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Flood Risk Planning London: Top Strategies To Know In 2023

This is a complete guide to flood risk planning in England.

It gives an overview of flood risk planning in England.

It provides information on

Flood sources.

FRA requirements for  flood risk planning

Flood assessment test

The article further elaborates on climate change and flood risk.

Flood management strategies in London.

Sustainable drainage Action Plan for London.

Planning principles for new developments

Basic Concepts

In this chapter, I’ll answer the question: ” what is flood risk planning, and which management strategies and overview of flood risk in London?”

The flood risk planning in the city includes developing flooding risk reduction strategies, identifying flood-prone areas, and minimizing the impact of flooding on these areas.

Let’s get started

Flood risk planning

Flooding can happen at any time and is a natural process. The best-known causes of flood are flooding from the rivers and seas, but it can also cause by intense rainfall. Moreover, climate change can increase its severity, and effective flood risk planning can help mitigate its impact on human lives.

Rural areas and major cities like London are at risk of flooding in England. This article aims to identify Flood risk planning in major cities like London. The flood risk planning in the city includes developing flooding risk reduction strategies, identifying flood-prone areas, and minimizing the impact of flooding on these areas. This can include;

• Building infrastructures for minimizing flooding embankments, flood walls, and other barriers

• Developing green spaces that can be helpful in absorbing excess water

• Improving the drainage system of the city

• Generating better emergency response systems and evacuation procedures

• Perpetrating the citizens for potential events of flooding.

Overview of Flood risk in London

The section flood risk in London. 

It provides information on 

Overview of Flood risk in London

The city of London has a low risk of flooding. However, some specific areas of the city have a high risk of river tidal and surface water flooding. The consequences of this flooding on the disruption of business and human lives have been quite high during times, and it can be tackled by taking local as well as regional actions.

As the city is located on the bank of the river Thames and with changing climate, the sea level increases, increasing the risk of tidal river flooding. On the other hand, with increased rainfall, the risk of surface water flooding increases, and the city requires certain resistance measures for a speedy recovery from flooding.

Flood risk assessment

In 2017 the flood risk areas (FRAs) and preliminary flood risk assessment(PFRA) for the city were revived by the London Corporation. Comprehensive information on the risk of flooding in the city of London was then presented by The City of London Strategic Flood Risk Assessment (SFRA) in 2012. It highlighted the risk of the city’s past, present, and future flooding.

Under the Flood and Water Management Act, the flood events are being investigated, and it has been concluded that as a result of heavy rainfall, the city undergoes some flooding which effected small numbers f buildings in the city. This flood risk investigation did not change the understanding regarding the flood risk in the London LLFA area. However, SFRA 2012 has enabled the local Flood Risk management strategy to reduce future flood risks in the regions.

Future flood risk

Implementation of Exception and Sequential tests is vital to determine the suitability of an area for development and make them able to cope with the challenges of flooding. In the sequential test, a sequential approach is used to start new development in areas that are less prone to flooding.

Exception test is used to demonstrate that the risk of flood can be managed in those areas where developments have been made. The city has been divided into different zones based on these tests, and the risk of vulnerabilities in these areas has also been identified.

Flood risk planning

Flood risk areas (FRAs)

The section outlines information on sources of flood risks in London. 

  1. Flood plains 
  2. Surface water flood risk 
  3. Tidal flood risk 
  4. Fluvial Flood risk

Flood risk areas(FRAs)

Flood Risk Regulations (2009), states that a FRA must identify such flood risk areas.

  • Greater London FRA, which includes the whole city of London, leads local flood authority areas (LLFA).

The environment agency has declared London as one of the ten indicative Flood Risk Areas in England, and this city has been constructed on a vast flood plain. Thus the majority of its areas are located within a flood zone. Central London faces multiple sources of flooding, and it is then fully protected by the Thames Barriers. Without those barriers, the city would have drained into floods by now.

Flood Plains

15 % of the city is in the flood plain, and flood defences protect these. Much of the city’s infrastructure relies on lies in flood plains, including homes, 49 railway stations, 10 hospitals, and 75 underground stations. Many of these properties are well-defended, but the area at the western end of the Thames is poorly protected and has a greater risk of flooding.

Furthermore, London can be affected by 6 potential flooding sources. Currently, 6% of the city is at high risk of tidal, surface, or river flooding, and 11% of the city is at medium risk of such flooding.

Surface water Flood risk

Due to its nature, the city is at a considerable risk of sewer and surface water flooding. It has many boroughs which are considered to be critical drainage areas. However, these are the areas where surface water cannot drain at the required rate, which eventually causes the flood.

Buildings with large roof areas, mainline rail terminals, schools, hospitals, and retail warehouses are at high risk of flooding. Through the Drain, London project more sustainable drainage system has been identified, and a proper mechanism for controlling such flooding has been made.

Tidal Flood Risk

The Tidal flood risk areas of London include areas to the north and south of London and central and inner London. Many flood barriers have already been made in these areas, including Thames Barrier, flood walls, and other moveable gates.

Fluvial Flood Risk

River Thames has many tributary rivers which collectively forms fluvial flood. This could happen due to colossal rainfall or a blockage in the channels of these rivers. The Environment Agency has produced many plans to reduce the risk of fluvial floods. The rivers in London are not in their natural stages and have been modified with concrete to reduce the risk of flooding.

