Experimental Study On Impact Of Landscape Structure Of City Underlying On Rainfall Infiltration In Different Gradients

City underlying surface includes water area,holt,grassplot,hard ground,farmland and bare ground in the city, which is the summation of city land using. The urbanization is developing quickly, lots of streets and buildings are built with the urban population centralizing and urban area increasing. There is a staunch layer, because the city underlying surface is covered with cement and bitumen. Much staunch area obstructs the urban rainfall infiltration. The rainwater is drained without using, so that the groundwater is dried up for short of supplement of surface water and water resource is wasted seriously; lots of rainwater is drained in short time when hard raining, so it brings a huge pressure on the urban drainage system and aggravates the flood disaster; it also can make the difference between urban surface water environment and natural environment, affect the energetic character of ground surface, and add the probability of the hot island impact in the city. The physiognomy is different in every city, and the ground gradients are also different in the same city. The gradient is the factor which affects the rainfall infiltration of city underlying surface, because it has an important influence to the forming of surface runoff and rainfall infiltration. Obviously, it is far-reaching meanings to the harmonious development and unification of society,economy and environment by solving the problems of using,management and control of urban rainwater resource.In this paper, the author adopts the simulation experiment in laboratory, and simulates city underlying surface,landscape structure and atmospheric rainfall to study on the relationship of landscape structure and rainfall infiltration in different gradients. Changing the proportion,shape,evenness and separation of staunch patch at an interval of 5°between 0°and 20°. Measuring the surface runoff yield and counting the rate of rainfall infiltration after simulating rainfall. After comparing, the results show that rainfall infiltration changes by changing the proportion,shape,evenness and separation of staunch patch, the proportion of staunch patch has the greatest influence, and the shape,evenness and separation of staunch patch have less influence; landscape instruction has greater influence to rainfall infiltration when the gradient is small, however, the influence is less and less, namely the greater influence of landscape structure to the rainfall infiltration has turned to the greater influence of the gradient to the rainfall infiltration with the gradient increasing.