Flood Concrete Channel Restoration in Urbanized Cities

Celia Fan, James Li , Grace Luk and Onyx Wai

ABSTRACT

Many rivers and streams throughout the world were severely affected by human activities in the past century including water abstraction, watershed land use changes, power generation, and dam and levee construction. In highly urbanized cities, engineering practices advocate straightening, enlarging, and converting the natural rivers and streams into concrete channels to maximize the efficiency of conveying the floodwaters away from populated areas. These engineering structures disrupt the natural equilibrium of fluvial systems and eliminate the macroinvertebrates, aquatic and riparian species in watercourses.

The objective of this research is to develop a general stream restoration approach for flood control concrete channels in highly urbanized areas. The approach consists of three phases: (1) modification of low-flow concrete channels to re-establish a natural and self-sustainable river system for selected fish habitats; (2) development of hydraulic and sediment transport relationships for the modified low-flow concrete channel; and (3) confirmation of the original flood control function after stream restoration. The restoration approach will be applied to a concrete flood channel in Hong Kong that drains into a nature reserve, the Mai Po Nature Reserve, in Deep Bay. Meanders, deflectors and instream covers will be applied to the low-flow concrete channel for pools and riffles creation in order to achieve the restoration objectives. A physical model representing an actual 2-metre wide meander channel section of the low-flow channel was constructed at The Hong Kong Polytechnic University’s Hydraulics Laboratory to investigate the hydraulic and sediment transport relationships.


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