Longton Brook, Trentham Gardens
Replacement of culvert with a bridge Background information July 2019
www.trentriverstrust.org
Written by Ruth Needham Senior Catchment Manager (West) Trent Rivers Trust The Old Coach House, Rock Terrace Buxton, Derbyshire, SK17 6HN E: [email protected] M: 0781 7776224
The Trent Rivers Trust: Registered Charity no. 1089239. Company no. 04225307. Registered in England & Wales.
Contents 1 Background and Introduction ...... 2 1.a Trent Rivers Trust ...... 2 2 The site ...... 2 2.a The Longton Brook and the River Trent ...... 2 2.b Trentham Gardens ...... 3 3 The issue ...... 5 5 The proposal ...... 6
1 Background and Introduction
The River Trent and many of its tributaries have suffered in the past from habitat modification and poor water quality.
This document relates to a project to carry out works to replace an existing culvert on the Longton Brook at Trentham Gardens with a bridge. This document has been prepared to provide all the relevant background information for the proposed works to enable a design engineer to tender to support TRT in delivering the project.
1.a Trent Rivers Trust The Trent Rivers Trust (TRT) is a registered charity. Through its work, TRT seeks to secure benefits for people, places and wildlife along the rivers and streams of the Trent Catchment. The TRT works with a variety of individuals and organisations to deliver a range of environmental projects on the river and in the catchment. Projects involve a range of issues including flood risk management, pollution control, improved habitats, access to rivers and community engagement.
2 The site
2.a The Longton Brook and the River Trent The Longton Brook is a major tributary of the River Trent in its upper catchment. It joins the Trent at Trentham Gardens, downstream of the City of Stoke on Trent. Just upstream of its confluence with the River Trent, it passes through a 20m culvert.
The catchment area of the Longton Brook is 2260hectares, draining Longton and the eastern edges of Stoke on Trent. The brook itself is over 4km long.
The Trent Rivers Trust: Registered Charity no. 1089239. Company no. 04225307. Registered in England & Wales.
There are very few fish in the Longton Brook due to the culvert at the downstream end. This culvert creates a barrier to fish migration from the Trent into the Longton Brook and its tributaries.
The water quality of the Longton Brook is classified as poor, caused by both point (a specific identifiable point) and diffuse pollution (no specific point of discharge).
Water quality and fish populations in the Trent have also historically suffered, however in recent years due to investment by a range of organisations both the water quality and the fish populations have undergone significant improvements.
2.b Trentham Gardens Trentham Gardens is a restored historic parkland with estate and a major tourist attraction to the south of the city of Stoke on Trent. It is owned by The Trentham Estate, part of St Modwens Properties Ltd.
The River Trent flows through the site. There are a range of public amenities on the site including farmland, Italian Gardens, shops and a large garden centre. The area receives a 100’s of thousands of visitors each year and hosts several high profile events. There is an access road over the top of the culvert which is regularly used for operational purposes by the Trentham Estate staff and others. The location of the site is shown on the two maps below.
The Longton Brook flows under an access road that is used for deliveries and estate management. The road is privately owned by the Trentham Estate.
NGR SJ 86718 40835 Nearest postcode ST4 8LH
The Trent Rivers Trust: Registered Charity no. 1089239. Company no. 04225307. Registered in England & Wales.
Figure 1 Location map
Figure 2 Map of Trentham Gardens with watercourses and culvert.
The Trent Rivers Trust: Registered Charity no. 1089239. Company no. 04225307. Registered in England & Wales.
3 The issue
The 20m culvert on the Longton Brook (see Figure 1) causes the following impacts:
The heavily engineered shape and position of the culvert prevents the passage of fish from the River Trent into the Longton Brook.
The shape of the base of the culvert prevents the natural processes of sediment and gravel travelling downstream.
The lack of natural features within the culvert results in a loss of habitats on the bed of the brook and a significant interruption for its role as a wildlife corridor. Figure 1 The Longton Brook in culvert
looking upstream. The culvert is positioned so that leaves and other debris accumulate at its upstream end causing a blockage. This blockage requires maintenance.
There is erosion on the south bank upstream of the culvert, which in the long term may threaten the stability of the corner of the garden centre.
The size of the culvert may restrict very high flows, potentially increasing flood risk upstream.
The Trent Rivers Trust: Registered Charity no. 1089239. Company no. 04225307. Registered in England & Wales.
View of road over existing culvert, looking View of the Longton Brook and the entrance from the north, including land upstream of to the culvert looking downstream. culvert.
Double culvert looking upstream with road View of road over existing culvert, looking over the top. from the north, including land downstream of culvert. Figure 2 Additional photos of the site.
Other considerations
There are two mature trees close to the existing culvert.
4 The proposal
The proposal is to replace the current double piped culvert arrangement with a single span bridge. More detail about what is required is included in the project brief. Images of another watercourse where this has been achieved is show in figure 4.
A location plan with broad concepts is shown in Figure 3.
The Trent Rivers Trust: Registered Charity no. 1089239. Company no. 04225307. Registered in England & Wales.
Figure 3 Location map of proposed works with possible backwater location.
Figure 4 Picture of another watercourse with double culvert replaced by a bridge. (Photo courtesy of Jack Spees, Ribble Rivers Trust). Note; the abutments on the right hand photograph are too close to the banks of the river. It would be better for the river if they were positioned further back.
The Trent Rivers Trust: Registered Charity no. 1089239. Company no. 04225307. Registered in England & Wales.