Weir Removal and Bridge Revetment Construction

This project was to break out an existing weir structure enabling migratory fish passage further up the river, re-model the bed of the river to suit the lowered water level and construct new revetments to protect the bridge immediately upstream of where the weir was.

Once measures to capture disturbed sediments were put in place downstream the weir was broken out and removed using a long reach excavator working from the bank above.

The bed downstream of the weir was then re-graded to suit the lower water level.

The banks and bed of the river under the bridge were carefully excavated to accommodate the gabion basket revetment.

A temporary dam was installed to divert the water down one half of the channel leaving the other half to be worked on. Diesel pumps were used to remove seepage into the working area through the dam.

Stone filled mattresses were installed across half of the bed of the channel to act as a footing to the new revetment and prevent scour underneath the bridge.

The stone filled gabion baskets were then installed above the reno mattresses in tiers taking the revetment up to ground level.

The temporary dam was then moved diverting the water down the completed half while the remainder was completed tying the reno mattresses to those previously installed on the first half to create one secure joined up footing and then carefully excavating the bank and installing the baskets above again as before.

The banks were narrowed above and below the bridge and gravels were imported to form two riffles, one upstream of the bridge and one where the weir was.