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Last edited 04 Nov 2021

Floodwater

This photograph, taken in January 2008, shows winter floods which are not infrequent along the waterfront at Kings Staithe in the centre of York. Typically, only a few properties are affected. When this photo was taken, the river had passed its peak and had dropped by some 10 to 15cm.

1 Introduction
2 Health dangers of floodwater
3 Damage caused by floodwater
4 Dealing with floodwater
5 Related articles on Designing Buildings
6 External resources

[edit] Introduction

Floodwater (also referred to as flood water) is defined as the water left behind from flooding caused by high levels of water from or in:

Lakes.
Streams.
Rivers (fluvial flooding).
The sea (coastal flooding).
Groundwater.
Surface water.
Sewers and drains.
Infrastructure failure (eg dam failure).
Compound flooding.

Floodwater can cover land and submerge buildings, vehicles, roads, infrastructure and so on.

[edit] Health dangers of floodwater

Drowning is one of the biggest dangers associated with floodwater. There is also the possibility of injuries caused by harmful objects (such as downed power lines, dangerous animals, poisonous insects, reptiles, debris, sharp fragments and so on) that may be hidden in the water. Toxic fumes can linger and parasites can be left behind after flooding has receded.

One illness that may be associated with floodwater is Legionnaires’ disease. This illness is a form of pneumonia that can be fatal. It can be caused by legionella bacteria that is commonly found in rivers, lakes and reservoirs. Legionnaires’ disease is generally contracted by inhaling airborne water droplets that contain this bacteria. The transmission of this bacteria can occur during a flood.

At certain times of the year, the cold temperatures of floodwater can cause shock. Dealing with floodwaters - not only at the time of the incident but also in the aftermath - may also impact the mental health of people who live through it.

Because accidents may occur due to fast flowing floodwaters, people are advised not to walk or drive in or around areas that are submerged in water. Areas around drains, trees, eroded river banks, harbours and estuaries may be particularly dangerous. In the Public Health England publication entitled ‘Flooding questions and answers’, the Government states that “six inches of fast flowing water can knock you over and two feet of water will float your car.”

Floodwater can also cause disruption to or contamination of drinking water supplies.

[edit] Damage caused by floodwater

Other problems associated with flooding may include:

Property damage including destruction of structures and long term issues of rot, mould and mildew.
Damage to equipment and machinery including permanent destruction or long term issues such as rust.
Infectious disease transmitted in the water.
Disruption to infrastructure such as utilities supplies, railways, highways and so on.
Pollution from chemicals or sewage left behind in the water.

[edit] Dealing with floodwater

In the event that floodwater might enter a property, people are advised to turn off gas, electricity and water well in advance, to move possessions to a higher level and if necessary to evacuate the area. Should water enter the property, it is advisable to take certain precautions, including:

Avoiding coming into direct contact with floodwaters.
Wearing protective clothing if it becomes necessary to go into floodwaters.
Using soap and hot water to thoroughly wash anything that comes into contact with floodwaters. Anything that can not be safely sanitised should be discarded.
Disposing of food that may have had contact with floodwater. This includes produce grown in areas that may have been flooded.
Professionally testing gas and electrical appliances before using them.

There are permanent measures that some regions take in order to control recurring incidents of encroaching floodwaters. These include flood defence embankments, dikes, flood walls and permanent levees. Temporary levees made from sandbags can also be used along with stone barriers, self-inflating flood defence systems or other devices. For more information see: Flood defences.