The Effectiveness of the Rainwater Garden under Different Rainfall and Different Soil Conditions in Hangzhou, Zhejiang

At present, there are still problems in applicability and lack of basic research in the construction of sponge cities in Zhejiang Province. In this paper, a generalized model of the rainwater garden box is established. The planting soil, park soil and soil mixed with fine sand and coarse sand in Hangzhou area are selected as the rainwater garden medium layer. The artificial rainfall test method is used to simulate seepage and storage efficiency of rain garden under the once every two years rainfall and once every five years rainfall of Hangzhou city. The test results show that under the same soil conditions, the maximum infiltration flow rate under the once every two years rainfall is 0.2 cm 3 /s more than that under the once every five years, and the maximum infiltration rate of planting soil has exceeded the maximum infiltration rate under the once every five years. Under the once every two years rainfall, the maximum infiltration flow of the planting soil, planting soil and fine sand are each composed of half, and planting soil and coarse sand are each composed of half are 2.1, 4.8 and 5.6 cm 3 /s, respectively; the maximum infiltration flow of the the park soil, park soil and fine sand are each composed of half, and the park soil and coarse sand are each composed of half, are 0.7, 7.7and 9.2 cm 3 /s, respectively. At the same time, after adding fine sand, the infiltration amount increases by about 1/4 compared to before mixing; after adding coarse sand, the infiltration amount increases by about 1/3 compared to before mixing. It can be seen that the infiltration capacity of the park soil is much better than that of the planting soil after the sand-grain mixing ratio. The results of this research can provide theoretical basis and technical reference for the construction of Hangzhou sponge city.