Options for communicating surface water flood forecasts

Surface water flooding is a recurring problem for UK towns and cities every year. Murray Dale and Kay Shelton explore some of the work we are doing to help develop forecasting systems for surface water flooding.

Surface water flooding happens when rain falls so hard that urban drainage systems struggle to cope with the rate of rainfall. It often occurs before the water has had time to reach a river, lake or water course.

It is also difficult to prepare for because it is particularly hard to predict.

JBA has pioneered new ways of visualising possible surface water flooding using the latest weather forecasting ensemble prediction systems. What are these? Simply put, these are systems that provide rainfall forecasts of many possible outcomes, rather than just one.  In this way they can capture some of the uncertainty of the forecast and give better, more reliable predictions. Working out how much rain is needed in a given amount of time to cause flooding is one of the technical challenges to overcome.

Communicating the flood risk effectively is even more challenging. One way this can be done is through use of real-time mapping using likelihood information.

Click on the image below, to see how this can been done, using experimental techniques over London from a rainfall forecast ensemble. We have also used this technology for recent flood events over other UK cities, with positive results.

Options for communicating surface water flood forecasts

Working with emergency response authorities, this technology can produce probabilistic flood extent maps with useful lead time (i.e. 24 or 12-hours before the event occurs) that can be used to aid decision making. For example, decisions might be:

  • What resources could be needed?
  • Are there ‘pinch points’ needing clearing to reduce water blockages?
  • Should collaborations with other organisations start now?

We are working on a R&D project with Network Rail employing this technology, and have recently worked with the University of Leeds, co-authoring this recent paper that explains some of the issues in more depth.

Want to know more?

Email Kay Shelton or Murray Dale for more information about our work in surface water flood forecasting.

You may also be interested in our blog: Future surface water flood risk | JBA Consulting


Leave a Reply