Flooding problem raised seriously in the watershed of Medjerda indeed flood risk factors still exists for some cities. Studies forecasting and flood management may be important to address these problems. The plain of Bou Salem had long known catastrophic floods. Sudden rain, releases of dams and tributaries flows caused historic flooding at the level of this plain. We recovered thirty floods in the station of Bou Salem during the period 1973-2013. Among the thirty floods, we distinguish mainly three Flash floods. In fact, Flash flood is a short and sudden local flood with great volume, it has a limited duration which follows within few (usually less than six) hours of heavy or excessive rainfall, rapid rain, or after a sudden release of water from a dam. This communication is designed to analyze the results of the flash floods forecasting by simple propagation models namely Muskingum and Regression. The method of forecasting depends on the upstream station flow and models coefficients of antecedent floods. Forecast periods range from 2 to 8 hours, with a pitch of 2 hours. We used numerical criteria, such as Nash coefficient, peak relative error and time separating observed and calculated pic, to evaluate the results. We noted that the satisfaction of all criteria together is not touched. The results were satisfactory with Nash coefficient ranging from 71% to 99.8%.