The River Joganji is one of the most wasted rivers in Japan because of its rapid flow and the great mass of debris eroded from volcanic mountain of Tateyama. In the tributaries of Joganji such as Yukawa, Makawa, Shomyo-gawa and others, Yukawa is most wasted.
The main reason why Yukawa was so wasted is the big landslide“Tombi-Kuzure” by the great earthquake in 1858. This landslide occured in the upper stream of Yukawa and its debris-flow filled up Doro-dani and Dashibara-dani. The vollume of its debris deposits is estimated about 3.3×10⁸m³. For more than 100 years, these deposits“Tombi-doro” has been eroded violently. Thus debris deposits from Tombi-Kuzure have been main supply source of earth and sand to Joganji River ever since.
In 1964, approx. 2.9×10⁶m³ of debris were moved by the big landslide and further in 1969 Yukawa basin got remarkably wasted because of the heavy rainfall.
Authors have been investigating this wasted area from the geological standpoint through photo-interpretation, photogrammetric method and field survey since 1965.
In this paper we first related on the state of landslide in Yukawa basin especially about Tombi-doro, and next on the effects of the disaster in 1969 including volume variation.

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The density of a photo or map supply us to many informations of land use and others.
The quantitative treatment as well as the qualitative is required in photo-and mapinter-pretations. It is necessary to determin the standard density in order to indicate the correlations between densities of many samples and is also necessary to establish method of automatic measurement and treatment in order to pick out the required informations.
The present paper is concerned with an establishment of the densito measurement system and with a classification of the base density by the reflection method into as many step as possible by use of the microdensitometer.

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The usual method of estimating the change of volume of deposits in a river bed has been to measure 2 or more sets of photographs which have been taken at different times.
It seems that in the past, an accuracy check of the measurements obtained has been neglected due to the fact that it involves many uncertain factors.
The systematic accumulation of data containing many different factors is needed to evaluate the estimated results objectively.
We will report on some of the results of tests conducted.

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