Land loss and subsidence in the Mekong River Delta: A Surface Elevation Table (SET) program Le Xuan Thuyen Natural Science University at Ho-Chi Minh [email protected].

Land loss and subsidence in the Mekong River Delta: A Surface Elevation Table (SET)

program

Le Xuan ThuyenNatural Science University at Ho-Chi Minh

[email protected]

Mekong River Delta

Ảnh: TUẤN VŨ

Evidence of continuous land loss

Initiation of SET-MH monitoring network in the Mekong River Delta

Future investigation

2006

2009

Camau cape

8/2009

2/2001

Shoreline retreat

USGS picture found at approximate location of maximum subsidence in the United States identified by research efforts of Dr. Joseph F. Poland (pictured). Signs on pole show approximate altitude of land surface in 1925, 1955, and 1977. The site is in the San Joaquin Valley southwest of Mendota, California

Harris-Galveston Subsidence District

Timing and degree of projected submergence (percentage of inundation) of a given land surface or feature 0.5 meter above current sea level heights in relation to a constructed sea level scenario based on maximum A1F1 projection (IPCC, 2007) and a net subsidence rate of 9 mm/yr.

Doyle, T.W., Day, R.H., and Michot, T.C., 2010, Development of sea level rise scenarios for climate change assessments of the Mekong Delta, Vietnam: U.S. Geological Survey Open-File Report 2010–1165, 110 p.

Scenarios of climate change, sea level rise for Vietnam. MONDRE, March 2012

Submergence risk maps of the Mekong Delta with sea level rise +1 m, corresponding to the worst scenario A1F1 in the reports of the Intergovernmental Committee (IPCC, 2007)

≈ 39 % surface under water in 2100

2070

Reason of these differences – likely land subsidence ?39

Submergence risk

emerging issue

Or imply an unexpected role of subsidence in mentioned scenarios of submergence risk

this 'unpredictable variability' behaves in a more predictable way than previously assumed

Surface change simulated from InSAR multidate imageries and ground water withrawal (2007 –

2010)Laura E. Erban, Steven M. Gorelick, Howard A. Zebker, Scott Fendorf, (2013). Release of arsenic to deep groundwater in the Mekong Delta, Vietnam, linked to pumping-induced land subsidence. PNAS | August 20, 2013 | vol. 110 | no. 34 | 13751–13756

Great speed of subsidence: 1- 3 cm/y ! (2007-2010)

Mean daily water level at Vung Tau gauge station (2007-2013)

Sea Level Upland

Initial Wetland Surface

Bench Mark with Geodetic Control

Surface Elevation Table (SET)Tide Gauge

Depth of SET measurement integration

Deep Subsidence

Subsided Wetland Surface

Rise

Shallow Subsidence

Holocene strata

Surface Elevation Table and Marker Horizon Network designed for shallow subsidence monitoring

http://www.pwrc.usgs.gov/set.

Global SET Network

This is not a strategically designed network. It is an ad hoc collection of study sites. However the data can be used to analyze higher order questions, such as comparisons among regions and wetland types.

The surface elevation table method provides high resolution measures (mm scale) of wetland elevation change

Cahoon, D., Reed, D., Day, J. 1995. Estimating shallow subsidence in microtidal salt marshes of the southeastern United States: Kaye and Barghoorn revisited. Marine Geology 128:1-9.

Surface Elevation Table (SET)

Rod Surface Elevation Table (RSET)

Salt marsh in New York City

Benchmark depth = 10 - 25 mThe method, which utilises a simple, low-cost tool, is financially and technically accessible to every country with coastal wet lands. Science daily, Apr. 25, 2013

Can Gio Biosphere Reserve, Mekong River Delta, July 2010

Rhizophora

Subsidence rate measuring by SET technics

SET measurement in the Cangio mangrove: intact and collapsed mangrove areas.

Energy spectrum of Durian Storm

00:10 GMT 5 Dec.2006

Natural disaster

Root decomposition accelerates subsidence

March 2013

Camau cape Highest coastal line modification

SET reading

August 2013

First mission, July 2010

Floodplain Tramchim national park

August 2012

Wetland training

Hoa An March 2013

Hoa An August 2013

Freshwater swamp

Preliminary results of land subsidence monitoring in the coastal zone - mangrove forest in the MRD

Hoa-an March 2013

Tramchim Agust 2012

Tongle Chma May 2013Tongle Sap May 2013

14.2mm/y

Surface change simulated from InSAR multidate imageries and ground water withdrawal (2007 –

2010)Laura E. Erban, Steven M. Gorelick, Howard A. Zebker, Scott Fendorf, (2013). Release of arsenic to deep groundwater in the Mekong Delta, Vietnam, linked to pumping-induced land subsidence. PNAS | August 20, 2013 | vol. 110 | no. 34 | 13751–13756

Great speed of subsidence: 1- 3 cm/y ! (2007-2010)

Future investigation

Future investigation

Expansion of SET – MH network

Different subjects

- Modelling at different scales

- Driving factors, integration

Oct 2012

June 2011

June 2011Mũi Cà Mau

March 2011 (Cù Lao Dung)

March 2013

August 2012 Tràm Chim

July 2010 Cần GiờJuly 2011

Dec 2013 Xuân Thủy

May 2013

April 2012

?

Cantho city

To raise the quality of dataset