Colne Brook, Fish Easement and Eel Pass

Background Information

A distributary of the River Colne, the Colne Brook leaves the River Colne at Uxbridge Moor where it flows through West Drayton and down to the village of Colnbrook. The brook then runs through Wraysbury before running into the River Thames downstream of Bell Lock Weir. Several barriers to migration are present along the brook and are impassable to fish. Measures are being taken to identify such structures and to help aid fish passage through the complete removal of impassable structures or to provide a fish passage solution.

Scope of the Project

The Colne Brook at Kingfisher Gardens is located in Iver, Buckinghamshire. The brook here is culverted for a short distance where it passes under Thorney Mill Road. The culverted stream runs over a concrete slope before exiting the culvert and returning to its naturalised state. Unless the river is in full flood the structure is impassable to fish through a lack of water depth and high velocities over the footing.

Our Solution

Aquamaintain Ltd designed a fish easement solution to overcome the shallow sloping weir beneath the road bride at Kingfisher Gardens. Owing to the location and difficulty of access, a baffle board solution was devised which incorporated recycled plastic baffles precisely positioned across the weir to increase water depth over the structure and reduce water velocity. Staggered low flow notches between the rows of baffles allow room for a wide variety of fish species to navigate their way over the obstruction. In addition to this, Eel passage was included in the form of removable Eel tiles fixed to the side of the culvert. These slide in and out of stainless steel brackets to allow for cleaning and maintenance.