Photograph and illustration of barrier preventing landslide of small Harakawa (Toyo-cho, Yatsushiro-shi)
History of erosion control business
Erosion control law was enforced at purpose called country maintenance like the old River Act (the 1896 enforcement), old forest law (the 1897 enforcement) in 1897 and hung in the 40, Showa generation from the enforcement those days and restrained the dilapidation and valley bank erosion such as bald mountains, the earth and sand outflow to the lower valley by maintaining erosion control facilities such as banks which did not get erosion control.
Because damage by mud flood (landslide) was frequent as factor by heavy rain flood caused by typhoon and seasonal rain front in the whole country when it was the around 50s of the Showa era, mud flood came to investigate mountain stream which might occur, so-called mud flood danger mountain stream.
Investigation into mud flood danger mountain stream is almost carried out together with five years, and, in Kumamoto, 1,710 under five mountain streams which there is exist mountain stream 2,120 places where there is house five or more in maintenance area, one or more (2002 public announcement number).
The maintenance situation of mud flood danger mountain stream in the prefecture
Erosion control construction maintenance rate in five maintenance house number of houses in the prefecture at the end of 2007 or more mud flood danger mountain streams remains in approximately 19% and is the situation that it cannot be said that enough maintenance is performed. We will maintain erosion control facilities at mud flood danger mountain stream in future to protect holy life of citizen of the prefecture and precious property.
Upper hut river (Ichinomiyacho, Aso-shi)
Ecosystem in erosion control business, consideration to environment
After having controlled the earth and sand of the abnormal flood period, in the bank which does not get erosion control, there is function to gradually supply the earth and sand to the downstream for the small and medium size flood period, but comes to often install bank (cf. chart below) which does not get erosion control of slit type that has begun to be adopted as new technology late in Showa recently. Slit type supplies the harmless earth and sand to the downstream side smoothly without intercepting continuity of the upper downstream and can minimize small animal, ecosystem such as fish, influence on environment. We will work on natural eco-friendly erosion control business from now on.
Figure of barrier preventing landslide image (slit type)