The , was an earth-fill

embankment dam An embankment dam is a large artificial dam. It is typically created by the placement and compaction of a complex semi-plastic mound of various compositions of soil or rock. It has a semi-pervious waterproof natural covering for its surface ...

in Sukagawa City,

Fukushima Prefecture is a Prefectures of Japan, prefecture of Japan located in the Tōhoku region of Honshu. Fukushima Prefecture has a population of 1,771,100 () and has a geographic area of . Fukushima Prefecture borders Miyagi Prefecture and Yamagata Prefecture ...

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

. It was established on the Ebana River, a tributary of the

Abukuma River The , with a length of , is the second longest river in the Tōhoku region of Japan and the 6th longest river in the country. It is designated as a Classification of rivers in Japan, Class A river. It runs through Fukushima Prefecture and Miyagi P ...

, west of the city office of Sukagawa City. Construction on the dam commenced in 1937 and it was completed in 1949 after construction was halted due to

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

. The dam's primary purpose was irrigation. It failed on 11 March 2011 after the

2011 Tōhoku earthquake Eleven or 11 may refer to: *11 (number) * One of the years 11 BC, AD 11, 1911, 2011 Literature * ''Eleven'' (novel), a 2006 novel by British author David Llewellyn *''Eleven'', a 1970 collection of short stories by Patricia Highsmith *''Eleven'' ...

Failure

On 11 March 2011, the dam failed 20 to 25 minutes after the Tōhoku earthquake as the nearly full reservoir overtopped the dam's crest. Locals reported hearing a loud burst before seeing a flood. The flood washed away five houses while damaging others, disabling a bridge and blocked roads with debris. Eight people were missing and four bodies were discovered after searches began at dawn. The failure of the earth-fill dam at the Fujinuma reservoir in Fukushima prefecture resulted in eight deaths in a village. On 12 March, 252 dams were inspected and seven dams were found to be damaged. Six embankment dams had shallow cracking on their crests and the reservoir at one concrete gravity dam had a slight

slope failure Slope stability refers to the condition of inclined soil or rock slopes to withstand or undergo movement; the opposite condition is called slope instability or slope failure. The stability condition of slopes is a subject of study and research i ...

. Four dams, including the Fujinuma, were inaccessible and could not be inspected. A preliminary survey of the dam and facilities conducted in April 2011 noted that the breach occurred at the tallest section of the dam. Within the dam's fill, there were layers of organic residual soil that in one area contained a tree stump. The residual soil was used as foundation and in layers as well – above

alluvium Alluvium (, ) is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluvium is also sometimes called alluvial deposit. Alluvium is ...

. This suggests that the foundation for the dam was not prepared properly, according to the study. In addition, the reservoir's auxiliary dam suffered a severe

on its upstream face while areas around the rim of the reservoir had mild slope failures or distress. It could not be confirmed whether the earthquake or a quick draining of the reservoir was the cause of this.

Design

The dam was a tall and long embankment-type with a structural volume of and crest width of . About to the south, there is an auxiliary dam with a height of about and length of approximately . The auxiliary dam helped the reservoir maintain it designed levels given the topography wouldn't allow the single main dam to do so. The dam sat at the head of a drainage area and its

reservoir A reservoir (; ) is an enlarged lake behind a dam, usually built to water storage, store fresh water, often doubling for hydroelectric power generation. Reservoirs are created by controlling a watercourse that drains an existing body of wa ...

had a capacity of . The reservoir had a surface area of . The dam was built by Shoji Kensetsu and operated by Ebana River Coastal Reclamation District.

Society Responses

After the dam’s failure, there were conflicts between the governmental reviews and the citizens’ understanding of why the dam experienced such failure. Japanese national and Fukushima prefectural governments inspected and considered that the earthquake’s impact was significant damage triggered and stated it a natural disaster. Oppositely, the failure mentioned above, such as lack of workforce, knowledge, and proper materials in the construction process, the citizens doubt that this failure is a human-made disaster and the consequences of the construction failures; especially Sukagawa city is far away from the ocean to experience Tsunami, so, they couldn't consider it as a natural disaster. These opposing opinions can also be seen in the discussion and conflict about disaster public assistance by the governing sectors. In Japan, when there is a natural disaster, there is a regulation of maximum financial support of 3 million yen, however, in this case, the citizens’ understanding of this dam failure was a human-made disaster, so the disaster public assistance financial support did not meet citizens’ needs and created this disaster to more complicated situation to battle against the governmental perspective on assistance and approach for dam failure, especially on recovery discussion.

Recovery

Reconstruction of the dam started in October 2013, and has been completed in April 2017.

Citizen's opinions

Although the recovery of this dam was completed in 2017, there were some unheard voices of citizens living near the once-failed dam. Three main arguments were: 1) recovery and water are needed for their agricultural business, 2) potential risk of flood to reconstruct at the same location, and 3) no dam is needed.

References