Spatial simulation of the ecological processes of stormwater for sponge cities

The ecological stormwater processes of a sponge city include the ecological processes of runoff and confluence, the thermal landscape and decontamination. In this study, elements of stormwater processes - short-duration heavy rainfall, rainstorm intensity, drainage networks, surface temperature, the scouring process and the cumulative process of pollutants (SS, COD, TP and NH3_N), and, finally, the low impact development (LID) facilities at different recurrence periods-are simulated using the rainstorm intensity model, the scoured exponential model and the split-window algorithm. Land-use types and LID facilities in sponge cities greatly influence the spatial distribution of ecological stormwater processes. Rainstorm intensity, cumulative volume, flow rate and drainage capacity all increase in the initial stage of rainfall and decrease in the later stage, with an increase in rainfall duration. Rainfall, infiltration amount, runoff and rainstorm intensity all increase; however, the runoff coefficient and infiltration proportion decrease with an increase in the rainfall recurrence period. LID facilities can increase rainfall, peak flood delay time, area of low temperature zone, annual runoff control rate and runoff pollutant reduction rate at the recurrence periods of 1 a, 3 a, 5 a, 10 a, 20 a, 30 a and 50 a, especially during short-duration rainfall. The paper concludes LID facilities of sponge cities play an important role in weakening the effects of rain-, heat- and pollution-islands.