Below are further details which were forwarded to the Society by Amersham Town Council. This is a background document to the intended works along the River Misbourne at Barn Meadow announced in Nov 2019.
WORK TO RESTORE THE RIVER MISBOURNE FROM BARN MEADOW TO CHURCH STREET
Over the centuries, chalk streams like the River Misbourne have been changed for many reasons including moving them to work with field boundaries, straightened and widened for mill channels, and historically dredged. These changes make the rivers less resilient to extreme climatic conditions such as drought and flood events.
Affinity Water is working with the Environment Agency and others to Revitalise Chalk Rivers, to make them more natural again. This will make them less likely to suffer from low flows and will create a good variety of habitats for wildlife.
The river restoration scheme on the River Misbourne addresses morphological issues within the section of the river from Great Missenden to the M25 at Denham.
WHERE WILL AFFINITY WATER BE WORKING?
The restoration works extend from Barn Meadow to Church Street along the River Misbourne in Amersham.
The map below shows the location of the works along the River Misbourne north of Old Amersham high street. This section of the river backs on to gardens on the right bank and a recreation ground on the left bank for 150 metres.
WHY IS AFFINITY WATER DOING THIS?
The work is being carried out to improve the morphology and the habitat of the River Misbourne.
This particular area of the River Misbourne is generally overwide and straight and is lacking in vegetation. The river runs alongside a brick wall on one side and is shaded by willow trees on the other; along with the slow and fast flowing areas of the river currently this makes it difficult for vegetation to grow.
The river then runs in a culvert (tunnel) underneath a listed art studio and then opens up between Pondwicks Meadow on the left bank and the back of gardens on the right bank for another 130 metres. The channel is heavily vegetated in some areas due to the slow flowing water and would benefit from being narrowed and creating a number of deeper pools to produce a more varied habitat.
WHAT RESTORATION WORK IS AFFINITY WATER DOING?
In February 2020, Affinity Water coppiced the willow trees through Barn Meadow to create dappled shade in the river and encourage vegetation to grown on the banks and in the river.
Further planned improvements include the:
- creation of wet ledges on the left-hand bank to enhance the habitat in the river, increase the capacity of the river, potentially reduce flood risk and increase flow diversity (slow and fast flowing areas)
- installation of pre-planted coir rolls to help create small meanders in the river, vegetate the banks and narrow down the river
- creation pool and riffle sequences. Pools are typically deeper, slower flowing areas and riffles are shallower, faster flowing sections of a river. These more natural features create habitat diversity for plants, fish and macroinvertebrates.
WHEN WILL THE WORK TAKE PLACE?
The timing for the main river improvement works in Barn Meadow and Pondwicks Meadow is yet to be confirmed.
(Received from Affinity Water on 5 Mar 2020)