

ins

seed

s of

loca

l pla

nts,

whi

ch

faci

litat

es th

eir

re-e

stab

lishm

ent.

• V

etiv

er to

lera

tes e

xtre

me

clim

atic

and

env

iron

men

tal v

aria

tion,

in

clud

ing

prol

onge

d dr

ough

t, flo

odin

g an

d su

bmer

genc

e, a

nd

tem

pera

ture

ext

rem

es r

angi

ng f

rom

-14

ºC t

o 55

ºC (

7º F

to

131º

F) (

Tru

ong

et a

l, 19

96).

• T

his

gras

s re

-gro

ws

very

qui

ckly

follo

win

g dr

ough

t, fr

ost,

salt

and

othe

r ad

vers

e so

il co

nditi

ons

whe

n th

e ad

vers

e ef

fect

s ar

e re

mov

ed.

Vet

iver

dis

play

s a

high

lev

el o

f to

lera

nce

to s

oil

acid

ity,

• sa

linity

, so

dici

ty a

nd a

cid

sulf

ate

cond

ition

s (L

e va

n D

u an

d T

ruon

g, 2

003)

.

Fig

ure

1: U

pper

: pr

inci

ples

of s

lope

sta

bili

sati

on b

y ve

tive

r;

low

er:

veti

ver

root

s re

info

rcin

g th

is d

am w

all k

ept i

t fr

om b

eing

was

hed

away

by

flood

.

32

Vet

iver

is v

ery

effe

ctiv

e w

hen

plan

ted

clos

ely

in ro

ws

on th

e co

ntou

r of

slop

es. C

onto

ur li

nes

of v

etiv

er c

an s

tabi

lize

natu

ral s

lope

s, c

ut s

lope

s an

d fil

led

emba

nkm

ents

. Its

dee

p, r

igor

ous

root

sys

tem

hel

ps s

tabi

lize

the

slop

es s

truc

tura

lly w

hile

its

shoo

ts d

ispe

rse

surf

ace

run-

off,

redu

ce

eros

ion,

and

trap

sed

imen

ts to

fac

ilita

te th

e gr

owth

of

nativ

e sp

ecie

s.

Hen

gcha

ovan

ich

(199

8) a

lso

obse

rved

that

vet

iver

can

gro

w v

ertic

ally

on

slo

pes

stee

per

than

150

% (

~56º

). I

ts f

ast

grow

th a

nd r

emar

kabl

e re

info

rcem

ent

mak

e it

a be

tter

cand

idat

e fo

r sl

ope

stab

ilisa

tion

than

ot

her

plan

ts. A

noth

er le

ss o

bvio

us c

hara

cter

istic

that

set

s it

apar

t fro

m

othe

r tr

ee r

oots

is

its p

ower

of

pene

trat

ion.

It

s st

reng

th a

nd v

igou

r en

able

it to

pen

etra

te d

iffic

ult s

oil,

hard

pan,

and

rock

y la

yers

with

wea

k sp

ots.

It c

an e

ven

punc

h th

roug

h as

phal

t con

cret

e pa

vem

ent.

The

sam

e au

thor

cha

ract

eriz

es v

etiv

er ro

ots

as li

ving

soi

l nai

ls o

r 2-3

m (6

-9 fe

et)

dow

els

com

mon

ly u

sed

in ‘

hard

app

roac

h’ s

lope

sta

bilis

atio

n w

ork.

C

ombi

ned

with

its

abi

lity

to b

ecom

e qu

ickl

y es

tabl

ishe

d in

dif

ficul

t so

il co

nditi

ons,

the

se c

hara

cter

istic

s m

ake

vetiv

er m

ore

suita

ble

for

slop

e st

abili

satio

n th

an o

ther

pla

nts.

3.2

Spec

ial c

hara

cter

istic

s of

vet

iver

sui

tabl

e fo

r w

ater

dis

aste

r m

itiga

tion

To r

educ

e th

e im

pact

of

wat

er r

elat

ed d

isas

ters

suc

h as

floo

d, r

iver

ba

nk a

nd c

oast

al e

rosi

on, d

am a

nd d

ike

inst

abili

ty, v

etiv

er i

s pl

ante

d in

row

s ei

ther

par

alle

l to

or a

cros

s th

e w

ater

flow

or w

ave

dire

ctio

n. It

s ad

ditio

nal u

niqu

e ch

arac

teri

stic

s ar

e ve

ry u

sefu

l:•

Giv

en it

s ex

trao

rdin

ary

root

dep

th a

nd s

tren

gth,

mat

ure

vetiv

er

is e

xtre

mel

y re

sist

ant

to w

asho

uts

from

hig

h ve

loci

ty fl

ow.

Vet

iver

pla

nted

in n

orth

Que

ensl

and

(Aus

tral

ia)

has

with

stoo

d flo

w v

eloc

ity h

ighe

r th

an 3

.5m

/sec

(10

’/se

c) i

n ri

ver

unde

r flo

od c

ondi

tions

and

, in

sou

ther

n Q

ueen

slan

d, u

p to

5m

/sec

(1

5’/s

ec)

in a

floo

ded

drai

nage

cha

nnel

.•

Und

er s

hallo

w o

r low

vel

ocity

flow

, the

ere

ct a

nd s

tiff s

tem

s of

ve

tiver

act

as

a ba

rrie

r th

at r

educ

es fl

ow v

eloc

ity (

i.e. i

ncre

ase

hydr

aulic

res

ista

nce)

and

trap

s er

oded

sed

imen

t. In

fac

t, it

can

mai

ntai

n its

ere

ct s

tanc

e in

a fl

ow a

s de

ep a

s 0.

6-0.

8m (

24-

31”)

.•

Vet

iver

lea

ves

will

bow

und

er d

eep

and

high

vel

ocity

flow

, pr

ovid

ing

extr

a pr

otec

tion

to s

urfa

ce s

oil w

hile

red

ucin

g flo

w

velo

city

.

33

• W

hen

plan

ted

on w

ater

-ret

aini

ng s

truc

ture

s su

ch a

s da

ms

or

dike

s, v

etiv

er h

edge

row

s hel

p re

duce

the

flow

vel

ocity

, dec

reas

e w

ave

run-

up (

lap-

eros

ion)

, ov

er-t

oppi

ng,

and

ultim

atel

y th

e vo

lum

e of

wat

er t

hat

flow

s in

to t

he a

rea

prot

ecte

d by

the

se

stru

ctur

es.

The

se

hedg

erow

s al

so

help

re

duce

so

-cal

led

retr

ogre

ssiv

e er

osio

n th

at o

ften

occ

urs

whe

n th

e w

ater

flow

or

wav

e re

trea

ts a

fter

it r

ises

ove

r w

ater

-ret

aini

ng s

truc

ture

s.•

As a

wet

land

pla

nt, v

etiv

er w

ithst

ands

pro

long

ed su

bmer

genc

e.

Chi

nese

res

earc

h sh

ows

that

vet

iver

can

sur

vive

lon

ger

than

tw

o m

onth

s un

der

clea

r w

ater

.

Fig

ure

2: R

oot d

iam

eter

dis

trib

utio

n

3.3

Tens

ile a

nd s

hear

str

engt

h of

vet

iver

roo

tsH

engc

haov

anic

h an

d N

ilaw

eera

(19

96)

show

that

the

tens

ile s

tren

gth

of v

etiv

er ro

ots

incr

ease

s w

ith th

e re

duct

ion

in ro

ot d

iam

eter

, im

plyi

ng

that

str

onge

r, fin

e ro

ots

prov

ide

grea

ter

resi

stan

ce t

han

thic

ker

root

s.

The

ten

sile

str

engt

h of

vet

iver

roo

ts v

arie

s be

twee

n 40

-180

MPa

in

the

ran

ge o

f ro

ot d

iam

eter

bet

wee

n 0.

2-2.

2 m

m (

.008

-.08

”).

The

m

ean

desi

gn t

ensi

le s

tren

gth

is a

bout

75

MPa

at

0.7-

0.8

mm

(.0

3”)

root

dia

met

er,

whi

ch i

s th

e m

ost

com

mon

siz

e of

vet

iver

roo

ts,

and

equi

vale

nt to

app

roxi

mat

ely

one

sixt

h of

mild

ste

el. T

here

fore

, vet

iver

ro

ots

are

as s

tron

g or

eve

n st

rong

er t

han

thos

e of

man

y ha

rdw

ood

34

spec

ies

that

hav

e be

en p

rove

n po

sitiv

e fo

r slo

pe re

info

rcem

ent -

figu

re

2 an

d ta

ble

4.

Tabl

e 4:

Ten

sile

str

engt

h of

som

e pl

ant

root

s.

Fig

ure

3: S

hear

str

engt

h of

vet

iver

roo

ts

Bot

anic

al n

ame

Com

mon

nam

eT

ensi

le s

tren

gth

(MP

a)Sa

lix s

ppW

illow

9-36

Pop

ulus

spp

Popl

ars

5-38

Aln

us s

ppA

lder

s4-

74

Pse

udot

suga

spp

Dou

glas

fir

19-6

1

Ace

r sa

char

inum

Silv

er m

aple

15-3

0

Tsug

a he

tero

phyl

iaW

este

rn h

emlo

ck27

Vacc

inum

spp

Huc

kleb

erry

16

Hor

deum

vul

gare

Bar

ley

15

-31

Gra

ss, F

orbs

2-

20

Mos

s2-

7kPa

Chr

ysop

ogon

zi

zani

oide

sV

etiv

er g

rass

40-1

20 (

aver

age

75)

35

In a

soi

l blo

ck s

hear

test

, Hen

gcha

ovan

ich

and

Nila

wee

ra (

1996

) al

so

foun

d th

at r

oot p

enet

ratio

n of

a tw

o-ye

ar-o

ld v

etiv

er h

edge

with

15c

m

(6”)

pla

nt s

paci

ng c

an in

crea

se.

In a

soi

l blo

ck s

hear

test

, Hen

gcha

ovan

ich

and

Nila

wee

ra (

1996

) al

so f

ound

that

roo

t pen

etra

tion

of a

two-

year

-old

Vet

iver

hed

ge w

ith

15cm

(6”

) pl

ant s

paci

ng c

an in

crea

se th

e sh

ear

stre

ngth

of

soil

in

adja

cent

50

cm (

20“)

wid

e st

rip

by 9

0% a

t 0.2

5 m

(10

”) d

epth

. The

in

crea

se w

as 3

9% a

t 0.5

0 m

(1.

5’)

dept

h an

d gr

adua

lly r

educ

ed

to 1

2.5%

at o

ne m

eter

(3’

) de

pth.

Mor

eove

r, ve

tiver

’s d

ense

and

m

assi

ve r

oot s

yste

m o

ffer

s be

tter

shea

r st

reng

th in

crea

se p

er u

nit

fibre

con

cent

ratio

n (6

-10

kPa/

kg o

f ro

ot p

er c

ubic

met

er o

f so

il)

com

pare

d to

3.2

-3.7

kPa

/kg

for

tree

roo

ts (

Fig.

3). T

he a

utho

rs

expl

aine

d th

at w

hen

a pl

ant r

oot p

enet

rate

s ac

ross

a p

oten

tial s

hear

su

rfac

e in

a s

oil p

rofil

e, th

e di

stor

tion

of th

e sh

ear

zone

dev

elop

s te

nsio

n in

the

root

; the

com

pone

nt o

f th

is te

nsio

n ta

ngen

tial t

o sh

ear

zone

dir

ectly

res

ists

she

ar, w

hile

the

norm

al c

ompo

nent

incr

ease

s th

e co

nfini

ng p

ress

ure

on th

e sh

ear

plan

e.

Tabl

e 5:

Dia

met

er a

nd t

ensi

le r

oot

stre

ngth

of

vari

ous

herb

s.

Che

ng e

t al (

2003

) sup

plem

ente

d D

iti H

engc

haov

anic

h’s

root

str

engt

h re

sear

ch b

y on

duct

ing

furt

her t

ests

on

othe

r gra

sses

. Tab

le 5

. Alth

ough

ve

tiver

has

the

sec

ond

fines

t ro

ots,

its

ten

sile

str

engt

h is

alm

ost

thre

e

Gra

ssM

ean

diam

eter

of

roo

ts (

mm

)M

ean

tens

ile

stre

ngth

(M

Pa)

Lat

e Ju

ncel

lus

0.38

±0.4

324

.50±

4.2

Dal

lis g

rass

0.92

±0.2

819

.74±

3.00

Whi

te C

love

r0.

91±0

.11

24.6

4±3.

36V

ET

IVE

R G

RA

SS0.

66±0

.32

85.1

0±31

.2

Com

mon

Cen

tiped

e gr

ass

0.66

±0.0

527

.30±

1.74

Bah

ia g

rass

0.73

±0.0

719

.23±

3.59

Man

ila g

rass

0.77

±0.6

717

.55±

2.85

Ber

mud

a gr

ass

0.99

±0.1

713

.45±

2.18

36

times

hig

her

than

all

pla

nts

test

ed.

3.4

Hyd

raul

ic c

hara

cter

istic

sW

hen

plan

ted

in r

ows,

vet

iver

pla

nts

form

thi

ck h

edge

s; t

heir

stif

f st

ems

allo

w th

ese

hedg

es to

sta

nd u

p at

leas

t 0.6

-0.8

m (2

-2.6

’), f

orm

ing

a liv

ing

barr

ier

to s

low

and

spr

ead

runo

ff w

ater

. Pr

oper

ly p

lann

ed,

thes

e he

dges

are

ver

y ef

fect

ive

stru

ctur

es th

at s

prea

d an

d di

vert

runo

ff

wat

er t

o st

able

are

as o

r pr

oper

dra

ins

for

safe

dis

posa

l. Fl

ume

test

s co

nduc

ted

at t

he U

nive

rsity

of

Sout

hern

Que

ensl

and

to s

tudy

the

de

sign

and

inc

orpo

ratio

n of

vet

iver

hed

ges

into

str

ip-c

ropp

ing

layo

ut

for

flood

miti

gatio

n co

nfirm

ed th

e hy

drau

lic c

hara

cter

istic

s of

vet

iver

he

dges

und

er d

eep

flow

s. F

igur

e 4.

The

hed

ges

succ

essf

ully

red

uced

flo

od v

eloc

ity a

nd l

imite

d so

il m

ovem

ent;

fallo

w s

trip

s su

ffer

ed v

ery

little

ero

sion

, an

d a

youn

g so

rghu

m c

rop

was

com

plet

ely

prot

ecte

d fr

om fl

ood

dam

age

(Dal

ton

et a

l, 19

96).

Fig

ure

4: H

ydra

ulic

mod

el o

f flo

odin

g th

roug

h ve

tiver

hed

ges

Whe

re:

q =

dis

char

ge p

er u

nit w

idth

y

= d

epth

of

flow

y

1 = d

epth

ups

trea

m

S

o =

lan

d sl

ope

S f =

ene

rgy

slop

e

N

F =

the

Frou

de n

umbe

r of

flow

37

3.5

Por

e w

ater

pre

ssur

eV

eget

atio

n co

ver

on

slop

ing

land

s in

crea

ses

wat

er

infil

trat

ion.

