Title:
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Methods for rainfall-runoff continuous simulation and flood frequency estimation on an ungauged river catchment with uncertainty
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Historic methods for time series predictions on ungauged sites in the UK have tended to focus
on the regionalisation and regression of model parameters against catchment characteristics.
Owing to wide variations in catchment characteristics and the (often) poor identification of
model parameters, this has resulted in highly uncertain predictions on the ungauged site.
However, only very few studies have sought to assess uncertainties in the predicted
hydrograph.
Methods from the UK Flood Estimation Handbook, that are normally applied for an event
design hydrograph, are adopted to choose a pooling group of hydrologically similar gauged
catchments to an ungauged application site on the River Tyne. Model simulations are derived
for each pooling group catchment with a BETA rainfall-runoff model structure conditioned for
the catchment. The BETA rainfall-runoff model simulations are developed using a Monte
Carlo approach. For the estimation of uncertainty a modification of the GLUE methodology is
applied. Gauging station errors are used to develop limits of acceptability for selecting
behavioural model simulations and the final uncertainty limits are obtained with a set of
performance thresholds.
Prediction limits are derived from a set of calibration and validation simulations for each
catchment. Methods are investigated for the carry over of data from the pooled group of
models to the ungauged site to develop a weighted model set prediction with pooled
prediction limits. Further development of this methodology may offer some interesting
approaches for cross-validation of models and further improvements in uncertainty estimation
in hydrological regionalisation.
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