Pluvial flooding in urban areas: the invisible hazard

2011 study for JRF by Donald Houston, Alan Werritty, David Bassett, Alistair Geddes, Andrew Hoolachan and Marion McMillan, JBA Consulting, University of Dundee and University of St Andrews.

This study assesses how many people in urban areas are at risk from 'pluvial' flooding – surface water accumulating from the result of intense rainfall. It also explores how socially deprived areas are at slightly higher risk of pluvial flooding.

What is pluvial flooding and who's at risk?

The report:

  • explores existing knowledge around flooding and how it has moved up the policy agenda in recent years;
  • outlines the risks posed by flooding;
  • examines who are vulnerable, and the proportion of the urban population living in risky areas, such as those at street level or below;
  • shows how national population growth has the potential to put around three times more people at risk from pluvial flooding by 2050 than climate change; and
  • concludes that adaptation responses need to be developed at local levels, and that local authorities have a pivotal role to play in leading on surface water management.


Pluvial flood risk accounts for approximately one-third of flood risk in the UK. Approximately 2 million people in UK urban areas are exposed to an annual pluvial flood risk of 0.5 per cent or greater ('1-in-200 year' event). The key points are:

  • An additional 1.2 million people in urban areas could be put at risk by 2050 due to a combination of climate change and population growth.
  • From a social justice perspective, it is important to know the characteristics of the population at risk, not just the number of properties in an affected area.
  • Settlements across the UK with higher rainfall tend to have greater levels of social deprivation, although the differences are small.
  • Changes to the cost and availability of insurance in the future have the potential to alter the socio-economic composition of flood risk areas and/or blight certain areas.
  • Pluvial flood risk can be heavily mitigated in new developments through a combination of avoiding the highest risk locations, investment in drainage systems, flood proof building design and innovative surface water management schemes.
  • A key challenge remains for existing built-up areas at high risk, although surface water management can ameliorate risk when opportunities for redevelopment arise.
  • While recent flood management legislation around the UK has improved the priority given to pluvial flood risk, concerns still exist about partnership working, uncertainty about levels of risk (which can hinder planning), competing demands and capacity to respond.
  • An interdisciplinary approach incorporating engineering, natural sciences and social sciences is required to better understand social vulnerability to flood risk.




Full Report