The project analyses evidence for long-term earthquake and flood hazard from the geomorphology of river profiles and terraces, and the sedimentological records of floods and debris flows in the Kathmandu region.
This links to a major UK government funded project entitled Tomorrow’s Cities aimed at integrating knowledge of multihazard risk in the Kathmandu basin (https://www.tomorrowscities.org/
Understanding the magnitude, distribution and recurrence interval of major natural hazards represents a critical cornerstone of risk management in the developing world. For many natural hazards, the historical records provide only a fraction of the possible magnitudes within a particular setting. The Himalaya are vulnerable to extreme rainfall, landslides, glacial outburst floods and earthquakes, and so the scope for compound cascades of natural hazards magnifies the potential risk to communities. As part of a major international project to reduce multihazard risk in 4 major cities of the world (https://www.tomorrowscities.org/
), this PhD project will generate evidence for major floods and earthquakes from the geomorphic and sedimentological records of the Kathmandu Basin. Evidence from river channel profiles and from alluvial terrace surfaces will explore evidence for ongoing fault displacements on a thousand year timescale; this will feed in to ongoing models of seismic risk. Sedimentological data from within the terrace deposits will evaluate evidence for mass flows and ponding associated with ancient floods; these data will feed into flood risk scenarios. Both of these datasets will underpin scientific evidence provided to stakeholders engaged in urban development in the outer margins of the Kathmandu Basin.
- Is there evidence of surface displacements due to thrust faulting in the geomorphic record of the Kathmandu Basin, and can we put time constraints on it?
- What are the extreme flood scenarios in the Kathmandu Basin?
- How should we integrate high magnitude, low frequency natural hazards into risk management strategies?
The methodological approach will initially be based around analysing the digital topography of the Kathmandu Basin using a newly acquired high resolution digital elevation model (ca. months 0-6). The analyses will evaluate the channel steepness normalised for upstream area in order to look for evidence of varying rock uplift fields across major structures. The DEM will also map probable terrace surfaces and modern floodplains across the basin; these analyses will use software developed in Edinburgh (https://lsdtopotools.github.io/
). These DEM-based analyses will be supported by fieldwork in spring 2021 to isolate the role of tectonics versus lithology in controlling channel steepness. It will also act as a ground control on terrace mapping which will be backed up by sedimentological analysis of the terrace fill successions. Evidence for fault displacement of terraces, and/or of evidence for major flood events will be dated in year 2 using either optically stimulated luminescence dating or cosmogenic nuclides of the sediment fill and/or terrace surfaces respectively. Throughout the project, the student will interact with a team of flood modellers, seismologists and social scientists working as part of the Hub project in Kathmandu, and engage with communities, NGOs and government stakeholders. Close collaboration with Tribhuvan University in Kathmandu will facilitate access and logistics. This project will also link closely with a parallel studentship working on sediment flux in the modern rivers of the basin.
The student will attend courses in Python coding in order to run the Topotools software, and in geomorphic analysis from attending courses and being part of the Land Surface Dynamics research group in Edinburgh where there is plenty of opportunity for learning from other post-docs and students. Field based training will be carried out on field trips in Scotland, and in the field area in Nepal; this will involve quantitative analysis of conglomerates as a record of bedload processes in Holocene rivers and surveying of terraces using laser range finders and differential GPS, for which training is provided. In addition, the University of Edinburgh Institute for Academic Development provide a wide range of training courses such as coding, paper writing, and other transferable skills.
Sakai, Harutaka, et al. "Pleistocene rapid uplift of the Himalayan frontal ranges recorded in the Kathmandu and Siwalik basins." Palaeogeography, Palaeoclimatology, Palaeoecology 241.1 (2006): 16-27.
Sakai, Tetsuya, et al. "Revised lithostratigraphy of fluvio-lacustrine sediments comprising northern Kathmandu basin in central Nepal." Journal of Nepal Geological Society 37 (2008): 25-44.
Devrani, R., Singh, V., Mudd, S. M. & Sinclair, H. D., Prediction of flash-flood hazard impact from Himalayan river profiles (2015), In : Geophysical Research Letters.42, 14, p. 5888–5894
Elliott, J. R., et al. "Himalayan megathrust geometry and relation to topography revealed by the Gorkha earthquake." Nature Geoscience 9.2 (2016): 174.)