Innovative Design of the Gravel System for an Underground Parking Garage

This study discusses the innovative design of the gravel infiltration retention system for the underground parking garage of the phases 5 and 6 of Project of the Hills in Panyu District, Guangzhou City. The runoff from this project site is mainly managed by an innovative subsurface detention gravel system that provides stormwater storage during storm event and irrigation reuse during the dry season. This gravel infiltration retention system is generally provided by a 20-cm layer of coarse gravel placed over the garage under the landscaping soil surrounding the buildings. The areas not treated by the gravel infiltration retention system will be treated by a bioswale and a rain garden designed to remove nutrients. The synthetic 133-mm 4-hour storm event with 10-year return period was used to design the gravel infiltration retention system, rain garden, bioswale, and other pipeline conveyance. The 24-hour historical rainfall of 389 mm was used to evaluate these low-impact development facilities responses to an extreme event. The simulation results show that the gravel infiltration retention system have very large flood control performance.