by Dr. Yugo Ono
The Chitose River is a tributary of the Ishikari, the biggest river in Hokkaido, and the second longest river in Japan. The Ishikari had historically high floods in 1976 and ’81. Damages exceeded 22 billion yen, and most of the alluvial lowland–primarily used for farming–was inundated. In response, a government agency has proposed an expensive "engineering fix" that would harm wetlands, fisheries and river-related habitat.
The drainage area of Chitose river is low-lying, especially between Chitose city and Ebetsu, situated at the confluence with the Ishikari. During floods, the Chitose cannot flow easily to join the main stream of the Ishikari, because the water level of the Ishikari becomes as high as that of the Chitose. Furthermore, because most of the Chitose’s alluvial lowland is topographically lower than the water level of the Chitose during the flood, the area suffers inundation, caused by the rain water which cannot drain to the river.
Just after the 1981 flood, the Hokkaido Development Agency planned the "Chitose Diversion Channel Project." This project proposes digging a new channel 38km long and 200-400m wide, between the middle reach of the Chitose south to the Pacific coast; and construction of three gates to control the river’s flow. During flood conditions, gates will force the Chitose’s waters to flow down into the diversion channel to the Pacific Ocean, thus reversing the river’s natural direction. The channel project – the biggest river development scheme now proposed in Japan – would cost 480 billion yen (US$48 billion) and take 20 years to complete.
The channel was first proposed to the River Management Advisory Council of the Ministry of Construction in 1982 by the Hokkaido Development Agency. The council decided very rapidly to support the project, despite the fact that there had been no representation in the deliberations by local governments, citizens, NGOs, or specialists in ecology, economy or other social sciences. A strong movement against the project arose soon after it was unexpectedly presented to the public.
The movement against the diversion channel involves not only local people, but also many environmental NGOs. The movement grew and became stronger, helping to postpone the project for more than 13 years. Despite growing opposition to the project, it continues to receive a budget of more than two billion yen every year. The money is for obtaining land for the diversion channel, but public outcry has prevented the agency from actually purchasing any land. As a result, the Hokkaido Development Agency has used this enormous budget only for research and propaganda supporting the project. Beautifully printed color explanation booklets were distributed to the inhabitants of the drainage area of the Chitose, to help convince them that this project is the only way to avoid future floods.
Less Destructive Alternatives
Japanese NGOs have proposed many alternatives to this destructive project, including widening the channel of the Ishikari, constructing a stream separating embankments between the Ishikari and the Chitose at the junction, and enlarging flood retaining ponds in the Chitose floodplain. Although they do not provide the same level of flood control as the Chitose Diversion Channel, these alternatives have many positive aspects. Unlike the diversion channel, they have minimal environmental impacts, especially to Lake Utonai, the fourth site in Japan to be designated under the Ramsar Convention as a wetlands of international importance.
Lake Utonai is located very near the planned route of the Chitose Diversion Channel, and would suffer damaging hydrological changes if the channel were built. Since the Chitose Diversion Channel will cut deeply into the ground surface, all ground water that nourishes Lake Utonai would seep to the diversion channel instead. This ground water comes to the surface in a small valley dissecting the volcanic plateau, through many beautiful springs. The spring waters join together and soon become the Bibi River which flow into the Lake Utonai. The construction of the Chitose Diversion Channel would cut completely the ground water flow which nourishes many springs of the Bibi and Lake Utonai.
On the occasion of the fifth Ramsar Conference at Kushiro, held in Hokkaido in 1993, the government of Japan promised that it would take steps to protect Lake Utonai. However, even after three years, the Hokkaido Development Agency has not presented any from the problems caused by the diversion channel. The agency proposed only unrealistic means to conserve the ground water. Their plan involves constructing an 12km-long underground wall to block the ground water flowing from the hills to the Diversion Channel, and a pumping system that would need to work eternally, 24-hours a day, to pump groundwater up and over the channel to replenish the water of the Bibi River.
The channel will affect not only the Ramsar site, but also the offshore environment. By directing flood waters containing silt and suspended material to the Pacific Ocean rather than to the river’s floodplain, the channel could cause serious damage to aquaculture (scallops and other mollusks) and off-shore fishing in the region. Following strong protests by fishers’ associations, the Governor of Hokkaido Prefecture declared that he would not approve the start of construction of the Chitose Diversion Channel, unless Hokkaido Development Agency presents effective measures to avoid such damage to fisheries.
But as with the problem of ground water flows, the Hokkaido Development Agency has not yet presented any effective proposal to solve this problem. The situation clearly demonstrates that it is impossible, with present technology, to avoid fisheries damage caused by flood-water flushing. But the Hokkaido Development Agency still insists on the construction of the Chitose Diversion Channel, and is trying to persuade the fishermen by giving them money.
Why does the Hokkaido Development Agency insists on pursuing this project? The answer lies in part because this project has already been approved by the Ministry of Construction. In Japan, once a project has been approved and authorized by the Ministry, it is very difficult to stop or change it. This damaging and illogical tradition has already been revealed in the case of the Nagara River Estuary Dam and many other dams in Japan.
The only argument for the Chitose Diversion Channel over other alternatives is based on the supposed value of standard flood discharge of the Ishikari, which was determined secretly by the River Management Advisory Council in 1982. In that committee, the Hokkaido Development Agency proposed 18,000 m3/sec for the standard flood discharge amount. But this value is much higher than the peak discharge experienced even in the two historical floods of 1976 and 1981. The peak discharge in the 1976 flood was 7,700m3 after three days’ continuous rain, and 12,000m3 in 1981, after three days’ rain.
After increased demands for information disclosure, the Hokkaido Development Agency recently revealed the process by which they determined this high value. A computer simulation produced seven different values, ranging from 12,000 m3/sec to 18,000 m3/sec. They chose 18,000 m3/sec, merely because it is the highest value. This demonstrated clearly that they never checked any environmental and social impacts resulting from the choice of this high value for the standard flood discharge. If the value was a mere 1,000 m3/sec less than the highest simulation value, the Chitose Diversion Channel becomes unnecessary, since it evacuates only a flood discharge of 1,000 m3/sec to the Pacific Ocean.
It is true that the drainage area of the lower reach of the Chitose needs flood management. But even if it can reduce flood damage from the Chitose better than other alternatives, the Chitose Diversion Channel is not a good plan. It causes too many serious environmental problems, which cannot be solved with present technology. But most importantly, it was determined in secret, completely hidden from the local people. This is unjustifiable for such a large public works project.
Fortunately, the construction of this project has been stopped for now by the opposition movement, which continues in its efforts to stop the channel from being built. The movement is working to change the system of how river public works projects are approved in Japan.
Yugo Ono is a professor at the Graduate School of Environmental Earth Science at Hokkaido University.
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