Flood Management & the River Severn Scheme

Two Philosophies of Flood Management

UK flood management broadly splits into two approaches. Hard engineering uses built structures to control where the water goes — dams, embankments, relief channels, straightened rivers. Soft engineering works with natural processes — restoring meanders, planting woodland upstream, warning people in advance, controlling what is built on the flood plain. Modern UK schemes usually combine both. The key exam skill is being able to weigh costs against benefits using a real example.

Hard Engineering Strategies

Dams and reservoirs. A dam blocks the river to store excess water in a reservoir; the water is released slowly to control discharge downstream. Kielder Reservoir in Northumberland holds 200 million m³ of water and supplies hydroelectric power as well as protecting downstream towns. Costs: very expensive (Kielder cost over £100 million in 1982); land is permanently flooded, displacing communities and ecosystems; sediment is trapped behind the dam, which can starve the channel below.

Channel straightening. Cutting through meanders to make the river flow faster and pass water through more quickly. Effective in the short term but can speed up flooding downstream by passing the problem on. Once common on UK lowland rivers but rarely used today.

Embankments. Raised banks of earth, concrete or stone built along the river to give the channel more capacity. Cheap and quick. Risk: a single failure can flood entire neighbourhoods; embankments also block normal interaction between the river and its flood plain.

Flood relief channels. Artificial channels that carry water around a town when river levels are high. The Jubilee River relief channel near Maidenhead diverts excess Thames water around the town — built in 2002 at a cost of £110 million.

Soft Engineering Strategies

Flood warnings and preparation. The Environment Agency issues three levels of warning — flood alert, flood warning and severe flood warning — and the public can sign up to free SMS alerts. Effective at saving lives and possessions but does not stop water reaching property.

Flood plain zoning. Local councils restrict construction on land identified as high-risk. This stops new property being added to the at-risk total but does little for existing buildings.

Planting trees (afforestation). Woodland in the upper basin slows runoff and increases lag time. The Pickering scheme in North Yorkshire planted 40 hectares of woodland upstream of the town and built leaky timber dams across small streams; flood discharge has fallen by an estimated 15–20%.

River restoration. Reversing past straightening — reconnecting the river with its meanders, removing concrete embankments, allowing the flood plain to flood naturally. Slows downstream flow at low cost. Used on the upper River Cole and parts of the River Tees.

Key Fact

Pickering's 'slow the flow' scheme planted 40 hectares of upstream woodland and built leaky timber dams. It cut flood discharge by an estimated 15–20% at a fraction of the cost of building hard defences for the town.

UK Flood Scheme: The River Severn at Shrewsbury and Bewdley

The River Severn is the longest river in the UK (354 km) and floods regularly — especially at Shrewsbury, Worcester and Bewdley. The 2007 floods saw the worst Severn discharge for 60 years, displacing thousands of people. The current scheme, which has evolved since the 1990s, combines hard and soft strategies.

Why the Scheme Was Required

The Severn drains a large basin (11,400 km²) reaching from mid-Wales to the Bristol Channel. Heavy winter rain falls on the steep, impermeable Welsh uplands and reaches the lowland Severn within hours. Bewdley flooded in 2000, 2007, 2014 and 2020. Climate change is making the storms worse: Met Office records show UK winters are now about 13% wetter than they were in 1961–1990. The scheme had to protect historic towns, farmland and roughly 750 properties in Bewdley alone.

The Management Strategy

A combination of approaches has been used:

Demountable barriers at Bewdley and Upton-upon-Severn. These steel walls are stored away when not needed and bolted into place when a flood is forecast. The Bewdley barriers (installed in stages from 2004) protect 70 properties and have been used dozens of times.
Permanent flood walls at Shrewsbury's Frankwell area — a 200 m sloping concrete wall protecting the historic centre.
Upstream tree planting and river restoration across mid-Wales to slow runoff.
Flood warnings and forecasts issued by the Environment Agency and Natural Resources Wales, with Bewdley residents receiving SMS alerts up to 36 hours before the river peaks.
Flood plain zoning stops new building on at-risk land alongside the river.

Effects: Costs and Benefits

Social benefits. Roughly 70 properties in Bewdley alone protected; warnings save lives; mental-health impact of repeated flooding reduced. Tourist trade in heritage towns continues during winter. Social costs. Some properties (particularly in Beales Corner, lower Bewdley) are still not protected and feel left behind; barriers can take hours to deploy and need willing volunteers.

Economic benefits. Estimated £7 of damage avoided for every £1 spent on the scheme. Tourism, retail and farming in protected areas continue without interruption. Economic costs. Bewdley barriers alone cost over £5 million; Shrewsbury walls another £4 million; soft engineering schemes cost less but need ongoing investment.

Environmental benefits. Tree planting upstream supports wildlife, sequesters carbon and improves water quality. River restoration reconnects the channel with its flood plain. Environmental costs. Hard barriers disrupt riparian habitats and disconnect the river from the flood plain at protected sections; some heritage townscape views are altered by walls.