Rainfall-runoff calibration for semi-arid ungauged basins based on the cumulative observed hyetograph and SCS storm model: Application to the Boukhalef watershed (Tangier,North Western Morocco)

The aim of the present study is to design urban storm rainfall distribution curve for semi-arid ungauged basins by which storm runoff can be predicted accordingly. the rainfall-runoff modeling is based on the storm event which occurred on the 23th of october 2008 on the boukhalef river basin (southwest of tangier),using modern simulation tools,namely the hydrologic model as well as remote sensing technic and geographical information system software (arcgis,hec-geohms). the study aims also to predict the design of peak flow for the 200-,100-,50-,20-,10-,and 5-years return periods. the problem most often encountered in this area is the need for estimating runoff from a watershed for which there are records of daily rainfall but no records of runoff. the objective of modeling the boukhalef watershed is to set up the rainfall-runoff model using the hec-hms hydrological model and gis. this model provides various meteorological and hydrological processes to obtain flood hydrographs. for this purpose,the determination of referential form of the hydrograph and hydrological parameters to predict frequency flows for different return periods was performed based on the concept of curve numbers of us natural resources conservation service (nrcs). the results of this study show that the scs-24 type i storm represents the best distribution to simulate the rainfall-runoff event for each return interval,because,during the same storm event,it is the most similar to the observed instantaneous rainfall at the neighboring gauged watershed called kalaya. © 2017 university of mohammed premier oujda morocco.