Glenbeg culvert baffles

The works to install the fish passage baffles in the Glenbeg Burn started today. On the way back from the smolt trap I called in the see how things were progressing. The works hadn’t really started but BEAR Scotland and the installation team were on site. The burn will be sandbagged above the culvert then overpumped so that the actual culvert will be as dry as possible. Although its cold they couldn’t have picked a better week as the flow was very low.

Roads team on site

Roads team on site

Last week we collected some pre works data on the culvert. The length was 38.6m and gradient  was 1.81%; not that steep but the water speeds and depths present in the middle of the culvert made it effectively impassable at a wide range of flows. At its shallowest the water depth was 5.5cm or just over 2″, too shallow to allow a large fish like a salmon to generate sufficient power with its tail to combat the water speed. Using a set of equipment for assessing barriers on loan from RAFTS we were also able to measure water speeds in the culvert. The maximum speed recorded was 2.1m/sec, well above the acceptable guidelines established by the Scottish Government which state that for a culvert over 30m long the maximum water speed for salmon is 1.75m/sec with lower speeds for trout.

Fast and shallow, the Glenbeg Culvert preworks

Fast and shallow; the Glenbeg Culvert preworks

BEAR reckon the baffles will be installed this week thereafter we will resurvey depths and current speeds. Salmon used to spawn in the very upper reaches of the Glenbeg Burn but not in recent years. The burn will be monitored and we hope to see a recovery in the fish population upstream.

 

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