Changing River Environments » Hazards of Living Near Rivers

What you'll learn this session

Study time: 30 minutes

The main hazards associated with living near rivers
Causes and impacts of river flooding
Different types of flood events
Human and physical factors that increase flood risk
Case studies of significant river flood events
How communities can manage and respond to river hazards

Hazards of Living Near Rivers

Rivers are essential for human settlements, providing water for drinking, agriculture and transportation. However, living near rivers comes with significant risks. Understanding these hazards is crucial for communities to develop appropriate responses and mitigation strategies.

Key Definitions:

Flood: When a river overflows its banks and water spreads onto the floodplain.
Floodplain: The flat area of land surrounding a river that experiences flooding.
Discharge: The volume of water flowing through a river channel at a given point (measured in cumecs - cubic metres per second).
Flash flood: A sudden and rapid flooding of an area, often caused by intense rainfall.

💧 Why Do Rivers Flood?

Rivers flood when the channel can't contain the volume of water flowing through it. This happens when inputs (precipitation, snowmelt) exceed outputs (evaporation, infiltration) and the river's capacity. The excess water spills onto the surrounding floodplain.

🚨 Why Do People Live Near Rivers?

Despite the risks, people continue to live near rivers because of the benefits they provide: fertile soil for farming, flat land for building, water for drinking and irrigation, transportation routes and opportunities for recreation and tourism.

Types of River Flooding

Understanding different types of flooding helps us predict and prepare for these events.

☔ Pluvial Flooding

Caused by heavy rainfall when the ground can't absorb water quickly enough. Common in urban areas with impermeable surfaces.

⚡ Flash Flooding

Rapid flooding that occurs with little warning, often in steep valleys or urban areas. Can be extremely dangerous due to the speed of onset.

❄ Seasonal Flooding

Predictable flooding that occurs during specific seasons, often related to monsoons or spring snowmelt in mountainous regions.

Factors That Increase Flood Risk

Both physical and human factors can increase the likelihood and severity of flooding.

Physical Factors

Natural characteristics that influence flooding:

Prolonged rainfall: Saturates the soil, reducing infiltration capacity.
Steep slopes: Water runs off quickly rather than infiltrating.
Impermeable rock: Prevents water from soaking into the ground.
Saturated soil: Cannot absorb additional water.
Snowmelt: Rapid melting in spring can cause significant flooding.
Channel characteristics: Narrow channels or meanders can restrict flow.

Human Factors

Human activities that can worsen flooding:

Urbanisation: Increases impermeable surfaces, reducing infiltration and increasing surface runoff.
Deforestation: Removes trees that intercept rainfall and whose roots help water infiltrate the soil.
River management: Straightening rivers (channelisation) can increase flow speed downstream.
Floodplain development: Building on floodplains reduces the area available for flood storage.
Climate change: Leads to more extreme weather events, including heavier rainfall.

Impacts of River Flooding

Floods can have wide-ranging consequences for communities and environments.

🏠 Social Impacts

Loss of life and injury
Displacement of people from homes
Damage to personal property
Disruption to education and healthcare
Psychological trauma and stress
Spread of waterborne diseases

💰 Economic Impacts

Damage to buildings and infrastructure
Business closures and job losses
Agricultural losses and food shortages
Cost of emergency response
Increased insurance premiums
Long-term reconstruction costs

🌿 Environmental Impacts

Soil erosion and deposition
Water pollution from sewage and chemicals
Damage to habitats and wildlife
Changes to river channels and floodplains
Beneficial deposition of fertile silt on floodplains

Case Study: UK Floods - Somerset Levels 2013-14

During the winter of 2013-14, the Somerset Levels experienced severe flooding that lasted for over three months. Around 600 homes and 17,000 acres of farmland were flooded.

Causes:

Exceptional rainfall (wettest January since records began)
Lack of river dredging in previous years
Clay soils with poor drainage
Low-lying land (much below sea level)

Impacts:

Villages like Muchelney cut off for weeks
£10 million in damage to farms
150 people evacuated from their homes
Roads closed, disrupting transport and access to services
Contamination of water supplies

Responses:

£20 million Somerset Levels Action Plan
River dredging to increase capacity
Construction of a new flood relief channel
Installation of pumping stations
Property-level flood protection measures

Managing River Flood Hazards

There are various approaches to managing flood risk, broadly categorised as hard and soft engineering.

🚧 Hard Engineering

Physical structures that control river flow:

Dams and reservoirs
Embankments/levees
Channel straightening
Flood walls
Flood relief channels

🌱 Soft Engineering

Working with natural processes:

Floodplain zoning
Wetland restoration
Afforestation
River restoration
Sustainable drainage systems

💡 Non-Structural Approaches

Managing human behaviour:

Flood warnings
Education and awareness
Flood insurance
Emergency planning
Building regulations

Living with River Hazards

As climate change increases the frequency and severity of extreme weather events, communities need to adapt to living with flood risk.

Sustainable Approaches

Modern flood management increasingly focuses on sustainability and resilience:

Making space for water: Allowing controlled flooding in designated areas.
Property-level protection: Flood-proofing individual buildings with measures like raised electrical sockets and waterproof floors.
Natural flood management: Using natural features like woodlands and wetlands to slow and store floodwater.
Integrated catchment management: Considering the whole river basin in flood planning.
Community resilience: Developing local flood action groups and emergency plans.

Case Study: Bangladesh Flooding

Bangladesh is one of the most flood-prone countries in the world, with about 80% of its land forming a giant floodplain.

Causes:

Monsoon rainfall (June to September)
Snowmelt from the Himalayas
Low-lying topography (much below 10m above sea level)
Confluence of major rivers (Ganges, Brahmaputra, Meghna)
Cyclones causing storm surges

Impacts of 2020 Floods:

Over 5 million people affected
More than 100 deaths
Approximately 150,000 hectares of crops damaged
Thousands of homes destroyed
Widespread water contamination and disease

Adaptations:

Flood forecasting and early warning systems
Raised platforms for villages (flood refuges)
Floating schools and hospitals
Flood-resistant crop varieties
Embankment construction
Community-based disaster preparedness

Conclusion: The Future of River Hazard Management

As our understanding of river systems improves and climate change alters flood patterns, approaches to managing river hazards continue to evolve. The most effective strategies combine multiple approaches, from traditional engineering to nature-based solutions and community resilience. While we cannot eliminate flood risk entirely, we can learn to live with rivers more sustainably and reduce the impacts when flooding does occur.

🧠 Test Your Knowledge!