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Why Do Rivers Flood?

Why do Rivers Flood?

The UK regularly experiences heavy rainfall, and while in most cases no harm is done, on some occasions severe rain can result in flooding.

In recent years, it has been normal to see certain areas flood with footage of homes, businesses and streets being covered in water becoming commonplace. In some instances, this flooding occurs when nearby rivers burst their banks which causes large volumes of water to flow into local communities and cause irreparable damage.

The destruction floodwater can cause can be severe, and in some cases, it may even pose a risk of harm to human life. No matter how severe the flooding is, it’s always worthwhile understanding how it occurs and what can be done to minimise the damage. 

With this in mind, in this article, the team at IBS Engineering will answer the question ‘why do rivers flood?’ explaining why the phenomenon occurs and what can be done to prevent it.  



Why do rivers flood?

Usually, when heavy rain occurs, the risk of flooding is heightened. 

River flooding, also known as fluvial flooding, is the most common cause of flooding in the UK and happens when the volume of rainfall becomes so vast that the river or stream breaks its banks. The water will then flow out of these bodies of water and flow into low-lying areas or natural floodplains where the flooding will occur. 

This happens when the heavy rain exceeds the natural capacity of a river, with the problem often exacerbated by blockages in the waterway. 

Different rivers will respond differently to heavy rain, but this will depend on a variety of factors including:

  • The size and slope of the catchment area
  • The permeability of the soil and underlying rock
  • Urbanisation in the local area  
  • How easily rainwater can be stored and released into neighbouring lakes and waterways

With all of this in mind, different rivers will often respond differently to the same type of storm so it’s important to know the conditions of the ones located near to you. 

A flooded river can happen over time or suddenly and with little warning, and again this will typically depend on the intensity of the rainfall as well as the specific factors relating to the individual river. 


What are the main reasons that rivers flood?

As mentioned above, rivers usually flood due to heavy rainwater. 

However, there are a range of other reasons why rivers can flood. This includes:


Some surfaces where flooding occurs are impermeable, and in these instances, it makes natural filtration difficult. This then leads to a higher level of run-off and severe flooding.

Steep slopes 

In parts of the country where the terrain is particularly steep (such as mountainous areas), water flow can be more rapid which encourages flooding. 


In agricultural settings, the use of land can also make flooding more likely. For example, ploughing fields can create channels where water can rapidly flow through and cause flooding to occur. 


As well as being a practice that is bad for the environment and which causes climate change damage, deforestation can also make flooding a more likely occurrence. This is because natural vegetation like trees, can intercept rainfall and slow its movement. 

When trees are chopped down, this natural barrier is lost which means flooding is more likely to happen. 


How to stop rivers from flooding

While a small amount of flooding can actually be beneficial due to the advantages it can provide to nearby soil (especially when this soil is used for agricultural purposes), severe flooding can be dangerous and detrimental to local communities. 

There are many ways to prevent rivers from flooding, with flood barriers the most common method used. 

At IBS Engineering, we provide a number of flood defence systems that can help stop river floodwater from causing damage. This includes our innovative glass flood defence system.

This product is used in areas where a permanent preventive solution is required, making it a popular choice in areas that are prone to regular flooding. An extremely robust solution, this provides a physical barrier that can stop water from getting through to homes, businesses and areas of land that need to be protected from damage.

As well as these man-made solutions, the planting of trees and developing wetlands can also help to mitigate the risk of flooding. However, these options take much longer and while can be put in place for the future, will not help with immediate problems. 

For more information on the range of flood protection systems that the team at IBS Engineering can provide you with, contact our team today.    

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