Weather Radar and Flood Forecasting.
For accurate flood forecasts, or any distributed hydrological modelling exercise, distributed rainfall data are required as the basic input. Smoothing of the rainfall data reduces peak flows due to the averaging of the rainfall-runoff process. Errors in rainfall sampling will reduce confidence in the optimized parameters. Locally intense rainfall might be missed entirely by rain gages or an intense rainfall in the immediate vicinity of a rain gage might lead to an over estimation of rainfall on a watershed. These problems all lead to the conclusion that rainfall rates measured with weather radar could greatly improve hydrological modelling and as a result, flood forecasts. Digital data from weather radar has been available for approximately 20 years but to date has not been widely applied to hydrologic applications. However, recent developments have made radar rainfall data readily available for hydrological applications, especially flood forecasting, in Southern Ontario. The purpose of this chapter is to describe a prototype on-line weather radar data acquisition system developed by the Atmospheric Environment Service (AES), Canada, for the flood forecasting purposes.
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