design of stream-road crossings for aquatic organism ... · • fine-grained beds are special...

Design of Stream-Road Crossings for Aquatic Organism Passage in Vermont

6 – Stream Simulation 1

1

Passage Design Process

Pre-Design

Design: Stream Simulation, No slope, Hydraulic, or other

FINAL DESIGN

Or other option

Project Objective

Project profile and alignment

Assessment, Suitability

Select design method

2

Vermont Alternative Designs

To satisfy objectives of aquatic organism passage, alternative designs should meet these

performance standards:

– Maintain bed composition and structure• Bed and bedforms• Profile consistent with adjacent reaches• Embedded for life of the project

– Maintain velocities, turbulence and depths of adjacent reaches

3

Culvert Design for Fish Passage

RemovalReplacementRetrofit

Adjust profile

Fishway

Roughness

Baffles NaturalBedRegradeRoughened

channelGradecontrols

New

Ecological solutions at Road Crossings- +

AOP

4

Flood capacity

Floodplain Continuity

Permit valleyand Floodplain

Processes

HydraulicDesign Pass target species Stream Simulation

Pass sediment, debris, all aquatic organisms.

Ecological solutions at Road Crossings- +



10

And this is was our conclusion – stream simulation

11

Design method determined by project objectives

Project objectives• Habitat protection, restoration• River and stream continuity• Passage of fish• Passage of other aquatic organisms• Wildlife passage• Traffic, road, safety, other• Funding limits and requirements• Regulatory

Design methods

• Hydraulic

• Stream Simulation

• Low slope (active channel, No slope)

• Alternative designs

12

Stream Simulation - Premise

• Low-slope: The design of an oversized culvert in a low risk site can be simplified and built with little risk

• Hydraulic: A structure with appropriate hydraulic conditions will allow target species to swim through it.

• Stream Simulation: A channel that simulates characteristics of the adjacent natural channel, will present no more of a challenge to movement of organisms than the natural channel.

13

Stream Simulation Design



14

What is stream simulation?

• Geomorphic design

• Simulate natural channel reference reach

– Bankfull cross section shape and dimensions

– Channel slope

– Channel structure

• Channel type

• Mobility – Process, not just structure 15

Stream Simulation Conceptual Details

• Equilibrium with stream gradient and alignment.• Contain stream bed to match to bankfull width and height or

more.• Sustain channel bed shape, bed forms, elevation.

• sediments are transported from and into structure.• culvert bed is mobile; key features are permanent

• Survive floods• Embedded to account for scour, grade adjustments, footings,

bed integrity.

16

Stream Simulation Design Process

• Watershed, Road

• Site assessment

• Physical survey

• Continuity

Bed shape and material

Mobility / stability

AssessmentStream simulation feasibility

Structure width, elevation, details

Design profile control

Project alignment and profile

Verify reference reach

Assess >>17

Some things stream simulation does not do within the culvert

• Riparian function– Natural bankline – cohesive soil, root structure– Food production– Flood refuge– Passage of terrestrial species?

• Light• Lateral channel and floodplain processes



18

Road Impounded Wetlands

• Stream simulation doesn’t apply because there is no continuity with reference reach. Other solutions might apply Yakima River

Oxbow

Reference reach

19

Suitable for Stream Simulation

• Rock, sediment dominated• Equilibrium

20


• Reference reach is simulated

• Template for dimensions, slope, bed, features

• Continuity with reference reach








21

Reference Reach

• Reference reach is simulated– Template for stream simulation dimensions, slope, bed

• Therefore geomorphic processes• Therefore AOP



22

Selection of Reference Reach

• Represents project channel– Primarily selected by project gradient– Consider confinement of project– Length of project reach

• Nearby, adjacent, upstream?– Provides “input” to stream simulation– Must be “connected” to crossing

reach– Out of the influence of existing

crossing

23

Stream Simulation Slope

• Substantial experience up to 6%• Some successful experience up to 15%• Recommend slope ratio not greater than 1.25

