Adaptive Structure Design of Raingarden in Shanghai Coastal Saline Alkali Area for Improving Urban Resilience

Shanghai is one of the demonstration sites of Sponge City which is a typical coastal saline-alkali area. To improve the urban resilience and mitigate storm water, green infrastructure as raingarden, bioswale and green roof, etc. are used to regulate runoff. However, the design of raingarden have the disadvantage of solutions for high groundwater levels and soil salinization in Shanghai. In order to improve the regional adaptability and optimize the design of the raingarden, the indoor rainfall simulation experiments and orthogonal experiments were used to analyze the effect of salt isolation and rain infiltration impacted by different structures (salt-insulated layer material, salt-insulated layer position, filler layer thickness). The results show that the order of influence on salt isolation is: salt-insulated material>filler layer thickness>salt-insulated layer position. The order of impact on rain infiltration is: salt-insulated material>salt-insulated layer location>filler layer thickness. Three types of rain garden structures are proposed. The first is strong salt-insulated rain garden suitable for severe saline-alkali areas. The second is suitable for the comprehensive rain garden in the moderate saline-alkali area. The third is suitable for the permeable rain garden in the light saline-alkali area.