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چکیده
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This paper presents the quantitative flood frequency analysis at the Kavalan hydrometric station on the Simineh River, northwestern Iran, using daily streamflow data from 2000 to 2015. Correspondingly, its 3,240 km2 catchment falls in semi-arid conditions, with mean annual precipitation of 578 mm and mean annual temperature of 11.5 °C. The results indicated that four probability distributions fitted the annual maximum series best when the Log-Pearson Type III distribution yielded the best fit and gave an A2 of 0.384 and a p-value of 0.892. The 100-year flood was estimated at 108.5 m3/s, with a 95% CI of 77.1–152.6 m3/s. There is also a strong positive correlation between annual maximum flow and annual precipitation, with the value of r = 0.89 (p < 0.001). The flow that represented the minimum in a period of 7 days with a return period of 10 years was 0.009 m3/s. Mann–Kendall analysis showed the low flows were significantly trending to decrease with a statistic value of − 0.321 and a p-value of 0.038. According to the flow duration curve, the median flow is 1.54 m3/s, while the Q95 is 0.031 m3/s. A dimensional analysis approach was used for developing a flood prediction equation calibrated with data from 50 gauged watersheds with R2 = 0.87. The derived equation developed maximum sensitivity to drainage area, coefficient = 1.381, followed by precipitation, 0.65; slope, 0.30; and channel length, 0.15. An extremely good correlation was found between peak flow and the total flood volume, with r = 0.94 and p < 0.001; thus, this reflects the implications for flood risk management strategies. The study's flood frequency analysis and prediction models provide critical insights for designing resilient floodplain infrastructure in semi-arid regions, enabling engineers to account for the unique hydrological variability and extreme event probabilities characteristic of these environments.
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