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Modeling Enhanced Meander Scar Zones using LiDAR Digital Elevation Models

In our quest to work out the details in regional mapping for Indiana's Fluvial Erosion Hazard  (FEH) Mitigation Program, we developed a new technique to enhance meander scar zones, the remnant paths of streams and rivers. Using LiDAR (Light Detection and Ranging) Digital Elevation Models (DEMs) from the 2011 – 2013 Indiana Orthophotography and Elevation Program we modeled an approximate alluvial plain for a reach of the Whitewater River in Southeastern Indiana. 

Our models show geomorphic similarities to the alluvial plain and are useful as a teaching tool that can help illustrate stream dynamics.  This image is an enhanced meander scar model overlain on a hillshaded LiDAR DEM.  The dark blues represent the main stream channel and the darker reds signify higher elevations.  In this image the yellow and orange color gradients represent areas of overland flow when bankfull conditions are reached.

It is important to note that meander scar models represent stream migration from the present as well as scaring that took place in the geologic past.  The modeling process can encompass multiple stream terraces making it appear that all areas of scaring are activated during periods of overland flow which is not the case.  Meander scar development typically occurs in lower gradient streams with broad floodplains.  Streams that exhibit the most meandering typically have an abundance of a soil type called alluvium.  Alluvial soils consist of coarser grained sediments such as sand and gravel.  These coarser grained sediments have a high erosion potential and be transported down stream.  These sediments erode in a way that over time the stream meander becomes large, bottlenecks, and the main stream channel captures the bottleneck.  

Although all flow pathways in meander scar zones are not as frequently activated, they can give insight as to where the stream might migrate towards in the future.  Meander Scar models have been useful in Indiana’s Fluvial Hazard Mitigation program by helping define erosional hazard boundaries.  LiDAR generated meander scar models combined with aerial photography and other LiDAR datasets are useful at temporally reconstructing approximate meander scar elevations.

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