It becomes common practice recently to take the natural environment into consideration in the design and construction of sabo facilities. From the view point of soundscape design, to make agreeable the sound of water flowing over groundsels and/or sabo dams is one of the design criteria for building better sabo facilities. It follows that it is essential to become familiar with characteristics of sound and to know how people feel if they hear any sound when it comes to the soundscape design. The purpose of this paper is to indicate the conditions which create agreeable sound.
In this study, analysis by questionnaire about the sound of sabo facilities, small falls and river flows was conducted by SD method. The power spectrum of sound, fluctuation of sound level with time and change of autocorrelation coefficient with time lag were analyzed.
Furthermore psychological factor related to the sound from sabo facilities was evaluated by factor analysis in SD method. Psychological factors related to the sound from sabo facilities were classified into three types. Types of factor are the aesthetic factor, the metallic sound factor and the powerful factor. The conditions of sound which human-being feels agreeable are as follows.
(1) The power spectrum of sound is in inverse proportion to the frequency of sound.
(2) Agreeable sound involves the high frequency as high as the range of over 5, 000 Hz.
(3) Agreeable sound has wide variety of level of sound pressure with time.

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For the purpose of finding the factors of slope collapses from the characteristics of the distribution of them in the Rokko Mountains triggered by the 1995 Hyogo-ken Nanbu Earthquake, we have extracted some frequency characteristics from the seismograms and performed the morphometry and the frequency analysis of the microtremors. Then we have tried to set them in correspondence to the distribution of the slope collapses.
The results are as follows:
1) It is presumed that the maximum acceleration of the Hyogo-ken Nanbu Earthquake was about 300-400 gal in the Rokko Mountains and its predominant frequency was 1 Hz or less.
2) The principal shock has excelled in the direction perpendicularly intersecting with the principal axis of the Rokko Mountains. This may have affected the direction of the surfaces of slope collapses.
3) The distribution of the aftershocks corresponds well with that of the slope collapses. Therefore, it is possible that the distribution of breaking energy on the fault plane is refrected in that of the slope collapses.
4) It is possible that the difference in the degree of weathering between the Rokko granite and the Nunohiki granodiorite is refrected in the distribution of the slope collapses.
5) To take a wide view, the slope collapses have occurred frequently in the areas where the faults existed densely.
6) The slope collapses tend to occur frequently at the ground where the vibration of a frequency band of 6-7 Hz is easy to be amplified. Therefore, the earthquake motion did not produce resonance in the ground.
7) To take a local view, a correlation between the topographical factors-elevation, inclination and irregularity-and the distribution of the slope collapses is not found. However, in the areas in which slope collapses have occurred frequently, a rate of slope collapse area increases with inclination.
8) It is considered that slope collapses have occurred frequently in the areas which satisfied the above 3) -6) simultaneously.

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Fishways are inevitable, when Sabo facilities are planned in torrents that have good environment for fishes. In this point of view, many fishways are built in this decade. However, most of them are classic type like “pool fish ladder” which needs, in many cases, discharge control like nappe velocity control, and maintenance of sediment blockade. In this situation, experiments on fish behavior with various nappe velocity as well as with various pool length are necessary, in order to gain the basic information for discharge control and maintenance above. In this study, the experiments or observations are carried out for Char (Salvelinus leucomaenis f. pluvius) which is typical upstream torrent fish, consequently next results are acquired;
Fishes need certain stimulation by flow, therefore maximum migration rate appears at specific over flowing velocity (in this case 70 cm/s), not more than that and not less than that. Since fishes can not settle against upstream direction and prepare to migrate in the resting section, adequate length of pool is more than “the length of area effected by nappe plus 2 times of fish length”. Filling up the condition above, pools have flow velocity of the Char's “prolonged speed” at the downstream of nappe, and it is suitable for fish to prepare to migrate. Char's prolonged speed is given as 20∼40 cm/s (depends on fish length) by the experiment in this study.

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In Japan, hillside landslides occur frequently in rainy seasons and give the great damage to human life and public property. It is necessary for disaster prevention, to promote positive hillside works. A model necessary for positive hillside works, that can evaluate these effects, was proposed in this study. Among hillside works, groundwater drainage works were picked up as an example. Stress acting on soil layer was estimated on three dimensions in this model. This simulation model is applied to the Tsuchisawa basin where many hillside landslides occured in 1969. The model explained locations of hillside landslides and estimated effects of groundwater drainage works with precision. It was confirmed that this simulation model was effective to execute positive hillside works to the slope judged to be insecure.

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Vegetation is organized by the species that is under the influence of the habitat condition. On steep slope, vegetation is related to surface disturbance. In this study, the author investigated the possibility that forest communities types would be the indexes of surface stability on steep slope along the Sagami river terrace, Kanagawa prefecture, central Japan. Forest communities were classified by typical species of tree layer on this area. Other measure items were surface geology, microtopography, and soil profile. Zanthoxylum forests (Com. C) were found on landslide sites, Quercus forests (Aa), Carpinus forests (Ab) and Zelkova forests (B) were not found on surface failure sites. Com. C showed aggregated distribution on study site. That suggested surface failure would occur on Com. C environs. Com. Aa were mainly found on upper side slope, Com. B were mainly found on lower side slope, and Com. Ab were found on middle parts of slopes. Soil was disturbed past time on Com. B site, and it was unstabler than Com. A site, such as not distuerbed long time. So, habitats of forest communities related surface stability. It was shown that classification of forest communities could be possible to judgement surface stability estimation on steep slope.

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Unzen volcano had many eruptions with emission of ash and pyroclastic flows during the period from 1990 to 1995. The pyroclastic flows were thickly deposited on the flank of the volcano. At the same time the surroundings were widely covered with fine volcanic ash. As a result of those, the hydrological regime of the flank of Unzen volcano was radically altered and surface runoff have frequently occurred on the hillslopes.
Observation stations of surface runoff were established on the pyroclastic flow deposit and in the Japanese cypress forest covered by fine volcanic ash. The observations aimed at making clear some features of surface runoff along the hillslope of Unzen volcano. In this paper, the characteristics of surface runoff are analyzed using the records of surface runoff observed from 1995 to 1996.

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