The Flood & Erosion Control Board has many powers derived from CT General Statutes. Among them is the authority "to plan, lay out, acquire, construct, reconstruct, repair, maintain,supervise and manage a flood or erosion control system." You should refer to those Statutes for specifics.
It is an appointed board, per Town Ordinance, whose formation was driven by the various issues with the Lake Williams Dam in the early 1980's. Since the work was completed on the Lake Williams Dam and related issues, the level of activity of the Board has diminished significantly. Typically, there is just one meeting per year. At the Annual Town Meeting on May 5, 2014 the Town passed an Ordinance which allows the Board of Selectmen to serve as the Flood and Erosion Control Board.