Robust multi-scale strategies for increasing the resilience of the Mekong Delta 

2021 ◽  
Author(s):  
Rafael Schmitt ◽  
Matteo Giuliani ◽  
Simone Bizzi ◽  
Mathias Kondolf ◽  
Gretchen Daily ◽  
...  
Keyword(s):  
Sediment Yield ◽  
River Sediment ◽  
Mekong Delta ◽  
Sediment Management ◽  
Sediment Supply ◽  
Land Loss ◽  
Sediment Trapping ◽  
River Deltas ◽  
Hydropower Dams ◽  
Sediment Model

<p>Rising sea levels, accelerated land subsidence, and changes in water and sediment supply from upstream basins put the major livelihoods and agriculture in global river deltas at risk. Identifying effective and robust strategies to make deltas more resilient will require to systematically address uncertainty while consider the coupling between global, basin and delta scale processes.</p><p>Here, we demonstrate a bottom-up exploratory approach to forecast land loss in the Mekong Delta by 2100 and to identify most effective management levers to fight that land loss through management on different scales. To our knowledge, this is the first time that such a robust approach is applied to study coupled delta and basin systems, thus considering the full range of drivers behind land loss and delta degradation.</p><p>For this analysis, we couple a network-scale river sediment model and a conceptual model of delta morpho-dynamics. Our land loss estimates cover a large range (20 – 90 %), driven mostly by uncertainty about accelerated subsidence from groundwater pumping. However, sediment supply from the basin plays an important role to maintain delta land, especially for low and moderate scenarios of accelerated subsidence. However, sediment supply from the basin is a function of counteracting and uncertain processes. Population growth and agriculture expansion are expected to increase erosion and sediment yield from the basin, but most of this increased sediment load will be trapped in existing and planned hydropower dams, ultimately reducing sediment delivery to the delta as a function of dam siting and design.</p><p>Using more than 2 million Monte Carlo runs of a river sediment model, we find that placement of hydropower dams is the dominant control on sediment supply, far outweighing increases in sediment yield due to land conversion or reduced sediment trapping in dams because of better sediment management. Thus, the future of the Mekong delta will be determined by renewable energy policies in the basin that strategically avoid excessive sediment trapping in dams as well as by effective water management in the delta.</p><p>Our results demonstrate (1) the need for connecting delta and basin scales for managing river deltas world-wide, (2) the contribution of basin-scale sediment management to maximize the resilience of delta land, and (3) the crucial control that dams and reservoirs exert on sediment continuity between rivers and deltas.  </p>

scholarly journals Strategic basin and delta planning increases the resilience of the Mekong Delta under future uncertainty

2021 ◽  
Vol 118 (36) ◽  
pp. e2026127118 ◽  
Author(s):  
R. J. P. Schmitt ◽  
M. Giuliani ◽  
S. Bizzi ◽  
G. M. Kondolf ◽  
G. C. Daily ◽  
...  
Keyword(s):  
Land Subsidence ◽  
Mekong Delta ◽  
Sediment Management ◽  
Sediment Supply ◽  
Sea Levels ◽  
Sediment Yields ◽  
Development Scenarios ◽  
Climate Resilience ◽  
Rising Sea Levels

The climate resilience of river deltas is threatened by rising sea levels, accelerated land subsidence, and reduced sediment supply from contributing river basins. Yet, these uncertain and rapidly changing threats are rarely considered in conjunction. Here we provide an integrated assessment, on basin and delta scales, to identify key planning levers for increasing the climate resilience of the Mekong Delta. We find, first, that 23 to 90% of this unusually productive delta might fall below sea level by 2100, with the large uncertainty driven mainly by future management of groundwater pumping and associated land subsidence. Second, maintaining sediment supply from the basin is crucial under all scenarios for maintaining delta land and enhancing the climate resilience of the system. We then use a bottom-up approach to identify basin development scenarios that are compatible with maintaining sediment supply at current levels. This analysis highlights, third, that strategic placement of hydropower dams will be more important for maintaining sediment supply than either projected increases in sediment yields or improved sediment management at individual dams. Our results demonstrate 1) the need for integrated planning across basin and delta scales, 2) the role of river sediment management as a nature-based solution to increase delta resilience, and 3) global benefits from strategic basin management to maintain resilient deltas, especially under uncertain and changing conditions.

