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A.Whitty
February 28, 2016, 01:56 PM
I know there are a lot of uncertainties over current climate change predictions and applications within hydraulic modelling, but I was after some input on how people currently apply current climate change predictions to model runs, in particular time series rainfall.

Design storms are relatively 'simple' with a standard uplift factor applicable ranging from anywhere between 5 - 30% obviously depending on location, design horizon etc.

However, from looking at time series rainfall there seems to be a lot more complications. Without going into too much detail the general consensus from UK CC predictions is that winters will get wetter and summers will get drier, but the storms in the summer will increase in intensity and frequency.

Therefore it seems applying a blanket uplift to TSR will over-predict for example spill performance of overflows when looking at including climate change.

Or am I looking into it too much and a blanket uplift approach is acceptable?

Kristian Ravnkilde
February 29, 2016, 01:26 AM
I don't think blanket uplift is acceptable, but that doesn't get us much further. It's a complex problem, and the uncertainties of made-up numbers on top of made-up numbers really is enormous. One solution is to use baseline and disturbed time series from UKCIP http://ukclimateprojections.metoffice.gov.uk/ to generate "current" and "future" TSR in Stormpac (if that's what you're doing), but you will probably have to obtain several projections and pick one that fits with expectations - an uncertain business in itself. Ideally, you'd run a whole load of them and get a good average prediction, but that's not all that practical and Stormpac has limits on how much input it can accept and how much output it can produce. Be VERY careful, describe exactly what you've done in your reporting and be sure to stress the uncertainties involved!

Duncan Kitts
March 2, 2016, 07:06 AM
I see the English EA have changed the way that allowances for Climate change are represented:- https://www.gov.uk/guidance/flood-risk-assessments-climate-change-allowances

DS Wessex
May 16, 2016, 01:16 AM
I see the English EA have changed the way that allowances for Climate change are represented:- https://www.gov.uk/guidance/flood-risk-assessments-climate-change-allowances

This is also of concern to us, although I cant offer much help,

Recent work by Marray Dale of CH2M:
http://www.floodandcoast.com/abstracts/mdale.pdf

Also Ciwem rainfall guide:
http://ciwem.org/wp-content/uploads/2016/03/CIWEM-UDG-Rainfall-Guide-2016.pdf