Sunando Bandyopadhyay

Bio: Sunando Bandyopadhyay is an academic researcher from University of Calcutta. The author has contributed to research in topics: BENGAL & Climate change. The author has an hindex of 7, co-authored 23 publications receiving 215 citations. Previous affiliations of Sunando Bandyopadhyay include Vidyasagar University.

Glacial lake outburst flood at Kedarnath, Indian Himalaya: a study using digital elevation models and satellite images

Abstract: Kedarnath (3,533 m, 30°44′05″N, 79°04′02″E) is situated within a kilometre of the termini of the Chorabari and Companion glaciers in the Indian Himalaya. An outburst flood from a lake (3,845 m) formed by right lateral moraine of the former caused severe damage to the village on 17 June 2013. We determined various physical parameters of the lake from three digital elevation datasets (CartoDEM, SRTM and ASTER) and selected the SRTM-derived data as they appeared to portray the region more accurately. The obtained parameters were used in predictive equations suggested by different authors to estimate peak discharge of the flood. We also compared high-resolution images of 10 December 1965 (Corona), June 2011 (Bing) and 25 June 2013 (Catrosat-1 Pan + LISS-4mx) to assess the damage caused to the village besides other geomorphic changes. The results showed that at least 149 mm of rainfall in its 291-ha catchment was required to fill up the lake, without considering the presence of antecedent water and loss from seepage and evaporation. At the point of breaching, the lake released 0.43 × 106 m3 of water with a peak discharge of 1,352 cumecs. The north-western section of Kedarnath village was on the direct path of the debris flow triggered by the flood and was almost completely destroyed. The southern and south-eastern sections were least affected. Out of 37,299 m2 of pre-event roof area of Kedarnath (259 structures), 44.2 % were obliterated and 26.7 % were partly damaged, representing 138 and 56 structures, respectively. Only one-quarter of the structures of the village emerged intact or slightly affected after the event.

River Systems and Water Resources of West Bengal: A Review

Abstract: West Bengal (88,752 km 2 ) is the only Indian state that extends from the Himalaya to the Bay of Bengal. It can be divided into nine physiographic provinces of which the Himalayas, the western plateaus, the northern and western alluvial fans and the Ganga delta are the most important. The development of the river system of the state was largely governed by tectonic evolution of the eastern Himalaya and western edges of the Bengal basin. The characteristics of the rivers as well as a number of aspects of water resources of the state can be linked to its physiographic regions. The principal issues associated with water in West Bengal include river degeneration, channel shifting, flood, urban waterlogging, drought, pollution, groundwater depletion and inland navigation. The management of water is practised by river impoundment projects in various scales and by drainage schemes. It is estimated that the western and eastern parts of the state are the most water stressed regions due to climatic and human factors respectively. The solutions for many of the water-related problems of West Bengal, progressive or cyclic, can be achieved by putting emphasis on participatory management besides organisational intervention.

Trend of sea level change in the Hugli estuary, India

Abstract: Trends of annual sea level records of four tidal observatories of the Hugli estuary—Sagar, Gangra, Haldia, and Diamond Harbour—are analysed from the records of Permanent Service for Mean Sea Level (PSMSL). The rates of sea level changes for the stations are found to be –3.82, +0.89, +2.43 and +4.85 mm yr respectively, connoting a significant positive relation between landward distances of the stations and the rates of sea level rise. This seems to be mainly controlled by disequilibrium in the morphological state of the landward-narrowing estuary with some contribution from sediment autocompaction. Sea level trends of the Hugli have no apparent relation with erosion and accretion of its tidal islands.

River Systems and Water Resources of West Bengal: A Review

Abstract: West Bengal (88,752 km 2 ) is the only Indian state that extends from the Himalaya to the Bay of Bengal. It can be divided into nine physiographic provinces of which the Himalayas, the western plateaus, the northern and western alluvial fans and the Ganga delta are the most important. The development of the river system of the state was largely governed by tectonic evolution of the eastern Himalaya and western edges of the Bengal basin. The characteristics of the rivers as well as a number of aspects of water resources of the state can be linked to its physiographic regions. The principal issues associated with water in West Bengal include river degeneration, channel shifting, flood, urban waterlogging, drought, pollution, groundwater depletion and inland navigation. The management of water is practised by river impoundment projects in various scales and by drainage schemes. It is estimated that the western and eastern parts of the state are the most water stressed regions due to climatic and human factors respectively. The solutions for many of the water-related problems of West Bengal, progressive or cyclic, can be achieved by putting emphasis on participatory management besides organisational intervention.

