A flood risk assessment considers flooding to the development and any effect the proposal could have elsewhere. We assess the relevant flood sources against the proposed use, access and layout, with mitigation built into the design where it is needed.
Flood Risk Assessment
Flood sources, future conditions, safe access, mitigation and effects on surrounding land considered for the proposed development.
Flood Risk Assessment enquiry
The flood setting
Relevant flood records, site levels and nearby drainage help establish the conditions requiring assessment.
Design implications
Access, proposed uses and building levels need to reflect the flood risks identified for the site.
Flood risk from rivers, surface water and other sources
River, coastal, surface-water, groundwater and other mechanisms can affect the same site in different ways. The mapped Flood Zone is important evidence, but it describes river and sea probability rather than every route by which water can reach the land.
Site levels, drainage information, local flood evidence and the proposed use help establish the assessment. Floor levels and safe access are most useful when considered with the layout, not added after the design has already been fixed.
Discuss flood risk assessment
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Flood risk over the development lifetime
The development lifetime and relevant climate-change allowances affect the scenarios considered. Mitigation should make the proposed use appropriately safe without simply moving flood risk onto neighbouring land.
Further modelling, design changes or a linked drainage strategy may be needed where the available evidence does not resolve the issue. The report assesses defined risks and assumptions; it cannot promise that a property will never flood.
Flood zones and wider flood-risk evidence
In England, a site in Flood Zone 1 can still need flood-risk assessment because of its size, surface-water risk, future flood risk, critical-drainage considerations or evidence in the strategic flood risk assessment. Low river and sea probability is therefore not an automatic exemption from assessment.
Flood Risk Assessment: common questions
Can a site in Flood Zone 1 still need assessment?
Yes. Other flood sources and the characteristics of the proposal can still require consideration.
Is a drainage strategy the same as a flood risk assessment?
No. They are related, but the strategy designs surface-water management while the assessment considers flood risk to and from the proposal.
Does the report guarantee no future flooding?
No. It assesses defined risks and scenarios and explains the assumptions and proposed mitigation.
Can flood risk be dealt with only by raising floor levels?
Not necessarily. Safe access, surface-water routes, the proposed use and effects on surrounding land also need consideration.
Why does the development lifetime matter?
The assessment considers flood risk over the intended lifetime of the development, including the relevant future climate-change allowances.