Since we removed three redundant weirs from a 1.5 km stretch of the Lesser Teise in 2016, the river has been doing a great job at repairing itself and turning back into a functioning system. With water levels upstream of the former weir sites now returned to a more natural state, the pool and riffle sequence is developing nicely with a number of bank slumps and newly exposed gravel berms helping to narrow the channel to a more suitable width.
During a site visit in October 2018, although we were very impressed with the recovery, we did notice that there was a clear lack of woody material and associated habitats. So to celebrate the second anniversary of the weir removals, we decided to give the ecosystem another kick start by introducing a number of woody deflectors and channel narrowing berms along a 550 m section of the same site.
Woody material entering rivers is a naturally occurring process which is normally initiated by trees falling in off the banks. However due to the low numbers of bankside trees along this stretch, we needed to bring some material in from some other local sites.
We were able to team up with three other environmental improvement projects in the local area which were generating a range of woody material as part of their environmental management plans.
A local contractor was used to transport the wood to the project site using a forwarder tractor and trailer which allowed us to unload it straight onto the bank. Our excavator operator then lifted the brash and woody deflectors into position so we could secure them.
Over a very cold week back in November in total we installed 15 habitat structures that will help the river to create a diverse range of habitats. These included:
- 5 x channel narrowing berms
- 6 x large wood deflectors
- 2 x hinged bankside trees
- 2 x coarse wood berms
A follow up site visit in late March 2019 has shown that all the channel narrowing berms have already filled up with silt to create new marginal habitat and reduce the sharp transition from aquatic to terrestrial habitat. Some of these were installed on existing riffles which will speed up the flow and keep the gravels free of silt.
The large deflectors have begun to scour out the gravels and have created some deeper pools which provide cover for adult fish. The clean gravels deposited into riffles downstream now look like prime spawning sites to be used over the coming months for fish like chub and dace.
The two hinged trees are developing buds which shows they are still growing happily. This will ensure they will provide lovely low cover for years to come.
The coarse woody berms have partially filled up with silt to create important features that will provide perfect cover for this year’s juvenile fish fry – warm, shallow conditions with cover.
It will be interesting to see how these structures develop and naturalise over the summer.
Many thanks to our very supportive landowner Robert Day, Peter Prince – Foal Hurst Wood, Mark Musgrave – Scotney Castle, Mark Herbert – Combwell Woods and Tom Barr – BARRK forestry management.