beach fill at two coasts of different configurations

8/11/2019 Beach Fill at Two Coasts of Different Configurations

1/15

CHAPTER 7 7

Beach

fillattwocoastsofdifferentconfigurations

+

IchiroDeguchi

and

Toru

Sawaragi

ABSTRACT

Movements

f

orrow

and

eplenished

t

wo

oasts

f

ifferent

configurationsrenvestigatedynalyzingheopographic

ata

whichereurveyederiodicallyfterheeach

ill

lacements.

One

s

ong

traight

each

nd

orrow

andaslacedehind

submerged

reakwater.

nother

s

ocket

eachhichas

n

rc-

shoreline

with

groyne

at

one

end

and

aheadlandatanother.

It

s

ound

hat

he

mountf

orrow

andoved

n

he

ong-

shoreirection

urpasses

he

mountforrowandransportedn

theross-shoreirectionegardless

f

he

hapef

he

oast.

clearorrelations

lso

oundetweenisplacementsfhoreline

andhangesfectional

reas.

heseesultsmplyhathee-

formation

f

he

rtificiallyourished

each

nd

he

issipation

rate

ofborrow

sandcanbe

predicted

by

theso-calledne-line theory.

1. Introduction

Artificial

eachourishment

sommonly

tilized

pproach

for

reatment

f

horerotectionroblemsuchseachrosion,

wavever-toppingndon.

t

s

lso

heirect

ethod

o

maintainand

improve

recreational

benefits

in

thecoastal zone.

Inapan,herereanyoasts

here

eachillaveeen

already

eplenished.

theseoasts,tructuresuchsnff-

shore

ubmerged

reakwater,

etached

reakwater

nd

royne

haveeenonstructed

imultaneously

nrderorevent

each

ill

from

flowing

ut

from

he

replenished

field.

Howeverecausehe

ffective

eachillesignnvolveso

manyhysicalactors,hereciseegreefeachilltilization

to

stabilizea

shoreline is

notalwayspredictable.

The

bjective

fhis

tudy

s

o

nvestigate

ehaviors

f

beachilleplenishedtwooastsfifferentonfigulationsy

analyzing

uccessivelyeasured

each

rofiles

o

ffer

nformations

as

ohats

he

overning

actor

n

heeterminationfhe

effctiveness

of

beach

fill.

+Associate

rofessor

nd

+

Professor,

epartment

f

ivil

Engineering,

saka

niversity,amadaoka

-1,

uita-city,saka

565, Japan

1032


2/15

BEACHFILL

AT

TWO

COASTS

1 0 3 3

2 .

Conf

igulations

of

Two

Coasts

and

Locationof

Beach

Fill

Locations

of

twocoastsareshown

i n

Fig.l.

Keino-Matsubara

Beach

S e t o

Inland

Sea

Osaka

Asakawaeach

Pacific

cean

Fig.l

Locations

of investigated

tw oeaches

One

s

e

ino-Matsubara-Beach

hich

s

n

he

ast

ide

f

he

Awaji

sland

acing

he

eto

nland

ea

nd

as

ong

traight

beachf

bout

kmongshownn

ig.

2 a).nhisoast,est

offshore

ubmerged

reakwaterf0mongnd0mideas

irst

constructedn983nd

orrow

and

fbout000m

3

aseplenished

behind

itabout

ne

yearafter

the

construction

of

the

breakwater.

Thepperurfacefheubmergedreakwatersbout.5m

below

.L..

.W.L.,.W.L.nd.W.L.orrespondo.L.+1.8m,

D.L.+1.2m

nd.L.+0.5m.

heater

epth

as

easured

pward

rom

D.L..

he

verage

eachlpoe

s

bout/7o/10n

he

hallow

water

eg

ion sha

lower

han

2m)

nd

bout

/30

n

he

eeper

resion.

ean

rain

ize

5

o

anges

rom

.2mm

o

mm

nd

here

s

no

orrelation

etween

5

o

nd

ater

epth.

ean

raion

izef

borrow

sand

is

1.5mm.

