Since part of the River Stour is tidal a river barrage or barrier, a sea wall and associated gates, is crucial to the control and management of water in the valley and the protection of properties and people who live there. Up until the 1970’s the Stour barrier was at Judas Gap near Flatford and you can see the remains of it if you walk south on the footpath from Flatford Lock. But in the 1970’s it was decided that all of the sea defences in East Anglia needed an overhaul so a new barrage was built at Cattawade two miles to the east. It is managed by the Environment Agency and on a damp November Monday morning Christine Dulake and Ben Grant who work at the barrier agreed to meet us and show us around.
Christine and Ben explained that the The EA are government funded (and Natural England?) and that their role is to carry out asset inspections and maintenance of flood defences and other assets including 123 sluices that control land drainage in order to protect domestic properties and local residents. 40 floodgates have to be closed with the prediction of a tidal surge, which are calculated from measurements at Harwich. Most recently the gates were used during a 1.5m surge on a high tide in 2013, but thankfully all of them held and the sea walls were not breached. The areas along the Suffolk and Essex coast have been divided up and theEA at Cattawade are responsible for the coastline and sea wall between Erwarton and Walton. Other catchments extend between Walton and Mersea, Mersea and the Dengie, Dengie to the Thames. Future proofing all of the assets is a big concern and repairing and refurbishing infrastructure with this in mind is paramount. Currently there is a 6 year programme to replace the large flood gates at Bures and Cornard which date from 1920’s and work on a float system which often traps trees and requires a large amount of effort in order to remove them. Another large system that needs careful management is the water transfer system, the Ely Ouse Essex water transfer scheme, which aims to keep water levels at sustainable levels across East Anglia. There is also a flood warning system for 33,000 properties across the area which alerts local residents to potential warnings via free text/email, and they work closely with the government, emergency services and even the army in case of any potential flood, weather or nuclear incidents.
Whilst tides can be prepared for, fluvial (river) floods are harder to predict but there are structures and systems in place, such as the large flood storage area near Haverhill. Recent legislation has placed more of an onus on landowners regarding riparian responsibilities and the EA try to work closely with as many people as possible along the valley to develop natural solutions to manage the wellbeing of the river. Pluvial (surface) flooding is the responsibility of local authorities and the Partnership and Strategic Overview Team (PSO) deal with housing permits.
Maintenance of the sea wall is very important and they use a radio controlled cutter to keep grass and certain plants from developing too much, especially Alexanders which shades out a lot of other plants. Certain plants are encouraged to grow, especially hogs fennel on which the larvae of the very rare Fisher’s Estuarine Moth depends. Cutting vegetation helps develop roots which in turn help strengthen the fabric of the wall and also enables close monitoring of rabbits and badgers whose actions can undermine the structures. No work is undertaken during bird nesting season however. Some plants have to be monitored and managed such as floating pennywort, which is a huge problem at the Parkstone Pumping Station, Himalayan Balsam, Giant Hogweed and Japanese Knotweed, all of which we have seen along the river.
As well as working along the estuary they also work up stream, above the barrier in the brackish and freshwater areas, surveying the river using hydromorphology techniques and telemetry stations along the waterways. River management ideals are constantly evolving and the aim now is to leave land more natural, with flood plains taking up water overflow, leaving and introducing water deflectors, and the removal of weirs to let rivers respond to climatic change in accordance with the Water Framework Directive. The EA also work with angling clubs to monitor fish and eel numbers using counters. Eels in particular have problems with obstructions on their extraordinary journey, annually migrating from their permanent home in the river to the Sargasso Sea in the Atlantic to spawn, so brush like eel passes have been installed to help them on their way.
All in all it was a very informative conversation and interesting to hear about the wider landscape and how so much is being done to protect it. Ben and Christine then took us outside and to explain how the barrier is constructed and operates. It provides a great vantage point for the surrounding area and you can certainly see why it is located there in such a critical spot. We made a few recordings and took a few photos before heading off to our other assignments for the day.
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