Sai River Research Articles

Progress of Flow Course in Sai River and its Flood Control Discussions

Progress of Flow Course in Sai River and its Flood Control Discussions

Upheaval of Sai River Dam by Zenkoji Earthquake in 1847 and Disasters by Water

Upheaval of Sai River Dam by Zenkoji Earthquake in 1847 and Disasters by Water

Subsurface Valleys and Landslide

The hill-land along the Sai River in Nagano Pref. is frequent in landslide. The upper part of the hill-land often contains the pyroclastic rock layers. When the valleys dissecting the hill-land is buried by dissolved pyroclastic rock, the landslide activities on and around the subsurface valleys are as characteristic as observed at Nishigawara and Chausuyama landslide areas in Nagano-city.1) Deposits filling the subsurface valleys scarcely slide secondarily; the landslide often transit and extend outward of subsurface valleys.2) Subsurface valleys may be the veins of ground-water, which promotes the sliding activity in and around subsurface valleys; especially, large-scale landslides are liable to occur at the terminal of subsurface valleys.3) Around subsurface valleys, the mountain streams show such unnatural phenomena as the discontinuity of valleys, the disappearance of the heads of former valleys or the new tributaries formed on both sides of subsurface valleys.

On Landslides in the Mountainous Area along Sai River and Hime River in the Northern Part of Nagano Prefecture (1)

On Landslides in the Mountainous Area along Sai River and Hime River in the Northern Part of Nagano Prefecture (1)

On Landslides in the Mountainous Area along Sai River and Hime River in the northern Part of Nagano Prefecture (3)

On Landslides in the Mountainous Area along Sai River and Hime River in the northern Part of Nagano Prefecture (3)

On Landslides in the Mountainous Area along Sai River and Hime River in the northern Part of NaganoPrefecture (2)

On Landslides in the Mountainous Area along Sai River and Hime River in the northern Part of NaganoPrefecture (2)