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 5 th World Water Forum, Istanbul, Turkey 16 – 22 March 2009

Contents: Contents: 1) Introduction (Background of Lao PDR and Mekong River) 1) Introduction (Background of Lao PDR and Mekong River) 2) The Condition in the Activity Area 2) The Condition in the Activity Area 3) Design of Riverbank Protection Works 3) Design of Riverbank Protection Works 4) Features and Installation of Soda Mattress 4) Features and Installation of Soda Mattress 5) Construction Cost 5) Construction Cost 6) Conclusion 6) Conclusion

Lao Peoples Democratic Republic Lao Peoples Democratic Republic  Area: 236,800 sq km.  Area: 236,800 sq km.  Population:5.6 million (2005).  Population:5.6 million (2005).  GNP or GDP:491 US$ (2005)  GNP or GDP:491 US$ (2005)  Capital city:Vientiane.  Capital city:Vientiane.  Bordering:China, Myanmar,  Bordering:China, Myanmar, Thailand, Cambodia and Vietnam. Thailand, Cambodia and Vietnam.  Altitude: m above MSL  Altitude: m above MSL  Climate: Tropical, monsoon.  Climate: Tropical, monsoon.  Temperature: 15  C to 38  C  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.

Water Level of Mekong River

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 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 Due to slope failure Severely eroded riverbanks form Vertical Cliffs mostly. Severely eroded riverbanks form Vertical Cliffs mostly. Damage by the erosion extends to many facilities (such as road, houses, oil bases, factories, electric cables). 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 local construction material as much as possible. Using manpower of Lao P.D.R. 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. 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 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 ; 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” ? MAY TIOU NAM, MAY TIOU NAM, MAY POHOU, MAY PAO, MAY MOUK, etc. TREES WITH STRENGTH AND TENACITY FOR HURDLE WORK: FOR HURDLE WORK: FLEXISIBILITY FLEXISIBILITY “SODA” IS BRANCHES OF BRUSH WOOD CUT FROM MISCELLANEOUS SMALL TREES IN FIELDS AND FORESTS STRUCTURE OF SODA MATTRESS

1) Preparation of Soda bundles 2) Making ‘Rensai’ (connection beam made of fascine) 3) Fixing node of Rensai lattice Foot Protection Work - Assembling and installation of Soda Mattress 4) Flooring ‘Siki- Soda’ work 5) Piling short wooden piles to combine upper and lower lattice structures and for hurdling work 6) Placing floating Soda mattress at the planned position by boat 7) Connecting Soda mattresses by manpower 8) Row of connected mattresses

Danxi Laksamsip Nongpen Kao Liao Ban Dongphosi Ban Sakai (50 km from city center) Nong Teng Donloun : Quarry site : Fascine material site : Stockyard 2 km Location of Material Collection Sites 2 km Xiangkhouan : Borrow site of sand, gravel and laterite Wat Chom Cheng Sibounheuang Riverbank Protection Works Activities

Features of SODA Mattress Flexible and Durable in water Flexible and Durable in water Porous for good habitat of aquatic life Porous for good habitat of aquatic life Suitable to sandy riverbed as foot protection Suitable to sandy riverbed as foot protection Effective against sand suction Effective against sand suction Mainly adaptable to mild slope river of less than 1/2000. Mainly adaptable to mild slope river of less than 1/2000. Setting condition: Below low water level Setting condition: Below low water level

Typical Cross Section Plan Foundation Work (Log Hurdle work) Foot Protection Work (Soda mattress work: 23 sheets) Slope Protection Work (Cobble stone with willow branch work) Total Length=156 m

Average Construction Cost Construction Method Average Cost (US$/meter) 1. Conventional Gabion Works implemented around Vientiane City 2, Work Types proposed in the Master Plan (1) (1) Riprap groyne work (L=50m, interval=150m) 190 (2) 1) Cobble stone with willow branch work covering whole bank, 2) stone foundation and 3) soda mattress 1,300 (3) 1) Cobble stone with willow branch work covering lower bank, 2) log hurdle work and 3) soda mattress JICA Pilot Works (Reference) (1) Ban Dongphosi Site 1,690 (2) Wat Chom Cheng Site 200 (3) Sibounheuang Site 810

Before construction (Oct. 2002) January 2004 June 2005 March 2005 Pilot Work at Ban Dongphosi (completed in May 2003) Continuous Monitoring The Climate in Laos is very much different from that in Japan (especially very long dry season in Laos). 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 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.

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. - 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. - 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. - 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.

Length of Existing Bank Protection Works Construction in Vientiane Capital ( ): 5.2km Construction in Vientiane Capital ( ): 5.2km –Donor’s financial assistance: 3,240 m (63%) –National budget: 1,950 m (37%)

Riverbank condition Severely eroded bank form vertical cliffs mostly. Severely eroded bank form vertical cliffs mostly. Geology: sandy gravel layer covered with 6-8 m clayey soil. These are not consolidated and easily be eroded. Geology: sandy gravel layer covered with 6-8 m clayey soil. These are not consolidated and easily be eroded. Bank protection works commonly used are gabion works. The existing works are effective, though some works are damaged due to poor foot protection. Bank protection works commonly used are gabion works. The existing works are effective, though some works are damaged due to poor foot protection.

Slope Protection Works - Cobble Stone with Willow Branch Works - 1) Embankment work by bulldozer 2) Compaction of slope and Kogui piling 3) Hurdle work using ‘Taisya’ and Siki-soda placing 4) Sand and gravel placing in Taisya hurdle (T=20cm) 5) Cobble placing by manpower 6) Finishing work: adjusting cobble by manpower