The Indus Flood of 2010 in Pakistan: a Perspective Analysis Using Remote Sensing Data
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The Indus flood of 2010 in Pakistan: a perspective analysis using remote sensing data Kumar Gaurav, R. Sinha & P. K. Panda Natural Hazards Journal of the International Society for the Prevention and Mitigation of Natural Hazards ISSN 0921-030X Nat Hazards DOI 10.1007/ s11069-011-9869-6 1 23 Your article is protected by copyright and all rights are held exclusively by Springer Science+Business Media B.V.. This e-offprint is for personal use only and shall not be self- archived in electronic repositories. If you wish to self-archive your work, please use the accepted author’s version for posting to your own website or your institution’s repository. You may further deposit the accepted author’s version on a funder’s repository at a funder’s request, provided it is not made publicly available until 12 months after publication. 1 23 Author's personal copy Nat Hazards DOI 10.1007/s11069-011-9869-6 ORIGINAL PAPER The Indus flood of 2010 in Pakistan: a perspective analysis using remote sensing data Kumar Gaurav • R. Sinha • P. K. Panda Received: 26 January 2011 / Accepted: 27 May 2011 Ó Springer Science+Business Media B.V. 2011 Abstract The Indus flood in 2010 was one of the greatest river disasters in recent history, which affected more than 14 million people in Pakistan. Although excessive rainfall between July and September 2010 has been cited as the major causative factor for this disaster, the human interventions in the river system over the years made this disaster a catastrophe. Geomorphic analysis suggests that the Indus River has had a very dynamic regime in the past. However, the river has now been constrained by embankments on both sides, and several barrages have been constructed along the river. As a result, the river has been aggrading rapidly during the last few decades due to its exceptionally high sediment load particularly in reaches upstream of the barrages. This in turn has caused significant increase in cross-valley gradient leading to breaches upstream of the barrages and inun- dation of large areas. Our flow accumulation analysis using SRTM data not only supports this interpretation but also points out that there are several reaches along the Indus River, which are still vulnerable to such breaches and flooding. Even though the Indus flood in 2010 was characterized by exceptionally high discharges, our experience in working on Himalayan rivers and similar recent events in rivers in Nepal and India suggest that such events can occur at relatively low discharges. It is therefore of utmost importance to identify such areas and plan mitigation measures as soon as possible. We emphasize the role of geomorphology in flood analysis and management and urge the river managers to take urgent steps to incorporate the geomorphic understanding of Himalayan rivers in river management plans. Keywords Flood disaster Avulsion Embankment breaching Siltation Himalayan rivers Á Á Á Á K. Gaurav R. Sinha (&) P. K. Panda DepartmentÁ of Civil Engineering,Á Indian Institute of Technology Kanpur, Kanpur, UP 208016, India e-mail: [email protected] 123 Author's personal copy Nat Hazards 1 Introduction Rivers are one of the prime sources of fresh water and have played a major role in the development of human civilization. In recent years, rivers systems have been significantly impacted by human interventions as well as climate change. As a consequence of climatic change, frequency and magnitude of occurrence of disastrous floods in Himalayan rivers have increased in past 2–3 decades (Dutta and Hearadth 2004; Shrestha 2008; Khan et al. 2009). Human interventions through the construction of embankments, barrages, dams, land clearance, and landuse change etc. have also disturbed the river system in terms of sediment load and their run-off, leading to more severe floods (Ali and De Boer 2007; Walling 2008; Sinha 2009). In 2010, heavy and spatially uneven rainfall during the monsoon period resulted in flooding in various parts of Pakistan. Heavy rainfall in the upstream reaches of the Indus River such as the Khyber Pakhtunkhwa region of Pakistan followed by breaches of embankments and canals along the river course devastated most parts of Pakistan. Flood trauma of the Indus started in mid-July of 2010 and continued till early September affecting the lives of more than 14 million people in Pakistan. According to EM-DAT (2010) report, this flooding event of Indus River killed more than 1,961 people and damaged property worth US $ 9,500, 000. The UN estimated that the humanitarian crisis was much larger than the combined effects of the three worst natural disasters in the past decade including the Asian tsunami and the major earthquakes in Kashmir and Haiti. Recent increase in the frequency of floods in this region and large-scale devastation in terms of human lives and loss