Working for and with nature – Morden Weir
Torrential rain and flooding in late 2020 destroyed the weir on the Morden stream, stopping water flowing down the leat to the mill. Without this water supply, the wheel at Cotehele Mill can’t turn and the hydro-electric plant is unable to generate electricity.
The weir on the Morden stream was over 200 years old and fed Cotehele Mill with water through the leat until the weir was destroyed in December 2020. The mill is one of the few working water mills looked after by the National Trust, but now with no supply of water the wheel is unable to turn.
What happened to the weir?
During December 2020 the weir on the Morden stream was damaged and washed away. There is very little left of the weir itself following the extreme and localised flooding.
The hydropower plant at Cotehele Mill was also flooded, but has not suffered major damage.
Friday 18 December
Heavy rain during December 2020 caused excessive amounts of water to flow down the Morden stream. This photo was taken by Ranger George a few hours before the flow of water damaged and washed the weir away.
Saturday 19 December
The weir was washed away and damaged after localised flooding in the area in December 2020. This photo of the weir was taken a few hours later than the previous photo by Ranger George.
A project is now underway to find a solution to get water from the river to the leat so that Cotehele Mill and the hydro-electric plant can continue to work. This may be a replacement weir, or it could be another solution that does not require such a structure. Whichever solution we find, we want to ensure that we can get enough water to the Mill and to maximise the amount of renewable energy we can generate from the hydropower plant.
Being a site of special scientific interest, the Morden is an important river for salmon and sea trout. Weirs often present a barrier to fish migration, even with a fish pass and we will be discussing the management of the stream and alternative options rather than a similar structure with partners such as the Environment Agency.
We will also look further upstream to see if there are any ways that we can slow the flow of the river so future storm events have less impact on our structures, as well as improve the natural wildlife habitats and improve water quality.
Walking around the weir
Over the last few months we have loved hearing why the weir is special to you. All the paths leading to and from the weir are open for you to enjoy. Following works, the bridge over the weir has now reopened.