Rainfall-to-reach, modelling of braided morphodynamics

Stott, Eilidh (2019) Rainfall-to-reach, modelling of braided morphodynamics. MSc(R) thesis, University of Glasgow.

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Abstract

Communities today are increasingly vulnerable to fluvial flood events due to increased development on floodplains and climate change impacts. This prompts a need to improve flood risk management strategies. In particular, the forecasting of high flow events via hydrological modelling. In piedmont regions, where sediment supply can be substantial and variable depending on seasonal hydrology and perturbations such as landslides, geomorphic change can influence channel conveyance and thus flood risk. However, the modelling of sediment transport and its impacts on geomorphic change and flood risk is rarely incorporated into flood risk management. This thesis therefore aims to assess an end-to-end modelling framework to predict discharge, sediment transport and morphological change on a braided piedmont river. First, Structure from Motion photogrammetry was used to monitor topographic change along a braided reach of the River Feshie, Scotland, to demonstrate how morphological data can be obtained to assess numerical model performance. The coupled numerical modelling framework used for this analysis included a catchment scale rainfall runoff model (CLiDE), and a reach scale geomorphic change model (CAESAR-LISFLOOD). Model results show that the parameterised rainfall runoff model could appropriately predict base and storm flow discharges. The geomorphic change model could predict the location and magnitudes of change for one to two years of model runtime. However, after multiple floods the morphodynamic model outputs substantially degraded. As lateral erosion rapidly carved out river banks and deposited sediment in the channel, resulting in a topographically smooth reach. Despite the limitations of the reach scale model to maintain braiding over multiple events, this work demonstrates how an end-to-end modelling framework could be implemented to predict geomorphic change and contribute to updating the topography in flood risk mapping and forecasting models. Results also illustrate how repeat topographic surveys can be used as input and verification data for flood risk modelling which incorporates geomorphic change.

Item Type: Thesis (MSc(R))
Qualification Level: Masters
Additional Information: Supported by an Angus Mitchell Studentship.
Keywords: Fluvial, geomorphology, braided river, river science, modelling, hydraulic modelling, river feshie, morphodynamics, 2D modelling, CLiDE, CAESAR Lisflood.
Subjects: G Geography. Anthropology. Recreation > G Geography (General)
Q Science > QE Geology
Colleges/Schools: College of Science and Engineering > School of Geographical and Earth Sciences > Earth Sciences
Supervisor's Name: Williams, Dr. Richard and Barrett, Dr. Brian and Hurst, Dr. Martin
Date of Award: 2019
Depositing User: Miss Eilidh Stott
Unique ID: glathesis:2019-70942
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 03 May 2019 10:09
Last Modified: 03 May 2019 10:10
URI: http://theses.gla.ac.uk/id/eprint/70942

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