Monday, 17 January 2022

Nant Fawr flooding

Anybody using the Nant Fawr site over the last few weeks will be aware there have been some extensive flooding issues in the meadows alongside Llanishen Reservoir and in the ‘dip’ just north of the old reservoir car park.  The ‘dip’ has always flooded, which is why we created an alternative route through the woods to bypass the flooding and raised the main footpath. 

During the Welsh Water main works in 2018 a new drain and soak-away was installed at the bottom of the dip to take the excess water away and keep the area drained but, surprisingly, it still continued to flood during very wet spells.  A camera was put into the pipe that drains the water from the drain into the stream in Rhydypennau Woods.  The pipe was found to be blocked so was jet-washed to try and remove the blocking material.  This was only partially successful as a couple of larger pieces jammed in the pipe couldn’t be moved, leaving the pipe partially blocked.  This allows the water to drain away, but slower than it should, which is why the dip still floods from time to time.  At the moment the only obvious way to solve this issue would be to open up the pipe and remove the blockage but this is currently prohibitively expensive, so we will have to live the problem for the foreseeable future and use the diversionary route through the woods when the path is flooded.  Once workdays can get back to normal, we will look to repair the path through the wood and improve its condition.

The meadows alongside Llanishen Reservoir have always been a wet area, hence the reason for one of them being called Boggy Meadow.  However, since the works to replace the water main that runs through the meadows in 2018 the natural drainage appears to have become impeded causing extensive flooding in the meadows during wet spells, of which we have had a lot recently.  The flooding has been so extensive that the path has become impassable on a number of occasions.  Unfortunately this leads to people trying to find drier routes across the wet meadows, which creates a lot of damage to the grasslands.   We are trying to find ways to alleviate this problem, both in the short and longer terms, having raised the issue with both the Council and Welsh Water.  Discussions are ongoing and we hope that these will lead eventually to us finding a permanent solution.  In the meantime we would only ask that you bear with us and be assured that we are trying to overcome these problems in due course.