Ecological rehabilitation of canals in Colombo: a design to harmonize flood control and physical heterogeneity
NRC Grant No: 17-066
Research Institute: Sri Lanka Institute of Information Technology
Area of Research: Civil Engineering
Status: Ongoing
Email: ishan_gomes@yahoo.com; ayantha.g@sliit.lk
Summary
Sri Lankan urban areas have an extensive network of canals, and most were built a few centuries back during the Dutch period. Currently fequent dredging is taken place to remove sediments and vegetation; the ultimate objective is to maintain the vital flood control function. It should be noted, these canals could be managed in ways to provide the flood control while maintaining ecological services that are beneficial to the environment and also valued by the citizens. Running waters have the capacity for recreational activities and to be biodiversity hotspots. This is also vital in the process of transforming Colombo to a world city as proposed by the Western region Megapolis development. One of the main reasons to have a very low ecological health in these canals is due to lack of suitable instream physical habitats. Increased physical heterogeneity is important for floral and fauna] colonization. Also, it influences the water quality in a positive way due to increased attenuation and assimilation of constituents. This research by way of field assessments, physical and numerical modelling would study how to increase physical heterogeneity while maintaining the flood control functions. Results could be incorporated in rehabilitation works of canals in Colombo and elsewhere. Merits of this research extend beyond Sri Lanka. Firstly, this type of study for manmade rivers (canals) are rare (studies are ongoing for the degraded natural ones). Secondly, no studies have been found for canals that flow under subcritical conditions, such as the Dutch canals in Colombo.
Objectives
To naturalize canals such that they would function similar to natural rivers/streams and provide a wide range of ecological services, while maintaining flood safety. The specific objectives are to:
l) maintain flood control function
2) establish appropriate pools, riffles, in-stream covers and similar meso-scale physical habitats to that support flora and fauna
3) improved assimilation and attenuation processes for contaminant retention and removal
4) provide a basis for future rehabilitation works and preparation of guidelines for canal rehabilitation