抄録
We had many calamitous disasters in 1972, 1973 and we wil lhave disasters in future, because we live in very dangerous land.
So it needs the Sabo works for the preventing the sand disaster but it's so many-that it cannot excute the Sabo works in anyplace at once.
Then, we need the alarm system for preventing the sand disaster. I propose the one method of alarm system with rainfall intensity ratio which is called σ, in where σ=tanθ1/tanθ2=dm·dT/dM·dt in Fig2.
As a result, I think σ is very useful factor for forecasting the sand disasters.
