北海道有珠山における泥流発生にかかわる降雨特性(II) : 降雨強度

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The rainfall intensity property which is one of the rainfall properties related to the occurrence of mudflows in the Mt. Usu area was studied by using rainfall amount data obtained from a special mesoscale raingauge network set up by the present workers and raingauge networks operated by other organizations. A total of 6 mudflows occurred during the two years from 1980 to 1981. Based on the analysis regarding the total rainfall amount distribution, the total rainfall amount distributions related to each event were classified into two groups which were less than 50 mm and more than 80 mm. One group under 50 mm was about one fifth to a half of the other group over 80 mm in total rainfall amount, but one group under 50 mm contained the same magnitude of rainfall intensity as the other group over 80 mm contained. Therefore, it was considered that the rainfall intensity was equally important as the total rainfall amount for rainfall triggering mudflows. The magnitude of the rainfall intensity in the Mt. Usu area was as follows. Based on the past rainfall amount data at Muroran Meteorological Observatory, the return periods of over 23 mm/hr and 20 mm/hr in rainfall intensity were about two years, and one and half a year, respectively. And the return period of over 9 mm/10 min in rainfall intensity was about two years. It was also shown from the data that the maximum 1-hour-rainfall-amount and 10-minutes-rainfallamount during this period were 51.3 mm/hr and 18.7 mm/10 min, respectively. When there were strong rainfall intensities in the Mt. Usu area, the distribution patterns of the rainfall intensity in Iburi district were analyzed and classified as follows. There were three distinct distribution patterns ; "Orographic rainfall" in which the maximum peak of rainfall intensity was concentrated on the southeastern slope in the Orofure Mountain Range, "Mt. Usu rainfall" in which the maximum peak was concentrated in the Mt. Usu area and "Seaside rainfall" in which the maximum peak was concentrated on the seaside region in the central Iburi district. During the two years from 1980 to 1981, "Orographic rainfall" was the most frequently seen pattern, and "Mt. Usu rainfall" and "Seaside rainfall" followed in the order of frequency. The regional characteristic of rainfall intensity was similar to that of daily rainfall amount reported in the previous paper.
北海道大学の論文
1983-08-15

北海道有珠山における泥流発生にかかわる降雨特性(II) : 降雨強度

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