Research On Mountainous Residential Area Landscape Design Strategy Based On Stormwater Management In Chongqing

Chongqing has abundant rainfall and its seasonal distribution was uneven. There were often torrential rains in flood season(May to September). As a typical mountainous city, it could not avoid the dramatic changes in elevation, slope, aspect and terrain, leading to the faster water runoff and lower permeability. In recent years, with the rapid development of the urban construction in Chongqing, the large area of the building roof and impervious surface disturbed the natural hydrologic cycle, causing water table falling and surface runoff increasing within the residential area.Although Chongqing has abundant river resources and rainfall, the landscape design did not take rainfall into consideration, and it still use the traditional rapid drainage way of stormwater management, so a large number of water resources were quickly discharged. In addition, the construction of urban drainage system is not perfect, that resulting in a great waste of water resource and increasing the urban drainage pressure. The stormwater problem appeared frequently.In order to alleviate these stormwater problems, developed countries have formed mature stormwater management systems and related technical measures, through years of research. They integrated stormwater management with the landscape, and the green space took an active role in increasing rainwater infiltration, reducing surface runoff, supplementing the groundwater, controlling runoff pollution, delaying flood peak emergence. However, the study on this subject in China is still at the starting stage. Some large cities began to integrate the rainwater utilization into the residential landscape, but the overall level of development is relatively low. In the unique geographical environment of Chongqing, the research on mountainous residential area landscape planning and design based on stormwater management remains blank.This study has took the combination of residential landscape and stormwater management as a starting point, analysed internal and external environmental conditions of the mountainous residential areas, summarized stormwater management characteristics and the main points, concluded that there was great potential to combine landscape and stormwater management. Through the investigation of the existing fifteen mountainous residential areas, generalized the landscape approaches, which was conducive to the stormwater management, and summarized the main existing problems from the three hydrological processes, these problems as follows: in the rainwater produce period, low utilization of the roof, short retention time of the rainwater and low water permeability were the three main problems, in the transmission period, the main problems were faster transmission and unpleasant transmission facilities, in the saving period, problems mainly included lacking of savings facilities and losing ecological function of the waterscape.Combined with the relevant stormwater management theories and successful cases in domestic and foreign, this study summarized the suitable landscape strategies and approaches as follows.In the produce period, the landscape strategies were increasing rainwater infiltration, prolonging retention time, controlling runoff pollution, and the approaches were green roofs, permeable paving, soil improvement and terrain design etc. In the transmission period, taking transmission channels as landscape, increasing the roughness of the channels, and extending the path were the main strategies, and the approaches included rain chain, downspout, simple soil ditch, gravel ditch, drainage ditch, dry creek and glassed swale, etc. In the saving period, the landscape strategies were making full use of the environmental characteristics, focus on the function of saving facilities, organizing rainwater reuse reasonably, and the approaches were landscape sketch of water storage, rainwater planting pool, multifunctional storage tank, rainwater ponds, stormwater wetland etc.Finally, it summarized and forecasted the landscape planning and design based on stormwater management in the residential areas. The exploration of stormwater management was still in initial stage in Chongqing, and there was still a large gap between the realities and the theories. This study has took the stormwater management as an important consideration, try to provide a new way to create conservation, ecological, sustainable residential landscape with regional features, to contribute to the construction of the sponge city in Chongqing.