C

once

rns

have

bee

n ra

ised

tha

t th

e ex

tra

wat

er w

ill i

ncre

ase

pore

w

ater

pre

ssur

e in

the

soil

and

lead

to s

lope

inst

abili

ty. H

owev

er, fi

eld

obse

rvat

ions

act

ually

sho

w i

mpr

ovem

ents

. Fi

rst,

plan

ted

on c

onto

ur

lines

or

mod

ified

pat

tern

s of

lin

es t

hat

trap

and

spr

ead

runo

ff w

ater

on

the

slo

pe,

vetiv

er’s

ext

ensi

ve r

oot

syst

em a

nd fl

ow t

houg

h ef

fect

di

stri

bute

s su

rplu

s w

ater

mor

e ev

enly

and

gra

dual

ly a

nd h

elps

pre

vent

lo

caliz

ed a

ccum

ulat

ion.

Seco

nd,

the

likel

y in

crea

se i

n in

filtr

atio

n is

off

set

by a

hig

her

and

grad

ual

rate

of

soil

wat

er d

eple

tion

by t

he g

rass

. R

esea

rch

in s

oil

moi

stur

e co

mpe

titio

n in

cro

ps in

Aus

tral

ia (

Dal

ton

et a

l, 19

96)

show

s th

at,

unde

r lo

w r

ainf

all

cond

ition

s, t

his

depl

etio

n w

ould

red

uce

soil

moi

stur

e up

to

1.5m

(4.

5’)

from

the

hed

ges.

T

his

incr

ease

s w

ater

in

filtr

atio

n in

tha

t zo

ne,

lead

ing

to t

he r

educ

tion

of r

unof

f w

ater

and

er

osio

n ra

te.

From

a g

eote

chni

cal

pers

pect

ive,

the

se c

ondi

tions

hel

p m

aint

ain

slop

e st

abili

ty. O

n st

eep

(30-

60º)

slo

pes,

the

spa

ce b

etw

een

row

s at 1

m (3

’) V

I (V

ertic

al In

terv

al) i

s ver

y cl

ose.

The

refo

re, m

oist

ure

depl

etio

n w

ould

be

grea

ter

and

furt

her

impr

ove

the

slop

e st

abili

satio

n pr

oces

s. H

owev

er, t

o re

duce

this

pot

entia

lly h

arm

ful e

ffec

t of

vetiv

er

on s

teep

slo

pes

in v

ery

high

rain

fall

area

s, a

s a

prec

autio

nary

mea

sure

, ve

tiver

hed

ges

coul

d be

pla

nted

on

a gr

adie

nt o

f ab

out

0.5%

as

in

grad

ed c

onto

ur t

erra

ces

to d

iver

t th

e ex

tra

wat

er t

o st

able

dra

inag

e ou

tlets

(H

engc

haov

anic

h, 1

998)

.

3.6

App

licat

ions

of V

S fo

r sl

ope

stab

iliza

tion

rela

ted

to n

atur

al

disa

ster

miti

gatio

n an

d in

fras

truc

ture

pro

tect

ion

Giv

en i

ts u

niqu

e ch

arac

teri

stic

s, v

etiv

er g

ener

ally

is

very

use

ful

in

cont

rolli

ng e

rosi

on o

n bo

th c

ut a

nd fi

ll ba

tters

and

on

othe

r sl

opes

as

soci

ated

with

roa

d co

nstr

uctio

n, a

nd p

artic

ular

ly e

ffec

tive

in h

ighl

y er

odib

le a

nd d

ispe

rsib

le s

oils

, suc

h as

sod

ic, a

lkal

ine,

aci

dic

and

acid

su

lfat

e so

ils.

Vet

iver

pl

antin

g ha

s be

en

very

ef

fect

ive

in

eros

ion

cont

rol

or

stab

ilisa

tion

in th

e fo

llow

ing

cond

ition

s:•

Slop

e st

abili

satio

n al

ong

high

way

s an

d ra

ilway

s.

Esp

ecia

lly

effe

ctiv

e al

ong

mou

ntai

nous

rura

l roa

ds, w

here

the

com

mun

ity

38

lack

s su

ffici

ent f

undi

ng f

or r

oad

slop

e st

abili

satio

n an

d w

here

it

ofte

n ta

kes

part

in r

oad

cons

truc

tion.

• D

ike

and

dam

bat

ter s

tabi

lisat

ion,

redu

ctio

n of

can

al, r

iver

bank

an

d co

asta

l ero

sion

, and

pro

tect

ion

of h

ard

stru

ctur

es th

emse

lves

(e

.g. r

ock

ripr

ap, c

oncr

ete

reta

inin

g w

alls

, gab

ions

, etc

.).

• Sl

ope

abov

e cu

lver

t inl

ets

and

outle

ts (

culv

erts

, abu

tmen

ts).

• In

terf

ace

betw

een

cem

ent a

nd ro

ck s

truc

ture

s an

d er

odib

le s

oil

surf

aces

.•

As

a fil

ter

stri

p to

trap

sed

imen

t at c

ulve

rt in

lets

.•

To r

educ

e en

ergy

at c

ulve

rt o

utle

ts.

• To

sta

biliz

e gu

lly h

ead

eros

ion,

whe

n ve

tiver

hed

ges

are

plan

ted

on c

onto

ur li

nes

abov

e gu

lly h

eads

. •

To e

limin

ate

eros

ion

caus

ed b

y w

ave

actio

n, b

y pl

antin

g a

few

ro

ws

of v

etiv

er o

n th

e ed

ge o

f the

hig

h w

ater

mar

k on

big

farm

da

m b

atte

rs o

r ri

ver

bank

s.•

In f

ores

t pla

ntat

ions

, to

stab

ilize

the

shou

lder

s of

acc

ess

road

s on

ver

y st

eep

slop

es a

s w

ell a

s th

e gu

llies

(log

ging

pat

hs/w

ays)

th

at d

evel

op f

ollo

win

g ha

rves

ts.

Giv

en i

ts u

niqu

e ch

arac

teri

stic

s, v

etiv

er e

ffec

tivel

y co

ntro

ls w

ater

di

sast

ers

such

as

flood

, co

asta

l an

d ri

verb

ank

eros

ion,

dam

and

dik

e er

osio

n, a

nd g

ener

al i

nsta

bilit

y.

It a

lso

prot

ects

bri

dges

, cu

lver

t ab

utm

ents

and

int

erfa

ces

betw

een

conc

rete

/roc

k st

ruct

ures

and

soi

l. V

etiv

er i

s pa

rtic

ular

ly e

ffec

tive

in a

reas

whe

re t

he e

mba

nkm

ent

fill

is h

ighl

y er

odib

le a

nd d

ispe

rsib

le, s

uch

as s

odic

, alk

alin

e, a

nd a

cidi

c (i

nclu

ding

aci

d su

lpha

te)

soils

.

3.7

Adv

anta

ges

and

disa

dvan

tage

s of

Vet

iver

Sys

tem

Adv

anta

ges:

• T

he m

ajor

adv

anta

ge o

f V

S ov

er c

onve

ntio

nal

engi

neer

ing

mea

sure

s is

its

low

cos

t and

long

evity

. For

slo

pe s

tabi

lisat

ion

in C

hina

, for

exa

mpl

e, s

avin

gs a

re in

the

orde

r of 8

5-90

% (X

ie,

1997

and

Xia

et a

l, 19

99).

In

Aus

tral

ia, t

he c

ost a

dvan

tage

of

VS

over

con

vent

iona

l eng

inee

ring

met

hods

ran

ges

from

64%

to

72%

, de

pend

ing

on t

he m

etho

d us

ed (

Bra

ken

and

Tru

ong

2001

). I

n su

mm

ary,

its

max

imum

cos

t is

onl

y 30

% o

f th

e co

st o

f tr

aditi

onal

mea

sure

s. I

n ad

ditio

n an

nual

mai

nten

ance

co

sts

are

sign

ifica

ntly

red

uced

onc

e ve

tiver

hed

gero

ws

are

esta

blis

hed

39

• A

s w

ith o

ther

bio

engi

neer

ing

tech

nolo

gies

, V

S is

a n

atur

al,

envi

ronm

enta

lly-f

rien

dly

way

to

cont

rol

eros

ion

cont

rol

and

stab

ilize

land

that

‘sof

tens

’ the

har

sh lo

ok o

f con

vent

iona

l rig

id

engi

neer

ing

mea

sure

s su

ch a

s co

ncre

te a

nd r

ock

stru

ctur

es.

Thi

s is

par

ticul

arly

im

port

ant

in u

rban

and

sem

i-ru

ral

area

s w

here

loc

al c

omm

uniti

es d

ecry

the

uns

ight

ly a

ppea

ranc

e of

in

fras

truc

ture

dev

elop

men

t. •

Lon

g-te

rm

mai

nten

ance

co

sts

are

low

. In

co

ntra

st

to

conv

entio

nal

engi

neer

ing

stru

ctur

es,

gree

n te

chno

logy

im

prov

es a

s th

e ve

geta

tive

cove

r m

atur

es.

VS

requ

ires

a

plan

ned

mai

nten

ance

pro

gram

in th

e fir

st tw

o ye

ars;

how

ever

, on

ce e

stab

lishe

d, i

t is

vir

tual

ly m

aint

enan

ce-f

ree.

The

refo

re,

the

use

of v

etiv

er i

s pa

rtic

ular

ly w

ell

suite

d to

rem

ote

area

s w

here

mai

nten

ance

is c

ostly

and

dif

ficul

t.•

Vet

iver

is

very

eff

ectiv

e in

poo

r an

d hi

ghly

ero

dibl

e an

d di

sper

sibl

e so

ils.

• V

S is

par

ticul

arly

wel

l su

ited

to a

reas

with

low

-cos

t la

bour

fo

rces

.•

Vet

iver

hed

ges

are

a na

tura

l, so

ft b

ioen

gine

erin

g te

chni

que,

an

eco-

frie

ndly

alte

rnat

ive

to r

igid

or

hard

str

uctu

res.

Dis

adva

ntag

es:

• T

he m

ain

disa

dvan

tage

of

VS

appl

icat

ions

is

the

vetiv

er’s

in

tole

ranc

e to

sha

ding

, pa

rtic

ular

ly w

ithin

the

est

ablis

hmen

t ph

ase.

Par

tial s

hadi

ng st

unts

its g

row

th; s

igni

fican

t sha

ding

can

el

imin

ate

it in

the

long

term

by

redu

cing

its

abili

ty to

com

pete

w

ith m

ore

shad

e-to

lera

nt s

peci

es.

How

ever

, th

is w

eakn

ess

coul

d be

des

irab

le i

n si

tuat

ions

whe

re i

nitia

l st

abili

satio

n re

quir

es

a pi

onee

r to

im

prov

e th

e ab

ility

of

th

e m

icro

-en

viro

nmen

t to

hos

t th

e vo

lunt

ary

or p

lann

ed i

ntro

duct

ion

of

nativ

e en

dem

ic s

peci

es.

• T

he V

etiv

er S

yste

m is

eff

ectiv

e on

ly w

hen

the

plan

ts a

re w

ell

esta

blis

hed.

Eff

ectiv

e pl

anni

ng re

quir

es a

n in

itial

est

ablis

hmen

t pe

riod

of

abou

t 2-3

mon

ths

in w

arm

wea

ther

and

4-6

mon

ths

in c

oole

r tim

es.

Thi

s de

lay

can

be a

ccom

mod

ated

by

plan

ting

earl

y, a

nd in

the

dry

seas

on.

• V

etiv

er h

edge

s ar

e fu

lly e

ffec

tive

only

whe

n pl

ants

for

m

clos

ed h

edge

row

s. G

aps

betw

een

clum

ps s

houl

d be

tim

ely

re-

plan

ted.

40

• It

is

diffi

cult

to p

lant

and

wat

er v

eget

atio

n on

ver

y hi

gh o

r st

eep

slop

es.

• V

etiv

er

requ

ires

pr

otec

tion

from

liv

esto

ck

duri

ng

its

esta

blis

hmen

t pha

se.

Bas

ed o

n th

ese

cons

ider

atio

ns,

the

adva

ntag

es o

f us

ing

VS

as a

bi

oeng

inee

ring

too

l ou

twei

gh i

ts d

isad

vant

ages

, pa

rtic

ular

ly w

hen

vetiv

er is

use

d as

a p

ione

er s

peci

es.

Wor

ldw

ide

evid

ence

sup

port

s th

e us

e of

VS

to s

tabi

lize

emba

nkm

ents

. V

etiv

er h

as b

een

used

suc

cess

fully

to

stab

ilize

roa

dsid

es,

amon

gst

othe

rs,

in A

ustr

alia

, B

razi

l, C

entr

al A

mer

ica,

Chi

na,

Eth

iopi

a, F

iji,

Indi

a, I

taly

, M

adag

asca

r, M

alay

sia,

Phi

lippi

nes,

Sou

th A

fric

a, S

ri

Lan

ka, V

enez

uela

, Vie

tnam

, and

the

Wes

t Ind

ies.

Use

d in

con

junc

tion

with

geo

tech

nica

l ap

plic

atio

ns,

vetiv

er h

as b

een

used

to

stab

ilize

em

bank

men

ts in

Nep

al a

nd S

outh

Afr

ica.

3.8

Com

bina

tion

with

oth

er ty

pes

of r

emed

yV

etiv

er is

eff

ectiv

e bo

th b

y its

elf

and

com

bine

d w

ith o

ther

trad

ition

al

met

hods

. Fo

r ex

ampl

e, o

n a

give

n se

ctio

n of

riv

erba

nk o

r di

ke,

rock

or

con

cret

e ri

prap

can

rei

nfor

ce t

he u

nder

wat

er p

art,

and

vetiv

er c

an

rein

forc

e th

e to

p pa

rt.

Thi

s ta

ndem

app

licat

ion

crea

tes

a fa

ctor

of

stab

ility

and

sec

urity

(w

hich

are

not

alw

ays

true

and

/or

nece

ssar

y).

Vet

iver

can

als

o be

pla

nted

with

bam

boo,

a p

lant

tra

ditio

nally

use

d to

pro

tect

riv

erba

nks.

Exp

erie

nce

show

s th

at u

sing

onl

y ba

mbo

o ha

s se

vera

l dr

awba

cks

that

can

be

over

com

e by

add

ing

vetiv

er. A

s no

ted

prev

ious

ly w

ashe

d ou

t bam

boo

can

crea

te s

erio

us p

robl

ems

on r

iver

s w

here

ther

e ar

e lo

w le

vel b

ridg

e cr

ossi

ng.

