MRCS/WUP-FIN Lower Mekong Modelling Project
27th of April, 2005
Bank erosion study on Nong Khai – Vientiane section of Mekong River
Introduction
Many sites in the Mekong River are suffering from bank erosion problems that
endanger nearby settlements and infrastructures. The Nong Khai – Vientiane area
on the border between Thailand and Lao PDR has been identified as a highly
critical area and is a trans-boundary issue between Lao PDR and Thailand. WUPFIN project will create tools for addressing these problems by developing an
advanced modelling tool for analysing river bank erosion processes and their
causes, whether natural or man-made, upstream or local. The conclusion strives
to provide help in designing bank protection structures.
At the National Consultations the Lao counterpart, similarly to the Thai counterpart,
has emphasized the necessity to cooperate closely with the Thai-Lao Border
Commission responsible for the trans-boundary procedures on the erosion issues.
It is also the custodian of the related data bases.
Tools
For the modelling the 3D EIA flow and water quality model is used. The pilot
model for the whole Modelling area has been set up (Figure 1). The coupled
sediment model plan including sediment transport, sedimentation and bed and
bank erosion is presented in the Inception Report. The model will be developed
mostly during the latter part of 2005 and in 2006.
Figure 1.
Vientiane pilot model: elevation grid with nesting.
Collection of existing data
Identifying and collection of existing data for the Nong Khai – Vientiane model
application and bank erosion study started in September 2004 and is still on-going
process.
MRCS/WUP-FIN Lower Mekong Modelling Project
27th of April, 2005
At the moment the following data sets have been received:
Mekong River Commission
 River topography from the digital Mekong Hydrographic atlas (Figure 2)
 River bank location from the Mekong Hydrographic atlas in early 1990s
 Hardcopy of old Hydrographic atlas from 1960s
 Digital elevation map for the land area with 50 m resolution from old
topographical maps and new SRTM elevation model with 90 m resolution
Lao PDR
 Historical TSS concentration measurements at Vientiane port
 Daily water level and discharge in Vientiane port
 Bed changes during time have been measured in two projects: JICA (2004)
and bank protection project in 1988
 Aerial photos from 1991 of Mekong around Vientiane and Nong Khai
Thailand
 Daily water level and discharge in Nong Khai
International
 Bank material analysis made by JICA (2004) and Miazawa et al. (2004)
 Bed material analysis made by Miazawa et al. (2004) and JICA (2004)
 Velocity profile measurements on Laos side on three sites done by JICA
(2004)
 Analysis of the bank erosion in Vientiane area made by Rutherford and
Bishop (1996) with some mapping comparing the old and new Mekong
Hydrographic Atlas
and the following data sets have been identified but not received:
Mekong River Commission
 Hourly WL data from AHNIP station in Nong Khai
Lao PDR
 Water level at three stations with recording meters were set up by JICA
(2004)
 Bank material analysis for Laos’ side by national agencies.
 Soil moisture data (NUoL and WAD are collecting the data)
Thailand
 Historical TSS concentration measurements at Nong Khai
 Depth integrated suspended sediment concentration measurements at
Nong Khai by Nong Khai Hydrological Centre
 ADCP measurements on Friendship bridge by Nong Khai Hydrological
Centre
 Bank material analysis for Thailand side by national agencies
 Aerial photos from 1960s of Mekong around Vientiane and Nong Khai
MRCS/WUP-FIN Lower Mekong Modelling Project
Figure 2.
27th of April, 2005
Mekong Hydrographic atlas for Nong Khai - Vientiane area.
Field measurements
Field Measurements and additional data requests have been planned for
supporting the modelling work and more comprehensive understanding of the
bank erosion process and geomorphological changes.
The following activities have been planned for the field work covering the flood
season of 2005 (May 2005 – April 2006):

Lateral (morphological) changes in river bank
o Data: aerial photos (from 1960s (?), 1991, and satellite images
(SPOT5/ICONOS if available) for the Nong Khai - Vientiane area
o Methods: compare the aerial photos and satellite images from
different years with GIS to map and analyse the lateral changes in
river bank. This can then be compared to the analysis made by
WAD and JICA bank protection master plan who have mapped the
critically eroded areas.
o Output: maps and gis-layers of the river bank in different years,
mapping the changes, report

