Henllys LNR Car Park Sustainable Drainage Solution Update

 Its very sad, but not uncommon to see the vast amounts of flooding across rural and urban areas and the devastation this brings. Locally, there are loads of blocked drains and copious damage to roads. 

Our own mini-SuDS project funded by Keep Wales Tiday was finisheed a couple of years ago and is reported in the previous blog entry. What we were seeing was the car park itself was getting flooded as the drains were blocked by silt. 

These 2 pictures were a regular occurance after heavy rains.

The silt was coming from the grassy hill adjacent to the car park. As people were walking up or down the bank, desirelines would muddying up and vegetation being trampled. The rain then washed down these desirelines taking silt downhill, emptying into the car park and blocking the drains. Our solution to this was very simple in that we roped off some of the desirelines, planted some shrubby vegetation on here, dug a few little trenches which fed into small shallow silt traps and most importantly at the botttom of the hill, we built a retaining wall of oak sleepers, backfilled these with soil and overlaid these with our favourite native wildflower turf

The retaining wall with wildflwoer turf on top. The main access path to the right remains.

 (htps://twitter.com/HenllysLNR/status/1314828591805411328). We've recorded on our Facebook page and Twitter how well these have worked (https://twitter.com/HenllysLNR/status/1397112031971577856 https://twitter.com/HenllysLNR/status/1335321551051366400). 

Trench and mini-silt trap

Silt settles into wildflower turf and clean water drains through the gaps in the oak sleepers as well as over the top of the turf.

Since these were installed just over 2 years ago, there have been many storms bringing heavy rain to South Wales as well as many other heavy rainfalls. We have not had any occurances of the car park flooding in that time. The wildflower turf has been really succesful too bringing a wide variety of wildflowers which have been totally under our own management which has meant it hasn't been cut back too early i.e. while it is still in flower. Its been a haven for insects and we even recorded seen in the vegetation in December. Another great success for us at no cost to the Local Authority.