Episode 137 - Flood Risk Assessments

This week we will be talking about Flood Risk Assessments. This episode content meets PC2 - Clients, Users & Delivery of Services & PC3 - Legal Framework & Processes of the Part 3 Criteria.

Resources from today's episode:

Websites:

• https://www.planningportal.co.uk/permission/commercial-developments/understanding-and-assessing-flood-risk/flood-risk-assessment
• https://www.gov.uk/guidance/flood-risk-and-coastal-change#para80
• https://www.gov.uk/government/organisations/environment-agency
• https://www.gov.uk/guidance/flood-risk-assessment-flood-zones-1-2-3-and-3b

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Transcript

Episode 137:

Hello and Welcome to the Part3 with me podcast. 

The show that helps part 3 students jump-start into their careers as qualified architects and also provides refresher episodes for practising architects. I am your host Maria Skoutari and this week we will be talking about Flood Risk Assessments. Todays episode meets PC2&3 of the Part 3 Criteria.

Make sure to stay until the end for todays scenario. 

Firstly, lets start by looking at what a Flood Risk Assessment is:

A Flood Risk Assessment looks at the risk and impact of flooding on a development site, helping to analyse the potential issues with building on sites, such as areas having an increased chance of flooding. 

To enable a development to take place, the flood risk assessment should prove that the site will remain safe in the future, taking the added effects of climate change into account when measuring the safety. When risks are found, the flood report can provide possible solutions to the risk of flooding on the development, helping applicants to plan and safely bypass these risks.

So how would you determine if a Flood Risk Assessment is needed to accompany a planning application:

Firstly, in order to access the right flood risk advice for a development, the applicant will need to carry out a number of steps, including:

• Using the Environment Agency Flood Map for planning to find if the development is in flood zone 1, 2 or 3
• Check the Local Planning Authorities Strategic Flood Risk Assessment to identify if the site is flood zone 3b
• Find out the vulnerability classification
• Check table 2 of the Planning Practice Guidance to find out if the proposed vulnerability classification is incompatible with the flood zone 
• check the Local Planning Authority’s Strategic Flood Risk Assessment to identify if the site is in flood zone 1 now but will be at risk of flooding from rivers or the sea during its lifetime
• check the Local Planning Authority’s Strategic Flood Risk Assessment to identify if the site is at risk from any other source of flooding or it will be during its lifetime
• Refer to check the long term flood risk for an area in England website to identify if the site is at risk of flooding from surface water, groundwater or reservoirs
• Check if the site is in an area with critical drainage problems
• Establish the site area and whether the development is major development
• Check if the development is a minor extensions - such as a household or non-domestic extension with a floor space of no more than 250 square metres.

Once this initial information is initially determined, then to assist with the planning application and flood risk assessment report, applicants should carry out:

• An assessment if the site is located within flood zones 2, 3 or 3b
• Or within flood zone 1 with a site area of 1 hectare or more
• Or within areas with critical drainage problems
• Or within flood zone 1 where the applicable Local Planning Authorities Strategic Flood Risk Assessment shows it will be at risk of flooding from rivers or the sea in future
• Or that the development increases the vulnerability classification and is in flood zone 1 where the applicable Local Planning Authorities Strategic Flood Risk Assessment shows it is at risk from other sources of flooding 

Key item to note is that flood risk assessments are required for all developments, including minor development (such as householder development, alterations that do not increase the size of the building and minor non-residential extensions) and changes of use, if they fall within the areas/classification I just mentioned. If a Flood Risk Assessment is required, the Local Planning Authority can refuse planning permission if one is not provided or if it is inadequate. 

Flood Risk Assessments are carried out by specialists, namely Civil Engineers. 

In addition to a Flood Risk Assessment, a Sustainable Drainage Strategy may also be required if the application is for:

• A major development with surface water drainage
• A development with surface water drainage in an area at risk of flooding such as flood zones 2 or 3, or at risk of surface water flooding 

The sustainable drainage strategy can be a separate document or be part of a Flood Risk Assessment.

