Numerical simulation on flood characteristics under different forest coverage rates of watershed

In order to study the influence of forest cover change on flood characteristics, a distributed hydrological model of Xiaoxi watershed was established. The parameters of the model were validated and verified by observed hydrologic data and its applicability was also evaluated. Then the seven-day rainfall series was selected and the model was used to simulate the flood process of Xiaoxi watershed with the forest coverage rates ranging from 0% to 100%. The results indicated that changing the forest coverage rates had a great impact on the flood characteristics of Xiaoxi watershed. The greater the forest coverage rate, the more obvious the effect. Compared with non-forest coverage condition, when the forest coverage rates reached the maximum, the flood peak flow was reduced by about 13.2%, the arrival time of the flood peak was delayed for about 4 hours, and the flood duration was extended by about 13 hours. Besides, when the forest coverage rate was less than 40%, there was a very limited reduction effect on the flood peak flow; when the forest coverage rate was more than 40%, an average of 10% increase in forest coverage could lead to 2% reduction of flood peak flow. Moreover, the shape of the flood process showed a trend from a single peak to double peaks with increasing forest coverage rate.