Journal of the Japanese Society of Snow and Ice
Online ISSN : 1883-6267
Print ISSN : 0373-1006
Volume 32, Issue 3
Displaying 1-4 of 4 articles from this issue
  • Masao SAEKI, Hiroo MATSUOKA
    1970 Volume 32 Issue 3 Pages 43-54
    Published: May 30, 1970
    Released on J-STAGE: July 23, 2009
    JOURNAL FREE ACCESS
    The function of broad-leaved young stands to prevent the occurrence of ground avalanche was analyzed by aerial photograph and field survey on the forest land in the basin of the River Uono, Niigata prefecture, northern central Japan, where the normal snow depth in winter was about 3 m. Result of the study is as follows :
    1) On the coppice land where no trees can overtop the snow cover, snow cracks occur on the slopes with the inclination angle of 25 degrees or so. Ground avalanches begin to occur on the slopes of about 27 degrees. On the slopes of 30 degrees or more ground avalanches occur almost usually.
    2) On the broad-leaved young stands with the height of 2-5 m above the snow cover and the diameter of 2-5 cm at the snow surface, it is estimated that the stands with the density over 200 coppicelike stumps per ha or so on the slope of 30 degress, 500 stumps 35 degrees and 800-900 stumps 40 degrees respectively, show the function against ground avalanche.
    3) It is concluded from the findings above mentioned that the distribution of dangerous site for ground avalanche could be defined on the whole by the aerial photograph pictured in the snowy season.
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  • Toshiharu SUGIYAMA
    1970 Volume 32 Issue 3 Pages 55-62
    Published: May 30, 1970
    Released on J-STAGE: July 23, 2009
    JOURNAL FREE ACCESS
    In order to measure the amount and distribution of snows in the experimental watershed, where the relation between changes in forest condition and runoff was being investigated, the snow survey by means of the aerial photograph was carried out at Takaragawa Experimental Forest (area : 20 km2, altitude : 800-1945 m) in snowy district of Japan, in the winter of 1965-1966.
    The depth of snow at the points corresponding to every intersection of grid overlaid with 100 meter interval on a map was measured as a difference of height between snow surface and ground surface, comparing vertical photographs of the watershed with snow and ones without snow. Mean depth and water equivalent of snow in the watershed, which were calculated using the said data along with the density of snows measured in on-the-spot survey, were about 3.4 meters and 1370 millimeters respectively at 1st of March.
    The distribution of the accumulated snow in the mountainous region depends strogly on the topographic features, but the grade of influence of each topographic factor upon the distribution was varried according to the extent of examined area. Although the distribution of the depth of drifted snow at each point in the basin was complicate, the mean depth on a certain zone was expressed as a function of the topographic factor, such as altitude or distance from main mountain range.
    It was shown in this experiment that the snow survey with the aerial photograph would be useful in analyzing the snow distribution in the mountaious watershed, though many problems remain to be solved in the future.
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  • Fumiaki KOBAYASHI, Akinori FUJINO
    1970 Volume 32 Issue 3 Pages 63-70
    Published: May 30, 1970
    Released on J-STAGE: July 23, 2009
    JOURNAL FREE ACCESS
    The writers have previously reported on artificially induced avalanche release to protect roads from avalanche damage. The removal of deposited snow on slope was carried out by using explosives packed in a vinyle chloride pipe and the blasting was done at certain time intervals. The deposited snow on slopes could be removed at will without injuring the slope surfaces by this method, but installations such as rock fences and guard rails along the road were damaged by the impact of falling snow masses or by road crews working to remove the released snow from the roads. At the same time traffic was blocked or restricted.
    In order to circumvent the above problems, a compression method (Avalanche prevention engineering) by which the snow cover on the slope is accumulated and blast melted was studied. This avalanche release protection work is applicable to slopes with a gradient of 30-40 degrees. The operation is carried out during the snow fall period to the height of winter when the snow cover is stable. The operation is most effective during this period and the period is safest for the handling of explosives.
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  • Nobuo TAKAHASHI, Hiroshi UOTSU
    1970 Volume 32 Issue 3 Pages 71-77
    Published: May 30, 1970
    Released on J-STAGE: July 23, 2009
    JOURNAL FREE ACCESS
    In a snow-lay region, it is impossible in particular, at the period of a snow-storm to measure the precipitation amount exactly. This is due to the influence of the shape of orifice type snow gages itself, that is, the upward component of air stream above the orifice.
    Then, in order to measure the vertical component of the wind velocity, the 3-bladed vertical anemomter (Thornthwaite type) is used. This anemometer is calibrated with the wind tunnel and field observation are made in a snow-lay region near the Sekiyama Park Hotel, Niigata Prefecture.
    The catching rate C of the snow gage (dia. 20 cm) is determined by the empirical formura
    C= (1-a·V/F) ×100
    where,
    V is the wind velocity in m/sec,
    a is a constant=0.1 to be determined from the wind tunnel test,
    F is the falling velocity of the snow-flakes in m/sec.
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