This project investigates how sediment transport can affect river morphology, flooding and flood prediction in the Kathmandu basin. This is part of a large interdisciplinary team working on disaster risk management in the Kathmandu region of Nepal.
Large volumes of sediment enter the river systems of Nepal from the hillslopes of the Himalaya mountain range. Sediment modifies the channel’s capacity to contain flood waters, and the movement of large quantities of sediment can alter the river course. Therefore, understanding the processes of sediment transport and erosion, particularly following major storms and earthquakes, is critical to predicting hazard cascades and flood risk under extreme scenarios. This is particularly important where embankments and other hard engineering flood protection strategies impact erosion and sedimentation in the channel network, as has been suggested for the Bagmati River channel running through Kathmandu. Current flood prediction maps for Himalayan rivers do not account for sediment mobility. We will further develop current models, to include sediment, and apply them to revising flood risk management strategies in the Kathmandu region. Future flood scenarios will investigate the integration of changing discharge signals in response to climate and land-use change. A major UK government funded project entitled Tomorrow’s Cities https://www.tomorrowscities.org/
is aimed at integrating knowledge of multihazard risk in the Kathmandu basin where urban expansion is forced into regions that are vulnerable to flooding.
How does incorporating sediment transport alter current flood prediction model results?
What is the most accurate method of incorporating sediment transport into a flood prediction model of the Kathmandu Valley, for bedload and suspended sediment?
How does the construction of river structures, such as embankments, affect sediment transport and alter the river’s capacity to contain flood waters?
0-6 months: Review of literature and archival data on hydrological history of the Kathmandu basin catchment in collaboration with the Department of Hydrology and Meteorology in Kathmandu. Building familiarity with the software Caesar-Lisflood (http://dvalts.io/HAIL-CAESAR/
) and testing how DEM resolution impacts model results. Training and courses as below, particularly in numerical methods.
6-12 months: Initial simulations of the Kathmandu Basin using a newly acquired high resolution digital elevation model and Caesar-Lisflood software. Running a series of experiments with varying sediment flux, sediment grainsizes and different hydrological scenarios. Explore possible sediment transport formulations.
12-30 months: Field trip(s) to Nepal to carry out surveys of river channels and discharge using an Acoustic Doppler Current Profiler (ADCP) in collaboration with linked PhD on landslide generated sediment flux and transport. Incorporate changes in the channel geometry from the ADCP surveys into the flood models, followed by a series of sensitivity analyses of sediment transport modes within the Caesar-Lisflood model. Extend model to include multiple grain sizes calibrated against data collected by linked PhD. Carry out sensitivity analysis for different flood scenarios that incorporate current and planned embankment configurations to test their impact.
30 – 36 months: Presentation of results to the partners in Kathmandu working in Tomorrow’s Cities Hub, including government-based and community oriented stakeholders. Consideration of how to incorporate sediment management into urban planning in Kathmandu basin.
A comprehensive training programme will be provided comprising both specialist scientific training and generic transferable and professional skills. The student will be trained in Python and C++, to facilitate the use of Caesar-Lisflood. There will also be training in the use of the ADCP and GPS systems during fieldwork. The University of Edinburgh Institute for Academic Development provides a wide range of training courses such as coding, paper writing, and other transferable skills.
Slater, L.J., Singer, M.B. and Kirchner, J.W., 2015. Hydrologic versus geomorphic drivers of trends in flood hazard. Geophysical Research Letters, 42(2), pp.370-376.
Stover, S.C. and Montgomery, D.R., 2001. Channel change and flooding, Skokomish River, Washington. Journal of Hydrology, 243(3-4), pp.272-286.
Sinclair et al., 2017, Improved understanding of flood resilience in the Terai, Nepal. Practical Action Knowledge report, 2017. https://www.research.ed.ac.uk/portal/files/46757472/Improving_Understanding_of_Flooding_and_Resilience_in_the_Terai_Nepal.pdf