The disastrous mudslide that hit the city of Atami on July 3 brought attention to the term “morido,” which has no real equivalent in English, though some people might use “landfill.” In some cases, morido does qualify as landfill, but as it literally means “added soil” it has a wide variety of applications. In the case of the Atami mudslide, the consensus now is that the disaster was caused by an accumulation of soil at the top of a ravine that came loose during torrential rains and rushed down the ravine toward the sea, destroying dozens of houses along the way. The soil in question was apparently deposited there by a real estate company more than ten years ago, though it hasn’t been clearly explained what the purpose of the soil was. Media reports say that the company submitted a “report” to local authorities saying that they planned to build housing on the land, which they owned at the time, but the local government never properly checked the progess of this plan. Neighbors, however, startled by the succession of dump trucks that constantly came through to deposit soil on the site, contacted the authorities, who then “warned” the real estate company that it might be breaking the law. The company never responded to the warning and, in any case, there is no indication that they ever really intended to build anything on the “added soil.” Local regulations only permit soil accumulation of up to 15 meters, but just prior to the disaster it is estimated that the mound was 50 meters deep. The volume of soil, rock, and what is deemed to be industrial waste that flowed down the ravine is estimated to be 56,000 cubic meters. 

Some anti-solar (i.e., pro-nuclear) elements have pointed to the subsequent owner of the land as being to blame for the mudslide, since they cleared trees above the already existing mound and installed a solar farm. For sure, the clear-cutting removed some of the area’s water-retention capability, thus contributing to the disaster, but the solar energy company did not create the morido, and whatever the drawbacks of so-called mega-solar installations in terms of environmental impact, it appears that the company was operating within the law. The real estate company, which has since gone out of business, has yet to explain what the purpose of the mound was, but circumstances seem to point to it being a place to simply dump refuse and excavated soil, probably from construction projects far away. The local residents, for instance, said that the dump trucks all had Yokohama license plates. And then, of course, the industrial waste mixed in with the mud. This sort of problem is becoming more prevalent as construction continues undeterred with a dwindling number of places approved for refuse landfill. We’ve written about this before and the measures some contractors go to in order to find places to get rid of soil and other junk. 

Another kind of morido is that which is used to fill in valleys or create terraces on the sides of inclines in order to create level land for residential or agricultural development. As with all situations where soil is deposited on existing land, drainage must be assured by laying pipes within the mound of soil and the soil itself must be manually compacted so that it will not come loose. Unfortunately, even these measures may not be enough, though from what we’ve learned the main problem with this kind of morido doesn’t come from excessive rain but rather from earthquakes, which can cause the soil to shift, or, if it contains lots of ground water, liquefy. This happened throughout residential subdivisions affected by the 311 earthquake. Consequently, when we were shopping for land in 2012-13, we consulted topographical maps of the areas we were interested in in order to find out if a particular property was the result of morido. If it was, then we avoided it. We also avoided low-lying properties because of Japan’s problem with typhoons and heavy rains. But, in any case, morido is more prevalent than you might think, and most of it is perfectly legal, though not necessarily safe. That said, media reports have also said that the kind of morido that caused the Atami disaster is also very prevalent, despite the fact that it is illegal, so we can probably expect more of this kind of catastrophe.