3.9

Com

pute

r m

odel

ling

Soft

war

e de

velo

ped

by P

rati

Am

ati,

Srl

(200

6) i

n co

llabo

ratio

n w

ith

the

Uni

vers

ity o

f M

ilan

dete

rmin

es th

e pe

rcen

tage

or

amou

nt o

f sh

ear

stre

ngth

that

vet

iver

root

s add

to v

ario

us so

ils u

nder

vet

iver

hed

gero

ws.

T

he s

oftw

are

help

s to

ass

ess

vetiv

er’s

con

trib

utio

n to

sta

biliz

e st

eep

batte

rs,

part

icul

arly

ear

then

lev

ees.

Und

er a

vera

ge s

oil

and

slop

e co

nditi

ons,

the

ins

talla

tion

of v

etiv

er w

ill i

ncre

ase

slop

e st

abili

ty b

y ab

out 4

0%.

Usi

ng

the

soft

war

e re

quir

es

the

oper

ator

to

en

ter

the

follo

win

g

41

geot

echn

ical

par

amet

ers

rela

ted

to a

par

ticul

ar s

lope

site

:•

Soil

type

.•

Slop

e gr

adie

nt.

• M

axim

um m

oist

ure

cont

ent.

• So

il co

hesi

on a

t a m

inim

um.

The

pro

gram

pro

vide

s th

e re

quir

ed n

umbe

r of

pla

nts

per

squa

re m

eter

an

d th

e di

stan

ce b

etw

een

row

s, c

onsi

deri

ng t

he s

lope

gra

dien

t. F

or

exam

ple:

• a

30°

slop

e re

quir

es s

ix p

lant

s pe

r sq

uare

met

er (

i.e.

7-10

pl

ants

per

line

al m

eter

) an

d a

dist

ance

bet

wee

n ro

ws

of a

bout

1.

7 m

(5.

7’).

• a

45°

slop

e re

quir

es 1

0 pl

ants

per

squ

are

met

er (

i.e.

7-10

pl

ants

per

line

al m

eter

) an

d a

dist

ance

bet

wee

n ro

ws

of a

bout

1

m (

3’).

4. A

PP

RO

PR

IAT

E D

ESI

GN

S A

ND

TE

CH

NIQ

UE

S

4.1

Pre

caut

ions

VS

is a

new

tec

hnol

ogy.

As

a ne

w t

echn

olog

y, i

ts p

rinc

iple

s m

ust

be

stud

ied

and

appl

ied

appr

opri

atel

y fo

r be

st r

esul

ts.

Failu

re t

o fo

llow

ba

sic

tene

ts w

ill re

sult

in d

isap

poin

tmen

t, or

wor

se, a

dver

se re

sults

. As

a so

il co

nser

vatio

n te

chni

que

and,

mor

e re

cent

ly, a

bio

engi

neer

ing

tool

, th

e ef

fect

ive

appl

icat

ion

of V

S re

quir

es a

n un

ders

tand

ing

of b

iolo

gy,

soil

scie

nce,

hy

drau

lics,

hy

drol

ogy,

an

d ge

otec

hnic

al

prin

cipl

es.

The

refo

re, f

or m

ediu

m t

o la

rge-

scal

e pr

ojec

ts t

hat

invo

lve

sign

ifica

nt

engi

neer

ing

desi

gn a

nd c

onst

ruct

ion,

VS

is b

est

impl

emen

ted

by

expe

rien

ced

spec

ialis

ts

rath

er

than

by

lo

cal

peop

le

them

selv

es.

How

ever

, kn

owle

dge

of p

artic

ipat

ory

appr

oach

es a

nd c

omm

unity

-ba

sed

man

agem

ent

are

also

ver

y im

port

ant.

Thu

s, t

he t

echn

olog

y sh

ould

be

desi

gned

and

impl

emen

ted

by e

xper

ts in

vet

iver

app

licat

ion,

as

soci

ated

with

an

agro

nom

ist

and

a ge

otec

hnic

al e

ngin

eer,

with

as

sist

ance

fro

m lo

cal f

arm

ers.

Add

ition

ally

, alth

ough

it is

a g

rass

, vet

iver

act

s m

ore

like

a tr

ee, g

iven

its

ext

ensi

ve a

nd d

eep

root

sys

tem

. To

add

to t

he c

onfu

sion

, VS

can

expl

oit

vetiv

er’s

dif

fere

nt c

hara

cter

istic

s fo

r di

ffer

ent

appl

icat

ions

. Fo

r exa

mpl

e, it

s de

ep ro

ots

stab

ilize

land

, its

thic

k le

aves

spr

ead

wat

er

42

and

trap

sed

imen

t, an

d its

ext

raor

dina

ry to

lera

nce

to h

ostil

e co

nditi

ons

allo

ws

it to

reh

abili

tate

soi

l and

wat

er c

onta

min

atio

n.

Failu

res

of V

S ca

n, i

n m

ost

case

s, b

e at

trib

uted

to

bad

appl

icat

ions

ra

ther

tha

n th

e gr

ass

itsel

f or

the

rec

omm

ende

d te

chno

logy

. Fo

r ex

ampl

e, i

n on

e ca

se, v

etiv

er w

as u

sed

in t

he P

hilip

pine

s to

sta

biliz

e ba

tters

on

a ne

w h

ighw

ay.

The

res

ults

wer

e ve

ry d

isap

poin

ting

and

failu

res

resu

lted.

It

late

r su

rfac

ed t

hat

the

engi

neer

s w

ho s

peci

fied

the

VS,

the

nur

sery

tha

t su

pplie

d th

e pl

antin

g m

ater

ial,

and

the

field

su

perv

isor

s an

d la

bour

ers

who

pla

nted

the

vet

iver

, la

cked

pre

viou

s ex

peri

ence

or

trai

ning

in th

e us

e of

VS

for

stee

p sl

opes

sta

bilis

atio

n.

Exp

erie

nce

in V

ietn

am s

how

s th

at v

etiv

er h

as b

een

very

suc

cess

ful

empl

oyed

whe

n it

is a

pplie

d co

rrec

tly.

Not

sur

pris

ingl

y, i

mpr

oper

ap

plic

atio

ns

may

fa

il. A

pplic

atio

ns

in

the

Cen

tral

H

ighl

ands

of

V

ietn

am sh

ow th

at v

etiv

er h

as e

ffec

tivel

y pr

otec

ted

road

em

bank

men

ts.

How

ever

, am

ong

mas

s ap

plic

atio

ns o

n ve

ry h

igh

and

stee

p sl

opes

w

ithou

t be

nche

s al

ong

the

Ho

Chi

Min

h H

ighw

ay,

failu

res

have

re

sulte

d. I

n sh

ort,

to e

nsur

e su

cces

s, d

ecis

ion

mak

ers,

des

igne

rs

and

engi

neer

s w

ho p

lan

to u

se t

he V

etiv

er S

yste

m f

or i

nfra

stru

ctur

e pr

otec

tion

shou

ld ta

ke th

e fo

llow

ing

prec

autio

ns:

Tech

nica

l pre

caut

ions

:•

To e

nsur

e su

cces

s, th

e de

sign

sho

uld

be c

reat

ed o

r ch

ecke

d

by

trai

ned

peop

le.

• A

t le

ast

for

the

first

few

mon

ths

whi

le t

he p

lant

is

beco

min

g es

tabl

ishe

d, th

e si

te sh

ould

be

inte

rnal

ly st

able

aga

inst

pos

sibl

e fa

ilure

. V

etiv

er m

anif

ests

its

ful

l ab

ilitie

s w

hen

mat

ure,

and

sl

opes

may

fai

l dur

ing

the

inte

rven

ing

peri

od.

• V

S is

app

licab

le o

nly

to e

arth

en s

lope

s w

ith g

radi

ents

tha

t sh

ould

nev

er e

xcee

d 45

-50º

• V

etiv

er g

row

s po

orly

in th

e sh

ade,

so

plan

ting

it di

rect

ly u

nder

a

brid

ge o

r ot

her

shel

ter

shou

ld b

e av

oide

d.

Pre

caut

ions

for

dec

isio

n-m

akin

g, p

lann

ing

and

orga

nisa

tion:

• T

imin

g: p

lann

ing

shou

ld c

onsi

der

the

seas

ons

and

the

time

it

take

s to

gro

w p

lant

ing

mat

eria

ls.

• M

aint

enan

ce a

nd r

epai

r: a

t an

ear

ly s

tage

, th

ere

is a

per

iod

43

duri

ng w

hich

vet

iver

is

not

yet

effe

ctiv

e. P

lann

ing

and

bud-

getin

g sh

ould

ant

icip

ate

repl

acem

ent o

f so

me.

• Pr

ocur

emen

t: A

ll in

puts

can

and

sho

uld

be p

rocu

red

loca

lly

(lab

our,

man

ure,

pla

ntin

g m

ater

ials

, m

aint

enan

ce c

ontr

acts

).

Em

ploy

men

t op

port

unity

pro

vide

s an

inc

entiv

e fo

r th

e lo

cal

com

mun

ity to

pro

tect

the

plan

ts d

urin

g th

eir

infa

ncy

and

ado-

lesc

ence

, and

to m

aint

ain

the

qual

ity a

nd s

usta

inab

ility

of

the

wor

ks.

• C

omm

unity

inv

olve

men

t: A

s m

uch

as p

ossi

ble,

loc

al c

om-

mun

ities

sho

uld

be in

clud

ed in

the

desi

gn, m

ater

ials

pro

cure

-m

ent,

and

mai

nten

ance

sta

ges.

Con

trac

ts w

ith l

ocal

peo

ple

shou

ld b

e dr

afte

d, g

over

ning

nur

seri

es, q

ualit

y/qu

antit

y sp

ec-

ifica

tions

, and

mai

nten

ance

/pro

tect

ion.

• T

imin

g: D

ecis

ion

mak

ers

shou

ld b

e re

ady

to in

nova

te a

nd to

co

nsid

er V

S in

the

ir p

lann

ing

and

budg

etin

g. F

or t

hat,

they

ne

ed i

ncen

tives

to

incl

ude

such

cos

t-ef

fect

ive

met

hods

in

thei

r pl

ans,

just

as

they

hav

e in

cent

ives

- j

ustifi

ed o

r no

t - to

ad

opt m

ore

expe

nsiv

e co

nven

tiona

l met

hods

.•

Inte

grat

ion:

Po

licy

mak

ers

shou

ld r

ecom

men

d V

etiv

er S

ys-

tem

as

part

of

a co

mpr

ehen

sive

app

roac

h to

inf

rast

ruct

ure

prot

ectio

n, a

pplie

d on

a s

cale

lar

ge e

noug

h to

ens

ure

a ta

n-gi

ble

incr

ease

in e

xper

tise

and

a gr

adua

l, sp

read

ing

effe

ct. V

S sh

ould

not

be

rega

rded

mer

ely

as a

fix

for

com

prom

ised

loca

l si

tes,

des

pite

its

abi

lity

to p

rovi

de a

con

cise

and

im

med

iate

ef

fect

.

4.2

Pla

ntin

g tim

eT

he i

nsta

llatio

n of

vet

iver

pla

nts

is c

ritic

al t

o th

e su

cces

s an

d th

e co

st o

f th

e pr

ojec

t. P

lant

ing

in d

ry s

easo

n w

ill r

equi

re e

xten

sive

and

ex

pens

ive

wat

erin

g. E

xper

ienc

e in

Cen

tral

Vie

tnam

sho

ws

that

dai

ly

or tw

ice

daily

wat

erin

g is

requ

ired

to e

stab

lish

vetiv

er in

the

extr

emel

y ha

rsh

cond

ition

s in

san

d du

nes.

Gro

wth

is

stun

ted

in t

he a

bsen

ce o

f w

ater

ing.

Sin

ce i

t is

dif

ficul

t to

sel

ect

the

best

tim

e to

pla

nt m

asse

s of

pla

nt m

ater

ial

on c

ut s

lope

s al

ong

the

Ho

Chi

Min

h H

ighw

ay,

for

exam

ple,

mec

hani

cal

wat

erin

g is

req

uire

d da

ily f

or t

he fi

rst

few

m

onth

s.

Vet

iver

gen

eral

ly n

eeds

3-4

mon

ths

to b

ecom

e es

tabl

ishe

d, s

omet

imes

44

up t

o 5-

6 m

onth

s un

der

adve

rse

cond

ition

s. S

ince

vet

iver

is

fully

ef

fect

ive

at t

he a

ge o

f 9-

10 m

onth

s, m

ass

plan

tings

sho

uld

occu

r at

the

beg

inni

ng o

f th

e ra

iny

seas

on (

i.e.

nurs

ery

deve

lopm

ent

and

prod

uctio

n of

pla

nt m

ater

ial

shou

ld b

e pl

anne

d to

mee

t th

at m

ass

plan

ting

sche

dule

).

Part

icul

arly

in N

orth

Vie

tnam

, it i

s po

ssib

le to

pla

nt d

urin

g th

e w

inte

r-sp

ring

per

iod.

Whe

n te

mpe

ratu

res

desc

end

low

er th

an 1

0ºC

(50

ºF)

in

Nor

th V

ietn

am, t

he g

rass

doe

s no

t gr

ow. H

owev

er, i

t ca

n su

rviv

e th

e co

ld w

eath

er a

nd r

esum

es g

row

ing

imm

edia

tely

whe

n th

e w

inte

r ra

in

star

ts a

nd th

e w

eath

er w

arm

s.

In c

entr

al V

ietn

am,

whe

re a

ir t

empe

ratu

re u

sual

ly s

tays

abo

ve 1

5ºC

(5

9ºF)

, mas

s pl

antin

g oc

curs

at t

he b

egin

ning

of s

prin

g. N

urse

ries

will

re

quir

e m

ore

care

to

ensu

re g

ood

grow

th a

nd m

ultip

licat

ion

of t

he

slip

s.

4.3

Nur

sery

The

suc

cess

of

any

proj

ect

depe

nds

on g

ood

qual

ity a

nd s

uffic

ient

nu

mbe

rs o

f ve

tiver

slip

s. L

arge

nur

seri

es g

ener

ally

are

not

req

uire

d to

pr

ovid

e su

ffici

ent p

lant

mat

eria

l. In

stea

d, in

divi

dual

farm

er h

ouse

hold

s ca

n se

t up

and

supe

rvis

e sm

all n

urse

ries

(a

few

hun

dred

squ

are

met

ers

each

). T

hey

will

be

cont

ract

ed a

nd p

aid

by th

e pr

ojec

t acc

ordi

ng to

the

num

ber

of s

lips

they

can

pro

vide

upo

n re

ques

t.

