03 - Fixed Flood Protection On Site

A site should be protected against a fluvial (river) flood event with an annual probability of occurrence of at least 1%. If your site falls within an area with a higher probability of flooding then additional flood prevention or protection measures need to be considered.

It is to be noted that climatic changes require close observation of adequacy of drainage systems and condition of building envelopes. Other flood protection mechanisms include barriers, dams, dikes, drainage systems, pumping equipment, retention basins, reservoirs etc.

This factor considers permanent on-site fixed flood protection, It does not include mobile equipment of a temporary nature. Note that flood protection systems do not provide absolute safety and can fail in case the event is larger than the design protection level. There is a need for a flood emergency and contingency plan to ensure adequate procedures are in place (see corresponding risk factor).


  • Presence of reliable on-site flood protection against at least a 1 in 100 year flood scenario.
  • Reliable fixed structures that do not need any manual intervention, eg. barriers, dams, dikes, automatic flood gates, drainage systems, pumping equipment, reservoirs, retention basins, etc.
  • Regular, well-documented maintenance programs are necessary to ensure reliability of such systems.

Risk improvement ideas

  • Permanent protection can include, but is not limited to, barriers, dams, dikes, drainage systems, basins, reservoirs etc.
  • Establish a maintenance and inspection plan to assess the condition of flood protection systems and equipment. The inspection plan should also include post-event condition and evaluation of performance.
  • If flood protection turns out to be inadequate, consider one or more of the following:
    • Improve existing flood defenses by strengthening and/or increasing the height of the flood defense structure.
    • Support existing flood defenses by building secondary embankments. These can be as simple as sloped grass / earth embankments ('soft') or more complicated with crest walls or concrete barriers ('hard').


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