River Ely – Thomastown Weir

 Much of the work the Trust has to do in the river valleys is in close proximity to housing and to overcome past work when the environment was a minor consideration. This site on the River Ely at Thomastown was quite challenging.  Natural Resources Wales had made it a priority under the work programme. The access was restricted due to the fact the bank was built up of gabion baskets and would have collapsed under the weight of a track machine. Only the use of a mobile crane to lower in the block stone made the work possible.

Thomastown weir is at the confluence of the river Ely and Nant Llanilid. It was a block for migrating fish to the upper Ely and the Nant Llanilid. There was a weir constructed of block stone in the river Ely with a drop of three quarters of a meter and a similar drop on the Nant Llanilid. A stream like this is a local gem to the Valley Rivers as immediately upstream of the weir and through the culvert is a well gravelled bottom and it is certainly a place that fish would spawn.  Every bit of spawning area so lacking in the valleys is essential in our work to improve the valleys for migratory fish as well as the local brown trout.

Future passage for fish to both the Ely and Llanilid needed to be taken into consideration. A small block stone weir in the Ely river channel below the confluence of the two waters would be the ideal solution as this would then improve the both for migratory fish.  A pair of oak baffles fixed to the edge of the Llanilid weir would produce a more concentrated flow over the lip on the entrance to the Llanilid as well as improving the migration possibilities on that stream.  It also made the access through the culvert very easy for fish migration.

Some careful tree cutting/coppicing was need to allow access for the crane this was carried out during the winter when there are no nesting birds.

Clean stone was laid onto the river bed to make a base for the block stone weir and the individual stone was lowered and guided in to position. Two layers of stone were used to make sure that there can be no wash out. Once completed it was immediately apparent that the work was achieving the desired effect as the water level behind the weir increased making the height fish had to surmount half of what it had been. Clean stone was used to seal off the gaps between block stone and it was left to winter high water to do the rest.

A visit during winter see pictures shows the work to be a success. Follow up visits to assess and monitor improvements will be necessary.

Below are a series of pictures taken prior to the work was being completed, during the work and on completion

Before the start of the work
Before the start of work
trees removed prior to work commencement
Trees removed during the winter prior to work commencement
Tree removal prior to work commencement
Tree removal prior to work commencement
the 2 obstructions visible and ready to be passed
the 2 obstructions visible and ready to be passed
Crane at work bringing in blockstone
Crane at work bringing in blockstone
positioning the blockstone
Positioning the blockstone
Finished work fish can now pass both weirs with ease
Finished work fish can now pass both weirs with ease
Both weirs working in a flood
Both weirs working in a flood