Abby CulvertSlope: 14%

Step-pool Bed Bob Barnard

24


• Project objective

• Simulate reference channel

bed material

• Margins, banklines, forcing features

• Bed forms, shape








25

Bed Design Objectives

• Simulate natural bed– Bed shapes– Diversity– Roughness– Mobility– Forcing features– Control of permeability



26

Bed Design by M&B* Channel Types

Based on channel type of reference reach– Dune-ripple; construct or recruit– Pool-riffle / Plane-bed; construct and

let form develop– Step-pool, forced channels; construct

steps– Cascades; construct

– Bedrock– Clay

Incr

easi

ng s

lope

Dec

reas

ing

mob

ility

* Montgomery and Buffington, 1997 27

Bed Material Design – Alluvial

• New installations: use undisturbed channel (consider contraction)

• Replacements: use reference reach gradation.• Pebble count of reference channel for

D100, D84 and D50

• Include dense gradation based on D50 for smaller material and impermeability.

• Fine-grained beds are special cases.

• Compensate for stability of initial disturbed condition.

• Account for large roughness and forcing features.

0

20

40

60

80

100

0.01 0.1 1 10Relative grain sizes

28

Well-graded Bed Material

02468

101214161820

Gravel BoulderCobble

%Fi

ner

Sand

29

0

10

20

30

40

50

60

70

80

90

100

0.1 1.0 10.0 100.0 1000.0

Grain sizes (mm)

Perc

ent f

iner

than

F-T n=0.45

F-T n=0.70

Stossel Tribreference reach

sand gravel cbl boulder

Small grains derived by Fuller-Thompson curve based on D50

Larger particles sized directly from reference channel

Verify 5% fines are included

Bed Material Design – Alluvial

Stossel Tribexample

Fuller-Thompson

P = percent finerd = diameter of particlen = Fuller-Thompson density; varies 0.45 to 0.70

Simplify to:D16 = 0.321/n x D50D5 = 0.101/n x D50

n

DdP ⎥

⎦

⎤⎢⎣

⎡=

100



30

Bed Material ExampleW Fk Stossel Cr

D5

Fines

Fuller-Thompson(assume n=0.7)

Strm SimReference

D16

D50

D84

D100

3”

10”

30”

50% cobble and boulder34% gravel16% medium gravel and fines

Which is:

5-10%

3”= 0.321/n x D50

= 0.101/n x D50

0.59”

0.11”

3”10”30”

31

Bed Material Example

• 1 scoop bank run dirt• 4 scoops 4” minus pit run• 4 scoops 8” minus cobbles (or quarry spalls)• 2 scoops 1.5’ minus rock• 1.5 to 2.5 foot rock added during installation

W Fk Stossel Cr – 6.4% slope

32

BankfullWidthHeight

Shoulder (or bankline if continuous)

Channel margins

~ 51

10 ft initial low flow channel

RockBand

Stream Simulation BedChannel cross-section

34

Rock Bands

Streambedmaterial

Space the lesser of: 5 times the width of channel or max. vertical difference between crests < 0.8 feet

Rock bands (D100 = 1 to 2

times bed D100)



35

Flat bed without roughness or banklines.

36

Darby Ck. rock bands just after construction

Barnard - WDFW

Darby Ck. rock band during first flood. Band has

altered; flow is centered.

37

Alluvial bed material mix

Profile View

Plan View

Step boulders simulate natural steps and spacing

Bank boulders

Culvert

Natural steps

Steps

38

Step pool channel

“Set up” step pools and forcing features

Steps

Alluvial bed material mix

Step boulders simulate natural steps and spacing

Culvert



39

Special bed design considerations

• Bedform diversity• Bed permeability• Channel cross-section• Banklines• Key features• Small-grain beds

40

Margin, bank

Reference channel shape

Debris

Margins, Banklines

Bankline or bands

41

Hydraulic, Bank diversity

Ore Creek, Oregon

From USFS, 2006

42

Stability of Banks and Key Features

• key pieces are likely permanent– Stability analysis

• Particle entrainment equations• Or bank protection design

Blue CreekLolo Nat’l Forest



43

Bed material example design and specW Fk Stossel Cr

5-10%Fines24” rock scattered at

15’ oc throughoutSpanning 6-12” debris

at 50’ spacingColluvium,

debris

0.1”sandD5

36” bankline rock at 25’ spacing or continuous

each bank

Bankline root structure protrudes 3’ at 25’

spacing

Banklines

DesignReference

D16

D50

D84

D95

0.6”

