Embankment risk lurking in residential areas January 13 21:08
What if our house suddenly collapsed under our feet?
A residential area that was once artificially created.
Recently, it has become clear that the risk of collapse is lurking.
However, little progress has been made.
(NHK special coverage group)
Mother and grandmother who disappeared in the earth and sand
The gatepost and nameplate still remain.
Twenty-eight years ago, the January 17, 1995 earthquake engulfed houses in the Inchon district of Nishinomiya, Hyogo Prefecture.
Junichi Nakamura (57 years old), a doctor, lost his mother Yoko (57 years old at that time) and his grandmother Aguri Mizumoto (83 years old at that time) who lived in this house.
After the strong tremors of the earthquake, Mr. Nakamura, who was working at a hospital in Osaka, was worried about his parents' home that could not be reached despite calling many times, so he drove to the Incheon area.
Mr. Nakamura:
“Well, I thought he was still alive, but when I drove up and crossed the last bridge, I saw a lump of dirt.”
A large amount of earth and sand jumped into Mr. Nakamura's eyes.
My parents' house was swallowed up by the earth and sand, and I couldn't see it.
It was the next night when my mother and grandmother were found in the sand.
Mr. Nakamura:
“They slept in the dirt for about two days, so if I touched them, my body would feel like ice.
Mr. Nakamura wrote the death certificates for the two by himself, borrowed sewing needles and threads, and sewed up the disfigured face of his mother, Yoko.
It was the last filial piety to the two people who raised me.
Mr. Nakamura:
“Until the earthquake, no one had thought that a landslide would occur. The house to return to would disappear in an instant. It was a sense of loss."
In this district, 13 houses, including Mr. Nakamura's parents' house, were damaged, and a total of 34 people died.
The cause was "embankment"
The landslide that struck Mr. Nakamura's parents' house was caused by the collapse of the slope of the reclaimed land on the opposite side of the river.
It collapsed 100 meters wide and 15 meters deep, and a large amount of earth and sand suddenly attacked.
Subsequent investigations revealed that the collapsed area was originally a valley, and that it was an embankment created in the 1950s in order to build a water purification plant.
Because it was originally a valley, underground water easily gathers and accumulates moisture, increasing its weight.
It is believed that the strong shaking from the earthquake loosened the ground and caused the embankment to collapse.
Increasing embankments Repeated damage
In fact, there are a lot of such "filling grounds" all over the country.
The period of high economic growth in the latter half of the 1950s.
Development spread to the suburbs when there was a shortage of housing land due to the rising demand for housing due to rapid economic growth.
"Valley-filling type embankment" that fills the places that were originally valleys and streams with earth and sand.
"Walling type embankment" that piles up earth and sand on a sloping land and attaches a retaining wall.
Flat land was made here and there, and a dream home was built.
At that time, it was thought that the embankment would become stronger and stronger over time as pressure from above was applied, so the need for management was not fully recognized.
After the Great Hanshin-Awaji Earthquake in 1995, the embankments that spread in this way suffered damage in successive earthquakes, such as the Niigata Prefecture Chuetsu Earthquake (2004), the Great East Japan Earthquake (2011), and the Kumamoto Earthquake (2016).
Even now, embankments that could collapse at any time are lying dormant all over the country.
Can't even start a risk study?
In 2006, the government finally started taking full-scale countermeasures.
We asked local governments to search for embankment land of a certain size or larger and inform residents of the area.
In response to this, local governments began to conduct surveys, and those municipalities with large-scale embankment land development sites are now releasing large-scale embankment land land maps.
There are 51,167 large-scale embankment sites nationwide (as of March 2022).
However, not all landfills are in imminent danger of collapse.
The national government is requesting local governments to carry out "risk assessments" by conducting field surveys and calculating the ease of collapse of large-scale embankment sites that have been announced.
This is to expose the dangerous embankment and proceed with countermeasure construction.
However, when NHK conducted interviews with prefectural capitals and ordinance-designated cities nationwide, it was found that about 60% of them had not started a survey for risk assessment.
Despite the fact that more than 15 years have passed since the national government embarked on full-scale measures, more than half of the local governments have not even started a survey.
* Details of the questionnaire to local governments are posted at the end of the article.
