A high court ruled Thursday that the deaths of over 23 Okawa Elementary School students in tsunami following the March 2011 earthquake in Tohoku could have been prevented if Miyagi Prefecture and the city of Ishinomaki had updated its disaster contingency plan.

The Sendai High Court ordered local authorities to pay around ¥1.4 billion ($13 million) in damages to the children’s families, raising the amount of compensation by about ¥10 million from a lower court ruling.

The authorities “failed to fulfill their obligation to revamp a risk management manual in line with the realities of Okawa Elementary School,” Judge Hiroshi Ogawa said, adding that “If the manual had designated a 20-meter-high location for evacuation” the deaths could have been prevented.

A total of 74 pupils and 10 teachers and officials died in the tsunami that followed the magnitude 9 earthquake on March 11, 2011. The tsunami engulfed the students and teachers as they began evacuating to an area near a 7-meter-high riverbank.

The ruling said it was “wrong” that the school, situated at a height of up to 1.5 meters above sea level, was not designated in the city’s hazard map as being in an area that could be hit by potential tsunami.

While the city claimed it was impossible to predict a tsunami that could engulf the school, which had never experienced such a disaster in the past, the ruling said “prediction was possible and there was a risk of tsunami,” citing the school’s location near a riverbank.

Hiroyuki Konno, the plaintiffs’ representative, said the acknowledgement of Ishinomaki’s systematic negligence was of “great significance for anti-disaster (measures) going forward.”

The school revised its risk management manual in line with a law on school health and safety that came into force in 2009, but retained the existing wording for potential evacuation points as “vacant space and parks nearby.”

Pointing to the low elevation of the school and the high risk of tsunami in the area close to rivers, the plaintiffs argued, “The manual was extremely inadequate as it lacked specific descriptions of evacuation sites and how to reach them. The school failed to evaluate and revise it.”

The city claimed that the school was only obliged to compile a manual and its content was adequate based on scientific knowledge at the time.

The plaintiffs had demanded that the local governments jointly pay around ¥2.3 billion, arguing that the school should have taken better anti-tsunami measures.

In October 2016 the district court ruled local authorities were negligent, ordering the city and prefecture to pay compensation. The court concluded the school should have evacuated children to a nearby mountain rather than to an area near a riverbank.

The city and a third-party panel have revealed that students at the school were kept at its playground for about 45 minutes despite a large-scale tsunami warning.