Analysis on the decay law of water retention of sponge city roads under cyclic clogging

The water retention capacity of sponge city pavement systems is substantially compromised by particulate sedimentation induced by vehicular and pedestrian traffic. To systematically evaluate the deterioration mechanisms of hydrological performance under cyclic clogging, a controlled rainfall-simulation experiments were conducted. This experimental framework enabled quantitative characterization of particle size-dependent clogging distribution patterns and temporal evolution of hydrodynamic performance. Key findings revealed that: (1) Primary clogging exerted disproportionate impacts on motorways and non-motorized ways, with median particle size retention rates decaying to 70.5 % (motorway) and 67.6 % (non-motorized way) of initial values during 2 nd –10 th sedimentation cycles, versus only 25.6 % for sidewalks; (2) Progressive clogging cycles triggered a phase transition in permeability dynamics, shifting the dominant hydrological process from subsurface infiltration to surface runoff generation; (3) The runoff modulation efficiency of water storage structures exhibited a multiphase trajectory (decline - recovery - stabilization), while the integrated stormwater management performance degraded from 94.23 % to 86.03 % baseline efficiency. • A test bench was built to comprehensively analyze the rainwater flow direction. • The actual circulation clogging situation was inverted by model test. • The water conservation capacity was analyzed under different congestion conditions. • The key maintenance nodes of the sponge city road was determined.