Author(s): Amir Norouzi; Ahmadreza Ghavasieh; Jalal Attari
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Keywords: Flood forecasting; Flood warning system; Reliability assessment
Abstract: One of the most effective non-structural measures of flood damage mitigation is flood warning system. Planning and design of a flood warning system requires reliability assessment to ensure its performance. The reliability of warning can be quantified in terms of the Relative Operation Characteristics (ROC - a relation between the probability of detection and the probability of false warning for a floodplain zone) and its transformation to numbers, the Performance Trade-off Characteristics (PTC - a relation between the expected number of detections and the expected number of false warnings per year for a zone). In this paper, flood warning system of Madarsou basin, located in North West of Iran, has been studied. Madarsou basin is one of the most vulnerable areas to flooding in Iran and its flood warning system has been installed in 2005. For reliability assessment of the flood warning system, the method developed by R. Krzysztofowicz has been applied. In this regard, one control cross section, three vulnerable areas, a periodic-time of 30 minutes for forecasting the flood crest height, two forecaster triggering stages (i. e. 2. 5m and 2. 7m) and three warning thresholds (i. e. 3m, 3. 5m and 4m) were considered. Due to lack of flood data in Madarsou basin, the flood crest heights were simulated by rainfall-runoff modelling and flood routing which was further compared with forecasted values. For prediction of rainfalls the intensity-duration-frequency curves were used. Uncertainties due to monitoring and forecasting procedure were quantified by probability analysis of False and True warnings and results were presented as ROC and PTC curves. For periodic forecasting time, the Potential Lead-Time (PLT) was computed for the representative vulnerable areas. A trade-off between potential lead time and system reliability was discussed and the associated risk was calculated. This can be useful for decision maker (s) to select the optimum operation point.
Year: 2007