Causes of floods in Afghanistan

Flooding, exacerbated by the combined effects of conflict and climate change, will continue to threaten Afghanistan in the future.

Afghanistan is likely to be subject to increased flooding due to more snowfall in winter and warmer summers. In recent years snow basins contained a lot more snow than usual (USGS, 2003), and in 2006 this combined with rising temperatures and heavy spring rains resulted in a great deal of meltwater and consequent flooding. The Afghan climate is typical of an arid or semiarid steppe, with a wet-cold season in winter and early spring, and in summer a dry season often marred by droughts. Precipitation fluctuates greatly over the year, and is characterized by sudden rainstorms that transform the episodically flowing rivers and streams from puddles into torrents. Invading armies have at times been trapped in these flooding waters, and nomadic and semi-nomadic Afghans have sometimes succumbed to the sudden flooding of their camps (Blood, 2001).

The effects of global warming on floods are not fully understood and no studies have researched this specifically for Afghanistan, although research conducted in other parts of the world has found that global warming can contribute to flood events. In Afghanistan and surrounding countries, the area of glaciation in mountains has decreased by nearly 40% over the past

40 years (Zonn, 2002). Glavgidromet mathematical models enabled evaluation of the effect of climate changes on river basins and an evaluation of the runoff (Chub, 2002). The results showed that a marked reduction of flow in may be expected during the growing season, and that increased intensity of rainfall in combination with higher temperatures will lead to a greater number of floods and mudflows (Chub, 2002).

The following information was deduced from a survey of interpolated climate data from the NOAA's National Climatic Data Centre: In Afghanistan, the temperatures have been steadily increasing over the past decades. Not only the summers have become hotter, but also the winters. The daily temperature differences have also increased. The precipitation has also increased over the past decades, yet it must be noted that this increase is solely in winter and spring. The combination of increased snow precipitation in winter and higher temperatures might be the cause of more intense spring floods in the valleys of Afghanistan.

War can magnify the proportions of disasters for populations, but natural disasters can also be partly caused by the impact of conflict. As a result of conflict, an estimated 30% of Afghan farmlands and pastures have been lost by either abandonment or degradation (Glantz, 2002). Agriculture plays an important role in mitigating the effects of floods; the small irrigation channels divert a lot of runoff, and the vegetation on the fields absorbs and slows the runoff. If these fields are abandoned they erode quickly, which increases the chance of flooding. In time of war, dams have often been a primary target of military strategists. At this moment the Helmand River's Kajaki hydroelectric dam, which supplies almost all the energy to southern Afghanistan, is a primary target for Taliban insurgents (Edelman, 2007). The Kajaki dam's strategic importance is its energy production, and a dam break flood (1.8 km3) resulting from its destruction would be immense. Without the mitigating effect of the dam, the Helmand River's agricultural lands would suffer each year from uncontrolled flooding.

Wars and conflicts have prevented mitigation infrastructure and planning from being undertaken. No major dam construction projects have been undertaken in Afghanistan for the past 30 years. The political situation has led to the neglect in maintenance of many dams, and the regular occurrence of dam bursts in Afghanistan emphasizes the necessity for maintenance.

Acknowledgments This contribution is part of a Afghanistan flood mapping research project, supported by the NATO C3 Agency. Furthermore the authors would like to thank Robert Brakenridge and Elaine Anderson of the DFO for sharing past inundation extents with us.

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