Removal of Dove Cliff weir - information page

Overview

Page created July 2019. Last updated 11 September 2020.

Our contractors, Stonbury, continue to work following current Government Coronavirus guidelines.

Archaeological discovery

The recent works carried out to isolate the temporary bypass channel resulted in a significant drop in water levels exposing a timber structure along the channel bed, pictured below.

Following the unearthing of these historic timbers, the project team has been working closely with key consultees such as Historic England and the Derbyshire and Staffordshire County Archaeologists, to agree and develop a plan to both record and mitigate the exposed timbers. As a result of everyone’s hard work we now have an agreed strategy and programme for managing the archaeology, and on the 6 August 2020 investigation works commenced on site.

Our contractor, Stonbury, has commissioned CFA, a specialist archaeology company, to undertake the investigation and mitigation.

After a thorough sampling process carried out by the archaeologists, early information indicates the timbers date back to 1296-1409 and 1485-1650. We are still not yet able to accurately determine what the structure was, but hope to have this information in the coming weeks.

The storms that the Midlands experienced in August raised water levels in the River Dove once more and for a few days it was unsafe to continue with the inspection and excavation on site. Working proactively with the archaeology team we are mitigating these few days and have now been able to install a more effective pumping system to lower the water levels in the temporary bypass channel much more quickly. With the pumping system upgraded, we have continued carrying out fish rescues to reduce the risk of fish being present within the temporary bypass channel after the high flows.

Once the archaeological inspection has been completed later this month and the strategy implemented, we will complete the construction of the temporary bypass channel and divert the River Dove. Once the river is flowing through the bypass channel, we will isolate the weir completely and commence with the weir removal works. The diversion of the river is expected to be completed in early October, with the results of the archaeology inspection and analysis a few weeks later.

We are taking all necessary steps to ensure that this archaeological discovery is protected, providing Historic England and the archaeologists with the support and time they need to record, investigate and preserve the findings before the works continue. We will update you further on this discovery when we have the details.

Fish rescues

We continue to carry out fish rescues in the temporary bypass channel. The latest fish rescue was carried out on the 3 September 2020, to remove any fish present in the bypass channel following the high flow event and the acquisition of new pumps to allow the archeologists to work in a dry bypass channel. It was a very successful day, with a number of different fish species rescued out of the temporary bypass channel and safely released back into the main river. The species rescued included brown trout, perch, chub, pike, lamprey, grayling (which are pictured below), dace, gudgeon, bullheads, stoneloach and minnow.

Accessing the site

We are still aware of members of the public illegally entering our live construction site. We would like to remind you that there are many dangers on site due to the changing layout and deep, fast-flowing water.

Trespassing or forcing entry into the contractors working area is an offence which can lead to prosecution. The health and safety of the public and our contractors is of the upmost importance to us, which is why we cannot emphasise enough how essential it is for the public to not access the site at any time.

Please can we ask, for everyone’s safety, that you refrain from entering our live construction site at all times.  

Background

We are removing Dove Cliff weir (pictured below) 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. 

We decided it was not safe or suitable to continue with the weir removal works until the flows were lower and could be managed in a safer manner. Construction was therefore suspended over the winter period.

Frequently asked questions

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 riverbed, 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. 

How will flows in the mill fleam be affected by this project?

Maintaining a similar flow split between the main river and the mill fleam (mill leat) was an important design criteria for this project.

Levels in the mill fleam may change this year due to current requirements for the construction works to divert water around the site and, therefore, may not reflect the historical flows until the works are completed. However, when they are completed the mill fleam will continue to experience similar flows as it has historically.

The flows in the mill fleam will be less during the construction works and more representative of low summer flows.

Further information

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

We will update the site working hours if they change but they are generally Monday to Friday, 7:30am to 5:30pm.

Thank you for visiting our project information page.

Please keep visiting this page as we will be updating it monthly and at key times. 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