Forest Service AOP Meeting Objectives of Stream Simulation:

Examples and Talking Points

Traci Sylte, P.E.Hydrology/Fluvial Geomorphology

Lolo National Forest

Is It True?Are Road Crossings a Dam …with a Little Hole? ....

Road-Stream Crossing Objectives: A Win-Win Scenario

Maximize Structure LifeMinimize MaintenanceOptimize SafetyProvide for Species PassageProvide for the Stream

Function and Water Quality

Overview:

Provide Examples and Talking Points of the Essentials to Meeting Primary Stream-Road Crossing Objectives

Designing By Stream Type Designing Dimension, Pattern, Profile Principles and Processes For Structures “Green” Considerations

“Simulate” adjacent natural channelPremise: If the stream channel through the crossing simulates the dimensions, character, and processes of the adjacent natural channel, it will present no more of an obstacle to movement of organisms than the natural channel.

Big Picture: Narrowing Watershed Processes

Floods Fire Mass Failures Debris Torrents Wind Throw Drought Organism Life Cycles Nutrient Cycling Cumulative Human Impacts

2. Wood Transport

3. Sediment Transport

Large Scale Processes What it Means toCrossing Design

4. Species Passage

1. Water Transport

Base Flow

Bankfull (normal high) Flow

Flood Flow

Water Transport

Base Flow

Bankfull (normal high) Flow

Multiple Channels: Base, Bankfull, Floodplain

Water and Scour

High Velocity

Scour

1979 – Siegel Ck, LNF 1998 – Siegel Ck, LNF

Wood Transport Stream Function – energy dissipation,

grade control Habitat Nutrient Cycling Structure Failure / Maintenance

Sediment Transport

Bars Upstream of Structures: An Indicator of Backwater Conditions

Okay Simulate: but what width, depth, profile, substrate……

Stream Simulation Design: 4 Primary Components

1. Geometric Alignment 2. Channel / Structure gradient 3. Bed width and shape4. Bed material design & channel

forms

From Rosgen 1994

The Channel: Dimension, Pattern, Profile

Some “A” Stream Types

A2

Aa+

A4

A1

- Avalanche chutes, headwaters, faults, bedrock areas

-Steep

-Well entrenched

-Low width/depth ratio

-Step-pools, cascades, waterfalls

-High energy

Montgomery & Buffington “Source or Transport” Streams

Some “B” Stream Types- Moderately steep to gently sloping terrain and basin types. -Moderately entrenched-Transport dominated (ripples and rapids)-Width/depth ratios greater than 12-Moderate slopes, generally 2-4%-Streambank erosion rates are low and stability is typically great.- moderate sinuosity-Relatively Stable-Plane-bed or Step-pool

B3

B2 B4

B3

Montgomery & Buffington “Transport” Streams

Some “C” Stream Types

C4 – altered with berm

C4 - Reconstructed

C4

C4 -Narrow to wide valleys with well developed floodplains

- Slopes, generally less than 2%

- Stability dependent on stream banks and vegetation

- Sinuous

- Riffle-pool dominated

- Width/depth ratios greater than 12

Montgomery & Buffington “Response” Streams

Some “D” Stream Types

D5

D4

D3

D4

- Multiple channels, braided, multiple bars.

-Steep depositional fans, glacial troughs, deltas, outwash areas, disturbed valley streams- low sinuosity-High bank erosion-Relatively Unstable- channel slope generally similar to valley slope

Montgomery & Buffington “Response” Streams

Some “E” Stream Types

E4

E5a

E4 – altered by grazing

E6

E5

-Very high sinuosity and low gradient, except where altered or in steep mountain meadows- only slightly entrenched/dominant floodplain- most efficient transport per unit width of all stream types-Highly stable, but very sensitive to disturbance and vegetation removal-Width/depth ratios less than 12

Montgomery & Buffington “Response” Streams

Barnard

Bankfull WidthBankfull Width

Stream Simulation

Culvert bed

Shoulder (or bankline if continuous)

Channel margins

10 ft low flow channel

Band

Bed Width and Shape

Stream reconstruction

Construction -

1.2’

4.5%

2.0’

Stream reconstruction

Construction -

Culvert Elevation

Bed profile elevationCul

vert

Ris

e

30% D

50% D

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

By simple math Culvert Rise > 5 x Range

“Like a two year old child, a river can’t sit still,” Mount, 1995

Planform...Meandering Tendency

Bending is a central tendency….it’s all about physics.

