Slowing the flow of water - Natural Flood Management

Willow bank protection (River Dee Trust)                Large woody debris (FCS)                                  Reconnecting the floodplain (River Dee Trust)

 

Dee Catchment Partnership 'Managing Flooding Naturally' Leaflet                                                        SEPA, Natural Flood Management Handbook

 

What is Natural Flood Management?

NFM involves techniques that work with the natural landscape to slow and store the flow of flood waters

Catchment Wide Measures

 

Creating woodlands to reduce soil erosion and runoff, provide shelter, improve soil strength and stability and increase infiltration. Trees can be targeted along the riparian edge creating a buffer strip, managed as wet woodlands or planted to reconnect streams to the floodplain

 

Creating, restoring and managing wetlands to store more water. This can include wetlands, bogs and offline storage areas. This can be aided by promoting the growth, structure and species composition of vegetation on land by limiting and managing grazing. The water table could be raised through dams, sluices, ditch blocking or outlet control.

Restoring peatlands to reduce drainage, store carbon, increase water quality and enhance biodiversity. This can be acheived through drain blocking, stabilising bare peat and restoring vegetation cover

Supporting raingardens, green roofs and living walls to gather water, allowing vegetation to flourish in urban areas.

Promoting good soil practise to reduce runoff by increasing     organic matter, introducing continous cover and crop rotations,   installing sediment traps or field bunds, tree planting and reduce      soil compaction through modifying farming practises and reducing stock densities

Designing swales, kerb planters, filter strips and rills to collect, move and clean surface water, before gathering in larger water bodies for storage.

River Corridor measures include:

 

Floodplain restoration to enable the temporary storage of flood waters. This can be achieved through removing barriers, using permeable surfaces

Protection of riverbanks (installing buffer strips, bunds) to develop a buffer zone alongside watercourses

In-channel measures include:

 

Placing flow restrictors in the watercourse (large woody debris, leaky dams)

Protecting banks from excessive erosion (willow spilling)

Restoring the shape of the channel to a more natural course (re-meander, re-connect).

 

By using these techniques in combination throughout the river system, and alongside traditional flood defence engineering flows can be held back, thereby increasing the overall capacity of the catchment and helping to reduce and delay flood peaks in both towns and country.

                  

Why do we need natural flood management?

In the face of a changing climate, a catchment-based approach to flood management in Deeside has much to offer. What happens in one part of the river system has knock on effects. For example, by building embankments and installing extensive drainage networks, we are speeding up flows that will affect the catchment downstream. Similarly, by taking steps to hold back flows in the upper catchment, we can help to reduce flooding further down the river system. By pooling resources and enhancing our land management practices, we can help to manage the flow of water better, and do this alongside existing land uses.

Environmental legislation such as the Floods Directive and Water Framework Directive are driving a move towards a more integrated, catchment based approach to the management of land and water. In Scotland, the framework for delivering a more sustainable approach to flood risk management has been established in legislation under the Flood Risk Management (Scotland) Act 2009. Under this Act, SEPA is required to work with local authorities and other responsible authorities to identify the most sustainable actions to manage flood risk, and this includes natural flood management in some areas.

What are the benefits of natural flood management?

Slowing and storing the flow of water can have benefits for;

  1. Reduced local flooding, erosion and run off 
  2. Improved water quality 
  3. Soil, seed and fertiliser retention 
  4. Habitat enhancements with benefits for biodiversity, carbon storage, recreation and health and wellbeing

Where the cost of traditional flood defences cannot be justified, such as where the number of properties at risk is very small, natural flood management can also be the most cost effective way for local communities to address flooding.

What is the role of the Dee Catchment Partnership?

The Dee Catchment Partnership is working to ascertain the best places to concentrate on installing natural flood management measures by developing maps that will show the opportunities where natural flood management could be effective. We aim to create fully-functioning demonstration sites where the techniques can be viewed, supported by information on design, construction, and costs. We are gathering expertise, resources and advice on how to connect these features in Deeside and offer help to co-ordinate their delivery. 

 

      

Our NFM leaflet                                                Flooding Education Sheet                                                                     Flooding Models

 

Further Information

SEPA - Natural Flood Management Handbook

Co-ordinating our efforts

Register for the NFM Network Scotland

Evidence Directory

Summary document

Working with Natural Processes evidence base

CIRIA: Developing guidance on the delivery of NFM

Educational Links

A 60 second guide to hard engineering, A 60 second guide to soft engineering - Royal Geographical Society.

 

Creating off-stream storage (JHI)                        Field bund, Tarland (JHI / Macrobert Trust)            Eddleston Water, re-meandering and tree planting                                                                                                                                                               (The Tweed Forum)