Floodwater

Revision as of 16:53, 3 November 2021

Introduction

Floodwater (also referred to as flood water) is defined as the water left behind from flooding caused by high levels of water in lakes and streams. Other flood sources include :

• Rivers (fluvial flooding).
• The sea (coastal flooding).
• Groundwater flooding.
• Surface water flooding.
• Sewer flooding.
• Infrastructure failure flooding (eg dam failure).
• Compound flooding.

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

Dangers of floodwater

Drowning is one of the biggest dangers associated with floodwaters. There is also the possibility of injuries caused by harmful objects (such as downed power lines, dangerous animals, poisonous insects, reptiles, 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.”

Damage caused by floodwater

There are other problems associated with standing water that is left behind after a flood. These issues may include:

• Property damage including destruction of structures and long term issues with rot, mould and mildew.
• Damage to equipment and machinery including permanent destruction or long term issues with rust.
• Infectious disease transmitted in the water.
• Pollution from chemicals or sewage left behind in the water.

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. 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 electric appliances before using them.

There are permanent measures that some regions must 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 riprap barriers, self-inflating flood defence systems or other devices.

Related articles on Designing Buildings

• Bridge scour.
• Coastal defences.
• Dyke
• Flood.
• FloodSax.
• Flood source.
• Legionnaires’ disease.
• Levee.
• Temporary flood defences.

External resources

• Public Health England, Flooding questions and answers.