Managing the Impacts of Natural Hazards » Flood Management Techniques

What you'll learn this session

Study time: 30 minutes

Different types of flood management techniques
Hard engineering vs soft engineering approaches
Advantages and disadvantages of each technique
Case studies of flood management in action
Sustainable flood management strategies
How to evaluate the effectiveness of different approaches

Introduction to Flood Management Techniques

Floods are among the most common and destructive natural hazards worldwide. As climate change intensifies, many regions are experiencing more frequent and severe flooding events. Understanding how to manage and reduce flood risks is becoming increasingly important for communities around the globe.

Key Definitions:

Flood: An overflow of water onto normally dry land, often caused by heavy rainfall, storm surges, or rapid snowmelt.
Flood management: The methods and techniques used to reduce the negative impacts of flooding on people, property and the environment.
Hard engineering: Physical structures built to control water flow, typically large-scale and expensive.
Soft engineering: More natural approaches that work with the environment to manage flood risk.

🛠 Hard Engineering

Human-made structures designed to control water flow and prevent flooding. These are typically expensive, large-scale projects that physically alter the river channel or coastline.

🌱 Soft Engineering

More natural approaches that work with the environment rather than against it. These methods are often more sustainable, cheaper and have fewer negative environmental impacts.

Hard Engineering Techniques

Hard engineering approaches involve building physical structures to control water flow. While effective, they can be expensive and may have environmental consequences.

Dams and Reservoirs

Dams are large barriers built across rivers to hold back water and create reservoirs. During heavy rainfall, they can store excess water and release it gradually to prevent downstream flooding.

👍 Advantages

Can store large volumes of water
Provide water supply during droughts
Can generate hydroelectric power
Create recreational areas

👎 Disadvantages

Very expensive to build and maintain
Can displace communities
Alter river ecosystems
Risk of catastrophic failure

Embankments and Levees

Embankments (also called levees or dykes) are raised banks built alongside rivers to increase channel capacity and prevent water from spilling onto floodplains.

👍 Advantages

Relatively simple to construct
Directly protect vulnerable areas
Allow development on floodplains

👎 Disadvantages

Can increase water velocity downstream
Need regular maintenance
Can create a false sense of security
May simply move flooding problems elsewhere

Flood Walls and Barriers

Concrete or metal walls built along riverbanks in urban areas where space is limited. Modern flood barriers can be temporary or permanent, with some designed to be raised only during flood events.

👍 Advantages

Take up less space than embankments
Can be aesthetically designed
Temporary barriers can be deployed quickly

👎 Disadvantages

Expensive to build
Can block river views
May fail during extreme events

Channel Straightening and Deepening

Rivers can be straightened (channelization) or deepened to move water more quickly through an area, reducing the risk of local flooding.

👍 Advantages

Increases channel capacity
Moves water away from vulnerable areas quickly

👎 Disadvantages

Increases erosion
Destroys natural habitats
Can increase flooding downstream
Requires ongoing maintenance

Case Study Focus: Thames Barrier, London

The Thames Barrier is one of the world's largest movable flood barriers, protecting London from tidal surges. Built in response to the devastating 1953 North Sea flood that killed over 300 people in the UK, it became operational in 1982. The barrier consists of 10 steel gates that can be raised when a flood threat is identified. It has been closed over 190 times since construction and protects 125 square kilometres of central London. While costing £534 million (£2.4 billion in today's money), it has prevented billions in potential flood damage. However, rising sea levels due to climate change may reduce its effectiveness by 2070.

Soft Engineering Techniques

Soft engineering works with natural processes to manage flood risk. These approaches are often more sustainable and environmentally friendly than hard engineering.

Floodplain Restoration

Returning developed floodplains to their natural state allows them to act as natural sponges during flood events, temporarily storing excess water.

👍 Advantages

Creates wildlife habitats
Improves water quality
Provides recreational spaces
Natural water storage

👎 Disadvantages

Requires land that could be used for development
May require relocating existing buildings
Benefits may take time to develop

Afforestation and Reforestation

Planting trees in catchment areas helps to intercept rainfall, increase infiltration and reduce surface runoff, slowing the movement of water into river channels.

👍 Advantages

Reduces soil erosion
Creates habitats for wildlife
Helps combat climate change
Improves water quality

👎 Disadvantages

Takes many years to become fully effective
Requires ongoing management
May reduce agricultural land

Wetland Creation

Wetlands act as natural buffers, absorbing and storing excess water during floods and releasing it slowly afterwards.

👍 Advantages

Creates diverse wildlife habitats
Filters pollutants from water
Can be recreational and educational resources

👎 Disadvantages

Requires suitable land
May attract mosquitoes and other pests
Limited capacity during extreme events

Case Study Focus: Pickering, North Yorkshire

The "Slowing the Flow" project in Pickering demonstrates successful natural flood management. After suffering four major floods between 1999 and 2007, the town implemented a combination of soft engineering techniques including 167 woody debris dams, 187 hectares of new woodland and a small bunded storage area that can hold 120,000 cubic metres of floodwater. During the severe Boxing Day floods of 2015, when many parts of Yorkshire were underwater, Pickering remained dry. The scheme cost £2 million, significantly less than a proposed £20 million hard engineering solution and provides additional benefits like improved biodiversity and carbon sequestration.

Integrated Flood Management

Modern flood management often combines both hard and soft engineering approaches, along with non-structural measures like flood warning systems, land-use planning and community preparedness.

📣 Prediction

Using weather forecasts, river gauges and computer models to predict flooding and issue timely warnings.

📝 Planning

Regulating development in flood-prone areas and designing buildings to be flood-resistant or resilient.

👥 Preparation

Educating communities about flood risks and developing emergency response plans.

Sustainable Urban Drainage Systems (SUDS)

SUDS mimic natural drainage processes in urban areas, reducing surface runoff and the risk of flash flooding. Examples include permeable pavements, green roofs, rain gardens and detention basins.

👍 Advantages

Reduces pressure on conventional drainage systems
Improves water quality
Creates green spaces in urban areas
Can be retrofitted into existing developments

👎 Disadvantages

Requires maintenance
May take up valuable urban space
Initial costs can be higher than conventional drainage

Future Challenges and Approaches

Climate change is increasing flood risks worldwide through more intense rainfall, rising sea levels and changing weather patterns. Future flood management will need to be adaptive, resilient and forward-thinking.

💡 Adaptive Management

Designing flexible systems that can be adjusted as conditions change and new information becomes available. This includes building defences that can be heightened later if needed.

🌐 Community Involvement

Engaging local communities in flood management planning and implementation, recognising that those affected by flooding often have valuable knowledge and insights.

Key Takeaways

Effective flood management usually combines multiple approaches
Hard engineering provides immediate protection but can be expensive and environmentally damaging
Soft engineering works with natural processes and provides multiple benefits but may be less effective for extreme events
Non-structural measures like planning regulations and warning systems are essential components
Climate change is increasing flood risks, requiring adaptive and forward-thinking approaches
The best solutions are often location-specific, considering local geography, climate and community needs

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