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MOUNTAIN ASH WEIR, RIVER CYNON

 

This weir was the site of the river crossing on the old colliery site. The picture before work shows how difficult it would be for migratory fish to move upriver due to the long flat weir. Only certain river heights would allow salmon and trout to surmount this obstacle. 

Working in partnership with Natural Resources Wales and using funds from the Cardiff Harbour Authority mitigation fund to improve migratory fisheries, administered by NRW, the Trust obtained land owner permission to carry out work on the weir. 

The work was to install timber baulks at intervals up the weir to create flows and depth that would allow migratory fish to pass over the weir at most water heights. 

Care was needed as the main trunk sewer runs down the east bank of the river. With permission from Welsh Water to work near the sewer and from Rhondda Cynon Taf Authority on their land, the work was carried out by a local contractor. The trust favours local contractors whenever possible. 

The picture story shows the weir before and the sequence shows the work in progress. 

This weir was initially classed by NRW as passable at high flows for salmon and trout. We would now say it is passable at all flows. The improvement work at the site now makes a further 13.5km of river accessible as far as the next in river barrier at Station Road, Hirwaun. We are working with NRW and RCT to put a fish pass in place on this weir. 


 

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