4.4

Pre

para

tion

for

vetiv

er p

lant

ing

In c

ases

whe

re m

ass

plan

ting

of v

etiv

er i

nvol

ves

the

part

icip

atio

n of

loc

al p

eopl

e, a

n ef

fect

ive

plan

ting

cam

paig

n sh

ould

inc

lude

the

fo

llow

ing

step

s:

Step

1:

Exp

erts

vis

it th

e si

tes,

and

con

duct

a s

urve

y to

ide

n-tif

y pr

oble

ms

and

desi

gn t

he a

pplic

atio

n of

the

tec

h-no

logy

;St

ep 2

: D

iscu

ss th

e pr

oble

ms

and

alte

rnat

ive

solu

tions

w

ith lo

cal p

eopl

e;

Step

3:

Use

wor

ksho

ps a

nd tr

aini

ng c

ours

es to

intr

oduc

e

th

e ne

w te

chno

logy

;St

ep 4

: O

rgan

ize

the

tria

l im

plem

enta

tion,

by

esta

blis

hing

45

nurs

erie

s,

cont

ract

ing

to

purc

hase

pl

ant

mat

eria

l, m

aint

enan

ce, e

tc.;

Step

5:

Mon

itor

the

impl

emen

tatio

n;St

ep 6

: D

iscu

ss re

sults

of t

he p

ilot,

follo

win

g w

orks

hop,

fiel

d ex

chan

ge v

isit,

etc

.;St

ep 7

: O

rgan

ize

mas

s pl

antin

g.

In c

ases

whe

re s

peci

aliz

ed c

ompa

nies

und

erta

ke t

he m

ass

plan

ting,

st

eps

1, 4

, 5

are

reco

mm

ende

d.

How

ever

, lo

cal

part

icip

atio

n is

stil

l ad

visa

ble

to r

aise

aw

aren

ess,

avo

id v

anda

lism

, an

d en

sure

tha

t th

e sl

ips

are

prot

ecte

d fr

om a

nim

als.

4.5

Lay

out s

peci

ficat

ions

4.5.

1 ‘U

plan

d’ n

atur

al s

lope

, cut

slo

pe, r

oad

batte

r, e

tc.

To s

tabi

lize

upla

nd n

atur

al s

lope

s, c

ut s

lope

s, a

nd r

oad

batte

rs,

the

follo

win

g sp

ecifi

catio

ns m

ay a

pply

:•

Ban

k sl

ope

shou

ld n

ot e

xcee

d 1(

H)

[hor

izon

tal]

:1(V

) [v

er-

tical

] or

45º

, gr

adie

nt o

f 1.

5:1

is r

ecom

men

ded.

Sha

llow

er

grad

ient

s ar

e re

com

men

ded

whe

reve

r po

ssib

le, e

spec

ially

on

erod

ible

soi

ls a

nd/o

r in

hig

h ra

infa

ll ar

eas.

• V

etiv

er s

houl

d be

pla

nted

acr

oss

the

slop

e on

app

roxi

mat

e co

ntou

r lin

es w

ith a

Ver

tical

Int

erva

l (V

I) b

etw

een

1.0-

2.0m

(3

-6’)

apa

rt, m

easu

red

dow

n th

e sl

ope.

Spa

cing

of

1.0m

(3’

) sh

ould

be

used

on

high

ly e

rodi

ble

soil,

whi

ch c

an in

crea

se u

p to

1.5

-2.0

m (

4.5-

6’)

on m

ore

sta b

le s

oil.

• T

he fi

rst r

ow s

houl

d be

pla

nted

on

the

top

edge

of

the

batte

r. T

his

row

sha

ll be

pla

nted

on

all

batte

rs t

hat

are

talle

r th

an

1.5m

(4.

5’).

• T

he b

otto

m r

ow s

houl

d be

pla

nted

at t

he b

otto

m o

f th

e ba

tter

at th

e to

e of

the

slop

e a

nd o

n cu

t bat

ter a

long

the

edge

of t

able

dr

ain.

• B

etw

een

thes

e ro

ws,

vet

iver

sho

uld

be p

lant

ed a

s sp

ecifi

ed

abov

e.•

Ben

chin

g or

ter

raci

ng 1

-3 m

(3-

9’)

in w

idth

for

eve

ry 5

-8 m

(1

5-24

’) V

I is

rec

omm

ende

d fo

r sl

opes

that

are

talle

r th

an 1

0 m

(30

’).

46

4.5.

2 R

iver

bank

s, c

oast

al e

rosi

on,

and

unst

able

wat

er r

etai

ning

st

ruct

ures

For fl

ood

miti

gatio

n an

d co

asta

l, ri

verb

ank

and

dike

/em

bank

men

t pro

-te

ctio

n, th

e fo

llow

ing

layo

ut s

peci

ficat

ions

are

rec

omm

ende

d:•

Max

imum

ban

k sl

ope

shou

ld n

ot e

xcee

d 1.

5(H

):1(

V).

Rec

-om

men

ded

bank

slo

pe is

2.5

:1.

Not

e: th

e se

a di

ke s

yste

m in

H

ai H

au (

Nam

Din

h) is

bui

lt w

ith b

ank

slop

e of

3:1

to 4

:1.

• V

etiv

er s

houl

d be

pla

nted

in tw

o di

rect

ions

:-

For

bank

sta

bilis

atio

n, v

etiv

er s

houl

d be

pla

nted

in

row

s pa

ralle

l to

flow

dir

ectio

n (h

oriz

onta

l),

on a

ppro

xim

ate

cont

our

lines

0.8

-1.0

m (

2.5-

3’)

apar

t (m

easu

red

dow

n sl

ope)

. A re

cent

layo

ut s

peci

ficat

ion

to p

rote

ct th

e se

a di

ke

syst

em in

Hai

Hau

(N

am D

inh)

incl

uded

spa

cing

bet

wee

n ro

ws

low

ered

to 0

.25

m. (

.8’)

.-

To r

educ

e flo

w v

eloc

ity, v

etiv

er s

houl

d be

pla

nted

in r

ows

norm

al (

righ

t an

gle)

to

the

flow

at

spac

ing

betw

een

row

s of

2.0

m (

6’)

for

erod

ible

soi

l an

d 4.

0m (

12’)

for

sta

ble

soil.

As

adde

d pr

otec

tion,

nor

mal

row

s ar

e pl

ante

d 1.

0m

(3’)

apa

rt o

n th

e ri

ver

dike

in Q

uang

Nga

i. •

The

firs

t ho

rizo

ntal

row

sho

uld

be p

lant

ed a

t th

e cr

est

of t

he

bank

and

the

last

row

sho

uld

be p

lant

ed a

t the

low

wat

er m

ark

of t

he b

ank.

N

ote:

sin

ce t

he w

ater

lev

el a

t so

me

loca

tions

ch

ange

s se

ason

ally

, vet

iver

can

be

plan

ted

muc

h fu

rthe

r dow

n th

e ba

nk w

hen

the

time

is r

ight

.•

Vet

iver

sho

uld

be p

lant

ed o

n th

e co

ntou

r al

ong

the

leng

th

of t

he b

ank

betw

een

the

top

and

botto

m r

ows

at t

he s

paci

ng

spec

ified

abo

ve.

• D

ue t

o hi

gh w

ater

lev

els,

bot

tom

row

s m

ay e

stab

lish

mor

e sl

owly

than

upp

er r

ows.

In

such

cas

es, t

he lo

wer

row

s sh

ould

be

pla

nted

whe

n th

e so

il is

dri

est.

Som

e V

S ap

plic

atio

ns p

ro-

tect

ant

i-sa

linity

dik

es; i

n th

ose

case

s, th

e w

ater

may

bec

ome

mor

e sa

line

at c

erta

in t

imes

of

the

year

, w

hich

may

aff

ect

the

grow

th o

f ve

tiver

. Exp

erie

nces

in

Qua

ng N

gai

show

tha

t ve

tiver

can

be

repl

aced

by

som

e lo

cal

salt-

tole

rant

var

ietie

s,

incl

udin

g th

e m

angr

ove

fern

.•

For

all a

pplic

atio

ns, V

S ca

n be

use

d in

com

bina

tion

with

oth

-er

tra

ditio

nal,

stru

ctur

al m

easu

res

such

as

rock

or

conc

rete

ri

prap

, and

ret

aini

ng w

alls

. For

exa

mpl

e, th

e lo

wer

par

t of

the

47

dike

/em

bank

men

t can

be

cove

red

by th

e co

mbi

natio

n of

roc

k ri

prap

and

geo

-tex

tile

whi

le t

he u

pper

hal

f is

pro

tect

ed w

ith

vetiv

er h

edge

row

s.

4.6

Pla

ntin

g sp

ecifi

catio

ns D

ig tr

ench

es th

at a

re a

bout

15-

20cm

(6-

8”)

deep

and

wid

e.• •

Plac

e w

ell-

root

ed p

lant

s (w

ith 2

-3 ti

llers

api

ece)

in th

e ce

ntre

of

eac

h ro

w a

t 100

-120

mm

(4-

5”)

inte

rval

s fo

r er

odib

le s

oils

, an

d at

150

mm

(6”

) fo

r no

rmal

soi

ls.

• Si

nce

soil

on s

lope

s, r

oad

batte

rs a

nd fi

lled

dike

/em

bank

men

t is

not

fer

tile,

it

is r

ecom

men

ded

that

pot

ted

or t

ube

stoc

k be

us

ed f

or l

arge

sca

le m

ass

plan

ting

and

rapi

d es

tabl

ishm

ent.

Add

ing

a bi

t of

goo

d so

il-m

anur

e m

ixtu

re (

slur

ry)

is e

ven

bette

r. To

pro

tect

nat

ural

riv

er b

anks

whe

re th

e so

il is

usu

ally

fe

rtile

and

ini

tial

wat

erin

g ca

n be

ens

ured

with

out

extr

a ef

-fo

rt, b

are

root

pla

ntin

g is

suf

ficie

nt.

• C

over

roo

ts w

ith 2

00-3

00m

m (

8-12

”) o

f so

il an

d co

mpa

ct

firm

ly.

• Fe

rtili

ze w

ith N

itrog

en a

nd P

hosp

horu

s suc

h as

DA

P (D

i -A

m-

mon

ium

Pho

spha

te)

or N

PK (

note

fro

m e

xper

ienc

e ve

tiver

do

es n

ot r

espo

nd s

igni

fican

tly f

rom

pot

ash

appl

icat

ions

) at

10

0g (3

.5oz

) per

line

ar m

eter

(row

). T

he s

ame

amou

nt o

f lim

e m

ay b

e ne

cess

ary

whe

n pl

antin

g in

aci

d an

d su

lfat

e so

il.•

Wat

er w

ithin

the

day

of p

lant

ing.

• To

redu

ce w

eed

grow

th d

urin

g th

e es

tabl

ishm

ent p

hase

, a p

re-

emer

gent

her

bici

de s

uch

as A

traz

ine

may

be

used

.4.

7 M

aint

enan

ceW

ater

ing

• In

dry

wea

ther

, w

ater

eve

ry d

ay d

urin

g th

e fir

st t

wo

wee

ks

afte

r pl

antin

g an

d th

en e

very

sec

ond

day.

• W

ater

twic

e w

eekl

y un

til th

e pl

ants

are

wel

l est

ablis

hed.

• M

atur

e pl

ants

req

uire

no

furt

her

wat

erin

g.R

epla

ntin

g•

Dur

ing

the

first

mon

th a

fter

pla

ntin

g, r

epla

ce a

ll pl

ants

tha

t fa

il to

est

ablis

h or

was

h aw

ay.

• C

ontin

ue

insp

ectio

ns

until

th

e pl

ants

ar

e su

itabl

y es

tab-

lishe

d.W

eed

cont

rol

48

• C

ontr

ol w

eeds

, esp

ecia

lly v

ines

, dur

ing

the

first

yea

r.•

DO

NO

T U

SE R

ound

Up

(gly

phos

ate)

her

bici

de.

Vet

iver

is

very

sen

sitiv

e to

gly

phos

ate,

so

it sh

ould

not

be

used

to

con-

trol

wee

ds b

etw

een

row

s.

Fer

tiliz

ing

On

infe

rtile

soi

l, D

AP

or N

PK f

ertil

izer

sho

uld

be a

pplie

d at

the

be

ginn

ing

of th

e se

cond

wet

sea

son.

Cut

ting

Aft

er fi

ve m

onth

s, r

egul

ar c

uttin

g (t

rim

min

g) i

s al

so v

ery

impo

rtan

t. H

edge

row

s sh

ould

be

cut d

own

to 1

5-20

cm

(6-

8”)

abov

e th

e gr

ound

. T

his

sim

ple

tech

niqu

e pr

omot

es th

e gr

owth

of n

ew ti

llers

from

the

base

an

d re

duce

s th

e vo

lum

e of

dry

lea

ves

that

oth

erw

ise

can

over

shad

ow

youn

g sl

ips.

Tri

mm

ing

also

impr

oves

the

appe

aran

ce o

f dry

hed

gero

ws

and

may

min

imiz

e th

e da

nger

of

fire.

Fres

h cu

t le

aves

can

als

o be

use

d as

cat

tle f

odde

r, fo

r ha

ndic

raft

, and

ev

en r

oof

that

ch.

Ple

ase

note

tha

t ve

tiver

pla

nted

for

the

pur

pose

of

red

ucin

g na

tura

l di

sast

ers

shou

ld n

ot b

e ov

erus

ed f

or s

econ

dary

pu

rpos

es.

Subs

eque

nt c

uttin

gs c

an b

e do

ne tw

o or

thre

e tim

es a

yea

r. C

are

shou

ld

be ta

ken

to e

nsur

e th

e gr

ass

has

long

leav

es d

urin

g th

e ty

phoo

n se

ason

. V

etiv

er c

an b

e cu

t im

med

iate

ly a

fter

the

typh

oon

seas

on e

nds.

Ano

ther

su

itabl

e cu

tting

tim

e co

uld

be a

roun

d 3

mon

ths

befo

re t

he t

ypho

on

seas

on b

egin

s.

Fen

cing

and

car

ing

Dur

ing

the

seve

ral-

mon

th e

stab

lishm

ent

peri

od,

fenc

ing

and

care

m

ay b

e re

quir

ed to

pro

tect

vet

iver

fro

m v

anda

lism

and

cat

tle. T

he o

ld

stem

s of

mat

ure

vetiv

er a

re to

ugh

enou

gh to

dis

cour

age

cattl

e. W

here

ne

cess

ary,

it

is a

dvis

able

to

fenc

e th

e ar

ea t

o pr

otec

t th

e gr

ass

duri

ng

the

first

few

mon

ths

afte

r pl

antin

g.

49

5. V

ET

IVE

R S

YST

EM

S A

PP

LIC

AT

ION

S F

OR

NA

TU

RA

L

DIS

AST

ER

RE

DU

CT

ION

AN

D I

NF

RA

STR

UC

TU

RE

P

RO

TE

CT

ION

IN

VIE

TN

AM

5.1

VS

appl

icat

ion

for

sand

dun

e pr

otec

tion

in C

entr

al

V

ietn

amA

vas

t are

a, m

ore

than

70,

000

ha (

175,

000

acre

s), a

long

the

coas

tline

of

Cen

tral

Vie

tnam

is

cove

red

by s

and

dune

s w

here

the

clim

atic

and

so

il co

nditi

ons

are

very

sev

ere.

