Construction began Sunday to reinforce areas afflicted by the eruption of Mount Usu that are believed prone to mudslides from heavy rain that has fallen in the past few days.
Authorities are placing sandbags along the Itaya River, which runs through the town of Abuta, and are removing sand and mud that has piled up against sand barriers erected in the area. They said they hope to complete the work by the end of May.
In upstream areas too dangerous to enter, authorities may use heavy machinery that can be operated by remote control. Similar machines were used during the eruption of Mount Unzen in Nagasaki Prefecture.
Authorities decided to use a remote control surveillance helicopter to survey upstream areas before construction work begins early next month and conducted a test flight Sunday.
The helicopter — weighing roughly 95 kg — is similar to those used to spray crops with pesticides but can automatically fly to a preset destination by using the global positioning system.
It can fly at altitudes of between 30 and 150 meters while sending digital images.
Meanwhile, Abuta officials said they would begin bus rides today to take one member from each of the 71 households taking shelter in evacuation areas to places near their homes so they can assess the amount of damage, if any, from within the vehicle.
Million-ton ash fall
DATE, Hokkaido (Kyodo) A joint team of experts released an interim report Sunday saying it is likely Mount Usu has belched more than a million tons of ash since it began erupting March 31.
The experts reached the figure by collecting volcanic ash from some 70 locations around the volcano and calculating the amount of ash per unit of area.
The report says at least 120,000 tons of ash was ejected in the initial explosion, even excluding such areas as the Lake Toya hot spring resort and the immediate vicinity of the crater, which were inaccessible.
About 200,000 to 300,000 tons of ash fell on the first day alone, the team said. in its report.
On April 4, roughly 30,000 tons of ash fell during the one-hour period between 4 p.m. to 5 p.m. when volcanic activity intensified, according to the report.
Because there have been at least six or seven eruptions on the same level as the April 4 eruption, the team estimates Mount Usu has released over a million tons of ash.