A practice of stream restoration project in urban area and its evaluation (#77)
River management work is turning from hard engineering method to ecological based restoration method in order to improve river environment worldwide. Especially, river environment in urban streams are degraded due to excessive hard covered revetment work, loss of longitudinal connectivity and so on. Thus stream restoration work in urban area is one of the most important issues on river management.
This study reports on a progressive stream restoration project and its evaluation from ecological aspect by fish inhabiting condition survey in urban stream in Japan. The project site is Kamisaigo river which runs through urbanized suburb area. The project site length was about 1000 meters on middle stream of the river. Major purposes of the project are restoration of ecological environment and flood control. Main points of restoration work are Broadening river width as twice as pre-restoration, Restoring longitudinal connectivity with concrete weir removal, Restoring riparian zone with concrete revetment removal, Restoring riffle and pool habitat using habitat improving structures.
Fish sampling survey and physical environment survey were conducted to evaluate the effect of restoration project. Survey was conducted in every autumn from 2009 (pre-restoration) to 2013 (post-restoration). Study site has approximately 1000 meter length. Five survey stations that have 50 meters length for each are installed in study site.
As a result, it is revealed that fish species richness and physical environment variety are remarkably improved. These results showed that Kamisaigo river restoration project succeeded in ecological aspect.