Evaluation of the FMS empirical model using sediment survey of small reservoirs in the Fars province

The scarcity of reliable data for the rate of erosion and sedimentation on numerous watersheds all over the country makes the application of empirical models inevitable. One of these models is the Factorial Scoring Model (FMS). The purpose of this research was to evaluate the model's efficiency in the Fars Province This study was conducted on 5 small watersheds where small check dams of the masonry and earth types were constructed at their outlets. These structures did not have spill ways; therefore, all the bed and suspended loads were retained on their upstream for a duration of 10 years. The volume of sediment deposited in reservoirs was obtained, by surveying. The bulk density (BD) of each sediment mass upstream of the check dams was determined at the site and the volume was converted into using the individual BDs. The tonnage of sediment was also determined by the FMS model. The results indicated that the uncalibrated FMS model overestimated the eroded materials. The relative root mean square error (RRMSE) of the model was 0.246, which indicated a low level of the error of the model. Results of the calibrated FMS model indicated a 75% compliance of the model; therefore, we can accept the estimated results of this model as somewhat reliable.