For the necessity of nature-wise planning of Sabo facility, recently the falling works of entire f ishway type are build as a part of a channel works. In this study, the soundscape induced by falling water of this kind of facilities are discussed comparing the concrete made with the stone made one under the nearly equal surrounding. Soundscape characteristic is concluded mainly described by sound range and sound fluctuation (Kubota 1995) from sound spectrum analysis. Hence, the focus is put on these two factors, and in consequence the results are summarized as below. (1) The sound fluctuation on stone made works shows 1/f fluctuation. And, the fluctuation on concrete made one changes to non-1/f, as the flow discharge increases. Here, f-frequency, and 1/f fluctuation is one of the feature of “bland” sound. (2) The sound fluctuation at the cross sectional upper side of falling water is closer to 1/f than the one of center portion of the cross section. (3) Portion of low frequency in the sound range comes prominent as the flow discharge increases. And this tendency is more notable on concrete falling works than on stone made one. Whereas, the sound that includes large low frequency part is known as non-bland sound.
Mount Bandai erupted in 1888. A large part of the mountain body collapsed and slid down, which turned into debris avalanche. Three methods were applied to simulate this debris avalanche. They are Marker and Cell Method (MAC), Discrete Element Method (Ball Model) and 2-dimensional flow model. All methods show some good results by choosing appropriate parameters. Only data we have is resultant deposition. It is difficult to evaluate the simulated results. It is necessary to establish a more reasonable model.
The present study aims at quantitatively determining the risk of collapse extension following an earthquake by comparing the rainfall levels causing a collapse before and after an actual earthquake. It is found that a collapse occurs at a lower rainfall level after an earthquake in areas affected by the faults and that its occurence clearly corresponds to the rainfall level.