Sediment flux combined with the ADCP measurements
o Data: MRC & other existing TSS data + new measurements
together with MRCS, LNMC, WAD, NUoL, TNMC, and Nong Khai
hydrological centre from two additional places for the Nong Khai
measurement station:
 Vientiane harbour and upstream model boundary
 ADCP runs are coupled with the SSC samples (black dots)
o Methods: using the ADCP, turbidity and sediment sampling to
understand the sediment fluxes in river on Vientiane municipality
area in different seasons. The historical data (SS sampling once a
month from surface layer on the middle of the river) will be used to
analyse the changes in suspended sediment concentrations during
the last decades.
o
Additional:
 particle size distribution in suspended sediment.
Equipment: Technical University of Budapest. Availability
MRCS/WUP-FIN Lower Mekong Modelling Project

27th of April, 2005
of the equipment will be declared. Other options need to
be clarified
Bed load: possible to do with ADCP coupled with the bed
samples. Other options need to be clarified.

Cross section changes
o Data: existing data from 1988, JICA bank protection project, other
(?). New data will be collected with echo sounder and/or ADCP.
Around 8 cross sections will be selected from the model’s
upstream boundary to the friendship bridge. Cross sections will be
identified later on together with MRCS, LNMC, WAD, TNMC, and
Nong Khai Hydrological Centre
o Method: comparing the cross-sections before flood, during the
flood and after the flood gives good understanding of the dynamics
of the changes in bed level and bank erosion. Intended months to
do the survey (flood season may 2005-april 2006) are
 May, July, August, September, October, December,
February, April

Longitudinal changes
o Data will be collected with echo sounder and/or ADCP.
Measurement work for longitudinal sections will be done in
cooperation with MRCS, LNMC, WAD, TNMC, and Nong Khai
Hydrological Centre
o Method: Comparing the changes in longitudinal section from
model upper boundary to the Friendship Bridge will enhance the
understanding of the longitudinal changes over one flood season
in the Vientiane area. Intended months to do the survey are
 May, September, December, April

Bathymetry of the river
o Data: Existing bathymetry data is limited for some parts of the
Mekong stretch around Vientiane. Especially the higher areas of
river bed, as sand bars which are inundated during the wet-season
but visible during the dry-season, are not well mapped. Thus, new
survey is needed to complement the existing information to be
sufficient for the modelling purposes.
o Method: using echo sounder/ADCP to enhance the bathymetry
map for areas where it is needed. Will be clarified later on together
with MRCS, LNMC, WAD, TNMC, and Nong Khai Hydrological
Centre.

Material analysis in river bed and bank
o Data: existing data have to be collected and analysed (soil type,
grain size analysis, etc). After identifying the gaps, the needed
samples have to be taken in both sides of the river.

Bank profile and landuse
o Slope profile/gradient
o Landuse on river bank

Recording current meter
o Method: Using the RM9 recording current meter the short term
fluctuation in flow speed can be measured. WUP-FIN has 2
equipments. Difficulty to put into the practice: find a proper place to
MRCS/WUP-FIN Lower Mekong Modelling Project
27th of April, 2005
set-up the velocity meter. Possible places need to be clarified
together with MRCS, LNMC, WAD, TNMC, and Nong Khai
Hydrological Centre.
Obligations of the counterparts
Thailand

Provision of data on
o river bathymetry and morphometry
o water levels and discharges
o ADCP measurements
o TSS concentrations
o River bank and bed material
o Landuse
o aerial photos from 1960s

Facilitation of the field work safeguarding the operations on the Thai side
of the river

Providing counterpart team for cooperating in data issues, field work,
modelling and training

Providing the equipment for the field work (especially the ADCP)
MRCS/WUP-FIN

Providing the bank erosion model software package and training
programme

Supervision of the field work

Covering the necessary cost of the field program

Providing recording current meter for field measurements