Comprehensive Sensitivity Analysis of HEC-RAS 2D for Flood Inundation Mapping

Abstract:

Floods are among the most devastating natural disasters in the world, threatening human lives and properties every year. Flood inundation modeling plays an important role in flood risk management. HEC-RAS 2D is a widely used hydrodynamic model for two-dimensional simulation of unsteady river flow. Similar to other hydrodynamic models, this model is subject to different sources of uncertainties leading to inaccurate and erroneous model outputs. Recently, Hydrologic Engineering Center (HEC) released a new version of this model that operates on the LINUX system. This product enables the user to perform a comprehensive sensitivity analysis that requires an extensive computational capacity. In this study, we use Variogram Analysis of Response Surfaces (VARS) method for the sensitivity analysis of HEC-RAS 2D model during the 2017 Hurricane Harvey flood over the San Jacinto Watershed in Huston Texas. We analyze the importance and the influence of different model configuration factors, including channel and floodplain Manning roughness coefficients, terrain resolution, mesh size, as well as river boundary conditions on the water stage outputs. We also investigated the impacts of changing the spatiotemporal resolution of modeling (mesh and computational time interval) on both model accuracy and efficiency and obtained the optimum configuration point for the applied cases.