“There are few local governments that want to take the initiative.”
Why isn't even a risk survey at the pre-construction stage progressing?
A local government official responded to the interview anonymously.
In this municipality, among the large-scale embankment redevelopment sites, there is one redevelopment site that is particularly likely to collapse and needs to be given the highest priority for risk assessment.
However, this fact has not been communicated to the residents and no investigation has been conducted.
The reason is said to be "high cost" and "difficulty to get the understanding of residents".
According to a survey conducted by NHK this time, more than 70% of local governments cited those two hurdles for countermeasures.
In this municipality that responded to the interview, if the risk assessment determines that "immediate construction is necessary", the cost may reach 100 million units for the entire area.
Although there is a national subsidy system, the burden on local governments is not small.
In the first place, since residential land is an individual property, it is the principle that the owner promotes measures.
There is a possibility that there will be voices opposing the use of tax money for countermeasure construction.
On the other hand, even if the residents are asked to bear the cost, the cost may reach several million yen per house, and it is difficult to get the approval of "I can't afford to pay such an amount".
According to the Ministry of Land, Infrastructure, Transport and Tourism, there are only three cases in which countermeasures have been taken in advance nationwide, all of which were fully funded by public funds.
As a general rule, there have been no cases where the owner has also paid the cost.
A local government official who responded to the interview said,
"Even if we ask residents to bear the construction costs, it is difficult to obtain their cooperation, and local governments are financially tight and unable to do so. I don't think there are many local governments that want to do it."
In this municipality, too, the "Large-Scale Embankment Redevelopment Area Map" is open to the public on the Internet.
However, there is little interest from residents, he said.
Here is what he says about it:
A local government official who responded to the interview said,
"Even though the map has been made public, there have been no inquiries from residents, and no one has noticed the embankments. That's honestly a relief."
Even local governments that have a policy of ``covering the costs'' in order to expedite safety measures are facing difficulties.
In fiscal 2023, Utsunomiya City plans to carry out countermeasure construction for three embankment sites that are at risk of collapsing due to shaking equivalent to a seismic intensity of 5 lower.
The total cost for the three sites was expected to be more than 1 billion yen.
However, the contractor who conducted a detailed survey for the construction told me that the strength of the ground was lower than I had expected, and that countermeasures would cost eight times as much as I had originally expected.
Even if the construction is changed to another method, the cost is expected to increase significantly, and the city is considering using "municipal bonds", which are debts.
Kenichi Kobayashi, Utsunomiya City Finance Division Manager
"There is no doubt that the larger the amount of borrowing, the more difficult it will be to repay in the future, so it is impossible to predict what kind of impact this burden will have."
"Hidden embankment" hidden under your feet
What makes the embankment problem even more complicated is the presence of embankments, which can be called “hidden embankments”.
Only large-scale embankments are listed on the large-scale embankment reclaimed land maps published by local governments.
However, there are also many embankments as small as a few houses.
This time, NHK, with the cooperation of a major survey company, verified how much embankment there is in an area in the Tokyo metropolitan area that has not been made public.
The area that was examined was about 4 kilometers long and 3 kilometers wide, where about 500,000 people live.
For verification, we use current and pre-war topographic maps.
On the current topographic map, areas with dark colors are valleys, and areas with whitish colors are flatlands.
On the pre-war topographic map, the area shown in blue was a valley.
If you overlay the two maps, you can see that some of the valleys on the old topographic maps are now flat.
These places may be places where valleys have been filled with embankments.
We conducted verification while correcting survey errors in old topographic maps, and actually walked around the site to investigate whether there were any traces of embankments.
The result.
Green indicates 21 large-scale embankment sites announced by local governments.
Areas in yellow are areas where it was found that there is a high possibility of embankment in this survey.
A total of 235 locations were visited.
Mr. Tatsuro Chiba, Asia Air Survey, who conducted the survey:
"There were more than I had imagined at first. There were quite a few small-scale gardens. It's important."
There are embankment land all over the country, and it is not realistic for local governments to grasp all of them and take countermeasures.
It is also dangerous to think that "my home is safe" based only on publicly available information.
Does the real estate company have to explain?
Locating embankments is not easy.
When we purchase a house, there is a procedure called "explanation of important matters" by a real estate company.
