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AbstractStudy region The Thames catchment in southern England, UK
. Study focus Modelling with 124 years of rainfall, potential evaporation (PE), temperature and naturalised flow data. Daily rainfall-runoff flow simulation using current and three historic land cover scenarios to determine the stationarity of catchment response examined through three time-frames of analysis – annual, seasonal and flow extremes. The criterion of response stationarity is often assumed in climate change impact studies. New hydrological insights The generally close correspondence between observed and simulated flows using the same model parameter values for the whole period is indicative of the temporal stability of hydrological processes and catchment response, and the quality of the hydrometric data. Changes that have occurred are a decrease in flood peak response times, typically two to three days pre and post the early 1940s, from change in agricultural practices and channel conveyance, and an increase of about 15% in summer flow from increase in urban land cover between the first decade of the 20th and 21st centuries. The water balance was found to be sensitive to the PE data used, with care needed to avoid discontinuity between two parts of the data record using different methods for calculation. Long-term mean annual rainfall shows little change but contrasting patterns of variation in seasonal rainfall demonstrate a variable climate for which simulated flow is similar to observed flow
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Pakistan is vulnerable to hazards of multiple nature and their frequent recurrence in recent years has significantly hampered our goal of sustained economic growth by causing massive losses to lives and property
. Floods have been more frequent and damaging with substantial negative effect on our economy.
Although disaster management system is still in its nascent stage, yet we have made progress in mainstreaming disaster risk reduction in development processes, which will lead to greater resilience against potential disasters. Formulation of National Disaster Risk Reduction Policy and implementation of National Disaster Management Plan which includes strengthening of flood protection and early warning systems, is likely to significantly reduce flood risk.
Keeping in view the changing climatic conditions and frequent recurrence of unpredictable and extreme weather events during the monsoon season, it is critical that relevant stakeholders, particularly at the district level, are fully prepared to handle potential disaster situation. The monsoon contingency planning process has accordingly been executed through a bottom up approach whereby the district level authorities of flood prone districts, through the provincial governments, were assisted in undertaking their hazards and risk analysis, identify their needs, plan effective deployment of available resources and prepare their Contingency Plans for likely scenarios keeping in view the available long term seasonal weather forecasts. On the basis of provincial plans, NDMA has finalized the National Plan in consultation with all stakeholders, which will provide national response back up against situations which appear to be getting beyond Provincial/ Regional capacity
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Flash floods are among the most destructive natural disasters in the Hindu Kush Himalayan region
. They are sudden events that allow very little time to react, and they often occur in remote and isolated mountain catchments where few, if any, institutions exist that are equipped to deal with disaster mitigation. Flash flood mitigation is generally addressed by community-based organizations, local non-governmental organizations, or district and local-level staff in government organizations. But these groups often lack adequate understanding of the processes causing flash floods and knowledge of flash flood risk management measures. To support the training of planners and practitioners in managing flash flood risk, in 2008 ICIMOD published two modules of a resource manual which focused on community-based management and non-structural measures. This publication, the third module of the series, deals with structural measures. It presents bioengineering techniques, physical measures for slope stabilization and erosion control, and physical measures for river training. The measures described are simple yet effective; they can be implemented using local and low-cost materials with a minimum of external materials and technical support and a low environmental impact. The publication also presents the concept of integrated flood management as a component of integrated water resource management. It emphasizes that structural measures are most effective and sustainable when implemented together with appropriate non-structural measures. The manual is aimed at junior to mid-level professionals with a civil engineering background working on flash flood risk management at the district level
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This final report on Glacial Melt and Downstream Impacts on Indus Basin-Dependent Water Resources and Energy summarizes trends in increasing variability in precipitation, seasonal temperature regimes, glacial melt, and water supplies, and the risk scenarios for climate change and its possible impacts on millions of people in downstream areas
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It aims to stimulate regionally coordinated interdisciplinary research to provide critical information for policy and decision makers to plan and design water resources development programs in an integrated manner.
