Anglian Water are carrying out River restoration to the Gadder within the National Trust Oxburgh Hall, this is part of our WINEP (Water Industry National Environment Programme) of works, between 2020 and 2025 we are investing approximately £7million in restoring key sections of our region’s most important rivers and streams. In total we are delivering work on 16 rivers across the region, which includes a section of River Gadder.

 

Aim of the works

Our overall aim is to increase the resilience of the river ecosystem, particularly during lower flows in the summer. We want to re-introduce nature-based features back into the river channel to help the river function more naturally and increase conditions for biodiversity to develop. This may include making in-channel enhancements, naturally stabilising the riverbanks, and/or riparian land management options.

Project Details:

  • The Gadder is a chalk stream that rises in Cockley Cley, Norfolk, and flows for ~10 km southwards to its confluence with the River Wissey (Lower) just south of the village of Oxborough.
  • Chalks streams are exclusively found within England and pockets of Northern France and provide an important habitat for an array of fauna and flora. In its present state, the Gadder is under pressure from extreme low flows, historical channel adjustments, degraded habitat and water abstraction from both river and aquifer sources.
  • Anglian Water Services (AWS) are working with delivery partner Binnies as well as the
  • National Trust to restore sections of the River Gadder through Oxburgh Hall.
  • The design development of the project has taken into consideration ecological baseline conditions, heritage and archaeology, flood risk, drainage impacts and amenity.
  • The works will consist of the following broad features:
     

Raised benches - In-channel benches will be constructed where the channel is overwide. These will sit slightly above the normal water level, helping to narrow the channel and increase flow and habitat diversity. Installation includes frontal brushwood fascines fixed in place using chestnut posts and backfilled with a mix of materials won on site, including branches, brash, wood and spoil. Fascines will be stacked 0.3 – 0.6 m high (single or 2 layers of fascines respectively) depending on channel substrate, with one layer being suitable where gravels are currently dominant, and two layers being required where the substrate is comprised of fine sediments (sand and/or silt) and compression is likely. Site won turves will used to cap bench features depending on availability.

 

Riffle Development - The substrate of the channel will be augmented with gravels at strategic points to create riffle features which are currently absent. The dimensions of these features will be variable, ranging from 8 – 12 m in length, 2 – 3 m in diameter with a depth of ~200 mm.

 

Re-meandered channel - A small length of the existing watercourse will be diverted around an existing culverted pedestrian bridge which is currently impacting channel connectivity, flow dynamics, geomorphic processes and fish migration through the locality.

 

Riparian Enhancement - Tree-thinning will be undertaken where the channel is heavily shaded by marginal trees to improve in-channel habitat. This will be focused on three areas along Home Covert. The reduction in shading will promote the growth of marginal vegetation, which will serve to further narrow the channel through increased sediment deposition. This will result in improved conditions under low flows.

 

Embankment Lowering and Development of Wet Woodland - A section of the true left bank will be lowered to enable high flows to enter Home Covert. Home Covent is seasonally wetted but disconnected from the River Gadder. Enabling high flows to enter Home Covert will promote its transition into wet woodland.

 

How might the work affect you?

Most of the work will take place in the river channel and along the riverbank. We will aim to keep any impact on visitors to a minimum. Our delivery partner Binnies UK will need to segregate the working area off to the public for safety reasons.

Location of the work:

Oxburgh hall, Oxborough. Click here for detail design

 

Timescales:

The work will start in June 2024.

 

Anglian Water delivery partner will start at the most Upstream section working away from Oxburgh hall. We anticipate the work continuing until the middle of July 2024.

As we carry out the work there will be a need to temporarily close and divert some of the footpaths which run alongside the river. The closures will be generally short term and in small sections as works progress.

 

Further background information on AWS and WINEP:

Anglian Water is the largest regulated water and water recycling company in England and Wales by geographic area, supplying water and water recycling services to almost seven million people in the East of England and Hartlepool.  

 

Anglian Water is committed to bringing environmental and social prosperity to the region it serves, through its commitment to Love Every Drop. As a purpose-led business, it seeks to contribute to the environmental and social wellbeing of the communities within which it operates.  

 

The Government has challenged water companies to increase their investment and to improve environmental outcomes by 2025. The ambitious measures set by the Environment Agency in the current Water Industry National Environment Programme (WINEP) will see up to £5 billion of investment by water companies in the natural environment between 2020- March 2025 during the current Asset Management Plan (AMP) period.

 

The Gadder has been identified as a priority for river restoration by the Environment Agency and Anglian Water instructed to investigate the effect of abstraction on the river. The project options appraisal, outline and more detailed design for this section (reach) of river are therefore being developed in collaboration with the Environment Agency.