We use some essential cookies to make this website work.
We’d like to set additional cookies to understand how you use forestresearch.gov.uk, remember your settings and improve our services.
We also use cookies set by other sites to help us deliver content from their services.
Preparing to search
Woodland soils typically have a relatively open, organic rich upper layer, which facilitates the rapid entry and storage of rain water
Forests are known to use more water than shorter types of vegetation. This is mainly due to the interception of rainwater by their aerodynamically rougher canopies. Interception can reduce the amount of rainfall reaching the ground by as much as 45% or more for some types of forests. A reduction of even half of this amount could therefore make a major contribution to flood control.
Another way that forests could affect floods is by their soils holding back and delaying the passage of rain water to streams and rivers. Forest soils tend to have a more open structure resulting from greater amounts of organic matter and the action of tree roots and soil fauna. They are also usually drier during summer periods due to the higher water use by forests. These conditions enhance the ability of the soil to receive and store rain water and is commonly referred to as a ‘sponge effect’.
The interception loss varies between forest types. While losses of 25-45% are typical of conifer forests, those by broadleaves are lower and tend to range between 10-25%. Losses from broadleaves are further reduced to 5-10% during the leafless period, when the risk of flooding is often greatest. Another important factor is that interception declines with the size and intensity of a given rainstorm, reaching a maximum of 5-7 mm in a day. Thus losses for major rain storm events may be <10% even for a conifer forest.
The forest sponge effect also has its limitations. Most major floods occur following periods of exceptionally heavy and/or prolonged rainfall, often during the wet season. Forest soils are generally fully rewetted by such times with a reduced capacity to receive and store storm water.
Cookies are files saved on your phone, tablet or computer when you visit a website.
We use cookies to store information about how you use the dwi.gov.uk website, such as the pages you visit.
Find out more about cookies on forestresearch.gov.uk
We use 3 types of cookie. You can choose which cookies you're happy for us to use.
These essential cookies do things like remember your progress through a form. They always need to be on.
We use Google Analytics to measure how you use the website so we can improve it based on user needs. Google Analytics sets cookies that store anonymised information about: how you got to the site the pages you visit on forestresearch.gov.uk and how long you spend on each page what you click on while you're visiting the site
Some forestresearch.gov.uk pages may contain content from other sites, like YouTube or Flickr, which may set their own cookies. These sites are sometimes called ‘third party’ services. This tells us how many people are seeing the content and whether it’s useful.