Flood Risk in a Sub-Basin of the La Antigua River, Veracruz. Mexico

The aim of this study was to apply the HEC-RAS hydraulic simulation model to delineate flood hazard areas in a sub-basin of the La Antigua River, Veracruz, using the methodology by the National Center for Disaster Prevention (Cenapred). This methodology takes into account the vulnerability and risk of a system to an extreme disturbance. The HEC-RAS model uses deterministic differential equations to simulate the behavior and dynamics of water levels in cross-sections of channels. By applying it under unsteady and mixed flow conditions, areas of flooding resulting from an unusually large flood can be defined. For hydraulic simulation, synthetic unit hydrographs were constructed using data recorded during an extreme hydrometeorological precipitation event. Channel geometry was obtained with HEC-GeoRAS, a tool which extracts and processes georeferenced information from a LiDAR land surface Digital Elevation Model (DEM). Roughness coefficients (In Manning) were estimated according to the physical characteristics of the channel. To calibrate the estimates calculated by the model, hydrometric information (recorded levels) was used from the Cardel 28003 station. The application of three test statistics - R, RMSE and DMA- showed a good fit between simulated and observed data, indicating the applicability of the HEC-RAS model to simulate, predict and delineate flood hazard zones.