China's urbanization process of 30 years equals to foreign urbanization process of 100 years (10-50%). Since 2003, the urban waterlogging problem has been occurring frequently. The survey of China’s 351 cities made by the Ministry of Housing and Urban-Rural Development of the PRC in 2010 shows: 62% cities of them had waterlogging problem in 2008-2010; the cities with the water depth of more than 15cm reached 90%; the cities with the waterlogging time of more than half an hour accounted for 78.9%. Currently, there are still three major problems in construction of the sponge city: focus on the scale of the micro-blocks but lack multi-scale ideas in river basin, region, city and neighborhood; focus on promotion of drainage capacity but lack understanding of development mode and land use control and planning; and difficult identification technology in key demonstration areas of the sponge city. In 1960s, the city development and waterlogging was highlighted in developed countries. These cities gradually had an in-depth understanding of the urban waterlogging reasons and the key points of prevention and control and a system was formed, which develops from the end drainage network in 1960s, imperviousness threshold control, urban land development mode to current research on control and planning of multi-scale urban land use parameters.

Therefore, since 2009, Su Weizhong has been focusing on research on the mechanism and regulation of the impact of multi-scale urban land use on flooding. First, the author identified that increasing of scale urban and rural land in Taihu Lake resulted in decrease of 8.29% in the overall infiltration rate, 7.5% reduction in water storage area, 16.44% reduction in natural confluence pathway, and a higher proportion of more than 37% in new land for construction in high-risk flooding area, about two-thirds of which came from new cities and new districts. Second, in terms of the new district scale, innovation was made in existing land patter planning method from the perspective of hydrological safety. Namely, the catchment area was divided into upstream, downstream, left and right banks, riverside area and other control units by taking rainwater catchment area unit and its main river and channel as references. Furthermore, land patter and runoff producing patter simulation platform was developed and established based on C# and Arc Engine and coupling CA and SCS-CN. The confluence process and waterlogging response scene of land space organization scheme of various cities under above space units were identified by simulation of the SWMM model. Finally, the following aspects were proposed to ensure the hydrological security in the urban land use: first, propose a three-dimensional land use pattern combining with the planning area division and hydrological unit; second, identify three types of key organization factors of each organization unit above, including the main confluence channel, low-lying area and urban and rural land; third, conduct simulation evaluation on rationality of space organization integrating hydrological model and planning means.

The above achievements are the core achievements of three projects of National Natural Science Foundation of China, two national key fund topics and several planning topics undertaken by the author. Currently, one achievement works has been published in China and ten papers have been published in China’s main magazines in the field of geography, resources and environment and foreign SSCI/SCI. See the home page: http: //people.ucas.ac.cn/~wzsu.