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Use of Japanese traditional river channel improvement methods in the Mekong River |
| Ichiro Morikawa, Director Shinanogawa River Office |
| Laos is located in the middle river basin of the Mekong and has an area of 240,000 km2, almost as large as Honshu (the main land of Japan with an area of 230,000 km2), and a population of approximately 5.2 million (Yokohama and Osaka have populations of 3.3 and 2.5 million, respectively). It is one of the least less developed countries. The former French colony achieved independence in 1953. The Lao People's Democratic Republic was established in 1975 after years of civil war. Laos became a socialist and devout Buddhist country. In 1986, the country changed its direction toward reform and renovation in step with the transition to a market economy in Vietnam under the slogan of "Doi Moi", or reconstruction. Still plagued by the aftereffects of the colonial rule and civil war, Laos is far behind other countries in terms of social infrastructure with a per-capita GDP (gross domestic product) of 300something dollars, approximately one-100th of Japan's. |
| I visited Laos for the first time in July 2002 for JICA's investigations. Someone likened the country to a "Japanese rural region 40 years before". I found paved roads only in central Vientiane, the capital, which were rugged. There was no railway services. The tallest building that I could see was an airport control tower completed with the aid from Japan. No outstanding industries were in operation. Beer was one of the local products with export potential. Newspapers were filled with reports on foreign aid. The local people were, however, gentle. I felt at rest and was moved by the sense of familiarity rather than being made aware of poverty. |
| The Mekong has a width of approximately 1 km and a bed slope of 1/10,000 near Vientiane. It has a maximum velocity of approximately 3 m/sec in the wet season and a mean velocity of less than 2 m/sec. It is characterized by a head of approximately 10 m between the wet and dry seasons. The riverbanks form cliffs with a height of a dozen meters during dry seasons. The city center of Vientiane, which is on a natural embankment, seems to have been subjected to the flooding of the Mekong once in dozens of years. People simply watched the flooding and relocated when the bank was eroded. Mr. Matsumoto who was sent to Laos as a JICA expert once reported that there was flood watching but no flood control and that no river improvement projects were implemented. |
| With the transition to reform and renovation, foreign aid from the West was resumed and river bank erosion control projects were launched. The existing revetments use gabions and mattresses because building stones are hardly available around Vientiane. High-cost gabions and mattresses were imported and the revetments collapsed in several years of construction in some places. It was then decided to adopt Japanese technology, especially traditional river improvement methods including fascine mattress construction. |
| The Ministry of Construction of Japan started the transfer of fascine mattress construction technology through Infrastructure Development Institute, Japan (IDI) in 1998. Fascine craftspeople in the Hokuriku area (north-central area of Japan) were sent to Laos who had continuously used fascine mattresses for river improvement, to investigate the local materials. Laotian engineers also visited the Shinano River and experienced the process from cutting sticks to assembling mattresses and burying them. The technology was transferred by means of gestures. Fascine mattresses were constructed in the Mekong on a trial basis during the 2000-2001 dry season. The trial construction made the local newspaper headline reflecting the great hope the Laotians laid on the project. |
| Year 2000 was the 400th anniversary of Japan-Netherlands relations, and various events were held throughout Japan in honor of J. de Rijke, a Dutch engineer who contributed to the modernization of Japan. J. de Rijke greatly helped Japan modernize through such projects as the diversion of the Kiso-sansen (three rivers), construction of the Yodogawa floodway, building of Osaka Port and sediment control projects in various locations. Fascine mattress construction was introduced to Japan by Dutch engineers including de Rijke and gradually applied in Japanese rivers through trial construction. I have a deep feeling about the plan for transferring traditional methods to Laos from Japan. |
| The JICA investigations started in 2002 following the surveys by IDI aim at the application of other traditional river channel improvement methods as well as fascine mattress construction. Effective ways for applying traditional Japanese river improvement methods to the Mekong with an annual head of 10 m, a sharp contrast to Japanese rivers, have yet to be identified through investigations. Investigations will be continued until March 2005. The objective is to transfer the trial and error process of test construction using as much local material as possible and subsequent monitoring, as a form of technology. The fascine mattress construction will be renewable and sustainable because it will use local material and be less costly and more friendly to the environment. The Laotians lay a great hope on the project creating local job opportunities. |
| Now I look at the situation in Japan. When the review of traditional river channel improvement methods was suggested in various locations, I honestly wondered why the methods that had been abandoned for some reasons should be adopted. There were cases where the cost exceeded the estimate because no sticks were available in the region. Reasons for hesitating the use of traditional methods abound with respect to the level of technology and work efficiency. More than ten years have passed since the distribution of a government circular encouraging nature-oriented river improvement in 1990. At present, gabion mattresses and environmentally friendly blocks are used in most cases. It is said that in the Edo era, each Han, or domain, developed its own river improvement methods in addition to a variety of methods used in areas under the direct jurisdiction of the Tokugawa Shogunate. In contrast to such diversity, the present methods are highly monotonous. Unlike the engineers who applied specific traditional methods suited for particular rivers, have the present engineers lost an eye for rivers? Technologies can actually be shared as long as they can be identified quantitatively based on numbers or models. An eye for rivers can be developed by applying traditional methods fit for respective rivers, a result of the accumulation of wisdom of our forerunners. |
| In the Hokuriku area, methods using sticks have been handed down since 1955 through the late 1960s while concrete and steel replaced them. Traditional methods have been improved and obsolete methods have been restored. In other areas, traditional methods have also been adopted for environmental reasons. It is my hope that a method will be found that uses the diverse natural characteristics of rivers by reviewing the traditional river channel improvement methods that were developed by trial and error in the region rather than applying them without modifications. |
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