INCREASE OF THE RUNOFF COEFFICIENT, HYDROLOGICAL SIMULATION AND RISKS OF FLOODING IN THE OUED FEZ UPSTREAM (FEZ, MOROCCO).

Abstract

Throughout the period that extended from 1912 to 2014 the city of Fez has experienced an intensive urban extension upstream of the river system mainly of Oued Fes, making the city more exposed to possible flooding. In this sense an approach was conducted based on the study of: artificial natural areas, increased runoff coefficient (CR), and cutting the area of sub-watersheds with independent parameters (Slope, CR, Surface) that are the basis of the hydrological calculation. The hydrological calculation is based mainly on the parameters of rainfall and on the parameters extracted from the division into sub-watersheds in order to obtain the peak flow generated by each sub-basin and then the downstream flow. This calculation was carried out primarily on the Oued Fes which is the main axis of the hydrography of the city. The formulas used are those of Macmat, Ziegler, and rational formula. The result of the hydrological simulation performed on two decimal centennial flood Q10 and Q100 show that the SAÂDIYINE bridge connecting the upstream portion and the channeled part of the Oued Fes is in pre-saturation in the normal state, the application of a hundred-year flood makes this hydraulic structure unable to deliver peak flow making its upstream area most exposed to possible flooding. Keywords: urban extension, runoff coefficient, hydrology, hydrological simulation, flood