ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Research and Application of a Flood Risk Early Warning Method for Data-Scarce Small and Medium-Sized Rivers Based on Same Frequency Method Correction
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Abstract:
For basins characterized by long-sequence precipitation data but complex runoff generation mechanisms and a lack of flow process data, this study employed the rational formula method to estimate the early warning time window for flood risk in small and medium-sized rivers. The Pearson Type III frequency curve, commonly used in hydrological frequency analysis, was applied to construct flood-triggering critical areal rainfall thresholds. These thresholds were calibrated using nearly 10 years of flood peak discharge data from small and medium-sized rivers in the middle reaches of the Yellow River. The methodology was then applied and tested for six flood events occurring in 2021 within the basin above the Dongwan hydrological station of Yi River, which lacks measured hydrological characteristics. The results demonstrate that using the rational formula to determine the warning time window is straightforward and practical. Calibrating the critical thresholds based on the same frequency method using historical flood data significantly improved the hit rate of risk warnings to 71.8%, while reducing the miss rate and false alarm rate to 20% and 29.4%, respectively. This forecast accuracy is comparable to the current flood forecasting standards in northern China. The method also performed well when applied in basins lacking hydrological characteristic values. Overall, the flood risk early warning method for small and medium-sized rivers, calibrated using the same frequency approach, effectively addresses the challenge of obtaining long-sequence hydrological data across different regions. It also fully leverages the advantage of meteorological departments possessing long-term precipitation records. This method can be further extended to small and medium-sized watersheds without hydrological stations, providing valuable technical reference for meteorological flood disaster warning efforts in similar basins. Future work could involve classifying small and medium-sized basins based on underlying surface conditions or establishing distinct calibration models for basins dominated by saturation-excess runoff by categorizing soil moisture levels, thereby further enhancing risk warning precision.
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