Stream Simulation: A Simple Example · Simple Stream Simulation Example May 2011 2-1 USDA-Forest Service Eastern Region-R9 Chippewa National Forest ... headwater depth does not cause

Designing for Aquatic Organism Passage at Road-Stream Crossings

2. Simple Stream Simulation Example

May 2011 2-1 USDA-Forest Service

Eastern Region-R9

Chippewa National Forest

Stream Simulation: A Simple Example

North Thompson Creek, CO

Paul T. Anderson U.S.D.A. Forest Service

Here’s How We Started…




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Here’s How We Finished…

Forest Service Aquatic Organism Passage Policy

“Protect and Restore the Physical, Biological and Chemical integrity of the Nations Waters” (CWA)

Primary Design Priority:

• Aquatic organism passage and ecological connectivity is the goal and the first design priority for crossing streams that provide habitat for aquatic life.

Other Design Considerations:

• Minimizing the consequences of plugging and overtopping, including the ability to prevent stream diversion.

• Sufficient hydraulic capacity, including the requirement that headwater depth does not cause pressurized flow at the maximum flood.

• Maximize benefits while minimizing life cycle cost.




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Basic Concepts

• Bankfull Flow: Bankfull flow describes the volume, width, depth

and elevation: where the water begins to spill on the flood plain.

The elevation of incipient flooding. It can also be thought of as

the streams physical expression of it’s natural size and power.

• Stream Simulation: Create a channel bed form, within a

structure, as similar as possible to the natural channel in both

structure and function. The simulated channel should present no

more of and obstacle to aquatic life than the adjacent natural

channel.

• Reference Reach: A natural stable channel section used as the

design template for stream simulation.

• 100 Year Flood: A backward looking estimate with Very High

Error. Does not account for Debris, Sediment, or Aquatic

Passage. At Best is an relative indicator or risk. Structure Life

Phase 1

Initial

Assessment Phase 2

Site Assessment

Phase 3

Stream Simulation

Design

Phase 4

Final Design &

Contract Preparation

Phase 5

Construction

Phase 6

Maintenance

& Monitoring

Stream

simulation

project

phases




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Phase 1 - Initial Assessment

• Road Context

– System road, heavy oil/gas, timber, recreation use.

• Resource Values

– Brook trout, CO cutthroat trout, and others?

• Watershed-Scale Risk Factors

– Stable sandstone geology, basalt cap, beetle kill

• Site Risk Factors

– Debris, floodplain constriction, channel stability

Initial Assessment (cont.) – Suitability and Objectives

• Road to remain in place with similar

dimensions

• Stream simulation is applicable and

appropriate

• Accommodate some floodplain processes

• Be prepared for some headcut, expect debris




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Phase 2 - Site Assessment

• Develop plan view sketch map

• Collect Site Data

– Site and road topography

– Longitudinal Profile

– Channel and floodplain cross sections

– Bed material descriptions

• Conduct preliminary geotechnical investigation

– Bedrock, groundwater, mass wasting, engineering props.

Upstream Channel

Aggraded inlet.

Sediment wedge upstream

Accessible floodplain




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Less sinuous but floodplain

present

Downstream Channel

Minor scour pool, no bedrock

Preliminary Site Sketch

Provides good notes for

Winter design sessions.




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Preliminary Site Sketch – Zoomed In

Topographic Survey Map +




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Longitudinal Profile

sediment wedge

Phase 3 –Stream Simulation Design

• Select project alignment and profile

• From selected reference reach determine

– Slope similar to project profile

– Channel shape

– Bed material gradation and grade controls

• Select structure width and minimum embedment depth

• Verify stability of new streambed inside structure

• Results:

– Structure size, shape, alignment. Bed material sizes and configuration of grade controls.




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New Structure Alignment

Headwalls considered to reduce

length but were too costly

Longitudinal Profile

Sediment Wedge

segment

elevation

change

(ft)

segment

length

(ft) gradient

% gradient

difference

betw een

successive

segments

maximum

residual

pool

depth

(ft)

number

of grade

controls

distance betw een

grade controls

(ft)

A 0.73 47.66 0.0154 0.65 2 47.66

B 0.59 20.94 0.0282 82.9 0.45 2 20.94

C 1.84 93.89 0.0196 -30.4 0.59 4 46.98, 30.8, 16.11

D 1.63 43.64 0.0374 90.4 0.31 3 13.49, 30.15

E 0.04 16.97 0.0025 -93.2 0.80 2 16.97

F 1.84 104.80 0.0175 592.4 1.09 4 16.64, 40.29, 47.87

G 0.36 17.31 0.0210 19.8 0.12 2 17.31

H 0.07 15.25 0.0046 -78.2 0.31 2 15.25

I 2.29 43.98 0.0520 1033.0 1.15 3 22.59, 21.4

J 0.46 25.38 0.0180 -65.3 0.59 2 25.38

K 0.30 32.32 0.0093 -48.2 0.47 2 32.32

L 0.35 12.90 0.0271 190.3 0.17 2 12.90

culvert 1.82 44.88 0.0405

Design Gradient 0.0352

Reference

Reach




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– Close gradient

match.

