Abstract
Abstract. Although many studies have explored the effect of teleconnection patterns on floods, few investigations have focused on the assessment of expected flood damage under such large-scale atmospheric signals. This study aims to determine the effect of the most emblematic teleconnection, El Niño, on the expected damage due to floods with short return periods in the Kan River basin, Iran. To determine the flood damage costs, the median of annual precipitation changes (ΔP) during El Niño conditions was used, although ΔP cannot necessarily be transferred to extreme values. Then the flooded area was determined under the increased rainfall due to El Niño for 5-, 10-, and 50-year return periods. The results showed that El Niño has increased the annual precipitation by 12.2 %. Flood damage assessment using damage–depth curves showed that the relative increase in expected damage during El Niño conditions is much higher for short return period floods than that for long return period floods. In general, a 12.2 % increase in the annual precipitation would increase the damage by 1671 % and 176 %, respectively, for the return periods of 5 and 10 years. However, in the case of a 50-year flood, this increased percentile decreased to 52 %. These results indicate the importance of small flood events in flood management planning during El Niño.
Highlights
In recent decades, the frequency of flood events and the resultant damage have been increasing dramatically in Iran
Analyses of the precipitation in the synoptic stations and southern oscillation index (SOI) using the average mutual information (AMI) method showed that there is no lag time between rainfall and SOI time series
Using Eq (4), for the 6 years with El Niño conditions, the precipitation change (PC) values range from −34 % to 45 %, while the latter is related to the year 1983 in which the high value of 334 mm of rainfall was recorded
Summary
The frequency of flood events and the resultant damage have been increasing dramatically in Iran. The magnitude and frequency of flood events in each region depends on several factors: (i) physiographical features of the catchment such as shape, slope, and river network density, (ii) hydrological features such as precipitation, storage and initial losses, evapotranspiration, and permeability, (iii) human activities, (iv) large-scale atmospheric signals, and (v) climate change (Noori et al, 2011; Ward et al, 2014a, b; AlizadehChoobari and Najafi, 2017; Hooshyaripor and Yazdi, 2017; Hooshyaripor et al, 2017; Saghafian et al, 2017; Hao et al, 2018) These factors affect the frequency and intensity of floods and the amount of damage costs.
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