of property has forced the planners and policy-makers to rethink about the strategies of river management (Sinha 2010). Apart from heavy rainfall, flooding in the Himalayan rivers is strongly influenced by hydrology and sediment transport characteristics. Siltation is a major problem in rivers originating from the mountainous terrain, and the rate of siltation is known to be quite high for the Himalayan rivers (Goswami 1985). Further, flood control strategies on Himalayan rivers are primarily embankment based, which have not only altered the natural flow regime of the rivers but also affected the flood intensity, frequency, and pattern. Apart from the embankments along the river, construc- tion of various barrages across the river, unplanned construction of roads, bunds, and other public utilities in the floodplain has severely affected the natural flow of the river system. As a consequence, rapid siltation of river bed, drainage congestion, and channel discon- nectivity have been reported in these regions (Sinha 2010; Jain and Tandon 2010). In present scenario, the effectiveness of river control strategies through the construction of barrages and embankments along the river, especially for the Himalayan rivers that carry high sediment load is debatable. The Yellow River flood in 1996, the Kosi flood in 2008, and the Indus flood in 2010 are a few glaring examples of the failure of these structures during floods (Sinha 2009; Wang and Plate 2002). Construction of barrages and dams along the river for flow regulation and water diversion has caused serious problem of sediment trapping close to these structures and has also reduced the sediment fluxes in downstream reaches (Walling 2008). One of the major requirements of flood disaster management is the real-time monitoring of maximum flood extent for taking up immediate response, short- and long-term recovery, and future mitigation activities (Wang 2004). The satellite remote sensing data, due their synoptic view and repetitivity coupled with the advent of geographic information system (GIS) techniques, have proved to be extremely effective in flood inundation mapping and monitoring on real-time basis. The availability of a variety of active and passive sensors, operating in the visible, thermal, and microwave 123 Author's personal copy Nat Hazards range of the electromagnetic spectrum has shown a great promise in the delineation of flood boundary and actual estimation of inundation area in a cost-effective manner (Sanyal and Lu 2004; Smith 1997). A couple of recent studies have highlighted the use of remote sensing and GIS techniques in flood risk evaluation of one of the flood-prone rivers, the Kosi in north Bihar plains, eastern India (Bapalu and Sinha 2005; Sinha 2008) wherein an integrated approach using geomorphology, landuse/landcover, topography, and population density on a GIS platform provided a flood risk map for parts of the Kosi river. This paper presents an analysis of the Indus floods that devastated a large part of Pakistan in July–September of 2010. A systematic analysis of hydro-meteorological data coupled with satellite images and digital elevation models has provided a first-hand doc- umentation of the series of events that led to this disaster. We argue that an integrated river basin approach is crucial for flood management of such rivers, and local engineering interventions cannot provide sustainable solutions. 2 The Indus River The Indus River (Fig. 1) is one of the largest rivers in the world in terms of its length (3,180 km), drainage area (960,000 km2), and average annual discharge (7,610 m3/s). Out of the total drainage area, about 506,753 km2 of area lies in the semiarid region of Pakistan and the rest lies in mountains and foothills (Hovius 1998; Khan et al. 2009). The Indus originates at an altitude of 5,486 m from the Mount Kailas range in Tibetan plateau on the northern side of Himalaya. The stretch from its origin to Guddu barrage in Pakistan is called upper Indus, and the stretch downstream of the barrage is called lower Indus (Jain et al. 2007). The upper and lower parts of the Indus experience very diverse rainfall pattern and weather condition. The northern part of the Indus basin is mainly characterized by high mountains and glaciers and cold-arid climatic conditions, whereas the lower part of the Indus basin experiences subtropical to tropical climate as it reaches the Arabian Sea (Ali and De Boer 2003). Barring the mountainous region of the basin, the entire Indus valley falls in the driest part of the subcontinent. Much of the flow of the Indus River originates from either glacier melt or monsoon rainfall. Summer monsoon and western disturbance in late winter and early spring are responsible for high precipitation in the Indus basin. The basin receives the highest rainfall during the monsoon season (July–September), and this often causes major flooding in Pakistan (Inam et al. 2007; Ali and De Boer 2007).