– Grade controls.

– Sediment size.

Reference Reach

Stream Simulation Design: Select Bed Material Gradations

• Stream simulation materials to give you similar

– stability

– permeability

– Complexity

• “Pebble count” gradation of streambed

– Is the same as an engineering gradation (% passing & sieve size)

• Construct grade controls with largest material

– Individual rocks or graded material




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particle size

interval name

size interval

(mm)

count or

frequency

percent

frequency

cumulative

percent

finer Project Name: North Thompson Creek

medium boulders 512 to 724 0.00 100.00 Sample ID: PC (Site 2 channel,10-12-06)

362 to 512 0.00 100.00 Sample Date: 10/12/2006

small boulders 256 to 362 10 6.90 93.10 Sampler Name: Weinhold, Grove

181 to 256 16 11.03 82.07 Sample Location: Riffle b/t XS 3 and 4

large cobbles 128 to 181 13 8.97 73.10 Sample Method:

90.5 to 128 6 4.14 68.97

small cobbles 64.0 to 90.5 11 7.59 61.38

45.2 to 64.0 16 11.03 50.34

very coarse gravel 32.0 to 45.2 21 14.48 35.86 percentile particle size (mm)

22.6 to 32.0 26 17.93 17.93 d95 282

coarse gravel 16.0 to 22.6 15 10.34 7.59 d84 192

11.3 to 16.0 6 4.14 3.45 d50 45

medium gravel 8.0 to 11.3 2 1.38 2.07 d16 21

5.7 to 8.0 0.00 2.07 d5 13

fine gravel 4.0 to 5.7 1 0.69 1.38

2.8 to 4.0 0.00 1.38 % boulders 6.9

very fine gravel 2.0 to 2.8 0.00 1.38 % cobbles 31.7

sand, silt, or clay < 2 2 1.38 0.00 % gravels 60.0

Total count 145 100.00 % sands,silts,clays 1.4

sampling frame on transects

approximately 1 meter apart,

within active bed width.

Bed Material Characterization

Sediment Design – From Reference Reach Data




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Key Pieces too… XS3-XS4 (Segment D Reference Reach). Summary of 10 largest particles for the key pieces.

particle number

long axis

(mm)

inter-

mediate

axis

(mm)

short

axis

(mm)

average

cubic

dimension

(mm)

long

axis/inter

mediate

axis ratio particle shape; roundness

1 400 340 230 315 1.18 blocky- to tabular-shaped; subangular

2 740 410 170 372 1.80 tabular- to disc-shaped; subangular









average 306 1.43

d95 percentile (mm) 746 421 273




441

390

292

225

average cubic dimension of d95 percentile




Stream Simulation Design: Structure Selection

• Analyze various structure sizes and shapes that meet design width:

– Minimize channel and floodplain constriction

– Room for debris as beetle activity increases (HW/D <<1 during design flood)

– Meets minimum cover requirements

– Adequate embedment – below expected scour line




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Structure Selection – From Reference Reach XSECT

Final Road Surface

Lower Vertical Adjustment Line

Structure Selection – Idealized (easy to build) XSECT

Final Road Surface





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Structure Selection – Trial Structure Types

Final Road Surface


12’-4” x 4’-5” Box

w/ concrete footings

Structure Selection – Trial Structure Types

Final Road Surface


Countersunk

12’ x 7’-8” CMPA




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Stream Simulation Design: Structure Selection

• Final choice: Choose 12’ x 7’-8” CMPA

– Economical shape, large opening, embedment depth

– No poured concrete, fast installation

• Check Bed Material Choice:

– Is mobility of particles in structure similar to natural channel?

– Are key pieces (grade controls, banks, etc.) stable in design flood?

Phase 4 – Final Design and Contract Preparation

• Produce drawings and specifications for:

– structure and foundation details, bed material

– roadway,

– erosion control, dewatering,

– bypass roads,

– stockpile sites.

– and everything else

• Determine quantities and estimate costs

• Develop Contract Documents

• Results: Contract solicitation package




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Site Plan, Profile, Survey Plan and Profile Drawing

Stream Simulation Channel Details




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Typical Sections

Phase 5 - Construction

• Inspection and control

• Documentation

• Design changes (minimize)

• Results: The completed project




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Pre-Construction Items

We (USFS) usually remove critters prior to construction

Inspecting the Work

Schedule Road Closures

(try to avoid bypass roads)

Verify Construction Staking




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Completed Project

Completed Road

Crossing for traffic

Completed Stream Crossing

for Aquatic Organisms

Phase 6 - Post Construction Maintenance and Monitoring

• Maintenance is minimal – some tweaking of bed structure

• Monitoring - intensive for this project

– Implementation – built as designed?

– Effectiveness – bed stability, shape, complexity




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“Our responsibility to the Nation is to be more than careful

stewards of the land, we must be constant catalysts for positive

change”

Gifford Pinchot

How long is the door going to be closed?

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