These

data

aresummerized

in

Table 1.

Figure

b)

ndicates

ocation

f

he

ubmerged

reakwater

andhe

egion

here

each

ill

ouldelaced

ased

n

he

measuredeachrofile

ust

fter

heonstruction

f

he

ubmerged

breakwater.

Another

ssakawa-Beachhichso-calledocketeachnd

has

n

rc-shoreline

f

bout

00m

ong

nd

he

adius

f

hich

s

260m

s

hown

n

ig.3.

here

s

ockey

ead

and

t

he

outh

end

f

he

each

nd

royne

f50mong

as

onstructedn

974

athethernd.each

lope

nhallowegionshallowerhan

-3m)

isabout1/7 o1/10andabout1/30

in

thedeeperregion.


3/15

1034

COASTAL

ENGINEERING-1986

SetoInland

Sea

1983.12

a)

v 3k m

SO '

Y(

25


4/15

BEACH

FILL

AT

TWOCOASTS

1035

Table1haracteristics

of

twobeaches

Keino-Matsubara-Beach

[ d . 5 0 ]

native

sand

0.2mm 3mm

borrow

sand

. 5 m m

[Beachslope]

shallowregion 1/7-1/10

deepregion

/3 0

[waves]

winter-spring

pr ob ab i l i t y

of

appearance

ofwaveshigherthan

l m

is3 5 . ( f r o m

W-NW)

summer autumnlarge

part

ofwavesare

less

than

40cm

Asakawa-

Beach

0 . 5 m m - 3 m m

0.

4m m

and

0 .

8m m

1/7-1/10

1/30

large

partof

wavesare

less

than40cm

waveshigherthanl m

incidents

severalt i mes

ayear

in

a

typhoon

seasons.(from

SE-E)

Table

2

rogress

of

beach

fill

andtopographicsurvey

beach

f i l l

placement

o

a )

PQ

a

D

c t

s

5000m

topographic

survey

1983.12.21

1984.1.13

1984.1.30

1984.2.20

1984.3.6

1984.3.27

1984.4.27

1984.5.30

-1984.10.18

-1984.11.18

-1984.12.1

topographic

beachfill^.urvey

placement

14180m

o

a )

< U

t 16845m

v3

C O

M

.

it

.,

>:,}x

J

.

xi

r5x

0.00

0.00

o.00

ao.t

HO.

00

SOT.00

340.00 210.00 380.00 3*0.00 400.00

440.00

4(0.00

T

CM

X

wave

reaking

oint

a)

s

i-

,

t

t

,

f

_

,

ii

8

3

>W


10/15

BEACH

FILL

ATTWO

COASTS

1041

22

Southward

Y j )

1979

Xshoreline

Fig.8

hange

o f

water

depth

tookplace

during

Sept.,1979and

March,1980whenborrowsando f

16845m

wasplacedaround

shoreline

between

surveying

lines

No.7andNo.15

a t

Asakawa-Beach

22outhward

(

1980.3 980.9

X

shoreline

Q

vorthward

X(m )

0+

l

Fig.

9hannge

o f

waterdepth

took

placeduring6-monthafter

beach

f i l l

placement

a t

Asakawa-Beach


11/15

1042

COASTAL

ENGINEERING-1986

From

hese twofigures,

it

is

easily

found

that

thereplenished

borrow

sand

moved

from

the

replenished

region mainly toward both

southward and

northward

along the shoreline. As is

the

case

of

K e

ino-Matsubara-Beach,

a

few

portion

of

borrow

sand

seemed

to

be

transported

in

onshore

and

ffshore

directions.

Figures0

nd

1

how

ross-shore

ndongshoreigen-

functionsi(i,t)

nd

i(j,t)hich

orrespond

o

he

argest

eigenvalues.

