Changing Course Streambed Restoration and Stabilization APWA Webcast

Changing Course: Streambed Restoration and Stabilization APWA Webcast January 19, 2006

Session Agenda A. Setting realistic expectations B. How urban streams work C. Design considerations for urban stream repair projects D. Sources of funding for local stream repair projects

Manual 4 Urban Stream Repair Practices First manual specifically focusing on urban streams 33 different repair practices Available from www. cwp. org

Setting Realistic Expectations 1. The ICM and stream repair 2. Range of stream repair objectives

Impervious Cover Sets Expectations for Urban Streams

Rock Creek BIBI = 48 (excellent)

Biological Integrity of Puget Lowland Streams Stream Health (BIBI score) 50 40 Sensitive Impacted Non-supporting Urban drnge. 30 20 10 Data from Sarah Morley, Univ. of WA 1997 -1999 0 0 10 20 30 40 50 60 Urban Development (TIA in watershed) 70

Biological Integrity of Puget Lowland Streams Stream Health (BIBI score) 50 UP PE R 40 LIM IT 30 OF OB SE RV ED DA TA 20 LOWE R LIM IT OF OBSER VED D ATA 10 0 0 10 20 30 40 50 Urban Development (TIA in watershed) 60 70

Management Strategies UP PE Stream Health (BIBI score) 50 R Protection 40 LIM IT OF 30 Rehabilitation OB SE RV ED DA TA 20 LOWE Stewardship R LIM IT OF OBSER VED D ATA 10 0 0 Source Booth 2004 10 20 30 40 50 Urban Development (TIA in watershed) 60 70

Numerous objectives for stream repair 1. 2. 3. 4. 5. 6. 7. 8. 9. Cleanup Stream Corridor Naturalize Stream Corridor Protect Threatened Infrastructure Prevent Bank Erosion Expand/Reconnect Stream Network Increase Fish Passage Improve Fisheries Habitat Achieve Natural (Stable) Channel Design Recover Aquatic Diversity & Function

The public has many perceptions on what’s a good urban stream

How Urban Streams Work 1. Basic stream geomorphology 2. 3 phases of urban channel evolution 3. Effects on stream biota

Lane’s Balance

Phase 1: Initial Construction More sediment load Increased discharge Temporary aggradation

Or live in this soup? Phase 1 Aggradation Caused by Upstream Construction

Stream Symptoms During Aggradation 1. 2. 3. 4. 5. Mid-channel bars Embedded riffles Siltation in pools Accretion on point bars Deposition in the overbank zone

Phase 2: Active Channel Adjustment Much Higher Discharge Increased Sediment (banks) Degradation/channel enlargement

Example of Extreme Channel Incision aka Downcutting

Symptoms of active channel enlargement 1. Cut face on bar forms 2. Headcutting and knickpoint migration 3. Suspended armor layer in bank 4. Terrace cut through older bar material 5. Exposed sanitary or storm sewers

Channel Enlargement As a Function of Impervious Cover

Why 2 -year peak discharge doesn’t work Traditional 2 year peak discharge control does not reduce frequency of bankfull and sub-bankfull flows that cause erosion Indeed, it may actually worsen conditions since it increases the duration by which they occur

Conventional 2 Year Peak Flow Control Approach

24 Hour ED of 1 -year storm One-year storm ranges from 1. 5 to 2. 5 inches of rainfall Entire volume stored and released with average 24 hour detention 12 hour ED for trout streams (warming) Reduces velocities below critical erosive levels Adopted or proposed in MD, NY, GA, PA, NY, MN

Phase 2: Active Channel Enlargement Continued channel incision/entrenchment Loss of habitat structure

Easter Lk. Outlet, Federal Way, WA

Symptoms of Active Channel Widening 1. Falling/leaning trees 2. Scour on both banks through riffle 3. Exposed tree roots 4. Fracture lines along top of bank 5. Exposed infrastructure

Phase 3: Eventual Adjustment to More Stable Channel Dimensions: 2 to 5 Decades After Subwatershed Buildout

Case Study: Has this stream adjusted yet?

Symptoms of Channel (re? )stabilization 1. Water reaches the toe of each bank 2. Moss on rocks or extending down to the bottom of the bank 3. Banks are stable 4. Erosion is slight and limited to meander bends

Effects on stream biota Stream warming Channel enlargement Habitat degradation Food chain effects Declining baseflow Possible toxicity Fish barriers Loss of spawning habitat

Urban Stream Repair 1. Subwatershed restoration approach 2. Review of stream repair practices 3. Design context for urban stream repair 4. Unique urban stream design constraints

Subwatershed restoration approach 1. Design stream repairs at the reach scale in the context of the larger subwatershed 2. Systematic assessment of repair potential across subwatershed 3. Integrate w/other restoration practices

Stream repair is only one of several restoration practices § Stormwater retrofits § Discharge Prevention § Riparian restoration § Source control § Municipal practices § Watershed forestry Should be part of an overall plan (& reserved for impacted urban streams)

http: //www. saveourstreams. org C 1 and C 2 Stream Cleanup and Adoption Practices

Stream Repair Practices Streambank Stabilization Flow Deflection Grade Control

Stream Repair Practices (cont. ) Habitat Enhancement Fish Passage Flow Diversion

The design context for urban stream repair

←← ← REACH Current IC: 22% IC at Buildout: 30% Time to Subwatershed Buildout: 25 years Pond Retrofit Potential: High Case Study: How might the following upstream factors influence restoration?

B. Important Project Reach Factors 1. Channel confinement 2. Longitudinal profile 3. Channel crosssection 4. Streambed 5. Streambanks 6. Water quality

Urban Channel Confinement – Not enough room in the Floodplain to allow for natural sinuosity. Energy must be dissipated vertically rather than laterally. The Harman Rule: Need 6. 0 Thewidth Urban Corridor at least 3. 5 X bankfull to Stream even think about sinuousity

Rosgen classifications and methods need to be carefully adapted for use in urban streams.

Source: UCMT, 2004 2. 0 Longitudinal Stream Gradient Critical

Upward Migration of Knickpoints

Grade Control Key In Urban Streams • Maintain streambed elevation • Prevent/reverse channel incision

3. 0 The Current and Future Stream Cross-section will seldom be the same

Forest Turf Stream Channel Geometry Influenced by Urban Riparian Conditions

4. 0 The Streambank under Assault

5. 0 The Streambed

6. 0 Water Quality

Make sure to consult w/ local fishery biologists

C. Downstream Factors are also critical

An Interrupted Stream Maidens Choice Subwatershed Baltimore, MD

Loss of Riparian Buffer Continuity: Hospital Branch, TN

Partial and Final Barriers to Fish Migration in the Anacostia Watershed

Most local stream repair projects w Are funded from local capital budgets w To protect threatened infrastructure or property w Are “band-aids” that solve the symptoms but not the underlying problem

More funding is available when: w Innovative stream repair projects are w w w demonstrated Is a part of a larger watershed plan Local watershed groups support it Partners are involved to leverage resources

Sources of Funding for Local Stream Repair Projects 1. Fish and Wildlife Service 2. National Fish And Wildlife Foundation (NFWF) 3. EPA 319 Grant Program 4. Salmon Recovery Fund 5. State Highway Mitigation

Other Sources 1. State Natural Resource Agencies 2. Trout Unlimited 3. U. S. Army Corps of Engineers 4. Local and State Permit Conditions 5. Stormwater mitigation fees