content@managingwater.co.uk Managing & Maintaining our water channels
River Restoration
the River Wensum Much of the Wensum is highly modified and has a deepened, widened channel exhibiting low habitat diversity
BY AMY CAPON, ENVIRONMENT AGENCY TEAM
Introduction T
he River Wensum is a chalk river of great value for its angling and wildlife, as well as being an important landscape feature of rural Norfolk.
The nature conservation interest of the river is recognised nationally through its notification as a Site of Special Scientific Interest (SSSI), and internationally through its designation as a Special Area of Conservation (SAC). In addition, chalk rivers such as the Wensum are a priority habitat of the UK Biodiversity Action Plan (BAP).
The Water Framework Directive (WFD) classifies the river as bad and the SSSI is in unfavourable ecological condition. The reasons for unfavourable condition include inappropriate water levels, water pollution from point sources and agricultural run-off, water abstraction, inappropriate weirs, dams and other structures, invasive freshwater species, and physical modifications to the channel (deepening, widening and straightening) that impede the river’s hydrological functioning.
A number of projects/initiatives are in place to remedy these pressures. The water quality problems are being addressed by phosphate removal at sewage treatment works. Plans have been put in place to reduce the impacts
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“The Water Framework Directive (WFD) classifies the river as bad and the SSSI is in unfavourable ecological condition”
of water abstraction on the river. The issue of agricultural run-off is being tackled by a Catchment Sensitive Farming project (lead by Natural England) and a Demonstration Test Catchment project lead by the University of East Anglia. The Norfolk non-native Species Initiative is taking steps to control invasive freshwater species.
This just leaves the physical modifications of the river, which are being addressed by the River Wensum Restoration Strategy (RWRS). The RWRS has been developed by the Environment Agency, Natural England and the Water Management Alliance to restore the physical functioning of the river so that it can sustain the wildlife and fisheries characteristic of a Norfolk chalk river.
In the past much of the Wensum has been widened, deepened and straightened for land
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drainage and to facilitate water milling. The river is disconnected from its floodplain by spoil banks resulting from these activities, and much of the river is impounded behind water control structures.
For the first time, whole river scale restoration has been explored to see what action needs to be taken to remedy each section of the channel. The main recommendations of the strategy include narrowing the channel, restoring the gravel bed, reducing the extent of impoundment, re-connecting the floodplain, improving channel sinuosity and increasing the amount of large woody material in the channel. There is no intention to return the river to some former “natural” condition that it might have had at a specified time in the past. Rather, the aim is to restore as much hydromorphological function to the river as possible within existing constraints such as flood risk to people and property.
The Environment Agency is responsible for implementing the RWRS. The key drivers are the Protected Areas programme and the implementation of the Programme of Measures for the WFD as set out in the Anglian River Basin Management Plan. The RWRS is aiming to deliver the WFD objective of achieving Good Ecological Potential by 2027.
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