Number of dragonfly larvae collected in each canal section during the survey period.

This is a record of some surveys conducted in the Ichinomiya Canal that is an irrigation and drainage channel, lined with two- and three-sided concrete revetments, that flows through paddy fields alongside the Tama River in Tokyo, Japan. The progressive collapse of these revetments in various sections of the canal prompted a construction project in early 2014. To enhance biological habitats associated with the canal, various improvements were undertaken, including a timber piling revetment constructed on one bank (section I-3), and lowering of the canal bottom by 30 cm beneath a bridge that spans the canal (section I-2). A preliminary larval survey was conducted in November 2013 (immediately before construction began).