Objective To quantitatively analyze the driving factors influencing peak discharges under storm conditions and to find the variations in peak discharges, conducting comprehensive storm flood surveys and investigating the causes behind gully peak discharges are crucial. This analysis is importance for regional post-disaster reconstruction planning as well as for disaster prevention and reduction strategies.

Method To analyze the drivers of peak discharges under extreme rainfall conditions, after the extreme rainfall event in Beijing on July, 2023, a research team surveyed 140 flood mark points across 56 gullies in the Mentougou district. Then, the random forest model was used to analyze the factors driving peak discharges, based on the spatial changes.

Result (1) In the Mentougou district, the peak discharge of gullies increases from north to south, with values ranging from 27.5 to 1072.0 m³/s. Gullies exceeding the peak discharge levels for 10-year, 20-year, and 50-year events account for 82%, 71%, and 42% of the total, respectively. (2) The main factors influencing the peak discharge differences in the Mentougou district under rainfall conditions are basin area, gully length, mean relief amplitude, runoff coefficient and sediment accumulation, with importance values of 1.000, 0.524, 0.471, 0.382, 0.346, respectively. The topographic factors have the greatest influence on the peak discharge in the gullies of Mentougou District under the current heavy rainfall conditions. (3) These factors exhibit a complex nonlinear relationship with the peak discharge.

Conclusion In post-disaster recovery and reconstruction, it is recommended to use the gully as the basic unit for management. Implement the strategy of “one gully, one policy”. Reasonable arrangement of flood control measures and improvement of project flood control standards. Focus on key controllable factors, such as the sediment accumulation and the runoff coefficient. Addressing the issue of encroachment on flood channels requires cross-departmental coordination and management. On the premise of meeting the needs of all parties, it is crucial to ensure the ability to cope with floods and to restore and rebuild in a systematic and rational manner.