抄録
A large-scale landslide occurred in May 2015 in headwaters of Tedori River at the foot of Mt. Hakusan. Highly turbid
water has been generated from the landslide, which has had wider and seriously influences on the downstream area
by such as rice paddy irrigation systems, ground water system, fresh water and coastal fisheries. Airborne LiDAR
data and series of air photos were employed to analyze topographical features, this landslide occurred within the old
landslide body. The suspended solids and sediments showed high pH and Ca concentrations, which gave the effects
on the early growth stage of rice plant and the uptake of essential microelements. Miyatake settling basin has a role
to prevent sediment from flowing into farmlands. Sediment heights of the sand settling channels were measured and
the volume of total sediment was estimated, then it was concluded that the settling basin has performed very well.
From May 2015 when the high turbid water occurred, the groundwater tables in the alluvial plane began to decrease
seriously. So, it has been required to analyze the water balance in the aquifer and evaluate the influence of turbid
water. A hydrologic model was developed for the analysis and evaluation. The model performance was very good
and it is expected that the model will be available to predict the influence of the turbid water. Since the sharp decline
of groundwater level has gave a serious damage to Pungitius sp.1, it is considered that the addition of spring-fed
ponds with groundwater lifting pumps is urgently required for the future depletion of spring water.