3”3”

10”10”

30”30”

44

Bed Retention Sills

• Purpose: retain bed material• Bed retention sills are not baffles or

weirs• Recommended maximum height

equal to half of depth of bed• Debatable value

– Anchors bed; keeps bed from sliding out of culvert

– Anchors bed steps– May conflict with function of

stream simulation– Safety factor for steep slopes

Bed Sill

45

Stream simulation in gravel, sand clay beds

Ranch Cr., TX 46

Bed material in channelswith small grain material

• Lower risk with high bed mobility • Less practical to design detailed bed material• When D84 < 20 mm

– Use natural bed material– Select borrow

• Does bed satisfy objective?– If mobile, allow natural filling

• Risk of timing, headcut?• Consider volume of culvert fill• Channel constriction could be

significant issue• Consider temporary sills to retain bed

Select Borrow

0 - 15150 um

30 – 704.75 mm

70 – 10025 mm

10075 mm

% by weightSieve size

Example spec



47

Last thoughts on bed material

• Mobility is a key to design of bed• No good spec or source for fine-grained bed other than the

channel itself• Carefully select and supervise source, mixing, and placement• Mitigate the mess• Round vs angular rock?• Does it meet project objective?

48









• Profile range

• Sustainability

• Floodplain function, connectivity

• Safety factor

49

Diameter, D or rise

Round Pipe

50% D maximum

Range of possible bed elevation from long profile analysis (VAP)

Bed profile elevation; average of mobile bedcross section

2’ or per scour analysis or foundation design

Bottomless Pipe

80% D; suggested maximum submergence

Culvert Rise, Elevation

Pool depth plus2.0 x D100 or min % of D

51

Stream SimulationHow big is it?



52

Culvert Size1. Based on Project Objectives:

• Passage of aquatic, non-aquatic species• Bed sustainability and stability • Hydraulic capacity of the culvert• Construction, repair, and maintenance needs • Protection of floodplain habitats

Barnard

Bankfull Width

53

Culvert Size2. Based on Site Conditions:

• Expected future channel width, location• Risk of blockage by floating debris or beaver activity• Large bed material relative to culvert width• Channel skew with road crossing • Ice plugging in severe cold climate

54

Stream SimulationFirst estimate of culvert width

First estimate: Culvert width to fit over

channel banks

Bankfull width

Banks

Stream simulation bed

55

Stream Simulation culvert width

a. Confined

c. Unconfinedwith floodplain culverts

b. Unconfinedwith wider culvert



56

Unconfined channel - consider these modifications• Hydraulic / Stability analysis when floodplain conveyance high• Increase culvert width• Improve inlet contraction• Add floodplain culverts (when either Q10 floodplain > 4 x BFW ?)• Add road dips• Increase bed material size

57

Reference channelbankfull cross section

Floodprone width

Road Fill Road Dip

Floodplain culvert in flood swale

Culvert width including floodplain

2. Design the culvert to fit

1. Design the channel and floodplain

Design for sustainability

59









• Failure modes

• Sustainability of stream simulation (mobility)

• Stability of key pieces

• Culvert capacity(regardless of design method) 60

Mobility / Stability AnalysisThree purposes

1. Is channel shape and bed material stream simulation? –project objective– Project objectives still satisfied?– Driven by moderate flood - bankfull to 50-yr flood?

Mobility

Stability

2. Does bed stay in place?– Banklines, key pieces stable?– Can fail at high flows– Gradual chronic failure

3. Is culvert stable?– Extreme flows– Headwater, pressurized pipe– Debris is usually a greater risk than flow– Diversion



61

Culvert Failure

Cedar FlatsThurston Co, WA12/2007

62

Stimson Ck.Width ratio = 1.0Slope = 2.2% (5%)

Originalprofile

Culvert too narrow, bed material too small.

