Clarborough Natural Flood Management Project
Community-initiated project supplements local flood risk management with nature-based solution
- 50 strategically placed Natural Flood Management features installed to reduce flood risk in Bassetlaw community
- 3 bunds
- 38 leaky barriers
- Construction of a 2-stage channel in an existing ditch to increase water storage capacity
- 5 storage ponds
- Two online storage areas
- 0.4ha of native woodland species to create a tree buffer zone
Clarborough and Welham, two villages located in North Nottinghamshire, have a long history of flooding issues. In November 2019, floods inundated the community, re-fuelling a call for improvements to local flood management. Earlier floods in summer 2007 and January 2008 demonstrated the village’s vulnerability to the incoming water. Over the years, ongoing local concern sparked a consultation which resulted in the launch of an ambitious Natural Flood Management project. The Trent Rivers Trust initially scoped the work and launched Capital Works in 2020. The Natural Flood Management project has been funded by Nottinghamshire County Council. Led by the Trent River Trust, the project has been made possible thanks to the support of local landowners who volunteered their land within the 4.7km2 catchment area. The collaboration has resulted in 50 strategically placed Natural Flood Management features.
Our approach – Slowing the flow with Natural Flood Management
Mapping landscape features and flow paths in the affected area, the Trent Rivers Trust introduced features that aim to reduce the peaking point of floodwater. Natural Flood Management, a still relatively new DEFRA-endorsed approach, quite literally tries to tackle the problem of too much water entering brooks and rivers at the same time.
‘The aim of such NFM schemes is to install many small interventions strategically across the catchment that will collectively store a large amount of water during heavy rainfall, thereby holding the water on the land and reducing river flows. This water is subsequently released more slowly, delaying the flood peak and protecting downstream communities vulnerable to flooding.’
Jon Lewis –Senior Catchment Manager at the Trent Rivers Trust
Natural Flood Management features installed at Clarborough include 3 bunds, 38 leaky barriers, construction of a 2-stage channel in an existing ditch to increase water storage capacity, 5 storage ponds, two online storage areas, and planting of 0.4ha of native woodland species to create a tree buffer zone. These features are focussed on the area to the southeast of Clarborough between Church Lane/The Baulk, Whinleys Road to the north, and Leverton Road to the south.
About the features installed
Once the water from tributaries enters the river, it compounds into a force that is difficult to control, leaving communities such as Clarborough at risk. Natural Flood Management (NFM) aims to control the issue at source, slowing the flow before it enters the main river. Rather than flushing the water through the channels causing a firehose effect further downstream, NFM aims to ‘time’ the flow and allow the land to absorb the water. To achieve a slower flow, NFM first scopes opportunities by modelling the flow of the water. It then recommends a range of features that either slow or block the water from entering the main river.
Clarborough used a wide range of tools from the NFM toolbox
Leaky barriers are used to slow the flow of the water in small streams. The logs are installed just above the water and remain untouched during low flow. During high flow events, the barriers slow the water.
2-way channels consist of a deep central channel, framed by two plateaus. During low flow the central channel transports the water downstream. At high flow the wider channel provides additional capacity, avoiding water flushing down a narrow channel, potentially bursting banks.
Bunds aim to capture, slow and store water strategically in the landscape. Typically positioned at the bottom of a slope it stores surface run-off including sediments behind a section of elevated land
Online storage areas provide additional water storage into existing watercourses, or adjacent to them. They are connected either through drainage pipes or open connections
Storage ponds create a new storage area based on water flow paths. The additional storage increases capacity providing more space for the water to flow.
Trees can absorb water and reduce the amount of water entering the watercourse. Foliage can also slow the water’s journey to the forest floor.
The impact – A win-win for communities and nature
There are other obvious advantages to a NFM scheme, particularly that it works alongside nature and creates new and better environments; it is considerably cheaper than many engineered schemes. However, its impact is generally seen as reducing risks by reducing the rate of flow of water.
Andrew Avery – Local resident
Whilst the primary aim of NFM features is to slow the flow of water and increase the capacity of water storage on the catchment, many of these features will also create additional habitat for wildlife, and boost carbon sequestration. As capital works have drawn to a close, Trent Rivers Trust will continue to monitor the performance of these NFM features under varying flow conditions in 2022.
Is flood risk an issue affecting your community? Get in touch to explore how we can help.