Transcript Slide 1

5th World Water Forum, Istanbul, Turkey
16 – 22 March 2009
Soda-Mattress Riverbank
Protection Measures
Ministry of Public Works and Transport
Department of Waterways
Lao, PDR
Mr. Houngla SENGMUANG
Mr. Phaknakhone RATTANA
Ms. Vanh DILAPHANH
Mr. Kazumitsu MURAOKA
Contents:
• 1) Introduction (Background of Lao PDR
• 2)
• 3)
• 4)
• 5)
• 6)
and Mekong River)
The Condition in the Activity Area
Design of Riverbank Protection Works
Features and Installation of Soda Mattress
Construction Cost
Conclusion
Lao Peoples Democratic Republic
 Area:
236,800 sq km.
 Population: 5.6 million (2005).
 GNP or GDP: 491 US$ (2005)
 Capital city: Vientiane.
 Bordering:
China, Myanmar,
Thailand, Cambodia and Vietnam.
 Altitude:
90 - 1500 m above MSL
 Climate:
Tropical, monsoon.
 Temperature: 15C to 38C
Mekong River

The world’s twelfth longest river, length
of mainstream 4,825 km, runs through
the Lao territory with a length of 1,865
km.

The tenth largest in terms of annual flow
with total drainage area 795,000 sq km.

Runs through six countries: China,
Myanmar, Lao PDR, Thailand, Cambodia
and Vietnam.
169
168
Water Level (m, MSL)
167
166
Max.
Mean
Min.
2002
2003
165
164
163
162
161
160
159
158
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Month
Monthly Average Water Level at KM4 in Vientiane (1992-2001)
Water Level of Mekong River
Dec
Mechanism of bank erosion
• Due to scouring at foot of riverbed
(Most of the eroded vertical riverbank cliffs are of this type)Due to
•
•
•
lowering river water level
Due to slope failure
Severely eroded riverbanks form Vertical Cliffs mostly.
Damage by the erosion extends to many facilities (such
as road, houses, oil bases, factories, electric cables).
Design Philosophy of Riverbank
Protection Work
• Using local construction material as
much as possible.
• Using manpower of Lao P.D.R. as much
as possible.
• Construction and maintenance work can
be done by people of Lao P.D.R. as much
as possible.
• To pay attention to keep riverine
environment
Japanese Traditional River Works
• Japanese traditional method of river
works are suitable for Mekong River
around Vientiane City, those are ;
– “SODA” Mattress esp. for foot
protection works
– Cobble-Stone with Willow Branches
Work
– Wooden Pile Dike Groyne Work
WHAT IS “SODA” ?
“SODA” IS BRANCHES OF BRUSH WOOD CUT FROM
MISCELLANEOUS SMALL TREES IN FIELDS AND FORESTS
• MAY TIOU NAM,
MAY POHOU,
MAY PAO,
MAY MOUK,
etc.
STRUCTURE OF SODA MATTRESS
TREES WITH STRENGTH
AND TENACITY
FOR HURDLE WORK:
FLEXISIBILITY
Foot Protection Work
- Assembling and installation of Soda Mattress
1) Preparation of
Soda bundles
4) Flooring ‘SikiSoda’ work
7) Connecting Soda mattresses
by manpower
2) Making ‘Rensai’
(connection beam
made of fascine)
5) Piling short wooden piles to
combine upper and lower lattice
structures and for hurdling work
8) Row of connected mattresses
3) Fixing node of
Rensai lattice
6) Placing floating Soda mattress
at the planned position by boat
Riverbank Protection Works Activities
Location of Material Collection Sites
Laksamsip
Danxi
Ban Sakai
(50 km from
city center)
Nong Teng
Kao Liao
: Quarry site
Sibounheuang
Donloun
Nongpen
Xiangkhouan
Wat Chom Cheng
: Fascine material site
: Stockyard
Ban Dongphosi
2 km
2 km
: Borrow site of sand,
gravel and laterite
Features of SODA Mattress
• Flexible and Durable in water
• Porous for good habitat of aquatic life
• Suitable to sandy riverbed as foot
protection
• Effective against sand suction
• Mainly adaptable to mild slope river of
less than 1/2000.
• Setting condition: Below low water level
Plan
Total Length=156 m
Typical Cross Section
Slope Protection Work
(Cobble stone with willow branch work)
Foundation Work
(Log Hurdle work)
Foot Protection Work
(Soda mattress work:
23 sheets)
Average Construction Cost
Construction Method
1.
Conventional Gabion Works implemented around Vientiane City
2.
Work Types proposed in the Master Plan
(1) Riprap groyne work (L=50m, interval=150m)
(2) 1) Cobble stone with willow branch work covering whole bank,
2) stone foundation and 3) soda mattress
(3) 1) Cobble stone with willow branch work covering lower bank, 2)
log hurdle work and 3) soda mattress
3.
Average Cost
(US$/meter)
2,000
190
1,300
700
JICA Pilot Works (Reference)
(1) Ban Dongphosi Site
1,690
(2) Wat Chom Cheng Site
200
(3) Sibounheuang Site
810
Continuous Monitoring
• The Climate in Laos is very much different from that in Japan
(especially very long dry season in Laos).
• It is essential to monitor the completed works at least 5 years
– to verify the appropriateness of Japanese method such as the effect of
protection, growth of vegetation, sedimentation
– to find the issues to be improved for localization.
Before construction (Oct. 2002)
January 2004
Pilot Work at Ban Dongphosi (completed in May 2003)
March 2005
June 2005
Conclusion
- Importance of a appropriate technology, the project has
introduced the Japanese traditional methods on the
riverbank protection (particularly Soda Mattress Method)
instead of high technology.
- One of the characteristics of the method is low cost, it is
easy to maintain by local people and can use of existing
material, it is suitable for developing country like Lao PDR.
- Therefore, the appropriate techniques is very effective to
make counterpart agencies to aware and strengthen
partnership with relevant organization and local people to
take the ownership.