Fact Check: Do Floods Occur Because of Covered Surfaces?
A screenshot of a Facebook comment shared with us claims that paved surfaces prevent water from sinking into the ground, causing flooding. This was on a Facebook post about a downpour in Namboole, Uganda, where water covered the road. 
This assertion is a typical story that has been shared by a lot of twitter users.
Fact check
The claim that covered surfaces cause flooding is misleading. According to an article published on Science Direct, a database of scientific and medical publications, urban surfaces like asphalt, concrete, and other hard surfaces have little to no effect on the amount of flooding that occurs in any given area.
Contrary to the claims that covered surfaces can cause flooding, an article defining floods published on National Geographic, a source of various geographical and scientific resources, states that floods occur when there is an excessive amount of water that cannot be absorbed by the ground or carried away by existing drainage systems. This can happen due to a variety of factors, including heavy rainfall, rapid snowmelt, or a combination of both.
Concrete and other impermeable surfaces can make flooding worse by causing more runoff, but they are not the only factor at work. Other factors, such as the amount and intensity of rainfall, the slope of the land, and the capacity of drainage systems, all play important roles in determining whether or not flooding occurs, according to an article published on the research gates that summarizes the factors that contribute to flooding as listed in the World Meteorological Organization’s report from 2008.
Verdict
While it is true that impermeable surfaces such as concrete can increase runoff during heavy rainfall, they do not directly or solely cause flooding. Because water doesn’t sink to the ground, it is false to say that paved surfaces made of concrete cause flooding. While impermeable surfaces can increase runoff and contribute to flooding, they are not the only cause of flooding and, in some cases, can help reduce the risk of flooding.
This fact-check was produced by the Debunk Media Initiative with support from Code for Africa’s PesaCheck, the International Fact-Checking Network, and the African Fact-Checking Alliance network.
