Understanding processes and drivers of torrential disasters in the Indian Himalayas
The Indian Himalayan Region (IHR) has repeatedly been affected by extreme torrential floods over the past few years with substantial economic losses and excessive death tolls not far from 10’000 persons. Among the most recent disasters in the area are the floods of Jammu and Kashmir in March 2015, the June 2013 disaster at Kedarnath (Uttarakhand) with > 6000 fatalities or the Ladakh floods in August 2010. All of the events have occurred in areas where documentary evidence and/or systematic records (gauge data) are poor or inexistent. This lack of data (or at best short series) render the analysis of return periods of specific magnitudes difficult (if not impossible), and thus also hamper attempts to improve resilience capacity of populations in often densely inhabited valleys against these extremes as well as proper hazard or risk assessments. In view of ever the increasing demographic pressure and land-use changes – often in relation with urbanization and tourism – as well as the impact of climate on their frequency and occurrence. In this FLASH project we aim at (i) realizing improved assessments and the overall understanding of underlying event processes and magnitudes of recent extreme torrential disasters in a longer-term perspective as well as at (ii) an analysis of their triggers so as to be in a better position to develop more suitable risk mitigation strategies. The objective of this FLASH project thus is to contribute to the understanding of the temporal occurrence and triggers of extreme torrential floods by means of a proper documentation and quantification of events in a representative set of ungauged headwater catchment in the Himalayas. The regional focus will be on Jammu and Kashmir, but comparisons will be made with catchments in Himachal Pradesh and Sikkim, where UNIBE and BSIP have been working on paleohydrological assessments in the past and currently and for which a database of information already exists. The project is divided in three tasks. The first task is dedicated to the collection of existing climatic data as well as of existing records of past torrential disasters. The second task, being the core of the project, will document the occurrence of past torrential events (floods, flash floods) in ungauged catchments and their magnitude based on paleohydrologic approaches (i.e. tree-ring reconstructions). The last task will consequently use the new knowledge obtained on torrential disasters and try to understand the climatic causes for their occurrence so as to be in a position to provide recommendations for the implementation of suitable strategies aiming at a reduction of fatalities during future floods. It is expected that results of this project will not only be of interest to hydrologists and climate change experts, but also of great value for practitioners, local as well as national authorities to define scenarios of future risks in inhabited valleys and therefore to improved resilience of local populations. The Swiss partner will focus on coordination and have the lead on the analysis and interpretation of paleohydrological records and triggers of past flood disasters The Indian partners will be in charge of the database construction and co-lead tree-ring sampling expeditions in headwater catchments (Birbal Sahni Institute of Paleobotany) and the hydraulic modelling (National Institute of Hydrology). The project team has long-standing, prime contacts with the Indian Meteorological Department (IMD) and the Indian Institute of Tropical Meteorology (IITM) and will use these contacts when it comes to the interpretation of results.
Prof. Markus Stoffel
Prof. Kumar Rakesh