2D Modelling Of Sediment Dynamics In High Energy Gravel Bed Rivers And Climate Impacted Glacier Fed River Basins

Abid-Waheed, Zayd

Abstract

This thesis sets out a novel method of 2D sediment modelling in high energy mountain systems. A new combined methodology using lidar, drone and dGPS survey along with HEC-RAS 2D river simulation has been developed. This methodology has been validated against survey on a high gradient UK gravel bed river (Blaze Beck) to identify the accuracy of the model. It was found that even when using the optimum parameters, the model shows an underprediction in area and an overprediction in volume when compared to the survey data. This methodology was then applied to two proglacial study sites (Findelngletscher and Gornergletscher) to investigate proglacial sediment dynamics. Simulations confirmed observations from prior studies regarding the loss of sediment connectivity in proglacial environments as the glacier retreats due to changes in basin morphology. At Findelngletscher most material is not delivered downstream, with most material being held on the alluvial fan. This results in similar exported material quantities despite increasing sediment input as the glacier retreats. At Gornergletscher, without an alluvial splay, there is better sediment connectivity. However, most material was held in the system due to a reducing slope downstream, allowing for similar processes to Findelngletscher. These results provide a novel high-resolution insight into likely coarse and fine sediment dynamics beyond that of previous studies.
Therefore, the unique contribution of this thesis is twofold. Firstly, in the establishment and validation of a 2D sediment modelling methodology, performed at a higher resolution (1-2 m compared to typical 10 m or higher in other studies) and applied to higher energy river systems than contemporary studies (using high mountain systems at over 60 m3/s of discharge over steeper systems). And secondly in the successful application of said methodology in a proglacial environment to model and confirm theoretical unobserved understandings of proglacial sediment connectivity.

• Thesis Type: Thesis
• Deposit Date: Dec 12, 2024
• Publicly Available Date: Jan 24, 2027
• Award Date: Jan 23, 2025