John Thomas, Project Director

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Hungry Canyons Alliance
Streambed Stabilization in Western Iowa
John Thomas, Project Director Hungry Canyons
Alliance
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Causes of StreambedDegradation
Straightened stream

• Highly erodible loess soils
• Stream straightening and land use changes
• Higher water velocities
• Channel downcutting
• Accelerated soil erosion

Old meander
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Streambed Degradation - Knickpoints
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Streambed Degradation Headcuts, Bank Failure,
and Stream Widening
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Gully Growth in 2 Years, Cass County
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Old streambed elevation
Bridge damage due to streambed degradation
Approximate old channel cross section
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• The HCAs purpose is to focus attention on the
  problems of, and develop solutions related to,
  stream channel degradation in 22 counties of
  western Iowa with deep loess soils

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HCA Streambed Stabilizationand Watershed
Consciousness

• Knickpoints affect entire watershed as erode
  upstream
• Stream videos to locate active erosion
• Streambed stabilization is key to preventing
  further erosion and protecting infrastructure
• Structures at regular intervals change the stream
  profile from erosive steep incline to stable
  stair-step pattern
• Site locations planned across political
  boundaries
• Structures planned on watershed scale

Old streambed elevation
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Streambed Stabilization Structures

• Raised weir section
• Steel sheet pile and rip-rap
• Decreases slope of streambed
• Prevents further downcutting
• Creates an upstream backwater condition
• Sediment settles out upstream
• Reduces sediment loads
• Protects bridge pilings

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Weir
Knickpoint
HCA Streambed Stabilization Structures
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HCA Streambed Stabilization Structures
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No bank scour
No degraded outlet
This design anticipates and allows for future
degradation because of mobile riprap and
elevation of channel at outlet
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3. Bank protection extends only ½ way up bank but
extends beyond end of weir to prevent scour
1. Grouted riprap no rock movement
2. Weir elevation set below streambed anticipating
bed degradation
4. Slight V-shape in weir and channel confines
flow to center of stream
Grouted riprap in channel forming pools and
riffles
Grouted riprap on bank
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Page County fish ladders with steel baffles
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HCA Streambed Stabilization Structures
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Northern Natural Gas Pipeline Structure
Protection Project- Before HCA Involvement
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Northern Natural Gas Pipeline Structure
Protection Project-After HCA Involvement
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In-Depth Project ProfileNorthern Natural Gas
Pipeline Structure

• 5 foot concrete grade control structure (GCS)
  built by Northern Natural Gas (NNG) in the early
  1970s
• NNG GCS destabilized and nearly destroyed by
  knickpoint migration of 11 vertical feet
• NNG was planning on re-drilling their pipelines
  much deeper, at a cost of 2.4 million, and
  allowing the structure to fail
• Structure failure would destabilize Walnut Creek
  upstream from the structure, endangering 23
  bridges and hundreds of acres of farmland
• Partnership formed between HCA, Pottawattamie
  County, and NNG to repair the current structure
  and construct three new structures downstream
• Repair work cost 68,000
• Construction of 3 new four-foot weirs cost
  372,000
• NNG and HCA paid for a total of 358,000 and
  82,000, respectively
• For 50,000, Pottawattamie County assumed
  maintenance responsibilities from NNG
• NNG has begun modifying their grade control
  structures throughout the Midwest in accordance
  with what they learned in western Iowa from the
  HCA
• Project saved NNG and its customers over 2
  million

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Cabled Concrete Block Weir
Gabion Basket Chute
Sheet pile waterway outlet
Retention Dam/Pond
Small Structures For Landowners
Riser Added to Road Culvert
Full-Flow Earthen Dam
High-water crossing
Grouted riprap check
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Benefits of Hungry Canyons Alliance Structures

• 310 bridges/culverts protected
• Protection of numerous utility lines (electric,
  phone, gas, sewer, water)
• Protection of farmland (537 acres)
• Reduced sediment loads and improved water quality
  (20.1 million tons of sediment)
• Prevention of soil movement into the Missouri
  River
• Reduction of the dead zone in the Gulf of
  Mexico
• For every 1 invested in Hungry Canyons Alliance
  structures, more than 4.25 in property value and
  1.11 tons of soil is protected.

