Changing River Environments » Impacts of River Flooding

What you'll learn this session

Study time: 30 minutes

The causes of river flooding and flood risk factors
Primary and secondary impacts of river flooding
Social, economic and environmental impacts of floods
Case studies of major flood events
How flood impacts vary between HICs and LICs
Flood management strategies and their effectiveness

Impacts of River Flooding

River flooding is a natural process that occurs when a river overflows its banks. While flooding is a natural part of a river's cycle, it can have devastating impacts on human settlements, infrastructure and ecosystems. This guide explores the various impacts of river flooding and how they affect different communities around the world.

Key Definitions:

Flood: The temporary covering of land by water that is not normally covered by water.
Discharge: The volume of water flowing through a river channel, measured in cumecs (cubic metres per second).
Floodplain: The flat area of land surrounding a river that experiences flooding when the river overflows.
Flash flood: A sudden and rapid flooding of an area, often caused by intense rainfall over a short period.

Causes of River Flooding

Understanding why rivers flood helps us comprehend their impacts better. Floods typically occur when rivers receive more water than they can handle.

🌧 Physical Causes

Heavy rainfall: Prolonged or intense precipitation exceeds the river's capacity
Snowmelt: Rapid melting of snow adds large volumes of water
Storm surges: High tides and storms push water upstream
Relief: Steep slopes cause rapid runoff into rivers

🏙 Human Factors

Urbanisation: Impermeable surfaces increase surface runoff
Deforestation: Fewer trees to intercept rainfall and reduce runoff
River engineering: Straightening rivers increases flow velocity
Floodplain development: Building on floodplains reduces natural storage

Impacts of River Flooding

The impacts of flooding can be categorised as primary (immediate) or secondary (long-term) and can affect social, economic and environmental aspects of a region.

Primary vs Secondary Impacts

⚡ Primary Impacts

These are the immediate effects that occur during or immediately after a flood:

Drowning and injuries
Damage to buildings and infrastructure
Loss of livestock and crops
Water supply contamination
Power outages
Transport disruption

⌛ Secondary Impacts

These develop in the days, weeks and months following a flood:

Spread of waterborne diseases
Food shortages
Homelessness and displacement
Economic losses and unemployment
Mental health issues
Long-term environmental damage

Social, Economic and Environmental Impacts

👥 Social Impacts

Loss of life and injuries
Displacement of people
Disruption to education
Damage to cultural heritage
Community stress and trauma
Increased inequality

💰 Economic Impacts

Property and infrastructure damage
Business interruption
Agricultural losses
Increased insurance costs
Cleanup and recovery costs
Reduced tourism

🌲 Environmental Impacts

Soil erosion and deposition
Water pollution
Habitat destruction
Changes to river morphology
Ecosystem disruption
Spread of invasive species

Impacts in HICs vs LICs

The impacts of flooding vary significantly between High-Income Countries (HICs) and Low-Income Countries (LICs) due to differences in preparedness, infrastructure and response capabilities.

🏢 Impacts in HICs

Economic: Higher financial costs due to valuable property and infrastructure
Social: Lower death tolls but significant psychological impacts
Response: Better warning systems, emergency services and insurance
Recovery: Faster rebuilding due to greater resources
Example: UK floods tend to cause major economic damage but fewer fatalities

🏠 Impacts in LICs

Economic: Lower financial costs but devastating relative to GDP
Social: Higher death tolls and disease outbreaks
Response: Limited warning systems and emergency services
Recovery: Slower rebuilding due to resource constraints
Example: Bangladesh floods often result in significant loss of life and long-term displacement

Case Study: UK Floods 2015-16

During winter 2015-16, the UK experienced severe flooding following Storm Desmond, Eva and Frank.

Impacts:

Economic damage estimated at £1.6 billion
16,000 properties flooded in Cumbria, Lancashire, Yorkshire
Major infrastructure damage including collapse of Tadcaster Bridge
Electricity supplies cut to 43,000 homes
Tourism industry severely affected
Only 5 deaths directly attributed to the floods

This case demonstrates how HICs experience significant economic impacts but relatively low loss of life due to effective warning systems and emergency response.

Case Study: Bangladesh Floods 2017

In 2017, Bangladesh experienced severe monsoon flooding affecting over 8 million people.

Impacts:

Over 140 deaths reported
700,000 homes damaged or destroyed
Approximately 480,000 hectares of cropland damaged
Widespread waterborne disease outbreaks including cholera
1.5 million children had education disrupted
Economic damage estimated at $3.3 billion (3% of GDP)

This case illustrates how LICs often face greater human impacts due to limited infrastructure, warning systems and emergency services.

Managing Flood Impacts

Communities can take various approaches to reduce the impacts of flooding, broadly categorised as hard engineering (physical structures) and soft engineering (working with natural processes).

🚧 Hard Engineering

Dams and reservoirs: Store floodwater upstream
Levees and embankments: Raise river banks to contain higher flows
Flood walls: Protect specific areas from flooding
Channel straightening: Moves water downstream faster
Pros: Immediate protection for urban areas
Cons: Expensive, can transfer problems downstream, environmentally disruptive

🌿 Soft Engineering

Floodplain zoning: Restricting development in flood-prone areas
Wetland restoration: Creating natural water storage
Afforestation: Planting trees to intercept rainfall and reduce runoff
Flood warnings: Early alert systems to evacuate people
Pros: More sustainable, environmentally friendly, often cheaper
Cons: May provide less immediate protection, requires more land

Responding to Floods

Responses to flooding can be categorised into immediate, short-term and long-term actions.

⚠ Immediate Response

Emergency evacuation
Search and rescue
Provision of emergency shelter
Distribution of food and clean water
Medical assistance

🛠 Short-term Response

Temporary housing
Water purification
Disease prevention
Clearing debris
Restoring essential services

🏠 Long-term Response

Rebuilding infrastructure
Implementing flood defences
Changing land use planning
Improving warning systems
Community education

The Future of Flooding

Climate change is expected to increase both the frequency and severity of flooding events globally. Rising sea levels, more intense rainfall and changing weather patterns will all contribute to greater flood risks. Communities will need to adapt their approaches to flood management, potentially moving from a focus on prevention to a strategy of resilience and adaptation.

Key Points to Remember

Flooding has complex causes involving both physical and human factors
Impacts can be categorised as primary/secondary and social/economic/environmental
HICs and LICs experience different types and scales of impacts
Management strategies include both hard and soft engineering approaches
Climate change is likely to increase flood risk in many regions
Case studies help illustrate the real-world impacts of flooding in different contexts

🧠 Test Your Knowledge!