Module # 16 Restoring Functions to Streams Through Design Iowa’s River Restoration Toolbox Level 1 / Base Training

Indicators of Geomorphic Instability Incision/Bedcutting Channel Filling Entrenchment/High Streambanks Lateral Migration Over Widening Lack of Habitat Eroded Banks Slope Instability

Incision/Bedcutting Caused by Excess Shear Stress Often Triggered by Downstream Straightening of Channel Will Propagate Upstream Increases Channel Entrenchment

Grade Control - Constructed Riffle

Grade Control – Vane Structures

Grade Control – Rock & Log Riffle

Channel Filling/Aggradation Caused by: Excess Sediment Supply Low Shear Stress High Width/Depth Ratio Can Lead to Lateral Migration Reduces Capacity of Culverts

Geomorphic Channel Design Multi-Stage Channel

Entrenchment/High Streambanks Very Significant Indicator of Instability Results in High Shear Stress Often Early Stage of Channel Evolution Results in Excess Sediment Supply

Bankfull Bench

Toe Wood Protection

Fabric Encapsulated Soil Lifts

Lateral Migration Often Due to: Slope Adjustment High Sediment Supply Downstream Channel Straightening Often Triggers Bank Erosion Belt Width Considerations

Geomorphic Channel Design

Over-Widened Streams Cannot Effectively Transport Sediment Can be High Maintenance Areas Poor Water Quality/Habitat Elevated Water Temperatures Bedrock Bottom Streams Often Overwidened

Geomorphic Channel Design

J-Hook/Straight Vane

Module # 16 Restoring Functions to Streams Through Design Iowa’s River Restoration Toolbox Level 1 / Base Training