Comparison of Flood Top Width Predictions Using Surveyed and LiDAR-Derived Channel Geometries

Abstract

This paper compares flood top width predictions generated by a one-dimensional flood model using surveyed and light detection and ranging (LiDAR)-based topographic descriptions for varying storm event return intervals. Three channel geometries are used in the analysis: (1) based entirely on survey data; (2) based entirely on LiDAR data; and (3) based on a hybrid file that merges survey-derived channel bank locations and LiDAR-derived cross sections. The study area is a 6.6-km river reach located in the Piedmont area of North Carolina. Four steady flow simulations are performed representing the 10-, 50-, 100-, and 500-year design storm events to understand the effect of storm return period on top width predictions using the three different topographic descriptions. The results from the study suggest that the LiDAR derived geometries generally predicted higher widths compared to the survey geometries, and that the magnitude of the difference is inversely related to the storm even return interval (12% average difference for a 10-year storm event to 4% for a 500-year storm event).