Abstract: The Yanqi Lake campus of University of Chinese Academy of Sciences was taken for a case study. Stormwater management model (SWMM) was used to model water overflow processes in all the subcatchments in the study area during the 48 rainfall events in 2016 and 2017. The relationships of spatial distribution of surface runoff with rainfall and underlying surface were explored. The results showed that there occurred higher runoff in the subcatchments with asphalt land cover, while there occurred lower runoff in the green-cover subcatchments. Asphalt land cover had the greatest possibility to produce overflow, green cover had much weak possibility, and brickwork cover was more likely to produce intermediate runoff. Although concrete land or roof cover produced more overflow than brickwork cover, they had similar patterns of producing runoff under different rainfall events. The surface runoff values of asphalt or brickwork land cover were linearly positively correlated with the slope value. For the subcatchments with asphalt-brickwork or asphalt-green cover, percent impervious cover (PIC) should be reduced to be below 60% to significantly control rainstorm and heavy rain runoff. To significantly control heavy rainstorm runoff produced within the subcatchments with asphalt-green cover, PIC should be lower than 30%. However, for the subcatchments with asphalt-brickwork cover, decreasing impervious area did not have obvious effect on mitigating heavy rainstorm runoff. The study may provide theoretical basis and decision-making suggestions for sponge city construction and urban flood prevention and control.

Key words: underlying surface type, underlying surface characteristic, percent impervious cover