Feasibility of sedimentation strategies for the Mekong delta to counterbalance relative sea-level rise

2021 ◽  
Author(s):  
Frances E. Dunn ◽  
Philip S. J. Minderhoud
Keyword(s):  
Land Use ◽  
Sea Level Rise ◽  
Sea Level ◽  
Mekong Delta ◽  
Sediment Deposition ◽  
Sediment Supply ◽  
Sediment Flux ◽  
Relative Sea Level ◽  
Fluvial Sediment ◽  
Relative Sea Level Rise

<p>As one of the largest deltas in the world, the Mekong delta is home to over 17 million people and supports internationally important agriculture. Recently deposited sediment compacts and causes subsidence in deltas, so they require regular sediment input to maintain elevation relative to sea level. These processes are complicated by human activities, which prevent sediment deposition indirectly through reducing fluvial sediment supply and directly through the construction of flood defence infrastructure on deltas, impeding floods which deliver sediment to the land. Additionally, anthropogenic activities increase the rate of subsidence through the extraction of groundwater and other land-use practices.</p><p>This research shows the potential for fluvial sediment delivery to compensate for sea-level rise and subsidence in the Mekong delta over the 21st century. We use detailed elevation data and subsidence scenarios in combination with regional sea-level rise and fluvial sediment flux projections to quantify the potential for maintaining elevation relative to sea level in the Mekong delta. We present four examples of localised sedimentation scenarios in specific areas, for which we quantified the potential effectiveness of fluvial sediment deposition for offsetting relative sea-level rise. The presented sediment-based adaptation strategies are complicated by existing land use, therefore a change in water and sediment management is required to effectively use natural resources and employ these adaptation methods. The presented approach could be an exemplar to assess sedimentation strategy feasibility in other delta systems worldwide that are under threat from sea-level rise.</p>

scholarly journals Holocene Sediment Production in Lillooet River Basin, British Colombia: A Sediment Budget Approach

2007 ◽  
Vol 45 (1) ◽  
pp. 45-57 ◽  
Author(s):  
Peter Jordan ◽  
Olav Slaymaker
Keyword(s):  
Sediment Yield ◽  
Debris Flows ◽  
Sediment Budget ◽  
Sediment Supply ◽  
Volcanic Complex ◽  
Minor Importance ◽  
The Holocene ◽  
Sediment Production ◽  
Clastic Sediment ◽  
Holocene Sediment

ABSTRACTA sediment budget approach is used to investigate the sources, storage, and yield of clastic sediment in Lillooet River watershed, in the southern Coast Mountains. The 3150 km2basin is heavily glacierised, and includes a Quaternary volcanic complex which has been active in the Holocene. The sediment yield has been determined from the rate of advance of the delta at the basin outlet. The floodplain of the main river valley is aggrading as the delta advances, and probably has been through most of the Holocene. Major sediment sources in the basin include glaciers and Neoglacial deposits, debris flows, and landslides in the Quaternary volcanic complex. Soil and bedrock creep, bank erosion of Pleistocene glacial deposits, and sediment from logging and agriculture are probably of minor importance. Estimates of sediment production from these sources explain only about half the observed clastic sediment yield plus the rate of valley aggradation. The unexplained sediment production may be associated with paraglacial sediments exposed by glacial retreat from the nineteenth century Neoglacial maximum; alternatively the frequency of occurrence of intermediate scale debris flows and landslides has been seriously underestimated. Sediment supply is highly episodic over time scales of centuries to thousands of years. Major factors in the temporal pattern of Holocene sediment supply are periods of volcanism, large landslides, the retreat of glaciers from the Neoglacial maximum, and recent river engineering works.

Relating sediment supply to the morphological and hydro-meteorological characteristics of torrent catchments

2021 ◽  
Author(s):  
Maxime Morel ◽  
Guillaume Piton ◽  
Caroline Le Bouteiller ◽  
Alexandre Mas ◽  
Guillaume Evin
Keyword(s):  
Sediment Yield ◽  
Prediction Method ◽  
Original Data ◽  
Sediment Supply ◽  
Set Covering ◽  
Sediment Retention ◽  
Multivariate Statistical ◽  
Catchment Basin ◽  
Mountain Areas ◽  
Data Set

