Floodplain
A floodplain is land adjacent to a watercourse over which water flows or would flow in times of flood, if defences were not in place.
The flood zone area classification system devised by the Environment Agency refers to:
- Flood Zone 1: Land outside the floodplain. There is little or no risk of flooding in this zone.
- Flood Zone 2: The area of the floodplain where there is a low to medium flood risk.
- Flood Zone 3: The area of the floodplain where there is a high risk of flooding.
Ref The HS2 London-West Midlands Environmental Statement, Department for Transport, November 2013.
NB Culvert, screen and outfall manual, (CIRIA C786) published by CIRIA in 2019, defines a floodplain as: ‘Land on either side of a river that is below the highest defined flood level.’
The National Flood and Coastal Erosion Risk Management Strategy for England, Glossary, published by the Environment Agency in 2020, suggests a floodplain is: ‘Land with a high probability of being partly or wholly covered with water during flooding from rivers or the sea – ignoring the presence of flood defences.’
[edit] Related articles on Designing Buildings
- Applying flood resilience technologies GG 84.
- Building flood resilience.
- Catchment flood management plans.
- Coastal defences.
- Dyke.
- Environment Agency.
- Flood.
- Flood and Water Management Act.
- Flood defences.
- Flood insurance.
- Flood mapping key to future development in Wales.
- Flood risk.
- Flood risk assessment.
- Flood risk management plans.
- Floodplain capacity.
- Floodscape.
- Functional floodplain.
- Future flood prevention.
- Pitt Review.
- River engineering.
- Sustainable urban drainage systems.
- Thames barrier.
- Water engineering.
Featured articles and news
Boiler Upgrade Scheme and certifications consultation
Summary of government consultation which closes 11 June 2025.
Deputy editor of AT, Tim Fraser, discusses the newly formed society with its current chair, Chris Halligan MCIAT.
Barratt Lo-E passivhaus standard homes planned enmasse
With an initial 728 Lo-E homes across two sites and many more planned for the future.
Government urged to uphold Warm Homes commitment
ECA and industry bodies write to Government concerning its 13.2 billion Warm Homes manifesto commitment.
Places of Worship in Britain and Ireland, 1929-1990. Book review.
The emancipation of women in art.
CIOB Construction Manager of the Year 2025
Just one of the winners at the CIOB Awards 2025.
Call for independent National Grenfell oversight mechanism
MHCLG share findings of Building Safety Inquiry in letter to Secretary of State and Minister for Building Safety.
The Architectural Technology Awards
AT Awards now open for this the sixth decade of CIAT.
50th Golden anniversary ECA Edmundson awards
Deadline for submissions Friday 30 May 2025.
The benefits of precast, off-site foundation systems
Top ten benefits of this notable innovation.
Encouraging individuals to take action saving water at home, work, and in their communities.
Takes a community to support mental health and wellbeing
The why of becoming a Mental Health Instructor explained.
Mental health awareness week 13-18 May
The theme is communities, they can provide a sense of belonging, safety, support in hard times, and a sense purpose.
Mental health support on the rise but workers still struggling
CIOB Understanding Mental Health in the Built Environment 2025 shows.
Design and construction material libraries
Material, sample, product or detail libraries a key component of any architectural design practice.
Construction Products Reform Green Paper and Consultation
Still time to respond as consultation closes on 21 May 2025.
Resilient façade systems for smog reduction in Shanghai
A technical approach using computer simulation and analysis of solar radiation, wind patterns, and ventilation.