San

d bl

ast o

ften

occ

urs

as s

and

dune

s m

igra

te u

nder

the

actio

n of

win

d. S

and

flow

als

o ta

kes

plac

e fr

eque

ntly

du

e to

the

act

ion

of n

umer

ous

perm

anen

t an

d te

mpo

rary

str

eam

s.

Blo

wn

sand

and

san

d flo

w tr

ansp

ort h

uge

amou

nts

of s

and

from

dun

es

land

war

d on

to t

he n

arro

w c

oast

al p

lain

. Alo

ng t

he C

entr

al V

ietn

am

coas

tline

, gi

ant

sand

“to

ngue

s” b

ite i

nto

the

plai

n da

y af

ter

day.

The

G

over

nmen

t ha

s lo

ng

impl

emen

ted

a fo

rest

atio

n pr

ogra

m

usin

g su

ch v

arie

ties

as C

asua

rina

s, w

ild p

inea

pple

, eu

caly

ptus

, an

d ac

acia

. H

owev

er, w

hen

fully

and

wel

l est

ablis

hed,

they

may

hel

p re

duce

onl

y bl

own

sand

. U

ntil

now

, th

ere

has

been

no

way

to

redu

ce s

and

flow

(t

rees

can

not

sta

biliz

e sa

nd d

unes

, esp

ecia

lly o

n th

eir

‘slip

-fac

e’, t

his

was

trie

d in

Nor

th A

fric

a by

FA

O a

t gre

at e

xpen

se a

nd f

aile

d).

In F

ebru

ary

2002

, w

ith fi

nanc

ial

supp

ort

from

the

Dut

ch E

mba

ssy

Smal

l Pr

ogra

m a

nd t

echn

ical

sup

port

fro

m E

lise

Pinn

ers

and

Pham

H

ong

Duc

Phu

oc, T

ran

Tan

Van

fro

m R

IGM

R in

itiat

ed a

n ex

peri

men

t to

sta

biliz

e sa

nd d

unes

alo

ng t

he C

entr

al V

ietn

am c

oast

line.

A s

and

dune

was

bad

ly e

rode

d by

a s

trea

m th

at s

erve

d as

a n

atur

al b

ound

ary

betw

een

farm

ers

and

a fo

rest

ry e

nter

pris

e. T

he e

rosi

on o

ccur

red

over

se

vera

l yea

rs, r

esul

ting

in a

mou

ntin

g co

nflic

t bet

wee

n th

e tw

o gr

oups

. V

etiv

er w

as p

lant

ed in

row

s al

ong

the

cont

our

lines

of

the

sand

dun

e.

Aft

er f

our

mon

ths

it fo

rmed

clo

sed

hedg

erow

s an

d st

abili

zed

the

sand

dun

e. T

he f

ores

try

ente

rpri

se w

as s

o im

pres

sed

that

it

deci

ded

to m

ass

plan

t th

e gr

ass

in o

ther

san

d du

nes

and

even

to

prot

ect

a br

idge

abu

tmen

t. V

etiv

er f

urth

er s

urpr

ised

loc

al p

eopl

e by

sur

vivi

ng

the

cold

est w

inte

r in

10

year

s, w

hen

the

tem

pera

ture

des

cend

ed lo

wer

10

ºC (

50ºF

), f

orci

ng th

e fa

rmer

s to

twic

e re

plan

t the

ir p

addy

ric

e an

d C

asua

rina

s. A

fter

tw

o ye

ars,

the

loc

al s

peci

es (

prim

arily

Cas

uari

nas

and

wild

pin

eapp

le)

beca

me

re-e

stab

lishe

d. T

he g

rass

its

elf

fade

d aw

ay u

nder

the

shad

e of

thes

e tr

ees,

hav

ing

acco

mpl

ishe

d its

mis

sion

.

50

The

pro

ject

pro

ved

agai

n th

at, w

ith p

rope

r ca

re, v

etiv

er c

ould

sur

vive

ve

ry h

ostil

e so

il an

d cl

imat

ic c

ondi

tions

- p

hoto

2.

Acc

ordi

ng to

Hen

k Ja

n V

erha

gen

from

Del

ft U

nive

rsity

of T

echn

olog

y (p

ers.

com

m.)

, ve

tiver

may

be

equa

lly e

ffec

tive

in r

educ

ing

blow

n sa

nd (

sand

dri

ft).

For

thi

s pu

rpos

e, t

he g

rass

cou

ld b

e pl

ante

d ac

ross

th

e w

ind

dire

ctio

n, e

spec

ially

at l

ow p

lace

s be

twee

n sa

nd d

unes

, whe

re

the

win

d ve

loci

ty ty

pica

lly in

crea

ses.

On

Chi

na’s

Pin

tang

Isl

and,

off

th

e co

ast o

f Fu

jian

Prov

ince

, vet

iver

hed

ges

effe

ctiv

ely

redu

ced

win

d ve

loci

ty a

nd b

low

san

d.

Follo

win

g th

e su

cces

s of

this

pilo

t pro

ject

, a w

orks

hop

was

org

aniz

ed

in e

arly

200

3. M

ore

than

40

repr

esen

tativ

es f

rom

loc

al g

over

nmen

t de

part

men

ts, d

iffe

rent

NG

Os,

the

Uni

vers

ity o

f C

entr

al V

ietn

am, a

nd

coas

tal p

rovi

nces

par

ticip

ated

. The

wor

ksho

p he

lped

the

auth

ors

of th

is

book

and

oth

er p

artic

ipan

ts to

com

pile

and

syn

thes

ize

loca

l pra

ctic

es,

part

icul

arly

re

gard

ing

plan

ting

times

, w

ater

ing,

an

d fe

rtili

zing

. Fo

llow

ing

the

even

t, W

orld

Vis

ion

Vie

tnam

dec

ided

in

2003

to

fund

an

othe

r pr

ojec

t in

the

Vin

h L

inh

and

Tri

eu P

hong

dis

tric

ts i

n Q

uang

T

ri p

rovi

nce

to e

mpl

oy v

etiv

er f

or s

and

dune

sta

bilis

atio

n -

phot

os

3-7.

51

5.1.

1 T

rial

app

licat

ion

and

prom

otio

n of

VS

for

sand

dun

e pr

otec

tion

in c

oast

al p

rovi

nce

of Q

uang

Bin

h

Ph

oto

2: S

and

flo

w in

Le

Th

uy

(Qu

ang

Bin

h)

in 1

999:

th

e fo

un

dat

ion

of

a p

um

pin

g s

tati

on

(u

pp

er);

th

is w

om

an’s

th

ree-

roo

m b

rick

ho

use

is

colla

psi

ng

bec

ause

san

d h

as b

een

blo

wn

fro

m fo

un

dat

ion

(lo

wer

).

52

Ph

oto

3: U

pp

er: s

ite

over

view

; lo

wer

: ear

ly A

pri

l 200

2,

on

e m

on

th a

fter

pla

nti

ng

.

53

Ph

oto

4: U

pp

er: e

arly

Ju

ly 2

002,

fou

r m

on

ths

afte

r p

lan

tin

g; l

ow

er:

Nov

emb

er 2

002,

den

se r

ow

s o

f g

rass

hav

e b

een

est

ablis

hed

.

54

Ph

oto

5: U

pp

er: V

etiv

er n

urs

ery;

low

er: N

ovem

ber

200

2, m

ass

pla

nti

ng

.

55

Ph

oto

6:

Up

per

: Vet

iver

pro

tect

s b

rid

ge

abu

tmen

t al

on

g N

atio

nal

Hig

h-

way

nr.

1; lo

wer

: Dec

emb

er 2

004,

loca

l sp

ecie

s h

ave

rep

lace

d v

etiv

er.

56

Ph

oto

7: U

pp

er: m

id-F

ebru

ary

2003

, po

st-w

ork

sho

p fi

eld

trip

; No

te: V

etiv

-er

su

rviv

es e

ven

th

e co

ldes

t w

inte

r in

10

year

s; lo

wer

: Ju

ne

2003

, far

m-

ers

fro

m Q

uan

g T

ri p

rovi

nce

vis

it a

lo

cal

nu

rser

y d

uri

ng

a W

orl

d V

isio

n

Vie

tnam

-sp

on

sore

d fi

eld

tri

p.

5.2

VS

appl

icat

ion

to c

ontr

ol r

iver

ban

k er

osio

n

5.2.

1 V

S ap

plic

atio

n fo

r ri

ver

bank

ero

sion

con

trol

in

Cen

tral

V

ietn

amW

ithin

the

fram

ewor

k of

the

sam

e D

utch

Em

bass

y pr

ojec

t men

tione

d ab

ove,

vet

iver

was

pla

nted

to

halt

eros

ion

on a

riv

erba

nk,

on t

he

bank

of

a sh

rim

p po

nd, a

nd o

n a

road

em

bank

men

t in

Da

Nan

g C

ity.

In O

ctob

er 2

002,

the

loc

al D

ike

Dep

artm

ent

also

mas

s pl

ante

d th

e gr

ass

on b

ank

sect

ions

of

seve

ral r

iver

s. T

here

afte

r, th

e ci

ty a

utho

rity

de

cide

d to

fund

a p

roje

ct o

n cu

t slo

pe s

tabi

lisat

ion

by in

stal

ling

vetiv

er

57

alon

g th

e m

ount

aino

us ro

ad le

adin

g to

the

Ban

ana

proj

ect i

n D

a N

ang,

ill

ustr

atin

g th

e pa

ce o

f ad

optio

n -

phot

os 8

-10.

Ph

oto

8:

Up

per

: D

ecem

ber

200

4: V

etiv

er,

com

bin

ed w

ith

ro

ck r

ipra

p,

flo

uri

shes

aft

er t

wo

flo

od

sea

son

s (D

a N

ang

); l

ow

er:

pla

nte

d b

y lo

cal

farm

ers,

vet

iver

pro

tect

s th

eir

shri

mp

po

nd

s.

58

Ph

oto

9: U

pp

er: M

arch

200

2: V

S tr

ial a

t th

e ed

ge

of a

sh

rim

p p

on

d, w

her

e a

can

al d

rain

s fl

oo

d w

ater

to

Vin

h D

ien

Riv

er;

low

er:

Nov

emb

er 2

002:

m

ass

pla

nti

ng

co

mb

ined

wit

h r

ock

rip

rap

to

pro

tect

ban

k al

on

g V

inh

D

ien

riv

er.

59

Ph

oto

10:

Up

per

: Vet

iver

an

d r

ock

rip

rap

an

d c

on

cret

e fr

ame

pro

tect

an

em

ban

kmen

t; l

ow

er:

a b

end

on

Per

fum

e R

iver

ban

k in

Hu

e -

pro

tect

ed

wit

h v

etiv

er.

5.2.

2 V

S tr

ial

and

prom

otio

n fo

r ri

ver

bank

pro

tect

ion

in Q

uang

N

gai

As

anot

her

resu

lt of

thi

s pi

lot

proj

ect,

vetiv

er w

as r

ecom

men

ded

for

use

in a

noth

er n

atur

al d

isas

ter

redu

ctio

n pr

ojec

t in

Qua

ng N

gai

prov

ince

, fun

ded

by A

usA

id. W

ith te

chni

cal s

uppo

rt b

y T

ran

Tan

Van

in

Jul

y 20

03, V

o T

hanh

Thu

y an

d hi

s co

-wor

kers

fro

m t

he p

rovi

ncia

l A

gric

ultu

ral E

xten

sion

Cen

tre.

60

Ph

oto

11:

Vet

iver

gra

ss p

lan

ted

on

riv

er d

ike

alo

ng

Tra

Bo

ng

Riv

er

(up

per

) an

d li

nin

g t

he

sid

es o

f an

an

ti-s

alin

ity

estu

ary

dik

e al

on

g t

he

sam

e ri

ver

(lo

wer

).

61

Ph

oto

12:

Up

per

: sev

erel

y er

od

ed b

ank

of

the

Tra

Kh

uc

Riv

er,

at B

inh

Th

oi C

om

mu

ne;

low

er: p

rim

itiv

e sa

nd

bag

pro

tect

ion

.

62

Ph

oto

13:

Up

per

: Co

mm

un

ity

mem

ber

s p

lan

t ve

tive

r; lo

wer

: N

ovem

ber

200

5: b

ank

rem

ain

s in

tact

follo

win

g t

he

flo

od

sea

son

.

plan

ted

the

gras

s at

fou

r lo

catio

ns, i

rrig

atio

n ca

nals

in s

ever

al d

istr

icts

an

d a

seaw

ater

int

rusi

on p

rote

ctio

n di

kes.

Vet

iver

thr

ived

in

all

loca

tions

and

, des

pite

its

youn

g ag

e, s

urvi

ved

a flo

od in

the

sam

e ye

ar

- ph

otos

11-

13.

Follo

win

g th

ese

succ

essf

ul t

rial

s, t

he p

roje

ct d

ecid

ed t

o m

ass

plan

t ve

tiver

on

othe

r di

ke s

ectio

ns i

n th

ree

othe

r di

stri

cts,

in

com

bina

tion

with

roc

k ri

prap

. D

esig

n m

odifi

catio

ns i

ntro

duce

d to

bet

ter

adap

t

63

vetiv

er t

o lo

cal

cond

ition

s in

clud

e pl

antin

g m

angr

ove

fern

and

oth

er

salt-

tole

rant

gra

sses

on

the

low

est r

ow to

bet

ter w

ithst

and

high

sal

inity

an

d to

eff

ectiv

ely

prot

ect

the

emba

nkm

ent

toe.

Enc

oura

ging

ly,

loca

l co

mm

uniti

es a

re m

ore

read

ily u

sing

vet

iver

to

prot

ect

thei

r ow

n la

nds

5.2.

3 V

S ap

plic

atio

n to

con

trol

riv

er b

ank

eros

ion

in t

he M

ekon

g D

elta

With

Will

iam

Don

ner

Foun

datio

n fin

anci

al s

uppo

rt a

nd P

aul T

ruon

g’s

tech

nica

l hel

p, L

e V

iet D

ung

and

his

colle

ague

s at

Can

Tho

Uni

vers

ity

initi

ated

riv

erba

nk e

rosi

on c

ontr

ol p

roje

cts

in th

e M

ekon

g D

elta

. The

ar

ea e

xper

ienc

es lo

ng p

erio

ds o

f inu

ndat

ion

(up

to fi

ve m

onth

s) d

urin

g th

e flo

od s

easo

n, w

ith s

igni

fican

t dif

fere

nce

in w

ater

leve

ls, u

p to

5 m

(1

5’),

bet

wee

n dr

y an

d flo

od s

easo

ns, a

nd p

ower

ful w

ater

flow

dur

ing

flood

sea

son.

