Last reviewed 29 July 2016

In this article, Caroline Raine discusses how to make sure that site managers are prepared for flooding on their construction sites and what to do in the event that the site does become flooded.


Over recent years, the UK has been exposed to a rapid increase in the number of floods. Flooding can be both predictable and unpredictable so it is important to ensure that site managers are prepared in advance.

A flood occurs when a river, stream or other watercourse bursts its banks, the resulting water spills onto the floodplain. Typically, this is as a result of heavy rainfall, and normally after a period of wet weather where the ground is already saturated. The faster that the water reaches the watercourse, the more likely it is to flood, as it cannot cope with such large volumes so quickly.

Be prepared

The first step is to understand the site location and surroundings. Are there any watercourses close to the construction site? Establish how far away they are and if there has been any history of flooding, and if so, how close the water came to the site. Bear in mind that just because the nearest river is 50 miles away and the area has never been flooded, it is still possible for flooding to occur.

Flood maps can be used to check the risk of flooding from rivers, seas, surface water and reservoirs. These flood maps can be accessed through the Environment Agency website where a simple search using the construction site postcode can be carried out. The map then shows in colour whether the risk of flooding is low, medium or high. The flood maps can be accessed here.

The flood history of the construction site should also be established and this can be done through the Environment Agency too; it is a free service and the turnaround time is typically 18 hours. In order to request the site flood history, an email should be sent to detailing the property address, with a map showing the location and contact details. In addition, a Land Registry “flood risk indicator” is available, but this is not a free service and costs £10.80 (including VAT).

The Met Office and the Environment Agency both provide flood warnings and it is advisable to subscribe to their free email or text alerts which give warnings of flooding.

Having carried out the research, the next step is to create a flood plan. This should include how to protect staff, hazardous equipment and minimise the risk of pollution. The Environment Agency provides a flood template that can be accessed here. The plan should help decide if it is necessary to have sandbags or other equipment on standby. The Environment Agency has also provided a document: Preparing your business for flooding. Contact details for further help in the event of flooding should also be included, for example, the fire service for pumping flood water, the National Grid in the event of a gas leak, the electricity supplier if an electrical hazard occurs. The plan should be available either in paper copy or be accessible away from the site in case power is lost — it is difficult to get help if you do not have the numbers.

Finally, make sure that the business is suitably insured to cover the costs in the event of flooding.

What to do in the event of being flooded

If having subscribed to be notified of the risk of flooding it looks likely that the construction site will be flooded, there are a number of initiatives that can be taken to minimise the damage. Use sandbags to prevent the flood water entering offices and other buildings. Move equipment and chemicals that will cause pollution to a safer area, for example, an upstairs office, but take care that the chemicals are still correctly stored away from incompatible materials and that additional risks are not being introduced by moving them. Sandbags can also be put in toilet bowls to prevent sewage backflow. If possible, move any vehicles to higher levels. Turn off the electrical supply to the site. Taking photographs both before, during and after can help with an insurance claim.

Public Health England has a number of useful resources on what to do after flooding, see

Avoid coming into contact with flood water — it can contain sewage and chemicals. Keep all cuts covered with waterproof plasters and wear suitable clothing to prevent the flood water coming into contact with the skin. Always wash hands and rest of the body thoroughly after coming into contact with flood water. Try not to walk in flood water as it can be exceptionally dangerous, manhole covers may have been lifted, and sharp objects may have been washed into the site.

Often, the flood water disappears almost as quickly as it appeared, but in some cases, the water may need to be pumped off site. The local fire service may help with that — although a fee for their services may be incurred. An environmental permit may be required to pump water from the site. It is always best to seek advice and permission from the Environment Agency if pumping to rivers, boreholes, ditches or watercourses, or the water company if pumping to sewers or Highways England if pumping into street drains, highways or highway ditches.

When attempting to clear up be aware that there are still dangers when the floods have cleared. Do not use gas or electrical appliances until they are checked for safety. Containers may have been damaged by the flooding, so extra care should be taken with containers of hazardous chemicals; also consider the fact that chemicals may have leaked and so may have contaminated the surrounding area, or released fumes that may be toxic. If the site contained asbestos it would be advisable to seek specialist advice.

Flood water can contain sewage as well as diseases, for example, rat’s urine can cause Leptospirosis. So always ensure that the whole site is thoroughly cleaned.

Any materials or fabrics that have become contaminated, eg carpets, doormats, curtains, clothing should be disposed of unless they can be thoroughly cleaned and disinfected.

Any plant equipment that has been contaminated must also be thoroughly cleaned. Pressure washing is an excellent way of ensuring minimal human contact with the contaminated machinery. Ensure that the washings are collected or go to foul waste drains. Once equipment has been rinsed, it may be sensible to consider the use of a disinfectant to ensure all contamination has been removed.

Dispose of any food that may have been in floodwater, and always boil tap water until supplies are declared safe.


In order to minimise the consequences from flooding, site managers must make sure that they are prepared and have done their research and planning in advance of any flooding. It is too late to do anything constructive once the rain starts coming. Both the HSE and the Environment Agency have useful information pages on flooding, the Environment Agency concentrates on preparation while the HSE covers recovery. Public Health England provides valuable information on protecting health, see here.