Approach to Digital Elevation Model Correction by Improving Channel Conveyance

Abstract

Digital elevation models (DEM) are important inputs for topography in modeling floods for remote and inaccessible regions. DEMs often lack in accuracy near water bodies and rivers. The objective of this research is to present a DEM correction technique to improve the accuracy of flood simulation and inundation mapping. The key feature of this method is the variability in thalweg (deepest point along a cross section) locations and depth based on the river meandering, width, and side slope. The DEM correction technique is demonstrated by adjusting a national elevation dataset (NED) DEM along the Cumberland River near Nashville in Tennessee. The original (base DEM) and modified DEMs are used as main input of the 1D Hydrologic Engineering Center River Analysis System (HEC-RAS) model and corresponding performances were analyzed. The model using surveyed topography was calibrated for a high flood event (May 2010) and later validated for an intermediate flood event (2003), a high flood event (May 2010), and a low flood event (May 2013) using the modified DEM. It was found that the model with base DEM is capable of simulating at a very high stage but fails during low and intermediate stages. The applicability of base DEM is also limited for any event above 127 m and