I want to begin this time with some rather cheering news about river levee engineering. Two months after the 2019 GEOASIA General Meeting, on October 12 and 13 last year, Typhoon 19 (Typhoon Hagibis) caused extensive flooding, notably along the Chikuma River in Nagano and the Abukuma River in Fukushima. In Japan as a whole, levee failures occurred in 142 places, with river overflow as the primary cause in 86% of these. The resulting damage was horrific, and included the flooding of some 35,000 hectares of land．In the aftermath of the Kinugawa River levee failures of 2015, there had already been some talk of the need for“structural measures of crisis management type,”but in the end, all that was painfully apparent once more was the inadequacy of the solutions offered．
　Accordingly, in February 2020, the Water and Disaster Management Bureau in the Ministry of Land and Transport decided to launch a discussion of technical issues concerning river levees, taking account of the damage from Typhoon 19. After three rounds of deliberation, the final report was published in August. Hearings were also conducted among civil engineers in the private sector to obtain a broad spread of views on developments in soil reinforcement methods from outside the discussion group. I cannot pass on here without pausing to recall the esteem I felt for civil engineers such as the ones from the Japanese Technical Association for Steel Pipe Piles and Steel Sheet Piles who saw this as their awaited chance to present already available Research and Development findings. They rose actively to the occasion.
　In the report, there is no explicit talk of “abandoning the earth embankment principle,” but there is a clear recognition that merely conventional “structural measures of crisis management type” of paved crowns and rear toe reinforcements have their limits. What is needed is a more“tenaciously effective”range of design, involving reinforcement techniques that can be classed roughly into three types of ① surface cladding ② section widening, and ③ limited local autonomy (the adding of steel pipes, steel sheets or soil-cement walls, etc.). The intention is to promote R & D in these several sorts of levee reinforcement methods, while also extending collaboration between public research institutes, private bodies and universities. According to a senior colleague who ventured out in the Coronavirus pandemic to inspect reconstruction site conditions in the Hoyasu district alongside the Chikuma River, the actions now being taken went beyond the “structural measures of crisis management type” of the past. The new levee was being built with a continuous covering of blocks along its rear wall to withstand overflow. Even in some cases where “non-structural” measures are enough to save lives, the loss of a home or of possessions may be enough to make some people lose the will to live. We see this happening year after year. I am repeating from last year, but the crux of disaster prevention lies in hard response measures. Civil engineers stand in the forefront of the effort to see that they are taken.
　No sooner do we reach this new departure point, but we find our attention being diverted again by another dire emergency placing a different question mark on the social responsibility of civil engineers. In the morning edition of the Tokyo Shinbun Newspaper of June 7, vying for attention with Tokyo virus alert,” another article turned up with the headlines: “2027 Linear Opening heading for postponement” and “Talks in Shizuoka: Governor to withhold construction approval.” Due to fears in Shizuoka that changes in the subsurface geology of the Southern Alps could provoke water catchment loss in the Oi River system, a likely delay was reported in the planned 2027 opening of the first section of the “Linear Central Shinkansen” between Shinagawa (Tokyo) and Nagoya. The gist of articles in the Asahi and other leading newspapers was the same: “Shizuoka to blame for Linear delay.”
　Between now and 2027, there are only 7 years to go. Even after completing the tunnel, there will be a spate of other tasks waiting. First, the installation of the driving equipment. This corresponds to the rails and concrete slabs of a conventional track, except that for a maglev it involves the building of four shielded vertical walls, made of concrete and fitted with magnetic coils to supply alternating forward impulsions from both outer sides of the advancing train. After that, more time is needed for driver training, and for evacuation drills in case of an accident. Assuming that all of this can be completed in two to three years, that allows just four or five years for boring the tunnels. For the 10.7 km Hida Tunnel, a boring time initially estimated at 5 or 6 years finally ran up to more than a decade．While the leading dailies are entitled to tune up for their welcoming of the Linear Shinkansen, it is another matter whether their thinking ought to be quite so set on the 2027 completion target being met.
