AFON WYBRNANT SPAWNING GRAVEL RESTORATION

Background and scope:

The Afon Wybrnant enters the Afon Lledr on the right bank just downstream of the Pont Gethin Viaduct. It is approx 3km long but only the lower 400m is accessible to migratory fish due to impassable waterfalls. Over the years, spates had washed out most of the spawning gravel in this section of the stream and the aim of the project was to create new areas with a combined approach of constructing bed-check weirs and re-introducing suitable substrate. The objectives of the project were to create riparian tall herb cover, with patches of riparian woodland and scrub. To increase the number of juvenile salmonids, to protect salmonid spawning and nursery habitat and to create habitat suitable for other species of conservation importance and biodiversity.

 

Work undertaken:

The work was carried out in September 2010 when two log weirs were secured across the width of the watercourse having firstly ensured that these could not present a barrier to migrating fish. The work was carried out to Environment Agency Wales (EAW) specifications. The logs were secured by stakes and the downstream side was protected by an apron of cobbles. Four boulder weirs were also placed in the stream at locations advised by EAW staff. It was important that the boulders were sufficiently large to prevent movement in flood conditions and ideally be ‘bedded in’ arched upstream. Care was taken to ensure that water could flow over the weir at all flow levels.

Selective thinning and coppicing of trees along 70m of bank was carried out in accordance with the EAW specification. The emphasis was to reduce instream shading to approximately 25% of stream bed area and to stabilise and prolong the life of existing trees while retaining all but the most problematic of trees. The work was carried out by an experienced contractor but Trust volunteers assisted in relocating the gravels following the construction of the log weirs. The project was funded through Afonydd Cymru from the European Fisheries Fund.

Unfortunately, flood damage resulted in the need for additional work to be carried out.  This further work was undertaken in October 2013.  This time, eight log weirs were installed in preference to boulder weirs which had previously been tried but which were not as successful as the log weirs due to them being regularly dislodged by the flood water.  The 2013 project was funded with Water Framework Directive (WFD) finance. Trust volunteers also assisted by moving gravel into position as part of this project as well.

Benefit:

400m of improved spawning area.

: A section of the stream where a new boulder dam is to be created marked out in readiness for the work to commence.

 

The improved spawning conditions created as a result of the construction of the boulder dam.