Natural Environmental Hazards and Their Management: A Case Study of Sagar Island, India

Abstract: The reclamation of Sagar island from the Sundarban mangrove wetlands of the western Ganga Brahmaputra delta was initiated in 1811. At present the island is almost wholly settled. The major natural environmental hazards (NEH) that affect the island are tropical cyclones, coastal erosion, tidal ingression and dunal encroachment. Human adjustments to these problems include acceptance, technological control, relocation, regulation and emergency measures. Seven different agencies manage the existing NEH-prevention projects of the island, often with little coordination. Important schemes managed by these agencies include coastal and interior embankments, mangrove plantations, storm refuges, resettlement projects and vegetation wind-breaks. Their efficiency ranges from excellent to very poor. Since a large outlay is inconceivable, the island’s hazard prevention projects should mobilise existing resources in a more rational and coordinated manner. The long-term solution to the problems, however, lies in an accelerated socio-economic development of the region.

Lake outburst and debris flow disaster at Kedarnath, June 2013: hydrometeorological triggering and topographic predisposition

Abstract: Heavy rainfall in June 2013 triggered flash flooding and landslides throughout the Indian Himalayan state of Uttarakhand, killing more than 6000 people. The vast majority of fatalities and destruction resulted directly from a lake outburst and debris flow disaster originating from above the village of Kedarnath on June 16 and 17. Here, we provide a systematic analysis of the contributing factors leading to the Kedarnath disaster, both in terms of hydrometeorological triggering and topographic predisposition. Topographic characteristics of the lake watershed above Kedarnath are compared with other glacial lakes across the north-western Himalayan states of Uttarakhand and Himachal Pradesh, and implications for glacier lake outburst hazard assessment in a changing climate are discussed. Our analysis suggests that the early onset of heavy monsoon rainfall (390 mm, June 10–17) immediately following a 4-week period of unusually rapid snow cover depletion and elevated streamflow was the crucial hydrometeorological factor, resulting in slope saturation and significant run-off into the small seasonal glacial lake. Between mid-May and mid-June 2013, snow-covered area above Kedarnath decreased by around 50 %. The unusual situation of the lake being dammed in a steep, unstable paraglacial environment but fed entirely from snowmelt and rainfall within a fluvial dominated watershed is important in the context of this disaster. A simple scheme enabling large-scale recognition of such an unfavourable topographic setting is introduced. In view of projected 21st century changes in monsoon timing and heavy precipitation in South Asia, more emphasis should be given to potential hydrometeorological triggering of lake outburst and debris flow disasters in the Himalaya.

The Indian Sundarban Mangrove Forests: History, Utilization, Conservation Strategies and Local Perception

Abstract: Covering approximately 10,000 km2 the Sundarbans in the Northern Bay of Bengal is the largest contiguous mangrove forest on earth. Mangroves forests are highly productive and diverse ecosystems, providing a wide range of direct ecosystem services for resident populations. In addition, mangroves function as a buffer against frequently occurring cyclones; helping to protect local settlements including the two most populous cities of the world, Kolkata and Dhaka, against their worst effects. While large tracts of the Indian Sundarbans were cleared, drained and reclaimed for cultivation during the British colonial era, the remaining parts have been under various protection regimes since the 1970s, primarily to protect the remaining population of Bengal tigers (Panthera tigris ssp. tigris). In view of the importance of such forests, now severely threatened worldwide, we trace the areal change that the Indian Sundarbans have undergone over the last two-and-a-half centuries. We apply a multi-temporal and multi-scale approach based on historical maps and remote sensing data to detect changes in mangrove cover. While the mangroves’ areal extent has not changed much in the recent past, forest health and structure have. These changes result from direct human interference, upstream development, extreme weather events and the slow onset of climate change effects. Moreover, we consider the role of different management strategies affecting mangrove conservation and their intersection with local livelihoods.

Climate change impacts on Indian Sunderbans: a time series analysis (1924–2008)

Abstract: Climate change induced sea level rise (SLR) added with anthropogenically altered environment leads to rapid land dynamics in terms of erosion and accretion; and alteration in species diversity and productivity, more pronouncedly in sensitive ecosystems such as river deltas. Here, we tried to analyze the historical records to understand the SLR with respect to hydrological conditions, sedimentation and morphological processes. We analyzed the land transformation of few islands in Indian Sunderbans using maps and satellite images in increasing order of temporal frequency between 1924 and 2008, which revealed that both the erosion and accretion processes go hand in hand. Increase of downstream salinity due obstruction in upstream has led to decrease in transparency of water causing decrease in phytoplankton and fish, density and diversity in the central sector of Indian Sunderbans. Analysis of the above ground biomass of three dominant mangrove species (Sonneratia apetala, Avicennia alba and Excoecaria agallocha) revealed better growth in the western sector compared to the central sector. The study reveals the cumulative effect of climate change and anthropogenic disturbance on the diversity and productivity in World’s largest ecosystem; and advocates mangrove plantation and effective management of freshwater resources for conservation of the most vulnerable and sensitive ecosystem.