An Assessment of the Number and Combination of Rainfall Gauges in Flood Warning System

The damages of floods can be reduced by evacuation if there is an on-time warning. The Fahlian Basin, in the south of Iran, has steep slopes and flash floods, so the location of rainfall-gauges and their distance from basin’s outlet might have a considerable effect on the estimation of the flood-warning lead time. Thus, the main purpose of this research is to assess the effect of the distribution of rainfall-gauges on flood-warning lead time using WMS/HEC-HMS model in this basin. Therefore, after calibration and validation of the model, double, triple and quadruple combinations of rainfall-gauges were examined. After flood simulation by WMS/HEC-HMS for various return periods, the lead times for the different rainfall combination were determined according tolegalistic river bed. The results showed that the lead time increases by increasing rainfall and decreasing the distance of the rainfall gauges from the basin’s outlet. Finally, a method is proposed to determine the lead time based on multivariate analysis which can be used in flood warning systems.