Experimental Investigation of an Inclined Horizontal Submersible Pump with a Preemptive Operation Strategy for Mitigating Urban Pluvial Flooding: A Full-Scale Validation Approach

Climate change and urbanization have intensified extreme rainfall, exacerbating urban pluvial flooding risks. Conventional pumps require substantial submergence to suppress air-entraining vortices, delaying early-stage drainage. This study evaluated an inclined horizontal submersible pump (IHSP) with an anti-vortex suction cover designed for preemptive drainage at an ultra-low water level (0.5D). A 390-ton full-scale facility simulated an extreme inflow of 21.0 m3 min−1. Compared to conventional activation at 1.9D, preemptive operation extended the time to reach the critical inundation level (1.80 m) from 6 min 52 s to 13 min 17 s, yielding an observed macroscopic delay of 6 min 25 s in the experimental tank. Geometrically scaling this by the tank-to-field area ratio (4.67) yields an idealized theoretical reference of 1 min 22 s, which serves as a conceptual baseline rather than a deterministic field prediction. During continuous low-load standby, motor-current deviations remained tightly constrained (maximum 2.07%), well within the study-specific ±7.5% screening criterion while eliminating chattering-induced electromechanical stress. Furthermore, an 11-year life cycle cost assessment revealed a 33.2% expenditure reduction, primarily from eliminating deep-sump excavations. These findings demonstrate that the IHSP provides stable low-water-level operation and preemptive drainage for enhanced urban flood response.