　Leaving aside questions of keeping to schedule, is this tunneling project feasible in the first place? Granting that the 15 km section under the main ridge of the Ina Mountains goes through quartz and should be easy drilling, the 25 km Akaishi Mountains stretch under the South Alps will be a different story. Geologically, the Akaishi Mountains belong to the Outer Zone of Southwestern Japan and make up part of the Shimanto Belt accretionary wedge, mainly formed between around 100 and 20 million years ago. Within this accretionary wedge, the Akaishi Mountains are known as strata of extremely heterogeneous material known as mélange, highly prone to structural shearing, in which rock fragments of every variety and scale, some pelagic, others terrestrial in origin, occur mixed together in a mud base. In addition to this, other vast changes 20 to 15 million years ago (enlargement of the Japan Sea, formation and curving of the Japanese islands, collisions with the Izu arc of islands) led to the creation of the north-south Itoigawa-Shizuoka Tectonic Line, which was then drastically transformed by being pressed on both sides by the east-west Median Tectonic Line until its initial pattern became overprinted with more complex internal lines. This explains how the Akaishi Mountains came to be the most intensely transformed part of the Shimanto Belt accretionary wedge. At the risk of repetition, I wish to reiterate that a mountain massif is quite different from a continuous mass of mountain. In an extreme case, the massif may turn out to be a mélange mountain mass, supported deep underground by accumulated water held in under enormous pressure. Finally, the Akaishi Mountains are a rising range. This has clearly been so for the past million years, but even in the past century, areas around the main ridges have been showing one of the world’s fastest rates of altitude gain: up to 4 mm annually. Even today, the Akaishi Mountains are a place of vigorous change in the earth’s crust. The tunnels, for the most part, run deep underground. The maximum distance below the surface is 1400 m. It is a basic practice in tunnel boring that no further drilling advance be made until the water pressure at the work face has been brought down sufficiently (to almost zero). For that reason, water extraction is unavoidable. But can the recent method of injecting a fracking fluid be trusted at an ultrahigh-pressure work site like this? And even if the tunneling goes well and we gradually learn to read the conditions in the surrounding environment, how is that to be used as the basis for a technical survey of the tunnel’s structural safety, durability, and earthquake stability, and who is to be entrusted with such surveys? Technical details like these have not yet been supplied at all to civil engineering experts outside of the project. Nothing is published. Many experts have not even viewed the diagrams showing the section area of the tunnels involved (100 m2class).
　We have already seen, there is precious little understanding in any of the newspapers of what civil engineering technology is about. As none of us engineers has had any experience either in tunneling deep under the Southern Alps, we should frankly admit as much to the media. And in all consequence, we should then be ready to say openly: “We do not have the confidence to tell you that we can bore a tunnel in a way that requires zero input of water from the Oi River System and will not lead to the loss of one waterdrop from the Fuji or Tenryu Rivers.” We cannot go for solutions to the Northern or Central Alps either. If we do something that leads to the drying up of the water-blessed Southern Alps, we will simply have gained nothing and lost everything.
　When a private corporation comes up with a vision for a megalopolis of 650,000 people, all carefully matching the “super-megaregion” concept of the current government, how is it that we find not a single newspaper prepared to publicize this vision and invite public views on the pros and cons of a national land use reform to allow the transit of a vast flow of people both ways on this Linear axis, at a cost in electricity said to be no more than the outlay for one nuclear reactor? I fail to understand the reason for this. At a juncture like this, we civil engineers are the only ones in Japan qualified to say right out, “The work really is difficult. Let’s stop a while here, to pause and take stock.” The Coronavirus emergency provides us with a good opportunity for doing this, I feel. And if at the end it seems that a detour from Shinagawa via Kofu works best, well, that’s not bad, either. We can do that. We’ll lend you a hand!

Akira Asaoka
Senior research advisor, the Association for the Development of Earthquake Prediction (reg. foundation);
Emeritus professor, Nagoya University