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As heavy rains and floods caused by climate change are occurring in many parts of the world and causing enormous damage
flood control measures to reduce and prevent flood damage from both rivers and drainage area have become a pressing issue for national and local governments
conducted a study from June to September 2022 in conjunction with the Higashine city government in Yamagata Prefecture
which has experienced flood damage due to heavy rainfall
all so as to take advantage of flood predictions for evacuation orders
thereby confirming the effectiveness of their system
the people in charge of the project talk about how their aim is for zero delays in evacuating residents
The technical basis for this joint research is Hitachi Power Solutions' DioVISTA software
which has been in operation for about 15 years and has been used mainly for simulating flood damage in urban planning
dramatic improvements in computer calculation speed and software feature enhancements in recent years have made it possible to incorporate rainfall and other information in real time
This has expanded the software’s range of applications
passionately states: "The evolution of DioVISTA has made it possible to predict what will happen with rivers and streams several hours into the future
We wanted to link this software to actual disaster prevention and management of river-related infrastructure facilities (such as dams
Matsui has long been involved in the development and operation of disaster prevention systems for national and local governments and is an expert at handling disaster prevention information
the company began approaching municipalities across Japan two years ago with a view to using DioVISTA in the construction of disaster prevention and river-related infrastructure
The Higashine city government in Yamagata Prefecture
known for producing the most cherries in Japan
The city government also had a strong interest in real-time flood predictions
Kenichi Misaka of the Crisis Management Office at Higashine City Hall recalled the torrential rainfall that occurred in July 2020
"The heavy rain that fell from July 27 to 29 of that year caused the Mogami River to overflow
flooding parts of Higashine City above floor level
and villages quickly issued evacuation orders
leaving some residents in Higashine to ask why their city had not been ordered to evacuate yet."
Evacuation orders are issued by each municipality in compliance with Japan’s Basic Act on Disaster Management and in line with its own rules and the judgment of the head of the municipality
Higashine City did not immediately issue an evacuation order because the water level of the Mogami River
had not reached the standard for issuing such an order
Misaka regretfully said: "We had to clearly inform the citizens of Higashine City why the evacuation order was issued later than the surrounding municipalities."
As the desire of Hitachi and the Higashine city government to predict flooding in real time and to apply the results to evacuation orders overlapped
The research used data on rivers and water levels in the Mogami River drainage basin maintained by Japan’s Ministry of Land
Transport and Tourism and the Yamagata prefectural government
as well as rainfall prediction data on the torrential rainfall that occurred in July 2020
to conduct a reproduction experiment to predict flooding at that time
it was found that flooding in Higashine City could be predicted 1.5 days before occurring
when flood forecasting was conducted using data from 6 hours prior to the disaster
97% of the area that was actually flooded was predicted to be flooded
the confluence of the Mogami River (main river) and the Shiromizu River (tributary) created a backwater effect whereby water flowed back into the tributary from the main river
causing the Shiromizu River to burst its banks and flood the area
Such a detailed analysis was possible because the system integrated data from the main river and its tributaries
enabling an integrated simulation of the entire Mogami River basin
the project also developed and demonstrated the Flood Prevention and Mitigation System which leverages flood predictions to help local government officials in issuing evacuation orders and conducting emergency activities
By linking DioVISTA with rainfall predictions
the system estimates the number of residents affected by flooding
predicts the locations of roads where traffic will be restricted
The joint research confirmed that the system is also effective in the event of a disaster
Misaka of the Higashine city government expressed his expectations for the system's use in the future:
"When the torrential rains hit in July 2020
there was all sorts of trouble when emergency vehicles could not pass through an expressway exit because it was flooded
we would have been able to respond flexibly by avoiding the flooded areas and getting off at the exits before the flooded areas
We felt that the simulation could be used to consider not only the timing of when to issue evacuation orders but also more-practical evacuation orders and disaster support."
Hitachi’s Matsui points out: "DioVISTA has its issues." For example
he says: "It would be difficult even if we had 100 years" to perfectly predict through simulations the locations where levees are likely to break or the occurrence of landslides
"If we can quickly and precisely direct evacuation in terms of placing the highest priority on people
if disaster response organizations can share among themselves information on what equipment and supplies can be deployed and delivered and where
so as to maintain the quality of life for evacuees
it should be possible to prevent health problems at evacuation shelters
if we can control river-related infrastructure such as dams
we can contribute to the mitigation of flood damage itself."
Regarding Matsui's comment about "zero evacuation delays"
Misaka of the Higashine city government expressed his hope for future development
saying: "It would be very helpful if information on people that need to be rescued could be immediately sent to rescuers
and rescuers could be informed of an appropriate route to get there."
Misaka then expressed his determination to continue working on disaster prevention activities:
"I would like to take advantage of the information obtained from this research to raise residents' awareness of disaster preparedness
We are already showing the simulation video to visitors at the Disaster Prevention Center
but we would like to consider more effective ways of presenting the data and images."
Heavy rain triggered extensive flooding in the northeastern Japan prefecture of Yamagata through Wednesday morning after a river burst its banks at several locations
the prefectural government has been trying to assess the extent of flood damage along the Mogami River
The land ministry has confirmed the river breached its banks at three locations in the town of Oishida as well as in Okura village
with at least 80 hectares of land inundated by Wednesday morning
The Mogami River is the seventh longest river in Japan and the river basin accounts for about 75 percent of Yamagata Prefecture
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around 90 homes have been damaged by the flooding and nearly 2,500 people have been evacuated
Rainfall of over 150 millimeters was recorded in some areas of Yamagata in the 24 hours through Wednesday morning
while the city of Nagai experienced 205 millimeters
Nagai and the prefecture's two other cities of Murayama and Higashine faced record rainfall across 72 hours
although it had mostly stopped by Wednesday morning
The Yamagata shinkansen bullet train temporarily suspended services on Wednesday
more than a dozen buildings in Hanamaki and Oshu have been flooded as of Wednesday morning
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