Abstract
Impermeable pavements and roofs in urban areas convert most rainfall to runoff, which is commonly discharged to local sewers pipes and finally to the nearby streams and rivers. In case of heavy rain, the peak flow of runoff usually exceeds the carrying capacity of the local sewer pipes, leading to urban flooding. Traditional facilities, such as green roofs, permeable pavements, soakaways, rainwater tanks, rain barrels, and others reduce the runoff volume in case of a small rain but fail in case of a heavy rain. Here we propose a novel rainwater buffer tank to detain runoff from the nearby sealed surfaces in case of heavy rain and then to discharge rainwater from an orifice at the tank’s bottom. We found that considering a 100m2 rooftop with 0.80 runoff coefficient and a 10cm rainfall depth for an hour, a cubic tank with internal edge side of a square of 2 m attenuates the peak flow about 45%. To reduce a desirable peak flow, the outlet orifice of the buffer tank must be optimized according to site-specific conditions. The orifice can be set at an elevation from the tank’s bottom to create a dead storage for harvesting rainwater.
Highlights
Urbanization has sealed natural permeable surfaces with pavements, roofs, and other impermeable surfaces
We have shown that runoff from a 100 m2 rooftop can be detained by a buffer tank for attenuating the peak flow about 20-70%
Runoff is converted to the tank and is discharged from an outlet orifice that sets at the tank’s bottom
Summary
Urbanization has sealed natural permeable surfaces with pavements, roofs, and other impermeable surfaces Rainwater falling on these surfaces generates runoff, which is diverted to local sewer pipes and ends up at nearby streams or rivers. Mainstream techniques include Low Impact Development [2], Best Management Practices [3], Water Sensitive Urban Design [4], Sponge Cities [5], and other similar projects [6,7,8]. While their names of these projects are different, the purposes of these techniques are similar. On-source techniques are developed to retain, detain, infiltrate, harvest, evaporate, transpire, and/or re-use rainwater for reducing the runoff volume and the peak flow
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