River Flooding in the UK: Causes and Risks

River Flooding in the UK

• Approximately 2 million properties in the UK face the risk of river flooding.
• River flooding is the risk that the river overflows and water spills out over the floodplain.
• Heavy rainfall increases the volume of water in rivers, contributing to flooding.
• Buildings on floodplains worsen flooding issues.
• River flooding risks stem from both natural and human-induced factors.

Factors Affecting River Flooding Risk

• Two categories of factors exist: those that reduce flood risk and those that increase it.

Factors Reducing Flood Risk

• Dry, sunny weather minimizes flood potential.
• Few tributaries contributes to lower flood risk.
• Building dams helps regulate water flow.
• Natural vegetation aids in water absorption.
• Absence of buildings on floodplains reduces risk.
• Planting trees and growing grass assist with water retention.
• Permeable rock allows water to drain, lowering risk.

Factors Increasing Flood Risk

• Heavy rain elevates flood potential.
• Numerous tributaries escalate flood risk.
• Melting snow increases water volume.
• Removing or cutting down trees reduces water absorption.
• Building cities leads to more impermeable surfaces.
• Road construction increases runoff.
• Cultivating soil can reduce its water absorption capacity.
• Impermeable rock prevents water drainage, heightening risk.

Costs and Benefits of River Flood Defenses: Dam and Reservoir

• Costs: Expensive to build; Valleys behind dams may flood, displacing people; Impedes fish migration.
• Benefits: Provides drinking water; Produces hydro-electric power; And attracts tourism through activities such as fishing.

Costs and Benefits of River Flood Defenses: Embarkments

• Costs: Need constant maintenance; Breaching can trap water; Spoils natural views.
• Benefits: Carries flood water; Provides attractive walking routes; Offers wildlife habitat.

Costs and Benefits of River Flood Defenses: Channel Straightening

• Costs: Increases flood risk downstream; Less natural and attractive.
• Benefits: Fast water reduces risk in the new section; Improves boat navigation.

Costs and Benefits of River Flood Defenses: Flood Relief Channel

• Costs: Requires people to move; Expensive to build.
• Benefits: Removes flood risk; Reduces insurance costs; Increases home values.

Factors Increasing Coastal Flooding Risk

• Low-lying coastal areas are more susceptible to flooding.
• Severe storms generate destructive waves.
• Low atmospheric pressure creates storms and raises sea levels.
• Rising sea levels, associated with high tides, cause flooding.
• Higher global temperatures melt ice, expanding ocean water and raising sea levels.

Coastal Flood Defence

• Coastal flood defense involves protecting coasts from coastal flooding through hard engineering methods.

Coastal Defenses: Sea Walls

• Description: Long concrete barriers with curved surfaces that deflect waves back to sea.

Coastal Defenses: Groynes

• Description: Wooden or stone barriers built perpendicular to the beach.

Coastal Defenses: Rock Armour

• Description: Dumped boulders along the coast.

Coastal Defenses: Gabions

• Description: Wire mesh cages filled with rocks.

Costs and Benefits of Coastal Flood Defense: Sea Wall

• Costs: About 500 pounds per meter to build; Not always visually appealing.
• Benefits: Its long lasting; Beach is unspoiled; can be built on top for cyclists and pedestrians.

Costs and Benefits of Coastal Flood Defense: Groynes

• Costs: Obstructs walking; Needs regular maintenance, 5000 pounds each.
• Benefits: Breaks people from the wind; Prevents beach from being washed away.

Costs and Benefits of Coastal Flood Defense: Rock Armour

• Costs: Difficult beach access; Needs regular maintenance.
• Benefits: Relatively cheap, 1000 pounds each; Quick construction; Versatile in where it can be be placed.

Costs and Benefits of Coastal Flood Defense: Gabions

• Costs: Needs regular maintenance; Easily damaged; Not very attractive.
• Benefits: Cheap to put in place; Built with local rocks.

Effects of Flooding

• Buildings/houses can be washed away.
• People and animals may drown.
• Communication disruptions arise from damaged roads, railway tracks, power lines, and telephone networks.
• There is damage to crops.
• Many Insurance claims are made.
• Drinking water becomes contaminated by sewage.
• A beneficial effect of flooding is Silt deposits support fertile soil for farming.