Background Information
The River Stiffkey is a chalk stream running through North Norfolk that originates in woodland close to Swanton Novers. The Stiffkey is approximately 29km long and flows through a range of geology including sand, gravel, clay and chalk.
Scope of the Project
This project aimed to reconnect the River Stiffkey with its floodplain in the headwaters. The current canalised and deepened channel was raised and pushed out onto the floodplain into a new channel. The new channel flows down the meadow, through two culverts where the channel crosses the footpath and then back into the existing channel via the existing ditch network. This project aimed to deliver benefits to habitat diversity, diversity of depth and flow in the river and reduce flood risk in times of high flow.
Our Solution
The work involved the excavation of 850m of new river channel. This was set out using a Leica GS18 Global Navigation Satellite System. The channel was excavated in two stages. Firstly, down to berm height and then a deeper channel was excavated within this footprint to maximise sinuosity and flow variation. This created a wide variety of water depths and velocities which mimicked the natural characteristics of the original river channel. The site was part of a working farm and contained a public footpath, so access had to be maintained for both walkers and farm machinery. As a result, three new culverts were installed, and an existing culvert was replaced and made larger. These consisted of 600mm twin wall pipe with some crossings being capped with concrete to allow for farm traffic. A series of scrapes of varying sizes and depths were also created within the field to increase habitat diversity. Once the new channel had been connected a series of bunds were introduced into the old channel to so that water could be retained. This was important for wildlife currently resident within the channel.
