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Hydrology Research In Press, Uncorrected Proof © IWA Publishing 2012 | doi:10.2166/nh.2012.157 Parameter sensitivity of a watershed-scale flood forecasting model as a function of modelling time-stepFiachra O'Loughlin, Michael Bruen and Thorsten WagenerFirst received 4 April 2011; accepted in revised form 10 October 2011. Available online 10 July 2012 ABSTRACT Although ongoing technological advances have alleviated data restrictions and most of the computational barriers to distributed modelling, lumped, parsimonious, conceptual and rainfall-runoff models are still widely used for flood forecasting. However both optimum parameter values and the fluxes of water through individual model components change significantly with the time step used. Thus, such models should be used with caution in applications such as hydrograph separation or water quality studies that require the fluxes through individual flow routes through the model or which try to relate parameters to physical features of the catchment. To demonstrate this time-scale limitation, a parameter sensitivity analysis was performed on the lumped conceptual SMARG model for a 182 km2 rural catchment in Ireland for a number of time-steps, flow regimes and evaluation metrics. A global sensitivity analysis method (HDMR) showed that sensitivity indices vary greatly with time-step and evaluation metric. The sensitivity of parameters also varied for different flow regimes. Certain parameters' sensitivities remain fairly constant across both flow regimes and time-step, while others are very much regime or time-step dependent. Care should be taken in using internal information from conceptual models because of this strong dependence on time-step. Keywords: flood forecasting; rainfall-runoff modelling; sensitivity analysis; SMARG; time-step |
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