Flood mapping using hydraulic modeling and Sentinel-1 image: Case study of Medjerda Basin, northern Tunisia

Abstract

In northwestern Tunisia, floods are the most widespread natural hazard. Indeed, this problem is posed seriously in the Medjerda basin. In fact, the plain of Jendouba - Bou Salem is the most affected area by this plague. It has the form of a shallows that collects runoff water and promotes flood extent and duration. So the main objective of this study is to determine the extent of the hydraulic hazard through the flood mapping of February 2015 event which has seriously affected the urban and peri-urban landscape of the plain. The hydraulic hazard extent mapping was determined through the HEC-RAS model. It's one of the most popular free hydraulic models developed by the Hydrological Engineers Center of the U.S. Army Corps. The new version (HEC-RAS v-5) is a two dimensional (2D) model based on the resolution of hydraulic Saint Venant which can simulate floodplain inundation, determine the water surface elevation and velocity distribution of floods. It allows modeling flow with permanent and non-permanent free surface by evaluating water flows and heights over the all sections of a river so it allows to integrate hydraulic works (bridge, dam …).The result showed that this flood reached heights of more than six (6) meters in flooded areas. The result from the HEC-RAS model was validated using the Sentinel-1 radar image acquired on February 28th, 2015.The study shows the applicability and the capabilities of the 2D HEC-RAS version for flood studies.