<p>In mountain areas, the quantification of sediment yield is essential in the diagnosis of a torrential watershed. The objective of this study is to present a prediction method based on multivariate statistical models calibrated from an original data set covering nearly 130 torrential basins in the Northern French Alps. Data on sediment yield and occurrence of torrential events were collected on these catchments thanks to registries from sediment retention basins (average monitoring period of 20 years) and historical archives of the catchment basin managers. On these catchments, several morphological and hydro-meteorological characteristics were calculated (e.g. geological and sediment connectivity indices, the rate of connected eroding areas in the catchment, the Melton index, the slope of the fan, etc.) in order to relate them to sediment production and the frequency of occurrence of torrential events. These models allow the estimation of quantiles of the sediment yield in small torrent catchments. These models could be useful to evaluate sediment yield and the occurrence of torrential events on catchment not equipped with sedimentation structures.</p>

scholarly journals Effects of Land-Use Change on Characteristics and Dynamics of Watershed Discharges in Babeldaob, Palau, Micronesia

2011 ◽  
Vol 2011 ◽  
pp. 1-17 ◽  
Author(s):  
Yimnang Golbuu ◽  
Eric Wolanski ◽  
Peter Harrison ◽  
Robert H. Richmond ◽  
Steven Victor ◽  
...  
Keyword(s):  
Land Use ◽  
Sediment Yield ◽  
River Sediment ◽  
Land Development ◽  
Fine Sediment ◽  
Sedimentation Rates ◽  
Large Variability ◽  
Circulation Patterns ◽  
Ultimate Fate ◽  
Effects Of Land Use

This study assessed the impacts of differing levels of land development in four watersheds in Palau on river sediment yield and on sedimentation and turbidity. Area corrected sediment yield was strongly related to land development (r2=0.96,P=0.02), varying from 9.7 to 216 tons km−2yr−1between the least and most developed watershed. Mean sedimentation rates on reefs ranged from 0.7 to 46 mg cm−2d−1, and mean turbidity ranged from 9 to 139 mg l−1. The higher values exceeded those known to harm corals. Because Palau's watersheds and estuaries are small, river floods were short-lived (typically lasting less than a day) and the estuaries adjusted just as quickly to a number of different estuarine circulation patterns that, in turn, generated a large variability in the export of riverine fine sediment to the reefs. The ultimate fate of the fine sediment deposited on the reefs depended on wind resuspension, local currents, and geomorphology (whether the bay was open or semi-enclosed). Palau's small estuaries were generally not as effective as bigger estuaries in trapping sediments and thus at sheltering the reefs. Therefore, greater efforts are needed to control and mitigate land activities that contribute to the increase in sediment yield.

scholarly journals Scenario modelling of basin-scale, shallow landslide sediment yield, Valsassina, Italian Southern Alps

2005 ◽  
Vol 5 (2) ◽  
pp. 189-202 ◽  
Author(s):  
J. C. Bathurst ◽  
G. Moretti ◽  
A. El-Hames ◽  
A. Moaven-Hashemi ◽  
A. Burton
Keyword(s):  
Sediment Yield ◽  
Shallow Landslide ◽  
Southern Alps ◽  
Sediment Supply ◽  
Channel Network ◽  
Landslide Occurrence ◽  
Sediment Yields ◽  
Basin Scale ◽  
Modest Reduction

Abstract. The SHETRAN model for determining the sediment yield arising from shallow landsliding at the scale of a river catchment was applied to the 180-km2 Valsassina basin in the Italian Southern Alps, with the aim of demonstrating that the model can simulate long term patterns of landsliding and the associated sediment yields and that it can be used to explore the sensitivity of the landslide sediment supply system to changes in catchment characteristics. The model was found to reproduce the observed spatial distribution of landslides from a 50-year record very well but probably with an overestimate of the annual rate of landsliding. Simulated sediment yields were within the range observed in a wider region of northern Italy. However, the results suggest that the supply of shallow landslide material to the channel network contributes relatively little to the overall long term sediment yield compared with other sources. The model was applied for scenarios of possible future climate (drier and warmer) and land use (fully forested hillslopes). For both scenarios, there is a modest reduction in shallow landslide occurrence and the overall sediment yield. This suggests that any current schemes for mitigating sediment yield impact in Valsassina remain valid. The application highlights the need for further research in eliminating the large number of unconditionally unsafe landslide sites typically predicted by the model and in avoiding large overestimates of landslide occurrence.