This is a procedure based on the Building Lots and Buildings Transaction Business Act (commonly known as the Building Construction Business Act), in which the seller informs the purchaser of the environment surrounding the house, payment method, and other important factors that affect the purchase decision. information” in writing.
The risk of natural disasters is also included in the items to explain, for example, if the house is included in the "Sediment disaster warning area", you must be sure to tell the purchaser.
However, the mere embankment is not covered by the “explanation of important matters”.
The reason is that "not all embankments are dangerous (Ministry of Land, Infrastructure, Transport and Tourism)."
The current situation is that you have to check the history of the land yourself.
Lawyer Kazuhiro Yoshioka, who is familiar with damage to residential land, points out that it is necessary to have a system that will make many people interested in the history of the land, such as making it mandatory to explain important matters.
Attorney Yoshioka
: "There are many cases where people buy risky properties without knowing it. In order to raise the awareness of owners, the history of the land should be added to the explanation of important matters. There is a limit to how much we can investigate, so we should institutionalize the introduction of third-party perspectives, such as obligating surveys by ground quality judges who are experts in the ground.”
To protect the life and property of myself and my family
Since risk information is directly linked to asset value, it is unavoidable for local governments and others to be cautious about information disclosure.
However, we must avoid situations in which damage is caused without knowing the risks.
I felt that there was an urgent need to disclose solid information.
Buying a home is a once-in-a-lifetime purchase for many people.
When buying a house, more and more people are concerned about the earthquake resistance of the building.
To protect myself, my family, and my property.
Would you like to think about the ground under your feet again?
NHK Special
Reporter Gentoku Munakata Shinya Fujishima Taisuke Uchiyama Mariko Takeda
Director Takayuki Kintake Yuki Takuma Manako Mukai Tokuji Iesaka Hiroshi Murata
The site below summarizes whether the ground of your home is an embankment and how to check the risk if it is an embankment.
Is the ground of my house safe? How to check the risk of embankment
Municipality questionnaire details
The details of the survey conducted by NHK in prefectural capitals and ordinance-designated cities nationwide, such as the number of large-scale embankment land development sites and the status of detailed embankment surveys, are as follows.
The answer is the number of large-scale embankment development sites / the situation of embankment detailed investigation / issues (multiple answers).
▼Sapporo City 183 / Already started / “Resident understanding” “Difficult to anticipate countermeasures” “Others/maintenance after countermeasure construction is unclear”
“Residents who do not feel the importance of improving the safety of residential land due to their age Residents who are thinking of selling residential
land
cannot understand the burden of the cost of countermeasures, and it is difficult to reach a consensus.
”
Done/"Cost", "Low priority", "There are many and it takes time"
, "Survey alone costs tens of millions of yen per site, and the cost for all embankments is immeasurable."
▼Sendai City 750/Not started/"
Akita City 240/Started/Understanding of Residents, Cost, Insufficient Government Subsidy
▼
Yamagata City 6/Started/No Issues
▼Fukushima City 139 / Already started /
Opinions such as ``Understanding of residents,'' ``Cost,'' ``It will take a lot of time,'' and ``There will be no damage from the Great East Japan Earthquake, so there is no need for countermeasures,'' may make it difficult to reach agreement on countermeasures. There is a limit to monitoring the embankment of
▼Mito City 19/Not started (“Investigation not started” because it was determined that the stability of the embankment was secured)/“Cost” “Low priority” “Difficult to reach agreement”
▼Utsunomiya City 84/Started/“Cost” "Insufficient government subsidies" "There are many and it takes time"
"All surveys are extremely difficult in terms of finances and the number of staff. I would like the government to show a survey method that can grasp stability more cheaply and efficiently. ▼Maebashi City 30/Already started/
“
Understanding of residents”, “Cost”, “Difficult to anticipate countermeasures”
▼Saitama City 198/Completed/“Others/projects have already been completed”
▼Chiba City 672/Already started/“Residents” "Understanding" "Difficult to anticipate countermeasures" "There are many and it will take time" "There are
various
opinions on how much the government should intervene in measures for residential land owned by individuals."
