The Trust in conjunction with  Environment Agency Wales had looked at a potential barrier on the River Clydach at Cwm Farm Railway Bridge approximately 300 yards upstream of where the river joins the Taff Grid Ref: ST 0801 9285.

Although not a total barrier it was felt after joint consultation with  Environment Agency Wales that access to the upper river could be improved. This could be achieved by making a weir downstream of the railway bridge that would  allow migratory fish increased access to an additional 10km (approx.) of the river Clydach enabling them to reach the headwaters to spawn.

The barrier consisted of a flat sloping face of bed-rock under the railway bridge arch, at a slope of approx. 30 degrees, across the full width of the river and extending downstream for approx. 4-5 meters. However, there were  a few channels within the sloping bedrock which migrating fish could use to swim up during higher water conditions. (see photographs)
  
The area under the bridge with no holding water.                                          The brige from above.

Note the channel on the left  is very shallow and in high water it would not give fish any holding water to rest. By increasing the depth of the pool below we are creating holding areas for fish betwen the boulders.

Downstream of this sloping bed-rock barrier was a scour pool approx. 0.4 meters deep (in normal low water conditions) the upstream neck of the pool was slightly lower than the downstream edge of the bed-rock slope (bottom of slope perched above water level) and did not allow migrating fish in the pool to access the lower part of the sloping bed-rock in all but high river flows. N.B. Traversing the scour pool was what appeared to be a 0.3 metre diameter  sewer pipe on concrete pillars. Concern was expressed about possible damage during the construction of the weir and subsequent increased levels of water in the scour pool. It was considered that the most effective option would be to build a pre-barrage weir type pool at the tail of the existing pool. This would raise the level of the existing pool by approx. 0.4 meters, effectively slowing down the flow, allowing migrating fish to rest in this deeper pool and to access the bottom of the sloping barrier and use the channels to swim through the barrier.

  
These pictures show the neck of the pool before and after the installation of the weir.  Note the large boulder  on the left of the first picture and the same boulder in the centre of the second picture showing the water now reaching it which was what we were trying to achieve.

South East Wales Rivers Trust was asked to manage the project in conjunction with  Environment Agency Wales  staff Mike Clyde and Dave Tavner.  This involved the Trust identifying the land owners and getting their permission to cross their land and use it as temporary storage for materials. We were also asked to comment on the estimates tendered  by contractors with Spencer Davies eventually winning the contract. Environment Agency Wales obtained the necessary land drainage consent.

Work began on Tuesday 12th October 2010 and comprised three  rows of large blockstone interlocked across the river and effectively keyed into both river banks. The work was completed to our satisfaction that same day. Due to the need for heavy equipment (360 hydraulic machine) to be used for this project, there was a considerable amount of damage to the fencing and access area. This damaged was later rectified to the owner’s satisfaction with a new fence being installed.

The above photograph show the new fence the Trust had installed for the owner of the land. We also used the machinary while on site to level the land

Photographs were taken of the identified barrier before, during and at the completion of the work to show the changes over time.
The effectiveness of creating this easement will be monitored  by requesting reports of migratory passing through this barrier and by the analysis of Environmewnt Agency Wales  electro-fishing surveys upstream of this location.
The Agency receives annual funding for projects such as this to be used to mitigate the effects of the Cardiff Bay Barrage on migratory fish.  The Trust was able to use its expertise to negotiate with contractors a suitable price for the work