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Water-related risks
Published in François Guerquin, Ahmed Tarek, Mi Hua, Tetsuya Ikeda, Vedat Özbilen, Marlies Schuttelaar, World Water actions, 2010
François Guerquin, Ahmed Tarek, Mi Hua, Tetsuya Ikeda, Vedat Özbilen, Marlies Schuttelaar
Although few actions relating to climate change appear to have been implemented, some of those under way are significant. One of these is in the Himalayan region, where climate change will lead to the melting of glaciers and glacial lakes, resulting in glacial lake outburst floods (GLOF). After an assessment study, the United Nations Environment Programme created an inventory of glacial lakes and developed the GLOF Monitoring and Early Warning System (action 857) in the Himalayan region. A pilot mitigation project is also under way, the Tsho Rolpa GLOF Risk Reduction Project (action 827) in Nepal. A global initiative is promoting information sharing and dialogue between the water and climate communities (action 71) and is now promoting regional and national dialogues on water and climate as well (actions 1111, 1213, 1214, 1215, 1216, 1217, 1218, 1219, 1584, 1585, 1587, 1589, 1591, 1592, 1593, 1595, and 1596). And efforts are being made to strengthen scientific and technical capacity in the project Assessment of Impacts of and Adaptation to Climate Change in Multiple Regions and Sectors (action 2137) and the Climate Affairs Capacity Building Programme (action 2012). These actions are intended to help reduce vulnerability to the intensified effects of hazards expected to result from climate change and to enhance people’s ability to cope with and adapt to climate change.
Main aspects in dam safety assessment and principles and concepts applied
Published in Ljiljana Spasic-Gril, Dams Safety and Society, 2023
Glacial Lake Outburst Floods (GLOFs) have been defined by the United Nations Platform for Space-based Information for Disaster Management and Emergency Response (UN-SPIDER) as “the sudden release of a significant amount of water retained in a glacial lake”. This hazard is specific to any proposed dam location that is within a glacial catchment containing a glacial lake.
Glaciers and Glacial Lake Outburst Flood Risk Modeling For Flood Management
Published in Ajai Singh, Wastewater Reuse and Watershed Management, 2019
Nity Tirkey, P. K. Parhi, A. K. Lohani
Worldwide receding of mountain glaciers is one of the most reliable evidence of the changing global climate. Globally, the impacts of climate change include rising temperatures, shifts in rainfall pattern, melting of glaciers and sea ice, the risk of glacial lake outburst floods (GLOFs), sea level rise and increased intensity and frequency of extreme weather events (Ganguly et al., 2010). The climatic change/variability in recent decades has made considerable impacts on the glacier lifecycle in the Himalayan region. The Himalayas are geologically young and fragile and are vulnerable to even insignificant changes in the climatic system (Lama et al., 2009). Glaciers and glacial lakes play an important role in maintaining ecosystem stability as they act as buffers and regulate runoff water supply to plains during both dry and wet seasons. The glaciers and glacial lakes are generally located in remote and inaccessible areas. The inventories are only possible using time series remote sensing data and geographic information system (GIS) technology. The mountain ecosystems are fragile and highly susceptible to global climate changes. GLOF occurs when a dam containing a glacial lake fails. This is mainly due to the glaciers retreat. As glaciers retreat, glacial lakes are formed behind moraine or ice dams or inside the glaciers. A sudden breach in its walls may lead to a discharge of huge volumes of water and debris. Several of such lakes have been burst in the recent past resulting in a loss of human lives and destruction and damages of infrastructure in the valleys below. Glacier-outburst floods cannot be predicted, and therefore, continuous monitoring and mapping, both spatial and temporal, as opposed to a limited frequency point measurement can reduce the devastating impact of such hazards. Sometimes it is not easy to avoid natural phenomena causing disasters such as GLOFs, but a prior knowledge about their nature and possible extent can develop a capacity of disaster management authorities to respond and recover from emergency and disaster events. Similarly, hazard maps cannot stop a disastrous event from happening, but an effective use of hazard maps can prevent an extreme event from becoming a disaster. Himachal Pradesh is a mountain state in Indian Himalayas covering an area of 55,673 km2. Himachal Pradesh has four major river basins namely Satluj, Beas, Chenab, and Ravi. Satluj basin alone covers 45% of the total geographical area of the state (923,645 km2). The basin is very active and experiences regular floods causing widespread damage in the down valleys.