Planform Considerations: Designing for Bends1. Avoid Sinuous Channels 2. Locate Crossings on

Straight Sections3. If Straightening is

Necessary - Do Not Straighten the Stream Longer than its Natural Meander Wavelength (Don’t make the distance between bends or pools longer than the natural ranges)

4. Accept Small Skews and Reinforce Banks If Necessary

5. May Need to Perform Channel Restoration to Recreate Natural Geometries

** Work Within the Natural Meander Geometry of Your Stream Type!!!!!

Differs by Stream Type

Crossing replacement accommodated the bankfull channel dimensions, but quickly filled again because it is located at a channel grade change between a C4 and D4 channel type. Moving the road 200 feet upstream to a B4 channel type would have transported all material efficiently through the crossing.

Gradient Considerations

Gradient Considerations

Gubernick, Furniss, and Clarkin, in press

Roads are often located at stream gradient changes. Look for these slope breaks and evaluate what it means to sediment transport, backwater, aggradation, and degradation.

Hogback Creek Pipe RemovalBefore/After Longprofile, 2006

4538

4540

4542

4544

4546

4548

4550

0 100 200

Distance (ft)

Elev

atio

n (ft

)

As BuiltPre-ConstructCulvert/RoadBridge BottomDebris

Degradation Downstream

Remedy to Degradation at Outlet

Bedform and Substrate

Profile Planform

A Cascade

B Step-pool

C Plane-bed

D Pool-riffle

E Dune-ripple

Channel Bed Form and Substrate

Finished profile

1. Sub-grade access pad

2. Bed material to final grade

3. Step pool footer

4. Additional bed material

5. Top step pool rock

6. Bed material to grade

Construction of Steps

Other Substrate Considerations

-Account for Armor Layer & assure fines are incorporated.

- Mimic natural substrate sizes & distributions

- Failure to do so can result in:

•Subsurface Flows

•Scour of Substrates

Other Talking Points

Floodplain Connectivity: Unconfined channel • 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

This is an E4 stream type where the culvert spanned the bankfull channel width, but did not allow for floodplain flows. It failed periodically requiring both road and culvert maintenance until a bridge structure was installed.

Landscape Position is Very Important

Deltas (lakes

Alluvial FansPossible D,E,F,G

Lightening Creek

Bankfull Identification- Responsible for general channel shape and size - Transports more sediment over time than any other discharge- Occurs on average every 1.0 –3.0 years- Common pseudonyms: “active channel”, “ordinary high water mark”, and “Q2”

Bankfull Indicators Top of Flat Depositional

Areas

Change in vegetation

Slope Breaks

Change in particle sizes between bed, banks, and floodprone area

Bank undercuts, root, and scour lines

Stain or lichen lines on boulders

tls 5/7/03

Bankfull Indicators

seek local expertise

verify local indicators!

Is it? Is it not?

Lolo Creek Boulder Clusters – 1980’s

Lolo Creek Boulder Clusters – 2005

Stability in Substrate Design

1 2 3

A Principle of Scour & Settlement Protection

Settlement and Mobility Process by Un-Protected Downstream Scour

Structure Design For Stability – Each of these will provide stability

Structures & Principles We must work with channel hydraulics with our structures.

Check structures impede velocity and bedload transport, often flank and/or scour, and over-widen channels

Bad, bad, bad……

Good, good, good……

DESIGNERS: Reality Check!!!!!!!!Average Stream Velocities(Spring Runoff or Slightly Greater)

Mountain streams - 4-5 ft/s.

Valley streams - 4-6 ft/s.

Velocity (feet/second)4 8 12 16 20 24 280 32 36

Chinook

Steelhead

Coho

Cutthroat

Brown Trout

Grayling

Whitefish

M. Bell 1989

Cruising SpeedSustained SpeedDarting Speed

Critical Velocities for our fish: 4-5 fps (We shouldn’t be surprised)

HEALTHY ADULTS

Lolo NF – Leaving a Site “Green”

Geomorphic and Analytical Approaches to Stream Rehabilitation Design and Reconstruction Have Taught Us A Lot. Incorporate them.

Design Advancements

“Bad Riprap”

“Good” Riprap

Good Riprap Design: 1. Used where excluding lateral stream movement is not a detriment or is not feasible2. Designed irregular bank line and rock protrusions dissipate energy and create habitat

niches at multiple flow levels3. Only protects to a designed flood level, often bankfull or Q100 are used4. Incorporates vegetation and creates habitat5. Of course, has necessary size classes and configuration to remain stable

Is It True?Are Crossings a Dam with a Little Hole? ...IT DOESN’T HAVE TO BE!

Acknowledgments for Slides and Photos

Lolo National Forest et. al.

Shane Hendrickson, R1 John Casselli, R1 John Kattel, R1 Pete Odegard, R1 Rod Blessing, R1 Chad Bensen, R1 Bob Gubernick, R10 Kim Johansen, R6 Dan Cenderelli, R6 Thomas Dunklin