Water

Flood-risk: building placement

Provided by Robert Barker: co-director of Baca Architects

 

What, Why, WhenHow, Extras

 

What is it?

Building Placement is a design measure to intelligently locate buildings to minimise flood-risk to users and property. This is based on considering the use of a building and the level of the flood-risk, guidance is given in planning policy. For instance, buildings for emergency services should be placed in the area least at risk of flooding, where as a boatyard may be possible to be placed in an area which is highly likely to flood (on the basis that it is more acceptable for it to be flooded).

 

Why use it?

Though rare flooding can have a devastating effect on people’s lives and livelihoods. Badly placed buildings can also be a barrier to flood flows and displace floodwater elsewhere, putting other areas at risk. Therefore, it is essential to consider the position of a building in a flood prone area above all other site planning considerations, as it is about reducing risk to people’s lives. Well-placed buildings can limit the risk of the most vulnerable users by locating them in areas of lowest flood-risk and in conjunction with flood tolerant landscape design may help to reduce flood-risk overall.

 

When to use?

Building placement should be considered for all sites (not just those close to a river or the sea), and particularly for large sites and new developments. When considering if a site is at risk of flooding, all forms of flooding must be considered, not just rivers and seas and changes in flood-risk based on the effects of climate change must also be considered. Ideally placement of buildings according to flood-risk should be done in conjunction with other issues such as access and landscaping to reduce flood-risk and create more sustainable development.

 

How to use?

Key points:

 

  • Consider which areas of the site are most at risk of flooding.
  • Flood risk may be different across parts of the site.
  • Identify if the use proposed is likely to put peoples lives at risk if a flood occurs (at any time of the day or night).
  • Determine whether it is possible to locate the building in a different part of the site or if it would be better located on another site altogether.
  • Consider changing the use of the building to make it less susceptible to flooding.

 

Design procedure:

 

  • Step 1: Identify if the site is at risk of flooding. The Environment Agency website and the Local Authority can provide details.
Environment Agency map

Flood maps and flood zones. (Click image to enlarge)

 

  • Step 2: Determine if and how this might change in the future due to climate change. Planning policy gives guidance on how climate change should be calculated. The Local Authority can provide maps and information on your area.
Climate Change impacts

Flood maps and flood zones. (Click image to enlarge)

 

  • Step 3: Establish the area of the site most susceptible to flooding and the likely depth and extents of a flood. Identify if it is possible to locate the buildings away from areas at risk of flooding.
Development flood risk

Flood maps and flood zones. (Click image to enlarge)

 

  • Step 4: Establish whether the uses of the buildings are appropriate for the site and whether it would be necessary to relocate or change the building use, if this is not possible then you would need to introduce other design strategies such as building resistance or resilience.
Floating amphibious resilient unit

Floodproof building types. (Click image to enlarge)

 

 

 

  • Step 5: Locate your access on the side least at risk of flooding and seek to locate above the height of the floodwater, in accordance with policy guidance and best practice.
  • Step 6: Orientate the building in line with the direction of flood flows to reduce the extent of the obstacle to flood flows.
Non-defensive flood risk management

Buildings set back from flood-risk areas. (Click image to enlarge)

 

 

Related strategies

Site planning Water conservation Waste management
SUDS Flood resilience Flood resistance

 

Conflicting strategies

Building orientation
 

Take this further

Case studies


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