Option 4: Weir Lowering & Rock Weirs within the Carshalton & Croydon Branches
Solution
This option which was originally put forward by CBEC Eco Engineering to improve fish passage and river habitat at Shepley Mill, consists of lowering the west weir by 1 m and constructing two fixed head rock weir/ramp structures on the Carshalton and Croydon branches of the River Wandle. The east weir would not be modified. In addition, to ensure the successful migration of fish through the west weir culvert, fish friendly modifications to the culvert, such as baffles, could be implemented.
Concept Design
Appraisal
Although Option 4 has the potential to allow for the safe passage of fish and eels through Shepley Mill, contribute to GEP under the WFD and comply with the Eels Regulations, it is unclear the impacts of low flows on pond inundation on Wilderness Island and flood risk, with the need for fish passage solutions most likely required downstream of the rock ramps/weirs. Overall the suitability of this option to meet the project objectives is considered Moderate.