Protection against floods of the urban watersheds of Sidi Thabet in the lower valley of the Medjerda catchment (Tunisia)

Abstract

This paper aims to protect against floods of the area of Sidi Thabet, which is located in the Lower valley of Medjerda catchment in the North of Tunisia and known by its wide variability of runoff between dry and wet seasons, with a diffuse distribution of urban and rural areas and the abundance of undeveloped water courses often causing flooding annoying to people and infrastructure. To identify the area of intervention and to propose the suitable accommodations in these ones, we was based on a refined cartography by using GIS tool, on a detailed hydrological study of the zone of the project, on a statistical analysis of the rainfall data using the statistical software HYFRAN, besides the application of the CAQUOT model to obtain the dimensioning flows of the projected hydraulic equipments. The protection primarily consists on establishing different collectors in the five sub-catchments responsible for channeling and routing the storm water to its natural discharge point and replacing the existent equipments unable to forward the flow with a return period (RT) of twenty years. The nature of the proposed channels depends on the area that they traverse, between buried collectors inside the city to especially solve the problems of water stagnation, open concrete and masonry channels in the towns and cities, and earth channels are projected in the areas non-urbanized in order to minimize the estimated cost of the proposed equipments, instead of respecting the width of the streets while avoiding establishing collectors in the narrow ones