London has many massive canals stretching up to many miles, and they have limited water input. Thus, these minimize the risk of flooding. However, fluvial flooding affected most of London’s Boroughs. As such, it affects many town centres, opportunity Areas and strategic infrastructure in the city.

The Impact of Climate Change

Due to climate change, rainfall patterns have changed, and the risk of flooding has increased on tributary rivers. Thus risk management authorities should consider the updated climate change allowance when making flood risk management strategies. The intensity of storms also increases with the rapid change in climate, and the drainage system of urban areas of London should be improved to cope with such storms.

Flood Risk Management Strategy In London

The London Flood Risk Management Strategy was developed by the Environment Agency and the Greater London Authority to manage and reduce the risk of flooding in London. The strategy aims to address the causes of flooding and provides a framework for investment in flood risk management.

London flood risk planning

Key elements of the strategy include:

• improving flood warnings and alerts,

• enhancing flood defence infrastructure

• increasing green spaces to absorb excess water

• raising public awareness of flood risk and

• Promoting sustainable drainage practices.

The strategy is regularly reviewed and updated to ensure it effectively reduces London’s flooding risk.

The height of flood defence walls has been increased to minimise the risks of Tidal floods. TE2100 plan is set up for future mitigation of flooding in London. The plan includes,

• Working in collaboration with the local authorities to make new developments to improve resilience measures for flooding in London.

• Preparing strategies to manage fluvial flooding, especially in west London, and continuing to forecast flooding in the area.

• Concentrating on the maintenance replacement of the upstream as downstream defences

Sustainable drainage Action Plan for London

Sustainable drainage measures must be adopted and applied across transport routes and buildings in the city to minimise the risk of flooding.

The London Sustainable Drainage Action Plan addresses a vital need for retrofitting and promotes awareness regarding sustainable drainage systems across the city.

The objective of the sustainable drainage plan is to get a 15 % reduction in surface water for the coming 25 years and a reduction of 25% inflow by 2040. Sustainable drainage includes the usage of good management practices and the use and installation of sustainable drainage techniques. The sustained drainage techniques include

  • Rainwater harvesting includes capturing rainwater into tanks and using that for irrigation, plant cleansing, and toilet flushing.
  • Green/ Brown /Blue roofs
  • To provide shallow roof covering for thermal insulation and attenuation of rainwater
  • Bo Retention
  • A chain of landscapes designed to hold surface water
  • Other methods include making permeable pavement surfaces, storage tanks, discharge to tidal and river or docks, and making ponds.

The action plans are developed by the Drain London program and are comprised of two parts. The first part of the plan sets out cases and backgrounds for sustainable drainage in London. Secondly, the plan set out a range of actions for major building and major land-use sectors, including schools, health, transport, retail, commercial offices, industries, and other public sector buildings. The sustainable drainage system is set to minimize the challenges of surface water management.

The city has a relatively old drainage system, and its surface prevents the soaking of water into the ground, making it prone to surface flooding. To minimize contaminated surface water flow into the Thames, the government gave permission for the Thames Tideway Tunnel, preventing severe sewer outflows in the river.

It is an essential element of the city’s Water-Sensitive Urban Design. London faces some challenges in implementing sustainable drainage measures, including the type of soil the city has and the density of development in central and inner London.

However, these are not reasons that can be made excuses to give up these plans but can be overcome by making some changes to the national planning policy framework. The drainage system is now set to include public organizations, property owners, local groups, and individual residents to use sustainable drainage within their buildings, local areas, and their land.

Such actions have high cost that needs to be considered as important as other maintenance and repair works. Many commercial businesses are being charged to maintain drainage systems.

Flood risk planning principles for new developments

The planning policy framework does not allow initiating developments in areas with a high risk of flooding. The Lead Local Flood Authority examines new developments and ensures that these will not increase flood risk in the future. The Planning Policy Guidance focuses on developing resilient measures for the current building properties.

The planning principles in England, especially in London, comprised of

• To undertake Flood Risk Assessment at all levels of the planning process

• Ensure that the risk of flooding is considered in all the levels of planning for new development.

• Avoiding inappropriate developments and clarifying all types of new developments that will build in areas with a range of flood risks.

• Ensuring that all new developments should be done by taking climate change into and not increasing the risk of flooding in the future.

• Such developments should reduce the risk of floods to communities by safeguarding the flood plains.

Conclusion

In conclusion, proper Flood Risk assessmentand flood risk planning are needed to apply a risk-based approach to implement actions and development plans in the flood plains of London. As the environment agency provides Flood warning services, such services are needed to mitigate the risk of flooding in London.

Future developments in the city should be undertaken by considering climate changes in mind and by considering the high risk of flooding due to such new developments. The improved drainage system, generating a better emergency response system, risk assessment, and planning can save the city from significant flooding catastrophes in the future. Apart from that, specific flood-resilient building materials should be used to minimize the effect of flooding on human lives in the city.

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Argemiro Rivera, <b>BEng(Hons) MSC CEng MICE MCIWEM C.WEM CEnv</b>
Argemiro Rivera, BEng(Hons) MSC CEng MICE MCIWEM C.WEM CEnv

Passion for Water, Flood Risk & Sustainability
I love to dig into complex flood risk and water engineering projects and deliver them. I focus on delivering reliable flood risk information to protect livelihoods and the environment.

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