Although the cause of the apparent increase in occurrence of severe weather patterns is a topic of significant discussion, the impact of severe rainfall events and the resulting sewer and stormwater flooding is readily apparent.
Whilst we could design infrastructure to accommodate flows resulting from extreme or severe storm events, it is unlikely to be sustainable and could result in significantly larger capital schemes with potentially high operational costs. In reality it is not viable to size infrastructure in this way and inevitably there would be a pinch point, maintenance issue or an even more extreme event that may exceed design parameters.
Local authorities and companies in the UK are becoming increasingly aware that we cannot continue to try to build our way out of the problem. In the UK some engineers and asset managers are trying to move towards managed outcomes rather than resolving all flooding risk.
The managed outcomes concept in its purest form is the design of infrastructure for a set of client approved criteria, with serious consideration given to what happens and how we sustainably manage the location of flooding resulting from severe storms and exceedance events.
The paper describes the approach I have adopted on a number of sewer and stormwater projects as a consultant working with a UK water company, the difficult decisions made and the managed outcomes achieved.