Controlling Rodents during flooding

 During flooding, rats flee from the underground and seek for a new nesting location above the ground, and incidentally, in your home, exposing your household to risks of diseases.

Sewer Rats

Rats traditionally nest in low-lying areas, often underground in sewers, or beneath buildings and shrubbery. Heavy downpours can cause sewers to overflow. Often, the rainfall can kill a number of young rats inhabiting sewers systems, but in many cases it causes rats to flee from their underground nests looking for a new location above ground. In order to escape the rainfall, rats may seek refuge in homes, garages and commercial buildings.

The damage caused by flooding can be an attractive opportunity for 'sewer rats', as the deserted and debris strewn streets and homes can provide an abundance of food and shelter. As rodents disperse into new areas they can quickly build large colonies, because of their ability to reproduce quickly.

There are two common species of rat that may live in sewers. The common rattus norvegicus known as the 'brown rat', and the rattus rattus or the 'black rat' (the latter is less commonly found as it is a foreign species). Rats naturally harbour diseases such as Lymes Disease, Salmonella and Typhus. By their nature, they can often spread disease contained in various parasites carried on their body. It is essential for your health to take a potential rat infestation very seriously. This means that precautions should be taken to prevent rats from entering your home, and if you are suffering from an infestation, then you need to be vigilant in eliminating the problem.


Disease risk 

Health risks increase massively during times of flooding. One concern is that water can become contaminated. Floods can kill populations of rats, but this in itself can become a health hazard. Dead rats can contaminate floor water with a number of diseases that can then enter the home during flooding.  

 Weil's disease is often associated with floodwaters. A report in 2005 suggested that 41 cases of Weil's were reported, mostly in areas of flooding. In most cases people coming in contact with rodent carcasses or wading through floodwater, which can be contaminated by as little as rodent urine, cause the spread of infection. It is important to note that around 50-70% of all UK rats carry this disease, which is harboured in kidneys and can be spread through excretion. The disease can live for 45 days in fresh water, or muddy riverbanks, but cannot multiply outside of the body of a rat.    

Although the disease is not usually fatal; it can have some nasty flu like symptoms such as, chills, vomiting and intense headaches. In the worst case it can cause liver damage.


  • Always wear boots in flooded areas. Floodwater can contain microorganisms such as Weil's, which may be infested by dead rodents or rodent excretion.  
  • Be sure to firmly cover any open wounds with water resistant bandages or plasters, to prevent any potentially contaminated floodwater from entering your body.  
  • Never swim in floodwater. Not only can microorganisms enter your body through open wounds, but also through the nose, eyes and mouth. 
  • Flooding can cause damage to property including clusters of damaged furniture, or loose debris. It is advised to clean up any flood damage as quickly as possible, as these areas can harbor rats. 

 If you are experiencing an infestation, then it is important to deal with your problem hygienically. Try to localise your rodent traps to a certain part of the house. The most durable trap to use in flooded conditions will be the classic snap trap.


Written by Marion C. European Ecommerce Content Specialist at Victor Pest.

Victor®, the global leader in rodent control, offers a variety of innovative rat control solutions such as  electronic rat traps, ultrasonic rat repellents and rodenticides to help you with all your rodent control needs. Victor® has all the information you need to get rid of the rat in your home. 



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