scholarly journals Challenges of ecosystem restoration in Louisiana – availability of sediment and its management

2015 ◽  
Vol 367 ◽  
pp. 455-462 ◽  
Author(s):  
S. M. Khalil ◽  
A. M. Freeman
Keyword(s):  
Ecosystem Restoration ◽  
Management Plan ◽  
Sediment Management ◽  
Sediment Sources ◽  
Land Loss ◽  
Comprehensive Management ◽  
Regional Strategies ◽  
Coastal Louisiana ◽  
Restoration Effort ◽  
Sediment Resources

Abstract. Human intervention has impaired the Mississippi River’s ability to deliver sediment to its delta wetlands, and as a consequence acute land loss in coastal Louisiana has resulted in an unprecedented ecocatastrophe. To mitigate this degradation, an unparalleled restoration effort is underway. For this effort to be successful and sustainable, various sediment input mechanisms must be integrated, including: building appropriate sediment-diversions; beneficially using the millions of cubic metres of sediment dredged annually from navigational channels; harvesting deposits of sand and suitable sediment from the river and offshore; and related sediment management activities that are compatible with other uses of the river. A comprehensive sediment management plan has been developed to identify and delineate potential sediment sources for restoration, and to provide a framework for managing sediment resources wisely, cost effectively, and in a systematic manner. The Louisiana Sediment Management Plan provides regional strategies for improved comprehensive management of Louisiana's limited sediment resources.

scholarly journals Suspended sediment yield mapping of Northern Eurasia

2015 ◽  
Vol 367 ◽  
pp. 326-332 ◽  
Author(s):  
K. A. Maltsev ◽  
O. P. Yermolaev ◽  
V. V. Mozzherin
Keyword(s):  
Soviet Union ◽  
Sediment Yield ◽  
Former Soviet Union ◽  
River Sediment ◽  
Global Scale ◽  
Northern Eurasia ◽  
Major Step ◽  
Sediment Yields ◽  
Single Method ◽  
Local Anomalies

Abstract. The mapping of river sediment yields at continental or global scale involves a number of technical difficulties that have largely been ignored. The maps need to show the large zonal peculiarities of river sediment yields, as well as the level (smoothed) local anomalies. This study was carried out to create a map of river sediment yields for Northern Eurasia (within the boundaries of the former Soviet Union, 22 × 106 km2) at a scale of 1:1 500 000. The data for preparing the map were taken from the long-term observations recorded at more than 1000 hydrological stations. The data have mostly been collected during the 20th century by applying a single method. The creation of this map from the study of river sediment yield is a major step towards enhancing international research on understanding the mechanical denudation of land due mainly to erosion.

scholarly journals Experimental study of sediment supply control on step formation, evolution, and stability

2020 ◽  
Vol 8 (4) ◽  
pp. 855-868
Author(s):  
Matteo Saletti ◽  
Marwan A. Hassan
Keyword(s):  
Sediment Yield ◽  
Sediment Concentration ◽  
Sediment Supply ◽  
Particle Interactions ◽  
Transport Capacity ◽  
Step Frequency ◽  
Bell Curve ◽  
Channel Response ◽  
Channel Outlet ◽  
Formation Step

Abstract. We present results from an experimental campaign conducted in a steep flume subject to longitudinal width variations and different sediment feed rates. The experiments were designed to study how sediment supply influences step formation, step location, and step stability. Our results show that steps are more likely to form in segments of the channel where the width narrows because of particle jamming, and these steps are also more stable. Sediment feed increases particle activity which generates a dynamic channel morphology with steps forming and collapsing. A comparison with experiments without sediment feed shows that sediment supply does not inhibit step formation. Time series of step formation, evolution, and destruction show that the maximum number of steps is achieved when the sediment feed is larger than zero but smaller than the transport capacity. We summarize this outcome in a conceptual model where the dependence of step frequency on sediment supply is expressed by a bell curve. Sediment yield measured at the channel outlet followed the sediment feed at the inlet closely, even when we fed 50 % more and 50 % less than the calculated transport capacity. This outcome challenges the applicability of the concept of transport capacity to steep channels and highlights the key role played by sediment feed in dictating sediment yield and channel response. Finally, we detected a positive correlation between sediment concentration and step destruction, which stresses the importance of particle interactions for step formation and stability.

Sign in / Sign up

Export Citation Format

Share Document