Note regradeBed Failure

Resultingprofile

63

Xt. Salt CkWidth ratio = 1.1

Slope = 2.9%

Rock bed control at inlet…

led to culvert bed failure

Bed Failure

Originalprofile

64Minimize lengthAdd safety factor to stability analysis *

Long culvert

• Limit headwater depth *• Larger culvert, additional culverts *

Pressurized pipe

• Verify potential profilesDownstream channel instability

• Compact bed• Consolidate bed• Increase bed material size

Lack of initial bed structure

• Larger culvert, Additional culverts *• Increase bed material size *

Floodplain contraction

• Minimize slope increase• Increase bed material size *• Increase bed culvert width *

Steeper than reference reach

Stream simulation culverts

• Build sag in road• Design for plugging, failure

Stream diversion

• Limit headwater depth• Efficient upstream transition

Debris blockage, flows

All culvertsDesign/construction strategyRisk

Ris

ks a

nd D

esig

n/co

nstru

ctio

n st

rate

gies

* = bed mobility / stability analysis required



65

Mobility / Stability Analysis - Process

• Mobility: compare design reach to reference reach– Design of D84 mobility the same in both channels

• D84 is important – roughness, form, mobility• One possible design assumption

– Calibrates analysis; therefore not sensitive to hydrology– Analyze for sensitivity

• Stability: analyze key pieces at high stability design flow

• Is it real? – Test sensitivity of parameters and compare alternatives.– Compare results to reference channel. – Is it a natural conclusion or are you forcing the channel? 66

Unit discharge – Bathurst (1987)

• Developed in: – steep channels; 0.23 < S < 9.0%, – Course bed material; 9 < D84 < 280 mm

• Lab and field data• relative submergence (water depth/D50) less than 10

or less than 4 (water depth/D84).

12.1

5.150

5.0

5015.0

SDgqcD =

b

icDci D

Dqq ⎟⎟

⎠

⎞⎜⎜⎝

⎛=

5050

⎟⎟⎠

⎞⎜⎜⎝

⎛=

84

165.1DDb

Critical unit discharge for D50

67

Procedure using Bathurst

12.1

5.150

5.0

5015.0

SDgqcD =

b

icDci D

Dqq ⎟⎟

⎠

⎞⎜⎜⎝

⎛=

5050

⎟⎟⎠

⎞⎜⎜⎝

⎛=

84

165.1DDb

Assumptions: • Total flow is the same in stream simulation and reference channels.• D84 has equal mobility in both channels.

FP

b

cD QwDD

SDgQ +

⎥⎥⎦

⎤

⎢⎢⎣

⎡⎟⎟⎠

⎞⎜⎜⎝

⎛=

50

8412.1

5.150

5.0

8415.0

Procedure:• Arrange Bathurst equations for total flow and set equal.• Vary conditions of stream simulation channel so total flow is the same.• Confirm floodplain flow.• Recalculate conditions(There are other possible assumptions, procedures) 68

FP

b

c QwDD

SDg

Q +⎥⎥⎦

⎤

⎢⎢⎣

⎡⎟⎟⎠

⎞⎜⎜⎝

⎛=

50

8412.1

5.150

5.0

8415.0

FP

b

c QwDD

SDg

Q +⎥⎥⎦

⎤

⎢⎢⎣

⎡⎟⎟⎠

⎞⎜⎜⎝

⎛=

50

8412.1

5.150

5.0

8415.0

equals

Reference channel Stream simulation channel

⎟⎟⎠

⎞⎜⎜⎝

⎛=

84

165.1DDb⎟⎟

⎠

⎞⎜⎜⎝

⎛=

84

165.1DDb

Qc84 is flow in the active channel



69

Schafer Cr trib

ScAnalysis >>70

Key Pieces - Stability Analysis

• Key pieces are permanent (up to stability design flow)• What is stability design flow?• Stability models - analytical

– Bathurst– Corps bank riprap– Corps rock chute– Moment stability analysis

71

D = median particle diameterq = discharge per unit widthS = energy slopeg = acceleration of gravity – 9.8 m/s

Sf = Safety FactorCv = Vertical velocity distribution coefficient

= 1.0 straight channel (R/W>26)= 1.0 inside of bend= 1.283-0.2log(R/W)

CT = Thickness coefficient> 1.0 when thickness > Dmax

Cs = Stability coefficient= 0.30 for angular rock= 0.375 for rounded rock?

