Removal of Dove Cliff weir - information page

Overview

Page created July 2019. Last updated 7 February 2020.

Background

We are removing Dove Cliff weir to improve biodiversity and improve fish passage through the entire Dove catchment. Dove Cliff weir was structurally assessed in 2016 and sections were found to be in a poor condition. This led to all options for managing the weir being investigated.

The best solution for fish passage in our rivers is to remove barriers, such as weirs and sluices. This is particularly important when they are in poor condition, can cost a lot of money to maintain and no longer serve a functional purpose.

Fish passes alone do not improve the habitat required for fish to spawn and grow. However, removing weirs does as it allows the sediments within the river to deposit naturally creating the right river environments.

Impact of rainfall in 2019

Since starting construction works in August 2019, we have experienced very high rainfalls in the Dove catchment, which has led to some very high flows. These include the second highest flow on record over the weekend of the 26 and 27 October 2019. The hydrograph below from the nearest river level and flow gauge at Marston on Dove, approximately 2 miles upstream, shows the depth (stage) of water at the gauging station over this period.

When the water depths at the Marston gauge are above 1 metre (m), shown by the blue line on the graph, the Dove normally starts to overtop its banks near Dove Cliff weir downstream, leading to potential flooding over the local area. The 2.6m peak on the hydrograph is the flood event of late October 2019, but there have been many other large flood events since September 2019 as can be seen.

The scale and frequency of the flood events had led to working conditions on site becoming very difficult and at times potentially dangerous for our contractors if they had continued. The safety of the contractor and our staff is our highest priority. 

Based on the experiences of the last few months, we decided it was not safe or suitable to continue with the weir removal works until the flows are lower and can be managed in a safer manner. Construction will therefore be suspended over the winter period, until further notice.

Current situation – February 2020

Contractors will be on site until mid-February to finish securing the site, which includes installing some stock proof fencing and ensuring that any temporary works do not impact on the flow of the river. Construction works will then stop on site until late spring, after which we plan to continue with the weir removal. We will provide you with a timetable of works as soon as possible.

Both Dove Cliff weir and the Mill Fleam (Mill Leat) weir remain in place, with no removal works having taken place due to the high flows.

During the winter suspension of works, the temporary bypass channel flows have been stabilised, returning the majority of the flows to the main river and Mill Fleam. Works to return the river back to its natural course has meant that there were occasional periods of low flows down the Mill Fleam. This work has now been completed and the original flow split between the Mill Fleam and River Dove will have returned to normal. This also means that pumps will no longer be in use on site, until work recommences in the spring.

Please note that even though we are suspending the weir removal works, contractors will still be attending site frequently during this period to ensure the site remains secure and the temporary works are operating as intended.

Health and Safety

With works suspended on site until late spring, we ask for your continued efforts not to access the site.

For your own health and safety, please do not enter the construction area.

Frequently asked question

Will the removal of the weir effect the water levels in the river?

Once Dove Cliff weir is removed, the water level upstream of the weir will drop. The water level is expected to drop by approximately 1 metre immediately upstream of the weir. Due to the natural slope in the river, the further upstream you go the less change in water level you will see. There will be no change in river level upstream of Rolleston Brook where it enters the River Dove.

The reduction in water level will be a benefit to the environment as it allows the river to function in a natural way, creating both shallow and deep sections within the river. Shallow river sections are just as important to biodiversity, especially fish, as they provide the right conditions for small fish to grow after they hatch. 

Further information

Look out for #Dovecliff updates on our twitter feed too @EnvAgencyMids.

Thank you for visiting our project information page.

Please keep visiting this page as we will be updating it at key times. We will provide a further update in March 2020. This page will be open to the public until the end of construction and during the following monitoring phase.

External website links that may be of interest

https://yearofthesalmon.org/
https://www.damremoval.eu/
https://www.worldfishmigrationday.com/home