Physical model investigation of flood control concrete channel restoration

Many natural rivers and streams in highly urbanized cities were converted into concrete channels to maximize the efficiency of conveying floodwaters away from populated areas. These engineering structures tend to disrupt the nature 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 restoration goals are: 1) to create a natural and self-sustainable river system in order to re-establish the aquatic species on the flood control channel; 2) to provide appropriate in-stream covers, pools and riffles for fish spawning and rearing; and 3) to maintain the flood control function after stream restoration. Meanders and deflectors will be applied to the low-flow channel to achieve the first two goals. A physical model representing an actual 2-metre wide meander channel section of the low-flow channel is constructed at The Hong Kong Polytechnic University Hydraulics Laboratory. Single and double deflectors at various locations along the meander are tested to determine the maximum pool volume creation. Different flow rates (0.030 m3/s and 0.150 m3/s) and flow depths (0.1 m to 0.45 m) are also applied to the physical model tests in order to reproduce the real situations.