What is pluvial flooding and why is it important?

9th Nov 2011

Around 2 million people are at risk from pluvial flooding, says Josh Stott. But what is it and who is at risk?

Flooding is probably the most significant natural hazard we face in the UK, and there is more to the issue than just coastal and river flooding. Around 2 million people are at risk from pluvial, or rain related, flooding, so we need a better understanding of who's vulnerable.

Explaining pluvial flooding

Pluvial flooding occurs when an extremely heavy downpour of rain saturates the urban drainage system and the excess water cannot be absorbed.

These unpredictable events occur without warning and in the worst cases, such as happened in Glasgow (2002) and Hull (2007), can cause huge destruction and devastate whole neighbourhoods.

The latest research on pluvial flooding

As our climate warms up, the increased incidence of extreme weather events seems inevitable. New research published by the JRF today highlights the risk of pluvial flooding in the UK and in particular its impact on vulnerable people and places.

Key findings from our research:

  • Around 2m people are at risk from pluvial flooding, which represents around one- third of all flood risk in the UK.
  • This figure could increase by 1.2m by 2050 due to a combination of climate change and population change. Population change has the potential to put three times more people at risk than climate change.
  • Existing flood risk assessments are based on the number of properties at risk as opposed to the number of people. This approach downplays the impact on people, and in particular potentially vulnerable groups such as the elderly.
  • Lower income groups and renters are slightly more exposed to pluvial flood risk because of the number that live in low lying areas around town centres dominated by higher density terraced housing and flats.

Preparing for the future

All of our research on the direct impacts of climate change (including work on coastal communities and heatwaves) highlights the importance of building community capacity to adapt and become more resilient to the changing climate. It goes without saying that engineering solutions are important but are not enough to protect the most vulnerable in our society. The importance of raising awareness of the risks and potential responses shouldn't be underestimated. Nor should the role of building stronger support networks to help people cope with and recover from flooding events.

We need more joined-up policy and delivery. This cuts across the roles and responsibilities of countless agents – Government departments; local authorities; healthcare providers; community groups; housing associations; water companies, property developers; and the insurance industry – to name a few. We also need more research collaboration between engineering, natural science and social sciences.

As a starting point we need a better understanding of how flood events impact on people and who the most vulnerable are when floods occur. We will be publishing new research examining these issues later this month. Please look out for our dedicated microsite launching on 24th November.