So when we refer to Flood Zones 1, 2 and 3, what does that mean:

• Flood Zone 1 has the lowest risk, indicating land having less than 0.1% annual probability of river or sea flooding
• Flood Zone 2 denotes medium risk, of land having between a 1% and 0.1% annual probability of river flooding or land having between 0.5% and 0.1% annual probability of sea flooding
• Flood Zone 3a has the highest risk, with land having a 1% or higher annual probability of river flooding or land having a 0.5% or greater annual probability of sea flooding 
• Flood Zone 3b comprises land where water from rivers or the sea has to flow or be stored in times of flood. Known as the functional floodplain, it typically comprises of land having a 3.3% or greater annual probability of flooding, with any existing flood risk management infrastructure operating effectively or land that is designed to flood even if it would only flood in more extreme events. Such land should be identified within the Local Planning Authorities Strategic Flood Risk Assessment.

Understanding these zones is critical for planning permissions and building designs, as architects must consider potential flooding impacts and mitigation strategies. They ensure safety and resilience, ultimately enhancing the longevity of structures in potentially hazardous zones.

Before even starting a Flood Risk Assessment, however, applicants will first need to determine if the development needs to satisfy a sequential test. A sequential test is designed to ensure that areas at little or no risk of flooding from any source are developed in preference to areas at higher risk and it compares an applicants proposed site with other available sites to show which once has the lowest floor risk. Avoiding flood risk through the sequential test is the most effective way of addressing flood risk because it places the least reliance on measures like flood defences, flood warnings and property level resilience features.

Sequential tests tend to be required for major and non-major development if any proposed building, access and escape route, land-raising or other vulnerable element will be in flood zone 2 or 3, or in flood zone 1 and the Local Planning Authorities Strategic Flood Risk Assessment shows it will be at increased risk of flooding during its lifetime or if it subject to sources of flooding other than rivers or sea. A development is not exempt from the sequential test just because a Flood Risk Assessment shows it can be made safe throughout its lifetime without increasing risk elsewhere.

The LPA may refuse planning permission if other, lower risk sites are identified through the sequential test.

Therefore, before applying for planning permission, applicants must always read the flood risk assessment guidance to determine if they need a flood risk assessment, a sustainable drainage systems strategy, which advice to follow and how to access flood risk information from the Environment Agency. 

Then once the site has been assessed and it has been determined which flood zone is applicable, the Flood Risk Assessment will need to be prepared to accompany the planning application. The Floor Risk Assessment itself, therefore, needs to be:

Appropriate to the scale, nature and location of the development and proportionate to the degree of flood risk. 

The Assessment itself will need to be site specific and include:

• The sites location and a description of its current use and which flood zone it is situated within
• A summary of the development proposal 
• For developments in areas identified as being at risk of any source of flooding now or in the future, a sequential test should be included 
• A description on how flood risk at the site will likely be affected by climate change 
• A description on site specific flood risk, meaning the risk of flooding to and from the proposed development over its expected lifetime, including appropriate allowances for the impacts of climate change
• A description of the arrangements for surface water management 
• A summary of the number of future occupants and users of the new development, the likely future pattern of occupancy and use and the proposed measures for protecting vulnerable people from flooding
• If the site falls under the exception, evidence will need to be provided within the assessment to support certain development proposals in flood zones 2 or 3 if following application of a sequential test, it applies for an exception test.
• A description of any residual risks that remain after the flood risk management and mitigation measures to be implemented and a description of how these risks can be managed to keep the users of the development safe over its lifetime. 
• And lastly, provide details of the author and date of the flood risk assessment.   

As mentioned, alongside the Flood Risk Assessment a sustainable drainage strategy should be provided either as a separate document or as part of the Flood Risk Assessment as part of a planing application. The Sustainable Drainage Strategy should describe the existing and proposed surface water management arrangements to ensure there is no increase in flood risk to others off site. The strategy will need to address:

• What the existing surface water drainage arrangements are for the site
• If known, what (approximately) are the existing rates and volumes of surface water run-off generated by the site
• What are the proposals for managing and discharging surface water from the site using sustainable drainage systems and accounting for the predicted impacts of climate changed what are the proposals for restricting discharge rates
• Demonstrate how the hierarchy of drainage options has been followed, explaining and justifying why the types of sustainable drainage systems and method of discharge have been selected and why they are considered appropriate.
• How have sustainable drainage systems been integrated with other aspects of the development such as open space or green infrastructure, so as to ensure an efficient use of the site
• What multifunctional benefits will the sustainable drainage system provide. For major developments, if multifunctional sustainable drainage systems are not being provided, what evidence is there that such techniques are not possible.
• What opportunities to reduce the causes and impacts of flooding have been identified and included as part of the proposed sustainable drainage system.
• How will run-off from the completed development be prevented from causing an impact elsewhere
• How has the sustainable drainage system been designed to facilitate maintenance and, where relevant, adoption and what are the plans for ensuring an acceptable standard of operation and maintenance throughout the lifetime of the development.