Fu

rthe

r, th

e ri

verb

anks

con

sist

of

soils

ran

ging

fro

m

allu

vial

silt

to

loam

, whi

ch a

re h

ighl

y er

odib

le w

hen

wet

. Due

to

the

impr

oved

eco

nom

y of

rec

ent

year

s, m

ost

boat

s tr

avel

ling

on r

iver

s an

d ca

nals

are

mot

oriz

ed, m

any

with

pow

erfu

l eng

ines

that

agg

rava

te

rive

rban

k er

osio

n by

gen

erat

ing

stro

ng w

aves

. N

ever

thel

ess,

vet

iver

st

ands

its

gro

und,

pro

tect

ing

larg

e ar

eas

of v

alua

ble

farm

lan

d fr

om

eros

ion

- ph

otos

14

and

15.

A c

ompr

ehen

sive

vet

iver

pro

gram

has

bee

n es

tabl

ishe

d in

An

Gia

ng

Prov

ince

, w

here

an

nual

flo

ods

reac

h de

pths

of

6

m

(18’

).

The

pr

ovin

ce’s

long

, 493

2 km

(30

65 m

iles)

, can

al s

yste

m r

equi

res

annu

al

mai

nten

ance

and

rep

air.

A n

etw

ork

of d

ikes

, 46

00 k

m l

ong,

pro

tect

s 20

9,95

7 ha

(52

5,00

0 ac

res)

of

prim

e fa

rmla

nd f

rom

floo

d. E

rosi

on

on t

hese

dik

es i

s ab

out

3.75

Mm

3/ye

ar a

nd r

equi

red

USD

1.3

M t

o re

pair.

The

are

a al

so i

nclu

des

181

rese

ttlem

ent

clus

ters

, co

mm

uniti

es b

uilt

on d

redg

ed m

ater

ials

tha

t al

so r

equi

re e

rosi

on c

ontr

ol a

nd p

rote

ctio

n fr

om fl

oodi

ng.

Dep

endi

ng o

n th

e lo

catio

ns a

nd fl

ood

dept

h, v

etiv

er

has

been

use

d su

cces

sful

ly a

lone

, and

tog

ethe

r w

ith o

ther

veg

etat

ion

to s

tabi

lize

thes

e ar

eas.

As

a re

sult,

vet

iver

now

line

s ri

goro

us s

ea a

nd

rive

r di

ke s

yste

ms

as w

ell

as r

iver

bank

s an

d ca

nals

in

the

Mek

ong

Del

ta. N

earl

y tw

o m

illio

n po

lyba

gs o

f ve

tiver

, a to

tal o

f 61

line

al k

m

(38

mile

s), w

ere

inst

alle

d to

pro

tect

the

dike

s be

twee

n 20

02 a

nd 2

005

64

- ph

otos

14

-15.

Bet

wee

n 20

06 a

nd 2

010,

the

11

dist

rict

s of

An

Gia

ng p

rovi

nce

are

expe

cted

to p

lant

202

5 km

(12

58 m

iles)

of

vetiv

er h

edge

s on

310

0 ha

(7

660

acre

s) o

f di

ke s

urfa

ce.

Lef

t un

prot

ecte

d, 3

750

Mm

3 of

soi

l lik

ely

will

be

erod

ed a

nd 5

Mm

3 w

ill h

ave

to b

e dr

edge

d fr

om t

he

cana

ls. B

ased

on

2006

cur

rent

cos

ts, t

otal

mai

nten

ance

cos

ts o

ver

this

pe

riod

wou

ld e

xcee

d U

S $

15.5

M in

this

pro

vinc

e al

one.

App

lyin

g th

e V

etiv

er S

yste

m in

this

rur

al a

rea

will

pro

vide

ext

ra in

com

e to

the

loca

l pe

ople

: men

to p

lant

, and

wom

en a

nd c

hild

ren

to p

repa

re p

olyb

ags.

Ph

oto

14:

In A

n G

ian

g v

etiv

er s

tab

ilize

s a

rive

r d

ike

(up

per

), an

d a

nat

ura

l ri

ver

ban

k (l

ow

er).

65

Ph

oto

15:

Up

per

: Vet

iver

bo

rder

s th

e ed

ge

of

flo

od

res

ettl

emen

t ce

ntr

es;

low

er:

the

red

mar

kers

del

inea

te a

bo

ut

5 m

(15

’) o

f d

ry l

and

sav

ed b

y ve

tive

r.

66

5.2.

4 Ve

tiver

Sys

tem

app

licat

ion

to c

ontr

ol s

ever

e ri

ver

bank

ero

sion

in

Cam

bodi

a

The

wat

er le

vel o

f th

e M

ekon

g ri

ver

sect

ion

in C

ambo

dian

fluc

tuat

es

wid

ely,

reac

hing

15m

and

mor

e du

ring

the

flood

sea

son

abov

e th

e le

vel

duri

ng th

e dr

y se

ason

. The

com

bina

tion

of v

ery

fast

cur

rent

and

wav

e ac

tion

duri

ng t

he a

nnua

l ra

iny

and

flood

sea

son

caus

es s

ever

e ba

nk

eros

ion,

ave

ragi

ng b

etw

een

5-10

m e

very

yea

r. G

ener

al s

oil e

rosi

on o

n th

e al

luvi

al p

lain

is

betw

een

10 a

nd 3

0cm

eac

h ye

ar. T

he l

oss

of t

his

fert

ile a

lluvi

al p

lain

sev

erel

y af

fect

s ag

ricu

lture

pro

duct

ion,

val

uabl

e ur

ban

land

and

inf

rast

ruct

ure

stab

ility

alo

ng t

he r

iver

. In

addi

tion

the

wat

er is

ver

y m

uddy

and

hig

h in

sed

imen

t loa

d.

A p

roje

ct w

as in

itiat

ed in

200

6 to

sta

bilis

e a

200m

long

str

etch

of

the

Mek

ong

bank

nor

th o

f Ph

nom

Pen

h, t

he c

apita

l of

Cam

bodi

a, w

hich

ha

s be

en s

ever

ely

erod

ed a

nd w

ill e

vent

ually

was

h aw

ay th

e na

tiona

l hi

ghw

ay to

nor

ther

n re

gion

s. O

n th

is s

ite, s

ever

e er

osio

n oc

curs

eve

ry

year

and

aft

er 1

0 ye

ars,

50m

hav

e di

sapp

eare

d th

at tr

ansl

ates

into

a lo

ss

of 5

0 m

x 2

00 m

(w

idth

) =

10,

000

m2

or 1

hec

tare

! Var

ious

sta

bilis

ing

optio

ns s

uch

as c

onve

ntio

nal

hard

str

uctu

res

incl

udin

g ga

bion

and

ro

ck w

all

and

loca

l ve

geta

tion,

bam

boo,

wer

e co

nsid

ered

, bu

t th

ese

mea

sure

s ar

e ei

ther

inef

fect

ive

and/

or to

o ex

pens

ive

to im

plem

ent.

As

a re

sult,

Vet

iver

Sys

tem

tech

nolo

gy w

as im

plem

ente

d as

a la

st r

esor

t.(T

uon

Van

, Coo

rdin

ator

Cam

bodi

an V

etiv

er N

etw

ork,

per

s.co

m.)

Res

ults

of r

iver

bank

stab

ilisa

tion

wor

ks in

Aus

tral

ia, C

hina

, Mad

agas

car

and

Vie

tnam

hav

e sh

own

that

the

stif

f ve

tiver

sho

ots

redu

ced

flow

ve

loci

ty, h

ence

ero

sive

pow

er, a

nd it

s de

ep a

nd e

xten

sive

roo

t sys

tem

re

info

rce

the

soil

and

hold

s it

firm

ly to

the

grou

nd, r

esul

ting

in a

ver

y ef

fect

ive

stab

ilisi

ng m

echa

nism

. It i

s ex

pect

ed th

at th

is m

echa

nism

is

also

eff

ectiv

e w

heth

er t

he v

etiv

er i

s al

ive

or d

ead

in t

he s

hort

ter

m.

The

refo

re w

hen

fully

est

ablis

hed

vetiv

er w

ould

con

trol

/red

uce

the

eros

ion

on th

e ba

nk o

f th

e M

ekon

g un

der

flood

.

Sout

h A

fric

an e

xper

ienc

e an

d C

hine

se r

esea

rch

show

ed t

hat

vetiv

er

coul

d su

rviv

e up

to

3 m

onth

s un

der

clea

n, c

lear

wat

er a

nd s

till

cond

ition

s. H

owev

er it

is n

ot k

now

n ho

w lo

ng v

etiv

er c

ould

sur

vive

67

Ph

oto

16:

Ero

ded

ban

k b

efo

re (

up

per

) an

d a

fter

ear

thw

ork

(lo

wer

).

unde

r m

uddy

, tu

rbul

ent

and

fast

flow

ing

cond

ition

s. I

t w

as e

xpec

ted

that

mud

dy r

iver

wat

er w

ould

aff

ect

vetiv

er g

row

th d

ue t

o lo

w l

ight

tr

ansm

issi

on.

The

ero

ded

bank

was

firs

t res

hape

d an

d fir

mly

pac

ked

to 3

00 g

radi

ent,

with

a v

ertic

al d

rop

of a

ppro

xim

atel

y 8m

- p

hoto

16.

To

prov

ide

max

imum

pro

tect

ion

vetiv

er w

as p

lant

ed in

a g

rid

patte

rn, b

oth

on th

e

68

cont

our

line

alon

g th

e ba

nk (

hori

zont

al r

ow)

to r

educ

e w

ave

eros

ion

and

up a

nd d

own

the

slop

e (v

ertic

al r

ow)

to r

educ

e flo

w v

eloc

ity. T

he

spac

ing

of t

he h

oriz

onta

l ro

ws

is 1

m a

part

with

pla

nt d

ensi

ty o

f 10

pl

ant/m

and

ver

tical

row

s ar

e sp

aced

at 2

m a

part

with

pla

nt d

ensi

ty o

f 5p

lant

/m. T

he p

lant

ing

was

fer

tiliz

ed w

ith b

oth

man

ure

and

chem

ical

fe

rtili

zers

to e

nsur

e m

axim

um g

row

th -

pho

to 1

7.

Ph

oto

17:

On

e m

on

th (

up

per

) an

d s

even

mo

nth

s af

ter

pla

nti

ng

(lo

wer

).

69

Seve

n m

onth

s af

ter

plan

ting,

with

int

ensi

ve m

aint

enan

ce (

fert

ilise

r, w

ater

ing

and

wee

d co

ntro

l), t

he v

etiv

er s

tand

was

1.5

m h

igh.

To

test

th

e su

rviv

al r

ate

of v

etiv

er u

nder

mud

dy c

ondi

tions

, som

e se

ctio

ns o

f th

e sl

ope

wer

e tr

imm

ed d

own

to 5

0cm

hig

h be

fore

floo

ding

.

Ph

oto

18:

Flo

od

wat

er s

tart

ed c

om

ing

up

(u

pp

er);

an

d d

ead

lo

oki

ng

vet

iver

on

low

er s

lop

e af

ter

wat

er r

etre

ats

(lo

wer

).

70

As

expe

cted

the

site

was

ful

ly fl

oode

d ni

ne m

onth

s af

ter

plan

ting,

co

veri

ng t

he w

hole

slo

pe a

nd h

ighe

r gr

ound

. A

lthou

gh v

etiv

er w

as

not f

ully

mat

ure

it su

cces

sful

ly s

topp

ed th

e er

osio

n. O

n th

e up

per

part

of

the

slop

e, w

here

sub

mer

genc

e tim

e w

as s

hort

er (

up to

two

mon

ths)

an

d sh

allo

wer

dep

th, v

etiv

er g

row

th w

as n

ot a

ffec

ted

and

cont

inue

d to

gr

ow u

nder

wat

er. I

t was

exp

ecte

d th

at p

lant

s on

the

botto

m p

art o

f the

sl

ope,

whi

ch w

as s

ubm

erge

d fo

r 6

mon

ths

and

unde

r 14

m o

f m

uddy

w

ater

, vet

iver

wou

ld b

e ba

dly

affe

cted

. But

sur

pris

ingl

y, a

lthou

gh th

ey

all l

ook

dead

onl

y a

few

wer

e ac

tual

ly d

ead

- ph

oto

18.

The

fol

low

ings

obs

erva

tions

and

con

clus

ion

wer

e re

cord

ed:

• th

e fir

st 3

row

s at

the

base

of t

he s

lope

all

surv

ived

! The

se ro

ws

wer

e su

bmer

ged

for

5-6

mon

ths

unde

r 14

m o

f m

uddy

wat

er.

The

y w

ere

not c

ut (

1.5m

tall)

bef

ore

the

wat

er s

tart

ed to

ris

e.•

the

next

5 r

ows

up,

the

vetiv

er w

as c

ut t

o 50

cm a

nd t

hey

all

died

bec

ause

they

wer

e al

l cov

ered

by

mud

.•

the

rest

of t

he s

lope

sta

rtin

g fr

om ro

ws

9, w

ere

also

cut

to 5

0cm

, bu

t all

surv

ived

bec

ause

the

mud

did

n't f

ully

cov

er th

em.

• pl

ants

from

upp

er s

ectio

n ac

tual

ly g

rew

und

er w

ater

dur

ing

the

flood

.•

Unc

ut p

lant

s su

rviv

ed b

ette

r -

phot

o 19

low

er.

• an

d th

e th

ick

mud

cov

er k

illed

them

- p

hoto

19

uppe

r.

But

mos

t im

port

antly

, ve

tiver

pla

ntin

g di

d no

t on

ly s

top

the

bank

er

osio

n, i

t al

so a

ccum

ulat

ed a

thi

ck c

over

of

allu

vial

silt

bet

wee

n th

e ro

ws

- ph

oto

20. O

n cl

oser

exa

min

atio

n, t

his

thic

k si

lt co

ver

was

the

ca

use

of v

etiv

er d

eath

in

som

e se

ctio

ns o

f th

e sl

ope.

Whe

re t

he m

ud

cove

r w

as n

ot to

o th

ick,

vet

iver

sho

ots

emer

ged

late

r -

phot

o 21

. The

de

ad p

lant

s ha

ve b

een

repl

aced

and

pla

ntin

g w

ill b

e ex

tend

ed to

eve

n lo

wer

are

a of

the

slop

e -

phot

o 21

.

The

abo

ve r

esul

ts s

how

that

:•

vetiv

er c

an s

urvi

ve u

p to

5-6

mon

ths

unde

r 14

m o

f m

uddy

w

ater

• un

cut s

hoot

s im

prov

e its

sur

viva

l und

er w

ater

• ve

tiver

is

kille

d w

hen

cove

red

with

or

buri

ed u

nder

thi

ck

allu

vial

mud

71

Ph

oto

19:

Dea

d v

etiv

er d

ue

to t

hic

k al

luvi

al s

ilt d

epo

sit

(up

per

); a

nd

re-

gro

wth

if t

he

mu

d w

as n

ot

too

th

ick

(lo

wer

).