This report is produced by consultants for a regional technical assistance on Promoting Climate Change Impact and Adaptation in Asia and the Pacific (RETA 6420)
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This condensed report on Glacial Melt and Downstream Impacts on Indus Basin-Dependent Water Resources and Energy summarizes trends in increasing variability in precipitation, seasonal temperature regimes, glacial melt, and water supplies, and the risk scenarios for climate change and its possible impacts on millions of people in downstream areas
.
It aims to stimulate regionally coordinated interdisciplinary research to provide critical information for policy and decision makers to plan and design water resources development programs in an integrated manner.
This report is produced by consultants for a regional technical assistance on Promoting Climate Change Impact and Adaptation in Asia and the Pacific (RETA 6420)
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Glacier thinning and retreat in the Himalayas has resulted in the formation of new glacial lakes and the enlargement of existing lakes due to the accumulation of meltwater behind loosely consolidated end moraine dams
. Such lakes are inherently unstable and can be subject to catastrophic drainage (glacial lake outburst flood or GLOF), which is a potential source of danger to people and property in the valleys below them. Equally, glacial lakes are an important potential natural resource for water supply, which has yet to be effectively investigated. This publication describes the results of a systematic and comprehensive study of the status of glacial lakes and glacial lake outburst flood (GLOF) risk in Nepal, including the vulnerability of downstream people and property and field studies of three of the most critical lakes. The assessment is intended to provide information for use in GLOF risk management in Nepal, as well as describing a detailed stepwise approach and methodology that can be applied throughout the Hindu Kush-Himalayan region. Region-wide cooperation is needed to develop a more coordinated approach and lay the foundations for a glacial lake outburst risk reduction policy
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Catastrophic partial drainage of Pangong Tso, one of the largest lakes in Tibet, is supported by the geomorphology of the Tangtse Valley, Ladakh, northern India and cosmogenic 10Be nuclide ages of roche moutonnées, strath terraces, and a flood deposit downstream from the former spillway
. The former spillway for Pangong Tso is ~ 20-m-high and likely allowed ~ 18 km3 of water to drain catastrophically down the Tangtse Valley over a period of about 2 days sometime during the latest Pleistocene to early Holocene. The largest flood deposit, composed of imbricated granitic boulders up to 4.5 m in length, is present ~ 33 km downvalley of the spillway. These boulders have a cosmogenic 10Be exposure age of 11.1 ± 1.0 ka, the age of the outburst flood. The minimum calculated discharge was ~ 110,000 m3 s- 1. One set of strath terraces, upvalley of the flood deposit along the flood's drainage path, shows that the rate of fluvial incision 0.3 ± 0.1 mm y- 1 during 122-10.5 ka increased to 1.5 ± 0.5 mm y- 1 during 10.5 ka to the present. The temporal overlap of this increase in the rate of fluvial incision with the main flood deposit suggests that the flood was important in defining the incision along the Tangste valley. A second set of strath terraces shows little change in incision, from ~ 0.6-0.9 to ~ 0.9-1.4 mm y- 1, sometime between 18 and 27 ka. Roche moutonnées, upvalley from strath terraces, yield a cosmogenic 10Be age of 35.8 ± 3.0 ka, defining the time when glaciers last occupied the Tangtse valley. However, the lack of glacial sediment along the Tangste valley suggests that the flood eroded glacial depositional landforms and sediments resulting in high sediment loads in the floodwater, which in turn increased fluvial incision to form strath terraces. Much of the eroded glacial sediment was subsequently redeposited as the main flood deposit. The catastrophic drainage of Pangong Tso may be the result of breaching of the Pangong-Tangste spillway during very high lake levels in a period of intensified monsoon (10.7-9.6 ka) and/or possibly the consequence of seismic activity along the Karakoram Fault that is associated with the initial formation of Pangong Tso
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