Abstract
It has been a great concern to minimize flood damage in the event of extreme rainfall beyond design level. In this paper, a structural method is presented with the concept that the urban drainage system must work properly to exclude stormwater in case of design rainfall events, while it should detain stormwater for a while to disperse inundation and reduce peak discharge into a receiving river in the event of extreme rainfall. To realize the concept, the hydrological effect of road detention and associated inlet structure are investigated.
The hydraulic function of the inlet, which comprises three phases of outflow depending on the water stage in front of the inlet, is modeled and numerical simulations are carried out to see its hydrological effect. The results showed that transversal road slope, length and the inlet configuration influence the efficiency of the road detention, and that it reduces outflow to 1/3 of incoming flow. The synthetic effect of road detention on runoff reduction is also computed in a small urbanized watershed using a distributed flow routing model.
