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Decoding the drivers of bank erosion on the Mekong River: the roles of the Asian monsoon, tropical storms and snow melt

Decoding the drivers of bank erosion on the Mekong River: the roles of the Asian monsoon, tropical storms and snow melt
Decoding the drivers of bank erosion on the Mekong River: the roles of the Asian monsoon, tropical storms and snow melt
We evaluate links between climate and simulated river bank erosion for one of the world's largest rivers, the Mekong. We employ a process-based model to reconstruct multi-decadal time series of bank erosion at study sites within the Mekong's two main hydrological response zones, defining a new parameter, accumulated excess runoff (AER), pertinent to bank erosion. We employ a hydrological model to isolate how snow melt, tropical storms and monsoon precipitation each contribute to AER and thus modelled bank erosion. Our results show that melt (23.9% at the upstream study site, declining to 11.1% downstream) and tropical cyclones (17.5% and 26.4% at the upstream and downstream sites, respectively) both force significant fractions of bank erosion on the Mekong. We also show (i) small, but significant, declines in AER and hence assumed bank erosion during the 20th century, and; (ii) that significant correlations exist between AER and the Indian Ocean Dipole (IOD) and El Niño Southern Oscillation (ENSO). Of these modes of climate variability, we find that IOD events exert a greater control on simulated bank erosion than ENSO events; but the influences of both ENSO and IOD when averaged over several decades are found to be relatively weak. However, importantly, relationships between ENSO, IOD and AER and hence inferred river bank erosion are not time-invariant. Specifically, we show that there is an intense and prolonged epoch of strong coherence between ENSO and AER from the early 1980s to present, such that in recent decades derived Mekong River bank erosion has been more strongly affected by ENSO.
asian monsoon, mekong river, river bank erosion, enso, indian ocean dipole, tropical cyclones, snowmelt
0043-1397
2146-2163
Darby, Stephen E.
4c3e1c76-d404-4ff3-86f8-84e42fbb7970
Leyland, Julian
6b1bb9b9-f3d5-4f40-8dd3-232139510e15
Kummu, Matti
b663f033-34e2-45e4-a5a3-d9987f72ca3b
Rasanen, Timo
29ababc4-fe57-44d1-b568-accc1b632f1d
Lauri, Hannu
ac66a1cd-8f44-45b7-8470-4a51eb07460d
Darby, Stephen E.
4c3e1c76-d404-4ff3-86f8-84e42fbb7970
Leyland, Julian
6b1bb9b9-f3d5-4f40-8dd3-232139510e15
Kummu, Matti
b663f033-34e2-45e4-a5a3-d9987f72ca3b
Rasanen, Timo
29ababc4-fe57-44d1-b568-accc1b632f1d
Lauri, Hannu
ac66a1cd-8f44-45b7-8470-4a51eb07460d

Darby, Stephen E., Leyland, Julian, Kummu, Matti, Rasanen, Timo and Lauri, Hannu (2013) Decoding the drivers of bank erosion on the Mekong River: the roles of the Asian monsoon, tropical storms and snow melt. Water Resources Research, 49 (4), 2146-2163. (doi:10.1002/wrcr.20205).

Record type: Article

Abstract

We evaluate links between climate and simulated river bank erosion for one of the world's largest rivers, the Mekong. We employ a process-based model to reconstruct multi-decadal time series of bank erosion at study sites within the Mekong's two main hydrological response zones, defining a new parameter, accumulated excess runoff (AER), pertinent to bank erosion. We employ a hydrological model to isolate how snow melt, tropical storms and monsoon precipitation each contribute to AER and thus modelled bank erosion. Our results show that melt (23.9% at the upstream study site, declining to 11.1% downstream) and tropical cyclones (17.5% and 26.4% at the upstream and downstream sites, respectively) both force significant fractions of bank erosion on the Mekong. We also show (i) small, but significant, declines in AER and hence assumed bank erosion during the 20th century, and; (ii) that significant correlations exist between AER and the Indian Ocean Dipole (IOD) and El Niño Southern Oscillation (ENSO). Of these modes of climate variability, we find that IOD events exert a greater control on simulated bank erosion than ENSO events; but the influences of both ENSO and IOD when averaged over several decades are found to be relatively weak. However, importantly, relationships between ENSO, IOD and AER and hence inferred river bank erosion are not time-invariant. Specifically, we show that there is an intense and prolonged epoch of strong coherence between ENSO and AER from the early 1980s to present, such that in recent decades derived Mekong River bank erosion has been more strongly affected by ENSO.

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Decoding the drivers of bank erosion on the Mekong river The roles of the Asian monsoon, tropical storms, and snowmelt - Darby - 2013 - Water Resources Research - Wiley Online Library.htm - Version of Record
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e-pub ahead of print date: 25 April 2013
Published date: April 2013
Keywords: asian monsoon, mekong river, river bank erosion, enso, indian ocean dipole, tropical cyclones, snowmelt
Organisations: Earth Surface Dynamics

Identifiers

Local EPrints ID: 350761
URI: http://eprints.soton.ac.uk/id/eprint/350761
ISSN: 0043-1397
PURE UUID: 0b7c1fc3-4b5b-42f1-94f2-5d70b210992b
ORCID for Stephen E. Darby: ORCID iD orcid.org/0000-0001-8778-4394
ORCID for Julian Leyland: ORCID iD orcid.org/0000-0002-3419-9949

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Date deposited: 04 Apr 2013 09:59
Last modified: 15 Mar 2024 03:24

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Contributors

Author: Julian Leyland ORCID iD
Author: Matti Kummu
Author: Timo Rasanen
Author: Hannu Lauri

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