Changing River Environments » Case Study - River Flooding Example

What you'll learn this session

Study time: 30 minutes

Causes of river flooding (physical and human factors)
Effects of river flooding on people and the environment
Management strategies to reduce flood risk
Detailed case study of the 2015 York floods in the UK
How to evaluate flood management approaches

River Flooding: Causes and Impacts

River flooding occurs when a river overflows its banks and water spreads onto the floodplain. It's a natural process, but one that can have devastating consequences for communities living nearby.

Key Definitions:

Flood: When water overflows from a river channel onto surrounding land that is normally dry.
Floodplain: The flat area of land surrounding a river that experiences flooding.
Discharge: The volume of water flowing through a river channel, measured in cumecs (cubic metres per second).
Hydrograph: A graph showing how a river's discharge changes over time following rainfall.

🌧️ Physical Causes of Flooding

Natural factors that increase flood risk:

Heavy rainfall: Intense or prolonged precipitation that exceeds the river's capacity
Snowmelt: Rapid melting of snow adding large volumes of water
Steep relief: Water flows quickly down steep slopes into rivers
Saturated soil: When soil is already wet and cannot absorb more water
Impermeable rock: Prevents infiltration, increasing surface runoff

🏙️ Human Causes of Flooding

How human activities increase flood risk:

Urbanisation: Concrete and tarmac create impermeable surfaces
Deforestation: Removing trees reduces interception and increases runoff
Channel modifications: Straightening rivers increases flow speed
Building on floodplains: Reduces natural flood storage areas
Climate change: Increasing frequency of extreme weather events

Effects of River Flooding

Flooding can have both immediate and long-term impacts on people, property and the environment. The severity depends on factors like flood depth, duration and warning time.

🏠 Social and Economic Effects

Loss of human life and injury
Damage to homes, businesses and infrastructure
Disruption to transport and communications
Water supply contamination and disease risk
Financial costs (insurance, repairs, lost business)
Psychological trauma and stress

🌿 Environmental Effects

Soil erosion and deposition
Pollution from sewage and chemicals
Damage to wildlife habitats
Deposition of fertile silt on floodplains
Waterlogging of agricultural land
Changes to river channel morphology

Managing Flood Risk

Flood management approaches can be divided into two main categories: hard engineering (physical structures) and soft engineering (working with natural processes).

🧱 Hard Engineering

Dams and reservoirs - store water and release it gradually
Embankments/levees - raise river banks to contain higher flows
Channel straightening - moves water downstream faster
Flood walls - concrete barriers to protect specific areas

Pros: Immediate protection, visible security
Cons: Expensive, can transfer problems downstream, environmentally disruptive

🌳 Soft Engineering

Floodplain zoning - restricting development in flood-prone areas
Wetland restoration - natural water storage areas
Afforestation - planting trees to increase interception
River restoration - returning rivers to natural meandering courses

Pros: Environmentally friendly, sustainable, often cheaper
Cons: Takes longer to implement, may not protect existing developments

📱 Non-Structural Approaches

Flood warnings - alert systems to give people time to prepare
Flood insurance - financial protection for property owners
Education - teaching communities how to prepare and respond
Property-level protection - flood gates, raised electrics, etc.

Pros: Cost-effective, empowers communities
Cons: Doesn't prevent flooding, relies on individual action

Case Study: The York Floods, UK (December 2015)

📍 Location and Background

York is a historic city in North Yorkshire, England, situated at the confluence of the Rivers Ouse and Foss. The city has a long history of flooding, with the River Ouse having flooded over 40 times since records began in 1263.

🌧️ Causes

The December 2015 floods were triggered by Storm Eva, which brought exceptionally heavy rainfall to northern England. The storm followed an already wet autumn, meaning the ground was saturated. Key factors included:

Record-breaking rainfall (215mm in 24 hours in some areas)
Saturated catchment from previous rainfall
Urban development reducing water storage capacity
Failure of the Foss Barrier flood defence system

💧 Scale and Impacts

The River Ouse peaked at 5.2 metres above normal levels, the second-highest level ever recorded. Impacts included:

Social: Over 600 homes and 130 businesses flooded; 4,000 properties lost power; hundreds evacuated on Christmas Day
Economic: £500 million in damages; tourism affected; many businesses closed for months
Environmental: Sewage contamination of floodwaters; debris spread across floodplain; erosion of riverbanks

🛡️ Response and Management

Following the floods, several measures were implemented:

Short-term: Emergency evacuation; temporary accommodation; military assistance; distribution of sandbags
Medium-term: £45 million invested to upgrade the Foss Barrier; repairs to damaged flood defences
Long-term: £45 million "York Five Year Plan" including new flood walls, embankments and pumping stations; natural flood management in the wider catchment; improved flood warning systems

📊 Evaluation

The York flood management strategy now combines both hard and soft engineering approaches:

Successes: Improved flood defences have protected the city from subsequent high water events; better warning systems; increased community preparedness
Challenges: Climate change likely to increase flood risk; continued pressure for development on flood-prone land; high costs of maintaining defences

Sustainable Flood Management

Modern approaches to flood management increasingly focus on sustainability and working with natural processes rather than against them. This includes:

Catchment-based approaches: Managing the entire river basin rather than just local areas
Natural Flood Management (NFM): Using techniques like tree planting, leaky dams and soil management to slow water flow
Community involvement: Engaging local people in flood planning and response
Adaptive architecture: Designing buildings that can cope with occasional flooding (raised floors, waterproof materials)

The most effective flood management strategies typically combine multiple approaches tailored to local conditions, considering both immediate protection needs and long-term sustainability.

✅ Exam Tip: Case Study Knowledge

For your iGCSE Geography exam, you should be able to:

Name a specific river and flood event (location, date)
Explain both physical and human causes of the flooding
Describe specific social, economic and environmental impacts
Outline at least three management strategies used
Evaluate the effectiveness of the management approaches

Use specific facts, figures and place names to demonstrate detailed knowledge!

🧠 Test Your Knowledge!