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Multidecadal fluvial sediment fluxes to major deltas under environmental change scenarios: projections and their implications

Multidecadal fluvial sediment fluxes to major deltas under environmental change scenarios: projections and their implications
Multidecadal fluvial sediment fluxes to major deltas under environmental change scenarios: projections and their implications
Deltas are important climate change hot spots that provide critical locations for human populations, agriculture, and aquaculture, as well as ecosystems and the services they provide. However, they are vulnerable systems as the sediment inputs which have historically offset relative sea level rise in undisturbed deltas appear to be threatened by anthropogenic activities. This thesis contributes to the understanding of future delta sustainability by projecting sediment delivery to a set of 47 significant deltas worldwide. This is the first study of future sediment fluxes to such a large group of major deltas, and for some of these individual deltas the projection of future sediment flux has never been done before. The hydrological model WBMsed was chosen after a review of possible models to project fluvial sediment delivery to each delta annually up to the year 2100. The model was forced by scenarios of climate change (RCPs 2.6, 4.5, 6.0, and 8.5), socioeconomic change (population and GDP data derived from SSPs 1, 2, and 3), and projected dam construction. On average, across all 47 deltas, fluvial sediment delivery is predicted to decrease by 36-41%, dependent on scenario, during the 21st century. The largest overall contributor to decreasing sediment delivery is reservoir construction. However, for some individual deltas socioeconomic changes can cause a larger decline in the supply of fluvial sediment than dam construction. In comparison, climate changes have a much smaller effect than both dam construction and socioeconomic changes, but the influence of climate change is generally of opposing sign (for 39 of 47 rivers), thereby increasing future sediment supply. There are large differences between the sediment flux changes projected between individual deltas, with some increases, but the majority of deltas (32 of 47) display decreases in sediment flux on average. The significance of the sediment delivery changes for each river was assessed by developing a new Sediment Starvation Risk Index (SSRI), which considers absolute sediment flux change versus delta area. The SSRI highlights those deltas most at risk from sediment delivery losses over the 21st century and also shows a correlation between the dominant drivers of sediment flux change for each delta and the degree of sediment starvation risk. Those deltas with sediment flux changes driven by socioeconomic change are likely to be at greater risk of sediment starvation, whereas those driven by climate change are likely to be at less risk. This research assesses projected changes in sediment load to deltas, the key drivers of these changes, and the potential significance of these changes for individual deltas using globally consistent methods. The research suggests widespread challenges for delta management and sustainability due to reduced sediment inputs over the 21st century.
University of Southampton
Dunn, Frances Eleanor
43ad074b-3134-4fc9-8c42-b330ee590f98
Dunn, Frances Eleanor
43ad074b-3134-4fc9-8c42-b330ee590f98
Darby, Stephen
4c3e1c76-d404-4ff3-86f8-84e42fbb7970
Nicholls, Robert
4ce1e355-cc5d-4702-8124-820932c57076

Dunn, Frances Eleanor (2017) Multidecadal fluvial sediment fluxes to major deltas under environmental change scenarios: projections and their implications. University of Southampton, Doctoral Thesis, 234pp.

Record type: Thesis (Doctoral)

Abstract

Deltas are important climate change hot spots that provide critical locations for human populations, agriculture, and aquaculture, as well as ecosystems and the services they provide. However, they are vulnerable systems as the sediment inputs which have historically offset relative sea level rise in undisturbed deltas appear to be threatened by anthropogenic activities. This thesis contributes to the understanding of future delta sustainability by projecting sediment delivery to a set of 47 significant deltas worldwide. This is the first study of future sediment fluxes to such a large group of major deltas, and for some of these individual deltas the projection of future sediment flux has never been done before. The hydrological model WBMsed was chosen after a review of possible models to project fluvial sediment delivery to each delta annually up to the year 2100. The model was forced by scenarios of climate change (RCPs 2.6, 4.5, 6.0, and 8.5), socioeconomic change (population and GDP data derived from SSPs 1, 2, and 3), and projected dam construction. On average, across all 47 deltas, fluvial sediment delivery is predicted to decrease by 36-41%, dependent on scenario, during the 21st century. The largest overall contributor to decreasing sediment delivery is reservoir construction. However, for some individual deltas socioeconomic changes can cause a larger decline in the supply of fluvial sediment than dam construction. In comparison, climate changes have a much smaller effect than both dam construction and socioeconomic changes, but the influence of climate change is generally of opposing sign (for 39 of 47 rivers), thereby increasing future sediment supply. There are large differences between the sediment flux changes projected between individual deltas, with some increases, but the majority of deltas (32 of 47) display decreases in sediment flux on average. The significance of the sediment delivery changes for each river was assessed by developing a new Sediment Starvation Risk Index (SSRI), which considers absolute sediment flux change versus delta area. The SSRI highlights those deltas most at risk from sediment delivery losses over the 21st century and also shows a correlation between the dominant drivers of sediment flux change for each delta and the degree of sediment starvation risk. Those deltas with sediment flux changes driven by socioeconomic change are likely to be at greater risk of sediment starvation, whereas those driven by climate change are likely to be at less risk. This research assesses projected changes in sediment load to deltas, the key drivers of these changes, and the potential significance of these changes for individual deltas using globally consistent methods. The research suggests widespread challenges for delta management and sustainability due to reduced sediment inputs over the 21st century.

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Frances Dunn final PhD thesis - Version of Record
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Published date: November 2017

Identifiers

Local EPrints ID: 417782
URI: http://eprints.soton.ac.uk/id/eprint/417782
PURE UUID: b426877c-6707-4894-b2ef-42dda1422cc2
ORCID for Frances Eleanor Dunn: ORCID iD orcid.org/0000-0003-3726-7158
ORCID for Stephen Darby: ORCID iD orcid.org/0000-0001-8778-4394
ORCID for Robert Nicholls: ORCID iD orcid.org/0000-0002-9715-1109

Catalogue record

Date deposited: 14 Feb 2018 17:30
Last modified: 12 Dec 2021 03:25

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Contributors

Author: Frances Eleanor Dunn ORCID iD
Thesis advisor: Stephen Darby ORCID iD
Thesis advisor: Robert Nicholls ORCID iD

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