Then once all the information and assessment have been prepared they are submitted as part of the developments planning application. 

One of the application statutory consultees alongside the Local Planning Authority that tend to be involved with flood risk applications in certain flood risk areas is the Environmental Agency. They also provide a free preliminary opinion to applicants in addition to the statutory consultation process. They can tell you which climate change allowances to use and how to use them in your assessments. There is a charge for more detailed pre-application planning advice which includes reviews of draft FRAs and flood risk modelling. 

The Environment Agency play a significant role in the Flood Risk Assessment process, in that they provide flood risk data and modelling information to inform Flood Risk Assessments and they also offer guidance on flood risk assessment requirements and best practices. They are essentially a non-departmental public body with responsibilities relating to the protection and enhancement of the environment in England. 

Some common challenges in Flood Risk Assessments includes:

• Data Availability: Obtaining accurate and up-to-date flood risk data can be challenging, especially for smaller watercourses or in areas with limited historical records.
• Climate Change Uncertainty: Predicting future flood risk under various climate change scenarios involves significant uncertainty.
• Balancing Development Needs and Flood Risk: In some areas, there may be pressure to develop in flood-prone locations due to housing demand or economic factors.
• Complex Hydrology: Some sites may have multiple, interacting sources of flood risk, making assessment and mitigation more challenging.
• Changing Regulatory Landscape: Flood risk policy and guidance can evolve, requiring FRA practitioners to stay updated with the latest requirements.

Best Practice, therefore, for effective Flood Risk Assessments involves:

• Early Engagement: Consult with the local planning authority and Environment Agency early in the process to understand specific requirements and potential issues.
• Comprehensive Data Gathering: Utilise a wide range of data sources, including historical flood records, topographical surveys, and the latest climate change projections.
• Site-Specific Analysis: While general flood maps are useful, site-specific modelling often provides more accurate risk assessments.
• Innovative Mitigation Measures: Consider a range of flood mitigation strategies, including resilient design, SuDS, and natural flood management techniques.
• Clear Communication: Present findings and recommendations in a clear, accessible manner for both technical and non-technical audiences.

And lastly, what is the future of Flood Risk Assessments:

As climate change continues to alter flood risk patterns, Flood Risk Assessments are likely to become even more critical in the planning process. Some emerging trends include:

• Increased Use of Technology: Advanced modelling techniques, remote sensing, and AI may enhance the accuracy and efficiency of flood risk assessments.
• Integration with Wider Sustainability Goals: FRAs may increasingly consider how flood mitigation measures can deliver multiple benefits, such as biodiversity enhancement or urban cooling.
• Adaptive Management Approaches: Given the uncertainty in long-term climate projections, there may be a shift towards more flexible, adaptive flood risk management strategies.
• Enhanced Community Engagement: There may be greater emphasis on involving local communities in understanding and managing flood risk.

To sum up what I discussed today:

• Flood Risk Assessment Purpose: A Flood Risk Assessment (FRA) evaluates the risk of flooding on a development site, ensuring the site's safety, particularly regarding future climate change. It also proposes solutions for mitigating flood risks.
• When FRA is Required: An FRA is needed if the development site is in flood zones 2, 3, or critical drainage areas, or if it will be at flood risk in the future, based on strategic assessments. Planning permission may be denied without an adequate FRA.
• Flood Zones and Risk Levels: Flood zones are categorized by risk: Zone 1 (low risk), Zone 2 (medium risk), Zone 3a (high risk), and Zone 3b (functional floodplain). Understanding these zones is essential for safe development planning.
• Sequential Test Requirement: Before conducting an FRA, a sequential test is often required to compare the proposed site with others to ensure lower-risk areas are prioritized for development. This helps minimize reliance on flood defenses and resilience features.
• Challenges and Future Trends: Common challenges in FRAs include data availability, climate change uncertainty, and balancing development needs with flood risk. The future of FRAs may see increased use of technology, integration with sustainability goals, and adaptive flood management strategies.