Slowing down the flow of water in upland areas can reduce flood risk (photo: John Beatty/2020Vision)
The impacts of the recent floods mean that there has never been a stronger incentive to re-think our relationship with water, and how we use and manage urban and rural land.
Flooding is the net result of many physical processes acting on varied landscapes, which change over time. The answer to reducing flood risk is NOT simple.
The Government must set out a clear strategy, based on science and best practice, for making communities and farmland more resilient to extreme weather events.
Dredging: effectiveness and risk
Nature is a major, cost-efficient ally that we can use to good effect as we adapt to a changing climate
On 14 February 2014 The Chartered Institution of Water and Environmental Management (CIWEM) published “Floods and Dredging - a reality check”. The report - available below - is endorsed by the Blueprint for Water coalition of environmental NGOs, of which The Wildlife Trusts are a member. It concludes that widespread dredging could make flooding in some communities worse in the future – not better. Carefully implemented dredging may have a limited role in some specific local lowland situations, but it is not a widespread panacea.
The report concludes that it is highly likely that targeted dredging along the Parrett and Tone rivers prior to the January 2014 floods would have led to a reduction in the flood duration on the Somerset Levels, but highly unlikely that it would have led to a drop in flood levels experienced.
Sensitive dredging regimes, undertaken as part of a considered package of measures, can increase the speed of water flow, reduce water levels and reduce small floods, BUT dredging can also:
• increase the risk of flooding for communities and businesses downstream
• destabilise river banks, causing erosion, risking damage to infrastructure
• cause a reduction in water quality
• damage wildlife and river ecosystems.
Thus, dredging is inherently risky and expensive and is rarely a one-off activity. Dredged channels require long-term maintenance and continued investment.
Dredging is NOT a universal solution to flooding: it would not have prevented the flooding in the Somerset Levels, or in the Thames catchment.
Compacted soils, the loss of water absorbent habitats, drained wetlands, dredged riverbeds, straightened concrete-lined channels, paved gardens and the large areas of hard surfaces in urban areas, all increase the rate that water flows through the landscape and into homes and businesses.
It is clear that flooding needs to be addressed through a range of solutions and that the key measures for a flood resilient future must focus around how we use and manage the land.
The solution: working with nature
Water issues need to be addressed in a holistic way across river catchments
Whilst the current focus is on flooding, water issues need to be addressed in a holistic way across river catchments – with integrated solutions designed to tackle the challenges of flooding, drought and water pollution.
Nature is a major, cost-efficient ally that we can use to good effect as we adapt to a changing climate. To make nature work for us we need the pooled expertise of Government agencies, academics and researchers, and NGOs.
The Wildlife Trusts strongly advocate the need for a fundamental shift in thinking. It is time to plan for large scale restoration and creation of networks of healthy habitats that will reduce our vulnerability and increase our resilience to extreme weather events.
Flooding: key measures for a resilient future
1. Restore water-retaining habitats over large areas
Make the land function more effectively to absorb and store rainfall. Better management of soils to reduce compaction, strategic tree planting, creating buffers along watercourses and restoring natural habitats like upland peat bogs and grasslands would all help soak up water, storing it in dry periods and releasing it gradually. A new initiative is needed to improve the water-retaining capacity of key areas in river catchments.
Case study: Pumlumon, Cambrian Mountains
The Pumlumon Project in Montgomeryshire covers more than 3,700ha of upland wetland habitats such as raised bog. Ditch blocking work has raised the water table and retained an extra 155 million litres of water on the land so far. Permeability has been improved by reducing stocking densities of animals in some areas, and by planting broadleaved trees.
ITV's science & medical editor Lawrence McGinty recently visited Pumlumon...
2. Create more multi-functional wetlands
Create more places where water can be held back or stored. Many areas designed with nature in mind also function to hold water during high rainfall events - preventing flooding downstream. Areas for storing floodwaters can be created in ways that make them attractive focal points for communities and visitors. Planning policy and Government investment must support the creation of multi-functional wetlands.
Case study: Crane Meadows
At Crane Meadows to the east of Heathrow airport, London Wildlife Trust is restoring meadows to improve their water management capabilities and enhance the site for wildlife: a win-win for local communities. About 30% of the site was formerly hard standing. Along the course of the river Crane, old meanders have been reconnected as backwaters, enabling the river to function more naturally with its floodplain.
3. Design water storage into farming systems
Create spaces on farmland that will store floodwaters and protect valuable areas for food production. Taken together, a series of small and low cost schemes across a number of farms can help reduce flood risk downstream and protect important food producing areas. A clear route for funding such schemes through agriculture budgets or payment for ecosystem services is needed.
Case study: Farming Floodplains
In Staffordshire, the Farming Floodplains for the Future project worked with farmers to create flood storage areas across a series of farms whilst also protecting farm businesses. The areas retain floodwaters when the watercourse spill level is exceeded and drain out slowly after the flood peak has passed.
4. Respect the natural role of floodplains
Make more space for rivers to function naturally through a better approach to spatial planning. A natural river channel and its floodplain work together to deal with high and low river levels coming from channels upstream. We should respect flood plains and implement strong protection through the planning process to halt the development of houses and businesses in high risk places.
Case study: Tame Valley Wetlands
The Tame Valley Wetlands partnership was set up in 2005 to deliver conservation throughout the Tame Valley between Birmingham and Tamworth, covering 9,500 hectares. There is increasing public recognition of the wider benefits of naturally functioning floodplains and their role in flood control, including enhanced protection for settlements downstream, the maintenance of a diverse and rich landscape and the restoration and re-creation of lost wetland biodiversity.
5. Better design to collect and capture water in urban areas
Design features that collect and capture water in our towns and cities, in order to avoid it rushing off hard surfaces into rivers. There are many examples of good practice in the design of sustainable drainage systems, permeable surfaces and creation of features like green roofs.
The Government needs to do more to ensure that these approaches are a standard element in planning and design, and to retrofit them into existing developments.
Case studies: Portbury Wharf and Lost Effra
Avon Wildlife Trust's Portbury Wharf lies on the land between Portishead and Royal Portbury Dock, adjacent to the Severn Estuary. Planning consent for the Port Marine housing development here was granted on condition that the developers designate a nature reserve on the adjoining land. The habitats and wetlands absorb run-off from the development, filter pollutants and provide flood protection in the event of a breach of the sea wall. The site also offers recreation and educational benefits.
London Wildlife Trust has an on-going flood-management project called Lost Effra - named after a river - which is working with local communities on a water management strategy for Herne Hill in south London, an area which is prone to flooding. See the PDF below of its recent report A new way to manage water pp.32-54 for relevant information. Key recommendations p.66.
Here, The Wildlife Trusts' Vice President, Professor Chris Baines, talks about how working with nature has a really positive part to play...
If you'd like to find out about more projects run by The Wildlife Trusts, visit http://www.wildlifetrusts.org/tacklingflooding