降雨是产生洪水的最主要原因。简单来说,当水流流量超过水渠、小溪或河流的承受能力时就会产生洪水。这一过程主要是由降雨引起,但同时又受到诸多因素的影响,如图1所示,这些因素随地点和时间不同而变化,每次洪水都是不同的。流域降雨产生洪水:降雨随流域特性不同而汇入溪沟或江河。土壤植被截留雨水:流域土壤植被会吸收一部分降雨。通常降雨越多,能够渗入或储存于土壤的水量就越少。因此,雨强越大,径流的可能性越大。降雨范围和持 Rainfall is the most important cause of floods. In short, a flood occurs when the water flow exceeds the capacity of a canal, stream or river. This process is mainly caused by rainfall, but at the same time is affected by many factors, as shown in Figure 1, these factors vary with the location and time, and each flood is different. Rainfall in the basin produces floods: Rainfall flows into the river ditch or river with different characteristics of the basin. Soil vegetation intercept rainwater: Watershed soil vegetation will absorb a part of the rainfall. The more often the rainfall is, the less water is able to penetrate or store in the soil. Therefore, the greater the rainfall intensity, the greater the probability of runoff. Rainfall range and hold