Since the Sabo works in the Joganji River was handed over to the national government in 1926, there have been a large scale of floods several times.
There have been few damages induced from the flood or sediment discharge in the Toyama Plain since 1969, due to the progress of the Sabo Works to some extent.
The implementation of the Sabo Works in the Joganji River has contributed to improve the safety in the Toyama Plain, thus increasing the number of the residential population, and attracting the business enterprises and the tourists including the foreign people.
However, we have more heavy rainfall events and abnormal weather due to the recent global warming. To address the issues, we are implementing Sabo projects for Tateyama Caldera where a large volume of collapsed sediment is still accumulated and other areas along the Joganji River in a carefully planned way.
A large volume of sediments remaining in the Tateyama Caldera (Tombidoro mud)
The sediment collapsed by the 1858 Earthquake is called Tombidoro mud. The total volume is estimated to be 0.41 billion m3 of which some 0.2 billion m3 remains in Tateyama Caldera. If this flushes into the Toyama Plains, the area will be filled with sediment as high as 2 m.
Growing Toyama Plain as the Hub of Hokuriku Region
Since a long time ago, the Toyama Plain has been developed as the 'Rice producing region' and 'Industrial area typical of light-metal and pharmaceutical industries. Nowadays it has been more developed because key railway network such as the Hokuriku Shinkansen Super Limited Express, the local train 'Ainokaze Toyama Railway', both of which was started in operation in 2015. The key road newwork such as Hokuriku National Express Highway, National Highway No.8 and No.41 has also supported the local industries in the area.
Toyama city, some of which is situated in the flooding area of the Joganji River, has a population of about 417,000 as of 2017, atter the consolidation of 7 municipalities in April 2005.
The opening of Hokuriku Shinkansen, under the recent trend of growing foreign tourists, is expected to increase the visitors to Toyama Prefecture even more in the coming years.
Positive Effects of Sabo Projects and Increasing Population in the Flood-risk Area
Change in Estimated Visitors to Toyama Prefecture
