Nick has been working hard producing a calibrated version of the Overflow model. The key different is a different rain time map (rainfall rate) is used throughout the storm event.
The result is a much closer match between the observed and simulated hydrograph at Isfield.
However there are are few issues with the new model;
The key issue is that when a hydrograph is simulated for the meadows area upstream of Uckfield, the largest flood peak now has a double peak. This is not expected and is slightly problomatic; the simulated peak discharge upstream of Uckfield now occurs only very slightly before the peak discharge at Isfield downstream, when perhaps a slightly bigger lag would be expected. If the peak were smoother, this would most likely bring the peak discharge just upstream of Uckfield forward a couple of hours.
On the positive side, the peak discharge is much more realistic.
As seems to be the way with modelling, as one aspect gets better, this can create a whole new set of problems. Just like a more comlex model can bring with it just as much uncertainty and a simple model.
Ill discuss the issue of the troublesome flood peak with Stuart Lane and I'm hoping that it wont be too much of a problem. The simulated hydrograph is now certainty much a closer fit to the previous uncalibrated model. Im looking forward to (hopefully) getting some final results I can properly work as time is running short in terms of my role in this study - I think we're all hopeful of some interesting results.
Whilst slightly frustrating to work on the previous model and then have to move on to a slightly different version, my previous work has allowed me to explore the behaviour of the model and get a better understanding of the uncertainties.
I have been now working on getting results of the screening runs (see previous updates) with the calibrated model, looking at the effects of increasing channel and floodplain roughness one reach at a time to represent the adding of a CRIM. Initial results to come...
