Improving PMP & PMF estimation for UK reservoir safety

Overview

A project funded by the Environment Agency has comprehensively reviewed methods for estimating the probable maximum precipitation (PMP) and probable maximum flood (PMF). It has also updated cataloguing of observed extreme floods and rainstorms in the UK, finding several exceedances of current estimates of the probable maxima. A review of research and international practice has identified many opportunities for improving current estimation methods applied in the UK and the project has identified a recommended way ahead for development of new methods. In the interim, a restatement of the current method has been produced, along with an Excel software tool to assist practitioners with applying it.

This talk will outline the findings of the project, the type of methods recommended for development and some of the challenges, including the desire to reconcile the concept of the probable maximum with a risk-based approach to reservoir safety management.

One topic the talk will not be able to cover is the effect that the new methods will have on the size of PMF estimates. Until the next phase of the project has developed the new methods, this will not be fully known.