It c

an b

e co

nclu

ded

that

whe

n co

rrec

tly d

esig

ned

and

impl

emen

ted,

ve

tiver

pla

ntin

g is

ver

y ef

fect

ive

in c

ontr

ollin

g er

osio

n on

the

bank

of

fast

flow

ing

rive

r eve

n un

der fl

ood

cond

ition

s an

d de

ep a

nd p

rolo

nged

su

bmer

genc

e in

mud

dy w

ater

. In

add

ition

it

enco

urag

es a

lluvi

al s

ilt

depo

sitio

n an

d ov

er ti

me

may

eve

ntua

lly r

ecla

im th

e er

oded

ban

ks.

72

Ph

oto

20:

Up

per

an

d lo

wer

: allu

vial

silt

dep

osi

t bet

wee

n v

etiv

er r

ow

s o

n

low

er p

art

of

the

slo

pe.

73

Ph

oto

21:

Fu

lly r

ecov

ered

aft

er th

e fl

oo

d (u

pp

er) a

nd

new

pla

nti

ng

on

the

bar

e lo

wer

sec

tio

n o

f sl

op

e (l

ow

er).

5.3

VS

appl

icat

ion

for

coas

tal e

rosi

on c

ontr

olH

uge

sea

dike

s w

ith re

vetm

ent p

rote

ctio

n bu

ilt fr

om tr

aditi

onal

“ha

rd”

mat

eria

l suc

h as

blo

ck c

oncr

etes

or

big

rock

hav

e gi

ven

good

res

ults

. T

he h

eigh

t of

the

se s

ea d

ikes

sho

uld

be s

uffic

ient

to

prot

ect

the

area

74

insi

de th

e co

asta

l floo

d de

fenc

e sy

stem

. How

ever

they

are

qui

te c

ostly

to

impl

emen

t and

mat

eria

ls a

re n

ot a

lway

s av

aila

ble.

In o

rder

to re

duce

to

tal

cost

, th

e tr

aditi

onal

rev

etm

ent

coul

d be

rep

lace

d by

che

aper

m

ater

ials

. A

com

bina

tion

of “

hard

” an

d “s

oft”

mat

eria

ls i

s a

good

al

tern

ativ

e so

lutio

n. V

etiv

er g

rass

is

wel

l-kn

own

as b

ioen

gine

erin

g sp

ecie

s in

sta

biliz

ing

inne

r slo

pes,

redu

cing

run-

off a

nd c

ontr

ollin

g so

il lo

ss. R

ecen

tly, i

t has

bee

n pl

ante

d on

out

er s

lope

as

sea

dike

pro

tect

ion

as w

ell

- ph

oto

22.

How

ever

the

und

erst

andi

ng o

f th

e pr

oces

ses

and

prop

ertie

s be

twee

n w

aves

and

Vet

iver

gra

ss is

stil

l lim

ited.

Ph

oto

22:

Vet

iver

pla

nte

d o

n t

he

insi

de

of

Hai

Hau

sea

dik

e (u

pp

er)

and

o

uts

ide

(lo

wer

).

75

Fig

ure

5: W

ave

run

up r

educ

tion

by

veti

ver

row

s (u

pper

) w

ave

run

up r

educ

tion

by

plan

t den

sity

(lo

wer

).

Rec

ently

the

Dep

artm

ent o

f H

ydra

ulic

Eng

inee

ring

at D

elft

Tec

hnic

al

Uni

vers

ity in

Hol

land

con

duct

ed re

sear

ch o

n th

e us

e of

vet

iver

gra

ss o

n th

e d

ike

oute

r sl

ope

to r

educ

e w

ave

run

up (

over

topp

ing

disc

harg

es)

76

Fig

ure

6: W

ave

run

on th

e ou

ter

wal

l (up

per)

and

con

stru

ctio

n co

st

savi

ng w

ith

and

wit

hout

vet

iver

(lo

wer

).

so th

at s

ea d

ike

cres

t can

be

redu

ced.

A p

hysi

cal m

odel

was

con

duct

ed

usin

g fu

lly g

row

n V

etiv

er g

rass

hed

ges

and

wav

e pa

ram

eter

s in

fro

nt

of th

e he

dges

. Exp

erim

enta

l res

ults

hav

e sh

own

that

:•

Res

ista

nce

to fl

ow b

y V

etiv

er h

edge

var

ies

with

gra

ss d

ensi

ty

77

- fig

ure

5.•

Res

ista

nce

(Man

ning

coe

ffici

ent)

var

ies

with

flow

dep

th a

nd

vetiv

er p

rovi

ded

2.5

times

gre

ater

res

ista

nce

than

bar

e sl

ope

• V

etiv

er g

rass

hed

ges

can

with

stan

d flo

w o

f ba

ckw

ater

up

to

near

ly 0

.4m

dep

th.

• T

he ro

ughn

ess

coef

ficie

nt o

f Vet

iver

gra

ss, d

epen

ding

on

gras

s de

nsity

var

ies

betw

een

0.33

and

0.4

1.

• T

he r

educ

tion

of w

ave

over

topp

ing

of m

ore

than

60%

- fi

gure

5.

Whe

n th

is m

odel

was

app

lied

on a

sea

dike

in V

ietn

am, r

esul

t sh

ows

that

a r

educ

tion

of 0

.5m

of

the

cres

t he

ight

is

feas

ible

fo

r up

grad

ing

the

pres

ent

sea

dike

in

Hai

Hau

, V

ietn

am.

In

dolla

r ter

m, t

he c

ost o

f con

stru

ctio

n pe

r met

er le

ngth

of $

147.

5 w

ithou

t vet

iver

, red

uces

to $

128.

96 w

hen

two

vetiv

er ro

ws

are

plan

ted

on th

e ou

ter

slop

e, a

red

uctio

n of

12.

6%.

Thi

s ca

se s

how

s th

at V

etiv

er g

rass

is

a go

od s

olut

ion

for

sea

dike

s in

or

der

to r

educ

e w

ave

run-

up o

n th

e ou

ter

slop

e an

d de

crea

ses

the

cost

fo

r s

ea d

ike

upgr

adin

g -

figur

e 6

(Vu

Min

h A

nh, 2

007)

.

With

sup

port

of

the

Will

iam

Don

ner

Foun

datio

n an

d w

ith t

echn

ical

su

ppor

t by

Pau

l T

ruon

g, L

e V

an D

u fr

om H

o C

hi M

inh

City

Agr

o-Fo

rest

ry U

nive

rsity

in

2001

ini

tiate

d w

ork

on a

cid

sulf

ate

soil

to

stab

ilize

can

al a

nd i

rrig

atio

n ch

anne

ls a

nd t

he s

ea d

ike

syst

em i

n G

o C

ong

prov

ince

. Vet

iver

gre

w v

igor

ousl

y on

the

em

bank

men

ts i

n ju

st

a fe

w m

onth

s, d

espi

te p

oor

soil.

It

is

now

pro

tect

ing

the

sea

dike

, pr

even

ting

surf

ace

eros

ion,

an

d fa

cilit

atin

g th

e es

tabl

ishm

ent

of

ende

mic

spe

cies

- p

hoto

23

and

24.

78

Ph

oto

23:

Pla

nte

d b

ehin

d n

atu

ral

man

gro

ve o

n a

n a

cid

su

lfat

e so

il se

a d

ike

in G

o C

on

g p

rovi

nce

, vet

iver

red

uce

s su

rfac

e er

osi

on

an

d f

ost

ers

the

re-e

stab

lish

men

t o

f lo

cal g

rass

es.

79

Ph

oto

24:

In

No

rth

Vie

tnam

; U

pp

er:

Vet

iver

pla

nte

d o

n o

ute

r si

de

of

a n

ewly

bu

ilt s

ea d

ike

in N

am D

inh

pro

vin

ce; l

ow

er: o

n th

e in

ner

sid

e o

f th

e d

ike,

pla

nte

d b

y th

e lo

cal D

ike

Dep

artm

ent.

80

5.4

VS

appl

icat

ion

to s

tabi

lize

road

bat

ter

Follo

win

g su

cces

sful

tria

ls b

y Ph

am H

ong

Duc

Phu

oc (

Ho

Chi

Min

h C

ity A

gro-

Fore

stry

Uni

vers

ity)

and

Thi

en S

inh

Co.

in

usin

g ve

tiver

to

sta

biliz

e cu

t sl

opes

in

Cen

tral

Vie

tnam

, in

200

3 th

e M

inis

try

of

Tra

nspo

rt a

utho

rize

d th

e w

ide

use

of v

etiv

er t

o st

abili

ze s

lope

s al

ong

hund

reds

of k

ilom

etre

s of t

he n

ewly

con

stru

cted

Ho

Chi

Min

h H

ighw

ay

and

othe

r na

tiona

l, pr

ovin

cial

roa

ds i

n Q

uang

Nin

h, D

a N

ang,

and

K

hanh

Hoa

pro

vinc

es -

pho

to 2

5.

Ph

oto

25:

Up

per

: V

etiv

er s

tab

ilize

s cu

t sl

op

es a

lon

g t

he

Ho

Ch

i M

inh

H

igh

way

; lo

wer

: b

oth

al

on

e an

d

in

com

bin

atio

n

wit

h

trad

itio

nal

m

easu

res.

Thi

s pr

ojec

t is

ce

rtai

nly

one

of

the

larg

est

VS

appl

icat

ions

in

in

fras

truc

ture

pr

otec

tion

in

the

wor

ld.

The

en

tire

Ho

Chi

M

inh

81

Hig

hway

is m

ore

than

300

0 km

(186

4 m

iles)

long

. It

is b

eing

and

will

be

pro

tect

ed b

y ve

tiver

pla

nted

und

er a

var

iety

of

soils

and

clim

ate

Ph

oto

26:

Up

per

- I

f n

ot

pro

per

ly p

rote

cted

ro

ck/s

oil

fro

m t

his

was

te

du

mp

will

was

h f

ar d

ow

nst

ream

. L

ow

er -

im

pac

tin

g a

do

wn

stre

am v

il-la

ge

in A

Lu

oi d

istr

ict,

Th

ua

Tie

n H

ue

pro

vin

ce.

from

ske

leta

l m

ount

aino

us s

oils

and

col

d w

inte

r in

the

Nor

th t

o ex

trem

ely

acid

ic a

cid

sulp

hate

soi

l an

d ho

t, hu

mid

clim

ate

in t

he

Sout

h. T

he e

xten

sive

use

of

vetiv

er t

o st

abili

ze c

ut s

lope

s w

orks

, for

ex

ampl

e:•

App

lied

prim

arily

as

a sl

ope

surf

ace

prot

ectio

n m

easu

re,

it gr

eatly

redu

ces

run-

off i

nduc

ed e

rosi

on, t

hat w

ould

oth

erw

ise

wre

ak h

avoc

dow

nstr

eam

- p

hoto

26.

• B

y pr

even

ting

shal

low

fai

lure

s, it

sta

biliz

es c

ut s

lope

s w

hich

gr

eatly

red

uces

the

num

ber

of d

eep

slop

e fa

ilure

s -

phot

o 27

.•

In s

ome

case

s w

here

dee

p sl

ope

failu

res

do o

ccur

, vet

iver

stil

l

82

does

a v

ery

good

job

in s

low

ing

dow

n th

e fa

ilure

s an

d re

duc-

ing

the

faile

d m

ass,

and

;•

It m

aint

ains

the

rur

al a

esth

etic

and

eco

-fri

endl

ines

s of

the

ro

ad.

Ph

oto

27:

Da

Deo

Pas

s, Q

uan

g B

inh

: U

pp

er:

Veg

etat

ion

cov

er i

s d

e-st

roye

d,

reve

alin

g u

gly

an

d c

on

tin

uo

us

failu

res

of

cut

slo

pes

; lo

wer

: V

etiv

er r

ow

s o

n to

p o

f th

e sl

op

e ve

ry s

low

ly s

qu

eeze

do

wn

, co

nsi

der

ably

re

du

cin

g t

he

faile

d m

ass.

On

a ro

ad l

eadi

ng t

o th

e H

o C

hi M

inh

Hig

hway

Pha

m H

ong

Duc

Ph

uoc

dem

onst

rate

d cl

earl

y ho

w V

S sh

ould

be

appl

ied,

as

wel

l as

its

ef

fect

iven

ess

and

sust

aina

bilit

y -

phot

o 28

.

He

care

fully

mon

itore

d th

e de

velo

pmen

t of

vet

iver

: its

est

ablis

hmen

t (6

5-10

0%),

togr

owth

(95

-160

cm

(37

-63”

) af

ter

six

mon

ths)

, till

erin

g ra

te (

18-3

0 til

lers

per

pla

nt),

and

roo

t de

pth

on t

he b

atte

r -

tabl

e 6.

83

Tabl

e 6:

Vet

iver

roo

t de

pth

on H

on B

a ro

ad b

atte

rs.

The

suc

cess

es a

nd fa

ilure

s us

ing

vetiv

er to

pro

tect

cut

slo

pes

alon

g th

e H

o C

hi M

inh

Hig

hway

are

inst

ruct

ive:

• Sl

opes

mus

t fir

st b

e in

tern

ally

sta

ble.

Sin

ce v

etiv

er i

s m

ost

help

ful

at m

atur

ity,

slop

es m

ay f

ail

in t

he i

nter

im.

Vet

iver

be

gins

to

stab

ilize

a s

lope

at

thre

e to

fou

r m

onth

s, a

t ea

rli-

est.

The

refo

re, t

he ti

min

g of

pla

ntin

g is

als

o ve

ry im

port

ant i

f sl

ope

failu

re d

urin

g th

e ra

iny

seas

on is

to b

e av

oide

d.

• A

ppro

pria

te s

lope

ang

le s

houl

d no

t exc

eed

45-5

0º.

• R

egul

ar t

rim

min

g w

ill e

nsur

e co

ntin

ued

grow

th a

nd t

iller

ing

of th

e gr

ass,

and

thus

ens

ure

dens

e, e

ffec

tive

hedg

erow

s.

Pos

itio

n on

th

e ba

tter

Roo

t de

pth

(cm

/inch

)6

mon

ths

12 m

onth

s1.

5 ye

ar2

year

s

Cut

Bat

ter

1B

otto

m

70/2

812

0/47

12

0/47

120/

47

2M

iddl

e 72

/28

110/

43

100/

3914

5/57

3To

p 72

/28

105/

41

105/

41

187/

74

Fill

Bat

ter

4B

otto

m

82/3

2 95

/37

95/3

7 18

0/71

5M

iddl

e 85

/33

115/

45

115/

45

180/

71

6To

p 68

/27

70/2

8 75

/30

130/

51

84

Ph

oto

28:

Ph

am H

on

g D

uc

Ph

uo

c, a

ro

ad p

rote

ctio

n p

roje

ct i

n K

han

h

Ho

a p

rovi

nce

, ro

ad t

o H

on

Ba)

: lef

t tw

o p

ho

tos:

sev

ere

ero

sio

n o

n n

ewly

bu

ilt b

atte

r o

ccu

rs a

fter

on

ly a

few

rai

ns;

rig

ht

two

ph

oto

s: e

igh

t m

on

ths

afte

r ve

tive

r p

lan

tin

g: V

etiv

er s

tab

ilize

d t

his

slo

pe,

to

tally

sto

pp

ing

an

d

pre

ven

tin

g f

urt

her

ero

sio

n d

uri

ng

th

e n

ext

wet

sea

son

.