/ Not started / “Cost” “Large number and time required”
▼Yokohama City 3271 / Started / “No issues”
▼ Kawasaki City 1093 / Completed / “Understanding of residents” “Cost” “Large number and time required”
▼ Sagamihara City 75/Already started/“Resident understanding,” “cost,” and “insufficient government subsidies”
▼Niigata City 0 *No answer as there is no large-scale embankment land
▼富山市 17／完了／「住民理解」
▼金沢市 97／未着手／「住民理解」「費用」「合意難しい」
▼福井市 110／未着手／「住民理解」「費用」「合意難しい」
「どこまで公費負担をすべきか意見が分かれ、かつ、受益者負担を求めても地権者は応じない可能性が高い」
▼甲府市 0 ※大規模盛土造成地なしのため未回答
▼長野市 4／未着手／「住民理解」「国の補助不十分」「対策見通し立てにくい」
▼岐阜市 97／未着手／「費用」「数が多く時間要する」
▼静岡市 42／未着手／「住民理解」「費用」「優先度低い」
▼浜松市 545／未着手／「住民理解」「費用」「数が多く時間要する」
▼名古屋市 635／着手済／「住民理解」「費用」「数が多く時間要する」
▼津市 118／未着手／「住民理解」「費用」「国の補助不十分」
▼大津市 113／未着手／「住民理解」「費用」「国の補助不十分」
「調査に入る時点で住民の不安をあおり、資産価値への影響が出る可能性がある」
▼京都市 245／完了／「住民理解」「優先度低い」「対策見通し立てにくい」
▼大阪市 0 ※大規模盛土造成地なしのため未回答
▼堺市 191／未着手（専門家の意見などを踏まえ「被害のおそれなし」と判断したため「調査未着手」）／「費用」「国の補助不十分」「数が多く時間要する」
▼神戸市 405／完了／「住民理解」「優先度低い」「数が多く時間要する」
▼奈良市 223／未着手／「住民理解」「国の補助不十分」
「数十年前に宅地造成された場所では高齢化が進んでいる。経済負担を伴う事業に協力が得られるかどうかという問題がある」
▼和歌山市 181／未着手／「住民理解」「国の補助不十分」「対策見通し立てにくい」
「土地所有者は当市の住民とは限らず、全員の所在を明らかにすることは困難」
▼鳥取市 22／着手済／「住民理解」「費用」「合意難しい」
▼松江市 39／未着手／「住民理解」「費用」「国の補助不十分」 ※現地確認の結果、変状がなかったため対策は「経過観察中」
▼岡山市 126／未着手／「住民理解」「費用」「対策見通し立てにくい」
▼広島市 333／未着手／「住民理解」「国の補助不十分」「数が多く時間要する」
▼山口市 47／未着手／「住民理解」「費用」「優先度低い」
「法的根拠がないため住民に断られた場合、事業が進まないと思われる」
▼徳島市 31／未着手／「住民理解」「費用」「優先度低い」
▼高松市 35／未着手／「住民理解」「費用」「その他・風評被害対策や費用負担の整理が必要」
▼松山市 57／未着手／「費用」「国の補助不十分」「数が多く時間要する」
▼高知市 388／未着手／「住民理解」「費用」「数が多く時間要する」
▼Fukuoka City 620/Not started/“Understanding of residents”, “Cost”, “Insufficient national subsidy”
▼Kitakyushu City 1697/Not started/“Understanding of residents”
▼Saga City 26/Not started/“Cost”, “Low priority” ``Difficult to reach an agreement''
``The survey is expected to cost a lot of money, and although government subsidies are available, it will be difficult to secure the budget''
▼Nagasaki City 323/Not yet started/Understanding of residents ``Cost'' ``Insufficient government assistance''
``The issue is how to promote seismic resistance of residential land on small and medium-sized embankment land that does not fall under countermeasure projects.
'
'
Started/“Understanding of residents”, “Cost”, “Difficult to anticipate countermeasures”
▼Miyazaki City 288/Not started/“Understanding of residents”, “Insufficient government assistance”, “Low priority”
▼Kagoshima City 991/Not started/“Cost” “Difficult to anticipate countermeasures” “There are many and it will take time”
▼ Naha City 112 / Not started / “Understanding of residents” “Cost” “Insufficient government subsidy”