Abstract: The concave herbaceous field is one of the important Low Impact Development（LID）facilities applied in sponge city construction. Concave herbaceous field was selected as the typical research object, the runoff control process of concave herbaceous field was simulated based on the three-dimensional numerical model, the precipitation process line and the total runoff amount were calculated according to the Chicago rain pattern formula suitable for short-duration design rainfall analysis, and the overflow reduction changes of LID facility nodes under different recurrence periods were studied. The results showed that with the increase of rainfall recurrence period, the overflow reduction of LID facilities gradually increased. Under different recurrence periods of 2a（a, year）, 10a and 30a, the overflow reduction rate of LID nodes gradually decreased, and the delay rate of peak flow time was 58.79%, 64.27% and 77.46%, respectively. Concave herbaceous field can effectively reduce the node overflow phenomenon caused by rainfall events in the study area. The smaller the rainfall recurrence period, the better the improvement of overflow phenomenon.

Key words: sponge city, numerical simulation, low impact development, concave herbaceous field, return period, runoff control