Reservoir flood estimation: Time for a re-think?

On Wednesday 18 October, the British Hydrological Society Pennines Section is holding an event at the University of Leeds entitled ‘Reservoir and Flood Hydrology’. Duncan Faulkner, Head of Hydrology, is presenting at the event on ‘Reservoir flood estimation: Time for a re-think?’ Andrew Coen from the Environment Agency is also presenting on ‘Utilising water supply reservoirs for flood risk management – balancing needs.’

Reservoir flood estimation

Reservoirs tend to reduce flood risk but they are often blamed for flooding. Duncan’s presentation will discuss a few recent examples of this.

If their contents are released in an uncontrolled way reservoirs can lead to catastrophic flooding. The safety of reservoirs is rightly taken very seriously by the water industry, and the UK has been mercifully free of catastrophic flooding from reservoir breaches for many years. Recent years have seen several concerning incidents of damage to spillways during extreme floods in England and Scotland. There has been a trend towards heavier rainfall and larger flood flows, particularly in upland areas where many reservoirs are located.

Design floods for high-risk reservoirs in the UK and Ireland are currently estimated using a method that in many respects has not changed since 1975. Although estimates of design rainfall for reservoirs in the UK have recently been updated, other aspects of the design method and the estimation of probable maximum precipitation (PMP) are dated. Methods for river flood estimation have moved on since the 1970s and there are new and longer-term sources of hydro-meteorological data. Research has shown instances of both PMP and probable maximum flood estimates being exceeded.

Duncan’s presentation will give an overview of aspects of the design flood estimation procedure that are in need of an update. He will offer suggestions for development of an up-to-date method for reservoir flood estimation that builds on existing methods and considers the effects of climate change on extreme floods. He will also give some hints and tips for practitioners carrying out reservoir flood studies in the meantime.

Want to know more?

Contact Duncan Faulkner for more information on his presentation and reservoir flood estimation. You can also visit our dams and reservoir web page to find out more about our work in this area.

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