Fluvial Processes

The Indiana Fluvial Erosion Hazard Mitigation Program is focused primarily on erosion that occurs due to the lateral movement of streams. The process of moving across a valley bottom is characteristic of alluvial streams,  or streams that build floodplains. As these streams move, or meander across the valley bottom they erode and deposit sediment in a series of  alternating cutbanks and pointbars. In the image below the features are labelled.  This process is how a stream  effectively transports its combined load of both water and sediment. Williams (1986) determined that natural streams  need an average  meander belt width of 6X bankfull width as they adjust to an equilibrium between erosion and deposition. This process forms the basis for fluvial erosion hazard mitigation. If a stream is given the room that it needs to make the lateral adjustments that are required by fluctuations in stream flow and sediment supply, most erosion hazards can be avoided.  Please see Stream Stability for details on how streams attempt to maintain a stable form, and Set-back distances under the FEH mapping tab for a discussion of how meander belt width is used to in FEH mapping. Disturbed or modified channels may require much more than 8X bankfull width as they attempt to reach equilibrium. Ongoing research is directed at determining the range of meander rates for Indiana streams.



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