SEA/General/TBT-SEA-009

Flood and Extreme Weather Response

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Flood and Extreme Weather Response

Toolbox Talk Record

Ref: TBT-SEA-009  |  Issue: 1  |  Date: March 2026
PresenterProject
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What?

  • Flooding on construction sites can occur from heavy rainfall, river overtopping, or groundwater rise.
  • Flood water is dangerous — just 150mm of fast-flowing water is enough to knock a person off their feet.
  • Excavations fill rapidly during storms, trapping workers and causing trench collapse from saturated ground.
  • Extreme weather also includes storms, high winds, lightning, and extreme heat or cold events.
  • The Met Office issues weather warnings (yellow, amber, red) that sites should monitor and act on.
  • A site-specific flood and extreme weather response plan should be in place before work begins.
  • Flood water may contain sewage, chemicals, and debris that create biological and contamination hazards.
  • Plant and equipment left in flood zones can be damaged, displaced, or create downstream obstructions.
  • Temporary works, scaffolds, and excavation supports are all vulnerable to damage in extreme weather.
  • CDM 2015 requires that emergency procedures cover foreseeable events including flooding and severe weather.

Why?

Prevent drowningWorkers have drowned in flooded excavations and been swept away by flash flooding on construction sites.
Structural collapseSaturated ground, rising water, and storm loading can cause excavations, scaffolds, and temporary works to collapse.
Legal dutyCDM 2015 and the Emergency Plan require that foreseeable weather events are assessed and planned for.
Do Don't
  • Monitor Met Office weather warnings daily and brief the team each morning.
  • Prepare a site-specific flood and extreme weather response plan.
  • Identify trigger levels for stopping work and evacuating the site.
  • Secure loose materials, plant, and temporary structures before storms arrive.
  • Pump out excavations and inspect support systems after any heavy rainfall.
  • Keep emergency equipment including pumps, sandbags, and barriers available on site.
  • Evacuate low-lying areas and excavations immediately when flood warnings are issued.
  • Inspect scaffolds, temporary works, and excavations after every severe weather event.
  • Know the site evacuation routes and muster points for flood emergencies.
  • Report any flood damage to structures, services, or environmental receptors promptly.
  • DON'T enter flooded excavations or attempt to wade through flood water on site.
  • DON'T ignore Met Office weather warnings; they exist to protect you.
  • DON'T leave unsecured materials or plant in areas vulnerable to flooding.
  • DON'T assume excavation support is safe after heavy rain without inspection.
  • DON'T drive vehicles through flood water of unknown depth on site.
  • DON'T continue working at height during storm conditions or high winds.
  • DON'T discharge pumped flood water containing silt or sewage into clean drains.
  • DON'T delay evacuation waiting for conditions to improve during a flood event.
  • DON'T resume work after flooding without inspecting all temporary works first.
  • DON'T store chemicals or fuels in areas at risk of inundation by flood water.

See also: Rain and Waterlogged Ground Conditions | Working in High Winds
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