γs = unit wt of rockγW = unit wt of waterα = Bank slopeφ = Rock angle of repose - + -43º

13/1

432.03/231

15

8550 '

KgSqC

DD

D ⎟⎟⎠

⎞⎜⎜⎝

⎛=

⎥⎦

⎤⎢⎣

⎡−

−=φα

γγγ

αTanTanCosK

ss

s11

⎥⎦

⎤⎢⎣

⎡−

=ws

wsTvf CCCSC

γγγ785.0)(3.5'

Corps model for Steep slopesCorps EM 1110-2-1601

73

Barnard



74

Failure. Risk consideration

Life of project, Tr

40%

20%

10%

5.0%

1.0%

50 years20 years10 years

Probability of occurrence (failure?)

Calculated design flow for specific project durations

n

r

rn T

TP ⎥⎦

⎤⎢⎣

⎡ −−=

11

100 yr40 yr20 yr

225 yr90 yr45 yr

500 yr200 yr100 yr

1,000 yr400 yr200 yr

5,000 yr2,000 yr1,000 yr

n = yearsTr = return intervalP = probability

75

The point is …

Design conservatively.

Design for failure.

76

6-Mile CkWidth ratio = 0.9

Slope = 5%Downstream control lost

Bed failureAt approx 500-yr flood

77

Diversion Culvert plugs and initiates stream diversion.

Flow diverted to other stream or scours new channel



78

DebrisIn forested watersheds, debris is the most prevalent cause of culvert failure. Culvert alignment is a major contributor to debris-caused failures.

Solutions: Culvert width, alignment, and transition.

79

Culvert Capacity

• Review range of project profiles.

• Analyze capacity with the high profile.

• Consider headroom and elbow room for debris.

• With debris, alignment critical.• Review risk of diversion.• What are consequences of

failure?

80

77

78

79

80

81

82

83

84

85

86

87

88

89

90

91

92

0 100 200 300 400 500 600

Distance (ft)

Ele

vatio

n (ft

)

StreambedWater SurfaceOld Pipe

Existingpipe invert

Culvert elevations, capacity

Range of potentialProfiles (VAP)

83.0 low profile bed

85.0 high profile bed

81

Elev 89.1

80% of rise

Elev 78.0

Alluvial pool depth+ 2 x D100

Final culvert designBox culvert 14.8’ wide x 12’ high

Culvert elevations

83.0 low profile bed

High Profile

Q100 = 92 cfs

86.9 at Q100 HP

85.0 high profile bed

Other height considerations:• debris headroom,• cover, • vertical alignment



82

O’Grady Cr – 2002

Reference ChannelD84 = 52 mmBFW = 11 ft

Stream simulation solution • Culvert 14.8 ft w x 12.0 ft h• D84 = 50 mm• D100 = 130 mm (or by key pieces)

83

Some last thoughts on stream simulation

• It isn’t this complicated. Use the tools that are appropriate.

• Check your conclusions with reality

84

Bob Gubernick

Standard const equip

PremixedKim Johansen, USFS

Stream Sim Construction



Bed Material Placement

•Dingo Loader

•Manually

•Trail equip

•Special equip

Rock Chute

87

Upper Stillwell Creek Case Study15-ft. Span Structural Plate Arch

2-ft. x 4-ft. x 82-ft. Concrete Footings

Adding stream simulation bed over a layer of 4’-minus well-graded select borrow.

Barb Ellis-Sugai, Geomorphologistand Rob Piehl, Civil Engineer

88 89



90 91

Pringle Ck.

Stream width 9.1 ft, slope 5%Culvert bed width 9.3 ft, slope 6%

Unit Power = 6.3 ft-lb/sec/ft3Barnard

92

Bankfull width structure after 16 years

Johansen

Width ratio: 1.0, slope 4.5%

design of stream-road crossings for aquatic organism ... · • fine-grained beds are special...

Documents