Abstract: As urbanization process speeds up, rainstorm and waterlogging disasters occur more frequently and severely threaten the residents’ safety of life and property. This study develops a stormwater management model (SWMM) combining with rapid urbanization process for assessing the impact of urbanization process on the basin hydrological process, and applies it to the Chebeichong basin, a typical basin in Guangdong-Hong Kong-Macao Greater Bay Area (GBA), to simulate its scenarios in the early 1980s, 2015 and 2050. Results support the conclusions: 1) Our SWMM is verified against rainfall measurements and shows a good adaptability to the study area. 2) In the study area, the proportions of urban landuse are 15.07%, 47.64% and 54.29% in the three scenarios respectively; and from 1980 to 2015, the urban landuse was expanded by 24.35 km2 and concentrated on an area around the middle lower Chebei River mainstream and its tributary Yangmei River basin. Of the new urban landuse of 1980-2015, cultivated land converted into urban land was its largest proportion of up to 86.49%. 3) At three typical cross sections of the river, flow hydrographs show a single peak shape with large fluctuations after urbanization completed while their variations were relatively mild in 1980. Besides, urbanization can also increase flood peak discharges, advances flood peak times, and raises flood risk. Under the design rainfall of 0.5-year return period, the flood peak discharge at the basin outlet is increased by 2.27 and 2.7 times in the 2015 and 2050 scenarios respectively, and the peak time is nearly an hour earlier. The results are useful in constructing the pipeline networks, flood control, and drainage of GBA.

Key words: urbanization, landuse change, SWMM, hydrological process, Guangdong-Hong Kong-Macao Greater Bay Area