6. C

ON

CL

USI

ON

S

Follo

win

g co

nsid

erab

le

rese

arch

an

d th

e su

cces

ses

of

the

man

y ap

plic

atio

ns p

rese

nted

in th

is h

andb

ook,

we

now

hav

e en

ough

evi

denc

e th

at v

etiv

er, w

ith it

s m

any

adva

ntag

es a

nd v

ery

few

dis

adva

ntag

es, i

s a

very

eff

ectiv

e, e

cono

mic

al, c

omm

unity

-bas

ed a

nd e

nvir

onm

enta

lly-

frie

ndly

sust

aina

ble

bioe

ngin

eeri

ng to

ol th

at p

rote

cts i

nfra

stru

ctur

e an

d m

itiga

tes

natu

ral d

isas

ters

, and

, onc

e es

tabl

ishe

d, th

e ve

tiver

pla

ntin

gs

will

last

for

dec

ades

with

littl

e, if

any

mai

nten

ance

. VS

has

been

use

d su

cces

sful

ly i

n m

any

coun

trie

s in

the

wor

ld,

incl

udin

g A

ustr

alia

, B

razi

l, C

entr

al A

mer

ica,

C

hina

, E

thio

pia,

In

dia,

It

aly,

M

alay

sia,

N

epal

, Phi

lippi

nes,

Sou

th A

fric

a, S

ri L

anka

, Tha

iland

, Ven

ezue

la, a

nd

85

Vie

tnam

. H

owev

er,

it m

ust

be s

tres

sed

that

the

mos

t im

port

ant

key

to s

ucce

ss a

re g

ood

qual

ity p

lant

ing

mat

eria

l, pr

oper

des

ign,

cor

rect

pl

antin

g te

chni

ques

.

7. R

EF

ER

EN

CE

S

Bra

cken

, N

. an

d T

ruon

g, P

.N.

(2 0

00).

App

licat

ion

of V

etiv

er G

rass

Te

chno

logy

in

the

stab

iliza

tion

of r

oad

infr

astr

uctu

re i

n th

e w

et t

ropi

cal

regi

on o

f A

ustr

alia

. Pr

oc.

Seco

nd I

nter

natio

nal

Vet

iver

Con

f. T

haila

nd, J

anua

ry 2

000.

Che

ng H

ong,

Xia

ojie

Yan

g, A

ipin

g L

iu,

Hen

gshe

ng F

u, M

ing

Wan

(2

003)

. A S

tudy

on

the

Perf

orm

ance

and

Mec

hani

sm o

f So

il-re

info

rcem

ent b

y H

erb

Roo

t Sys

tem

. Pro

c. T

hird

Int

erna

tiona

l V

etiv

er C

onf.

Chi

na, O

ctob

er 2

003.

Dal

ton,

P. A

., Sm

ith, R

. J. a

nd T

ruon

g, P

. N. V

. (1

996)

. Vet

iver

gra

ss

hedg

es f

or e

rosi

on c

ontr

ol o

n a

crop

ped

flood

plai

n, h

edge

hy

drau

lics.

Agr

ic. W

ater

Man

agem

ent:

31(1

, 2)

pp 9

1-10

4.H

engc

haov

anic

h, D

. (1

998)

. V

etiv

er g

rass

for

slo

pe s

tabi

lizat

ion

and

eros

ion

cont

rol,

with

par

ticul

ar r

efer

ence

to

engi

neer

ing

appl

icat

ions

. Te

chni

cal

Bul

letin

N

o.

1998

/2.

Paci

fic

Rim

V

etiv

er N

etw

ork.

Offi

ce o

f th

e R

oyal

Dev

elop

men

t Pr

ojec

t B

oard

, Ban

gkok

, Tha

iland

.H

engc

haov

anic

h, D

. an

d N

ilaw

eera

, N

. S.

(19

96).

An

asse

ssm

ent

of

stre

ngth

pro

pert

ies

of v

etiv

er g

rass

roo

ts i

n re

latio

n to

slo

pe

stab

ilisa

tion.

Pro

c. F

irst

Int

erna

tiona

l V

etiv

er C

onf.

Tha

iland

pp

. 153

-8.

Jasp

ers-

Fock

s, D

.J a

nd A

. Alg

era

(200

6). V

etiv

er G

rass

for R

iver

Ban

k Pr

otec

tion.

Pro

c. F

ourt

h V

etiv

er In

tern

atio

nal C

onf.

Ven

ezue

la,

Oct

ober

200

6.L

e V

an D

u, a

nd T

ruon

g, P

. (20

03).

Vet

iver

Sys

tem

for E

rosi

on C

ontr

ol

on D

rain

age

and

Irri

gatio

n C

hann

els

on S

ever

e A

cid

Sulp

hate

So

il in

Sou

ther

n V

ietn

am.

Proc

. T

hird

Int

erna

tiona

l V

etiv

er

Con

f. C

hina

, Oct

ober

200

3.Pr

ati A

mat

i, Sr

l (20

06).

She

ar s

tren

gth

mod

el. "

PRA

TI A

RM

AT

I Sr

l"

info

@pr

atia

rmat

i.it

. T

ruon

g, P

. N. (

1998

). V

etiv

er G

rass

Tec

hnol

ogy

as a

bio

-eng

inee

ring

to

ol f

or i

nfra

stru

ctur

e pr

otec

tion.

Pro

ceed

ings

Nor

th R

egio

n Sy

mpo

sium

. Q

ueen

slan

d D

epar

tmen

t of

Mai

n R

oads

, C

airn

s

86

Aug

ust,

1998

.T

ruon

g, P

., G

ordo

n, I

. an

d B

aker

, D

. (1

996)

. To

lera

nce

of v

etiv

er

gras

s to

som

e ad

vers

e so

il co

nditi

ons.

Pro

c. F

irst

Int

erna

tiona

l V

etiv

er C

onf.

Tha

iland

, Oct

ober

200

3.X

ia, H

. P. A

o, H

. X. L

iu, S

. Z. a

nd H

e, D

. Q. (

1999

). A

pplic

atio

n of

the

vetiv

er g

rass

bio

-eng

inee

ring

tec

hnol

ogy

for

the

prev

entio

n of

hig

hway

slip

page

in

sout

hern

Chi

na.

Inte

rnat

iona

l V

etiv

er

Wor

ksho

p, F

uzho

u, C

hina

, Oct

ober

199

7.X

ie,

F.X

. (1

997)

. V

etiv

er f

or h

ighw

ay s

tabi

lizat

ion

in J

ian

Yan

g C

ount

y: D

emon

stra

tion

and

Ext

ensi

on. P

roce

edin

gs a

bstr

acts

. In

tern

atio

nal

Vet

iver

W

orks

hop,

Fu

zhou

, C

hina

, O

ctob

er

1997

.

87

IND

EX

Chr

ysop

ogon

zi

zani

oide

s i,

9cl

imat

ic v

aria

tion

3C

. nem

oral

is 9

coas

tal e

rosi

on 1

7, 4

6co

asta

l ero

sion

con

trol

73

coas

tal e

rosi

on c

ontr

ol

- ap

plic

atio

ns

73co

asta

l san

d du

nes

5co

mm

unity

in

volv

emen

t 43

ompu

ter

mod

ellin

g 40

cons

and

lim

itatio

ns

of p

lant

ing

vege

tatio

n on

sl

op 2

6cu

lver

t abu

tmen

ts 3

8cu

lver

t inl

ets

38

culv

ert o

utle

ts 3

8cu

t and

fill

batte

rs 3

7cu

t slo

pe 1

9, 4

5C

. ziz

anio

ides

9

D debr

is fl

ows

17

deci

sion

-mak

ing:

pr

ecau

tions

42

Dep

artm

ent o

f H

ydra

ulic

E

ngin

eeri

ng a

t D

elft

Tec

hnic

al

Uni

vers

ity 7

5di

ke a

nd d

am b

atte

r st

abili

satio

n 3

8di

seas

es a

nd fi

re.

2di

ssol

ved

nutr

ient

s

such

as

N a

nd

P an

d he

avy

met

als

in

pollu

ted

wat

er.

3di

stur

bed

land

s. 4

driv

ing

forc

es 1

9dr

ough

t 3

E eart

hqua

kes

18

ecol

ogic

al

char

acte

rist

ics

4

Elis

e Pi

nner

s ii

extr

eme

acid

sul

phat

e

6ex

trem

e te

mpe

ratu

re 3

F farm

dam

bat

ters

38

fast

cur

rent

66

fenc

ing

and

cari

ng 4

8fe

rtili

zing

48

Fiji

-vet

iver

cul

tivar

14

fire

4fla

sh fl

oodi

ng 1

7flo

od 3

flood

miti

gatio

n 4

6fr

ost

3, 6

G grad

ed c

onto

ur te

rrac

es

37gr

avita

tiona

l for

ces

20

grav

itatio

nal s

tres

ses.

A acid

ity 3

adap

tabi

lity

rang

e 7

adva

ntag

es a

nd

disa

dvan

tage

s of

V

etiv

er S

yste

m

38al

kalin

ity 3

appl

icat

ions

of

VS

in

natu

ral d

isas

ter

miti

gatio

n an

d in

fras

truc

ture

pr

otec

tion

37

appl

icat

ion

to c

ontr

ol

rive

r ba

nk

eros

ion

63

B bam

boo

28

bioe

ngin

eeri

ng

tech

niqu

e 1

bio-

filte

r 3

0br

idge

s 3

8

C Can

Tho

Uni

vers

ity 6

3C

asua

rina

s tr

ees

28

char

acte

rist

ics

of

vetiv

er s

uita

ble

for

slop

e st

abili

satio

n 2

9C

hrys

opog

on la

wso

nii

9C

hrys

opog

on

nem

oral

is 9

Chr

ysop

ogon

nig

rita

na

13, 1

4

88

19gr

id p

atte

rn 6

7gu

llies

38

H hard

str

uctu

res:

pr

otec

tion

38

heav

y m

etal

s 3

hedg

erow

iH

engc

haov

anic

h 3

5H

engc

haov

anic

h, D

iti

iiihe

rbic

ides

3hi

ghw

ays

37

high

way

sta

biliz

atio

n

iiiH

o C

hi M

inh

Hig

hway

80

hydr

aulic

for

ces

20

hydr

aulic

mod

el o

f flo

odin

g 3

6

I infr

astr

uctu

re

prot

ectio

n 4

9in

terf

ace

- co

ncre

te a

nd

soil

38

iver

ban

k er

osio

n co

ntro

l 56

J John

Gre

enfie

ld 2

K Kar

nata

ka -

vet

iver

cu

ltiva

r 1

4

L land

slid

es 1

7, 1

8lo

ngev

ity.

38

M Mad

upat

ty -

vet

iver

cu

tivar

14

mag

nesi

um 3

mai

nten

ance

and

rep

air

42m

aint

enan

ce c

osts

39

man

grov

e tr

ees

28

Mek

ong

Del

ta 6

3M

ekon

g ri

ver

66

Mon

to -

vet

iver

cu

ltiva

r 9

, 14

N natu

ral d

isas

ters

17,

49

natu

ral m

angr

ove

78

nort

h In

dian

acc

essi

ons

9nu

rse

plan

t 4

Nur

sery

44

P Paul

Tru

ong

iipe

stic

ides

3pe

sts:

res

ista

nce

2ph

ysio

logi

cal

char

acte

rist

ics

3

plan

ning

and

or

gani

satio

n:

42pl

antin

g: p

repa

ratio

n

44pl

antin

g tim

e 4

3pl

ant s

hadi

ng 4

plan

t sho

ots

2pl

ant:

wat

erin

g ne

eds

47

poin

t sou

rce

ipo

re w

ater

pre

ssur

e

21, 3

7Pr

ati A

mat

i 40

proc

urem

ent

43

R railw

ays

37

resi

stin

g fo

rces

19,

21

rhiz

omes

2ri

gid

stru

ctur

e:

prot

ectio

n 2

4ri

ver

bank

ero

sion

17,

56

rive

r ba

nk p

rote

ctio

n

59ri

ver

bank

s 3

8ri

verb

ank

stab

ilisa

tion

66

road

bat

ter

19,

45,

65

Rob

erty

1ro

ot d

epth

83

root

dep

th o

n ro

ad

batte

r 8

3ro

ot d

iam

eter

di

stri

butio

n 3

3ro

ot g

row

th -

eff

ect o

f so

il te

mpe

ratu

re

7ro

ots

2, 1

2

S salin

ity 3

sand

dun

e pr

otec

tion

49

sea

dike

- a

cid

sulp

hate

so

ils 7

8se

a di

kes

18

sedi

men

t filte

r 2

slop

e an

gle

limita

tions

on

esta

blis

hmen

t of

vege

tatio

n 2

7

89

and

eros

ion

copn

trol

19

V Vet

iver

Gra

ss -

A

Hed

ge A

gain

st

Ero

sion

2V

ietn

am I

nstit

ute

of

Geo

scie

nces

an

d M

iner

al

Res

ourc

es i

i

W wat

er r

etai

ning

st

ruct

ures

in

stab

ility

46

wat

er s

prea

der

2w

ave

actio

n 3

8, 6

6w

ave

run

up r

educ

tion

75

Wes

t Afr

ica

13

Will

iam

Don

ner

Foun

datio

n

63,7

7W

orld

Ban

k 1

slop

e fa

ilure

22

slop

e pr

ofile

19

slop

e st

abili

ty 1

9sl

ope

stab

ility

- g

ener

al

phys

ical

eff

ects

of

veg

etat

ion

26

sodi

city

3so

il an

d w

ater

co

nser

vatio

n 1

soil

pH 3

sout

h In

dian

ac

cess

ions

14

stab

iliza

tion,

hig

hway

iii

stab

ilize

roa

d ba

tter

65

stol

ons

2su

bmer

genc

e 3

Suns

hine

- v

etiv

er

culti

var

9, 1

4

T tech

nica

l pre

caut

ions

42

tens

ile a

nd s

hear

st

reng

th o

f V

etiv

er r

oots

33

tens

ile s

tren

gth

of

vetiv

er r

oots

35

tens

ile s

tren

gth:

oth

er

plan

t roo

ts 3

4tim

ing

42

timin

g: p

lant

ing

43

Tra

n Ta

n V

an i

i

U unde

rgro

und

crow

n 2

Upl

and

natu

ral s

lope

st

abili

zatio

n

9091

92