X ( i )

>f,-

J

3

-

'0

* - > .

-

9J

,

*J

)

Fig.10 C r o s s - s h o r eempi ric a l

e i

genfunctionc o r r e s p o n d i n g

t o

thelargeste i genvalue .

10.0

f

l3

*3

**^?J.J.

i9

so.,

e,,;i9t

t

' ' ,

20

Y(j)

**>l

*, /J

J

.7

Fig.

11

Lo n g s h o r eempi ric a l

e i

genfunctionc o r r e s p on d i n g

to

thelargeste i g e nva l u e


12/15


13/15

1044

COASTALENGINEERING-

1986

s

/

i

i

*xxxxxxxxietitfxiu*tx*r

t

x

r

>

*'*

K

'?'l'f *

. rf->

[

*'>fw*-x

,

B)

f>rir '

Jt

*

Jt

-

t-

S^\N _:tt'?:

0.5~/s

e-oo

o.eo ac.co

uo.co itc.oo

JM.OQ 49.00

stc.oo

:;o.w

Jtc.co


14/15

BEACH

FILLATTWO

COASTS 1 0 4 5

i V ( r a )

3000

2000

1000

0-8-16

J-10-14

100(t)

6 0

4 0

2 0

Fig.13 Remaining

ratefborrowsandandvolumetric

changeatKeino-Matsubara-Beach

AV(m')

4000

3000

2000

1 0 0 0

Volume

of

replenished

borrowsand

100(X)

6 0

2 0

Fig.

14

Remaining

rate

f

borrow

sand

and

volumetric

changeat

Asakawa-Beach


15/15

1046

OASTAL

ENGINEERING-1986

Althoughorrowandf000m

3

as

lacedehindhe

ubmerged

breakwater,he

ncreasefheandolumeetweenheurveying

lines

o.8

nd

6

as

bout

300m

3

.

herefore,n

healculation

of

tn)

from

q. 4),

weused

3300m

3

for Vb.

It

s

ound

rom

his

igure

hat

he

and

olume

ust

ehind

the

ubmerged

reakwaterecreasedastndnly08 emainedwo

month

fter

heeach

ill

lacement.n

he

ther

and,

ore

han

30

f

he

orrowand

emained

etween

he

urveying

ines

o.8

nd

No.16.hiseanshatheigrationpeedforrowandsoto

fastndnly0 forrowandovedfforehan0mromhe

replenished

region.

Figure

4howsheolumetrichanges

nd

emainingatef

borrow

and

t

sakawa-Beach.t

his

each,

heolumef

and

n

the

hole

each

ncreased

t

very

each

ill

lacement.

owever,

the

emaining

ate

f

he

otal

orrow

and

eplenished

n

he

beach

rom

q. 4)

ecreasesraduallyrom0 ndinallyeaches

6 0 .hismplieshathere

s

ertainimito

eep

andithin

aocketeach

hich

illeetermined

y

he

eometrical

roperty

of thebeach,

wave

climate

andso

n.

6.

Conclusions

Movementsf

orrow

and

eplenished

t

ong

traight

each

and

ocket

each

hich

as

n

rc-shoreline

re

nvestigated

y

analyzing

he

eriodically

easured

ottom

opography

fter

he

beach

fillplacements.

It

s

ound

hat

he

mountforrow

and

oved

n

he

longshore

irection

urpasseshe

mount

forrow

andransported

inhe

ross-shore

irectionegardless

f

hehapesf

he

shorelines.learorrelationslso

ound

etweenhe

horeline

displacementsandthechangesof

sectional

areas.

References

S a w a r a g i ,

T. ,.

eguchi

nd

.S.

Lee

(1985),A

new

modelfora

p r e d i c t i o nof

beach

d e f o r m a t i o naroundarivermou t h,Proc.nt.

Sympo.Ocean

Space

Utilization'85,

2 ,

pp.229-237.

beach fill at two coasts of different configurations

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