| This study was sponsored by the Project of the National Natural Science Foundation of China "Impact of forest vegetation based on watershed as a unit on floods in the Three Gorges area". From the influence of factors such as rainfall, rainfall intensity, rainfall duration and underlying surface on runoff, whether the PRMS_Storm model was suitable for the simulation of rainstorm process in a small watershed was fitted and validated. By adjusting the parameters, a suitable model for this watershed was fitted, which was important to the extension of the PRMS_Storm model.By processing the DEM data with ArcGIS, parameters of the basic topographic data was obtained. According to the division of HRU, characteristic parameters of HRU were obtained by dividing Heicaohe watershed into 22 river networks. Based on the analysis of the measured data of the study area, data of rainfall and runoff was obtained. With the observation data of the runoff plots, soil parameters were obtained.By using typical rainstorms to fit PRMS_Storm model and determining every parameter in the fitting process, rainfall processes were validated by the fitted model. To Heicaohe watershed, the average values of Nash uncertainty coefficients and correlation coefficients were 0.74 and 0.88, respectively and the pass rate for flood prediction was 88%, which was precise. Meanwhile, this model could be used to simulate flood process. By analyzing the sensitivity of this model, it showed that runoff error and flood error were significantly affected by rainfall duration, pre-rainfall and flood duration in the rainstorm simulation process. Comprehensive governance of soil and water conservation to the flood process indicated that after the governance, the total runoff and the peak discharge decreased approximately 20% and 30, respectively. And the peak appearance was delayed 60min. It showed that the governance had significant impact on flood peak subduction, runoff decrease and flood interception.
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