Mitigating cavitation on high head orifice spillways
Published in ISH Journal of Hydraulic Engineering, 2021
R.R. Bhate, M.R. Bhajantri, V.V. Bhosekar
The studies were conducted for orifice spillway on 101.5 m high and 213.7 m long concrete gravity diversion dam. Seven orifice openings of size 6.1 m wide x 12.6 m high with crest level at El. 990 m. have been provided to pass a design flood (PMF) of 11,811 m3/s along with Glacial Lake Outburst Flood (GLOF) of 1,170 m3/s. The discharge intensity for design discharge is 300 m3/s/m. The velocity is about 30 m/s on the spillway surface. The FRL has been fixed at El. 1045 m. Radial gates have been provided at the downstream face of breastwall for controlling the outflow discharge. The equation of the downstream profile is X2 = 195 y. Figure 1 shows cross-section of the spillway. Experiments were conducted on a 1:40 scale 2D sectional model in a flume for assessing the pressure profiles. The accepted equations for similitude, based on Froudian criteria were used to express mathematical relationship between the dimensions and hydraulic parameters of the model and the prototype. Photo 1 shows the view of the model.
Earth observation and sustainable development goals
Published in Geomatics, Natural Hazards and Risk, 2020
Raj (2010) has used satellite remote sensing data for a hazard assessment of glacial lakes in the Zanskar basin, Jammu and Kashmir, India. Using multi-temporal satellite data, Bhatt et al. (2017) performed an assessment of one of the worst floods in the past 60 years in the state of Jammu and Kashmir in North India, which occurred in the first week of September 2014. The flood disaster footprints were extracted by using Indian Remote Sensing (IRS) satellite RISAT-1 and Canadian satellite Radarsat-2. The spatial and temporal dynamics of flood inundation and an evaluation of impacts were undertaken. Aggarwal et al. (2016) used multispectral satellite images of Landsat and IRS satellites and have mapped glacial lake outburst flood (GLOF) and evaluated risk assessment in the Teesta river basin in the Sikkim state of India. They have utilized normalized difference snow index and slope map of the area for risk evaluation from the GLOF in 140 lakes in Sikkim area.
Sediment removal from run-of-the-river hydropower reservoirs by hydraulic flushing
Published in International Journal of River Basin Management, 2019
Punatsangchhu hydroelectric project is proposed on Punatsangchhu river in Wangdue District of Bhutan. The dam site is located about 7 km downstream of Wangdi Bridge and 80 km from the Capital Thimpu (Figure 1(a)). Wangdi Rapid gauging site is about 500 m downstream of Wangdi Bridge. The river Punatsangchhu, which originates from the Himalayan ranges in North–West Bhutan at an elevation of about 7000 m is a tributary of the Brahmaputra river. The rivers Phochhu and Mochhu join at Punakha to form the river Punatsangchhu. The total catchment area of Punatsangchhu river upto the project site is 6390 km2. 3115 km2 of the catchment is snowfed and the remaining 3275 km2 is rainfed. Monsoon and high discharge season is from June to September. The average monthly flow during the above period is about 800 m3/s. The river flow is to be passed through the diversion tunnels during the construction period. The diversion tunnels are designed to pass the flood of 967 m3/s which is the 25-year return period flood computed using non-monsoon peaks at Wangdi G & D site for the period 1991–2004. The project is designed for the Probable Maximum Flood (PMF) of 11,500 m3/s and the Glacial Lake Outburst Flood (GLOF) of 4300 m3/s.