Abstract
Recent evidence of regional climate change impacts on hydrological cycle directed us to study the floods in a high elevated and rapidly urbanized river basin, the Kabul River basin (KRB), Pakistan, which is susceptible to frequent flooding. Therefore, we analyzed the changes in flood regime at various spatial and temporal scales and their possible causes, which is accomplished by using flood indicators, trend analysis, change point analysis, and hydrological modeling. The results showed that the northern and northwestern parts of the KRB were more exposed to flood hazard than the southern parts under long-term scenario (1961/64-2015). However, after the change points, the flood risk decreased in the northern and increased in the southern regions. This spatial shift increased the vulnerability of population to the flood hazard, because the majority of population resides in the southern region. The extreme precipitation has also increased, especially the maximum one-day rainfall and maximum five-day rainfall throughout the basin. Particularly, the major cause of the decrease in different flood indicators in the northern parts of the KRB is the corresponding decrease in the annual and monsoonal rainfall and corresponding positive mass balance of glaciers in the northern region after the occurrence of change point in flood regime. However, the major cause of the increase in flood hazard on the southern part of the KRB is associated with maximum five-day rainfall. A 68% variability of annual maximum flood for the Kabul River at Nowshera and an 84% variability of annual maximum flood for Bara River at Jhansi post are explained by maximum five-day rainfall. In addition, a considerable decrease in forests (–5.21%) and increase in the urban area (88.26%) from 1992–2015 also amplifies the risk of higher flood peaks. The results of hydrological modeling suggest that the six-hourly flood peak increased by 6.85% (1992–2010) and 4.81% (2010–2015) for the extreme flood of 2010 for the Kabul River at Nowshera. The flood peak per decade will increase by 8.6%, as compared to the flood peak under the land use scenario of 2010. Therefore, consideration of proper land use planning is crucial for sustainable flood management in the KRB.
Highlights
The global mean surface temperature is predicted to increase by 0.3–0.7 ◦ C for the near future 2016–2035 relative to 1986–2005 [1]
The present study has focused on the Kabul River basin (KRB), Pakistan, because the whole KRB was flooded during the 2010 flood, and ten districts within the KRB were severely affected [20]
The overall analysis after the occurrence of the change point revealed the interesting fact that all the flood indicators decreased insignificantly on the northern part of the KRB, while the southern part of the KRB depicted an increase in all the flood indicators except in the magnitude of the peak over threshold (POT)-based flood series (POT3M) for the Bara River at Jhansi Post
Summary
The global mean surface temperature is predicted to increase by 0.3–0.7 ◦ C for the near future 2016–2035 relative to 1986–2005 [1]. The warming climate can intensify the hydrological cycle at global as well as regional scales [2,3]. Observed variations in extreme weather and climate events since the 1950s suggest increased risks of floods and droughts because of more extreme precipitation, lengthening dry span, high peak flows, and increased intensity of most extreme tropical cyclones [1,4,5,6]. Climatic extremes are the key drivers of meteorological and hydrological hazards, such as floods and droughts [7]. The changes in climatic extremes, especially in temperature and precipitation, may alter the occurrence, duration, and intensity of floods and droughts [6,8,9]. Climate models suggest that extreme precipitation events will become more common [9]. Losses due to catastrophic natural hazards have aroused public awareness of extreme events [10,11]
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