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Hydrologic Considerations in Rehabilitating Existing Open Drains

Author(s): Ting Fong May Chui; Palanisamy Bakkiyalakshmi

Linked Author(s): Ting Fong May Chui

Keywords: River restoration; Low impact development; Water sensitive urban design; Riparian vegetation; Hydrologic modeling

Abstract: Riparian zones support a high level of biodiversity, mitigating flooding impacts and preventingpollutants from reachingthe rivers. They are, however, often replaced with concrete lined surfaces in urban areastobetter convey storm water. With increased environmental awareness in the recent decades, there are now rising interests in rehabilitating open storm water drains in heavily urbanized environment. This study designs and evaluates such engineered vegetative structuresby applying Storm Water Management Modeling (SWMM) on a generic catchment in Singapore. The first design involves decking a green channel cover on an existing conventional drain, which treats the overland flow from the upland areas before releases it to the drain. The second design constructs a vegetative swale along a conventional drain together with an upstream storage pond to maintain a perennial flow in the swale. To understand the performance of these engineered structures, the model is also run without the structures so that the hydrologic and hydraulic behavior of the original, conventional drainis understood. The modeling results depict that the green channel cover established atop of the draindelays and reduces peak runoff. The vegetative swale has a similar, but even larger, impacton the peak runoff. In addition, it maintains a low flow throughout the simulation period with the release from the upstream storage pond during non-rainy days. Overall, the modeling results show that these structures could slow down the release of overland flow to the drainand also maintaina low flow and green cover year around, enhancing the growth of flora and fauna in Singapore drainage system.


Year: 2013

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