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Old Design
Stream flow
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Face of weir
80,000
Modified Design
Stream flow
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120,000
V - notched
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Recent Research Funded by HCA

• Optimized Weir Hydraulics for Fish Passage
• 115 weir slopes provide enough flow depth (gt 1
  foot) and have slow enough water velocities (lt 4
  feet/sec) to allow fish passage
• IIHR - University of Iowa
• HCA (25), Iowa DOT Highway Research Board (50),
  and Iowa DNR Fisheries Bureau (25)
• Evaluation of Fish Passage and Fish and
  Macroinvertebrate Communities in Streams Modified
  by Grade Control Structures
• GCS can have negative impact on fish passage if
  vertical or steeply sloped
• Documented fish passage over 115 weir slopes
• Higher fish community (IBI) scores at weirs vs.
  no weirs
• Macroinvertebrate abundance and diversity greater
  at weirs vs. no weirs
• Natural Resource Ecology and Management
  Department - Iowa State University
• HCA (17), US Geological Survey (22), US Fish
  and Wildlife Service (15), Iowa State University
  (35), and Iowa DNR Fisheries Bureau (11)

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Other Continuing HCA Projects

• Modification of Weirs Inhibiting Fish Passage
• Streams classified by fisheries potential
• Structure locations prioritized for modification
• 93 structures blocking fish passage (24 HCA)
  11 modified so far (4 HCA)
• Modifications done with HCA, DNR, and Fish and
  Wildlife Service funds
• Measuring the Cost Effectiveness of Small
  Structure Types
• Done in cooperation with Natural Resources
  Conservation Service (NRCS)
• Total structure cost divided by the multiple of
  the drainage area (acres) and the grade
  controlled (ft) Cost / (DA x GC)
• This ratio is inversely proportional to the
  structures cost effectiveness
• Structures not recommended for use - similar
  structures more cost effective
• Concrete block, cattle panel, or hog slat weirs
• Steel or aluminum toe walls

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Continuing Research by HCA

• Knickpoint Migration - Causes and Rates
• Stage-sensors, instrumentation of two
  knickpoints, and frequent surveying
• IIHR - University of Iowa
• HCA (20) and Iowa DOT Highway Research Board
  (80)
• Aerial Video Stream Classification
• 85 of identified stream reaches flown in
  helicopter
• 50 of collected video analyzed
• six-stage channel evolution model describing
• dominant channel processes
• 5,330 miles of streams in 21 western Iowa
  counties
• Study performed by HCA with 100 HCA funding
• Stage-Discharge Relationships for Ungaged Streams
• No gaged medium to small sized streams in western
  Iowa
• Semi-automatic, permanent, stage-sensor network
  installed on 11 ungaged streams
• Stage-discharge relationships will be developed
• IIHR - University of Iowa
• HCA (39) and Iowa DOT Highway Research Board
  (61)

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As directed by an ISU research study, scrap tires
were arranged in layers, bolted together with lag
screws, and filled with soil cement. However,
the soil cement was not resilient, so the loose
soil cement was removed and the structure was
covered with a layer of concrete grout. Another
scrap tire structure similar to this will be
built.
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Helping Eastern Nebraska

• Eastern Nebraska also has streams in areas of
  deep loess soils that have been channelized
• Streams responded in same way by actively
  downcutting
• Unlike Iowa, nothing ever done at federal, state,
  or local level to prevent streambed degradation
  in eastern Nebraska
• HCA asked to provide guidance to several parties
  in eastern Nebraska that are concerned about
  downcutting streams

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Thank You
Any Questions?
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Contact Information

• For questions or comments about the information
  presented in this presentation, contact John
  Thomas, Hungry Canyons Alliance Project Director
• Office phone [phone]
• Office fax [phone]
• Golden Hills RCD Office
  P.O. Box 189
  
  712 S. Hwy.
  6 59
  Oakland, IA 51560-0189