砂防学会誌
Online ISSN : 2187-4654
Print ISSN : 0286-8385
ISSN-L : 0286-8385
61 巻, 2 号
選択された号の論文の18件中1~18を表示しています
口絵〈災害報告〉
口絵〈観測の現場を訪ねて-9〉
口絵〈報告〉
論説
平成20年度砂防学会賞の受賞
論文
  • 宮崎 知与, 山田 孝, 丸谷 知己
    2008 年 61 巻 2 号 p. 5-15
    発行日: 2008/07/15
    公開日: 2013/09/02
    ジャーナル オープンアクセス
    Understanding how sediment supply from lateral source influences on sediment distribution along a channel reach is a key issue for preliminary surveying of sediment disaster. Sediment pulse formed by storm-induced sediment supply from lateral source was investigated for four years after 2003 storm at Kita-iwanai-ninosawa Creek located in a headwater catchment of Tokachi River, Eastern Hokkaido, Japan. Cross-section measuring and sediment sampling were conducted on site, and the relationship between longitudinal changes in sediment volume transformed to a sediment mass curve and grain size distribution was examined. In this paper, the ratio of sediment delivery magnitude (M) against quasi-stream power (Ps) was employed as an efficiency index (M/PS) of sediment transfer. The result is as follows : 1) Although storm-induced sediment pulse formed by quite lots of sediment input is not identified by deference in grain size, sediment pulses gradually reproduced by low-water flow after storm event have characteristics of grain size distribution. 2) Magnitude of sediment delivery with large materials (>75 mm) decreases downstream because of their short travel distance even by flooding. However, selective transport of smaller materials by low-water flow increases the magnitude of sediment delivery. 3) Comparing sediment mass curves, the wave peak by largemagnitude flooding is higher than that by small-magnitude flooding, and the wave length by large-magnitude flooding is shorter than that by small-magnitude flooding. 5) The efficiency index (M/PS) of sediment transfer yielded by storm induced sediment supply is quite high, but it gradually decreases with time after the initial sediment supply.
報文
  • 村上 隆博, 菊井 稔宏, 嶋 大尚, 清水 基成
    2008 年 61 巻 2 号 p. 16-22
    発行日: 2008/07/15
    公開日: 2013/09/02
    ジャーナル オープンアクセス
    When we discuss about the rainfall related to occurrence of sediment-related disaster, it is important to understand the amount of rainfall as accurate as possible. However, it has not yet defined clearly about the effective area of rain gauge in case there is no rain gauge near the point sediment-related disaster occurred, and about the distance from the certain ground-based rain gauge by which estimation of risk of disaster is possible in case its rainfall exceeds the standard level. Some reports say about the spatial density distribution of rain gauges required for understanding the accurate rainfall near the area disaster occurred. But rain gauges are not placed spatially uniformly, so the correlations of each rain gauge depend on the spatial density distribution of them. Furthermore, it is very difficult to know the deviation between estimated value and true value by using current rain gauge network. In this paper, we examine the effective area of ground-based rain gauge around Hakone area in Kanagawa prefecture by using radar-AMeDAS data which are spatially uniform.
  • 桜井 亘, 徳永 良雄, 光永 健男, Michael M Alpassan, Jerry E Fano , 綱木 亮介, 万膳 英彦, ...
    2008 年 61 巻 2 号 p. 23-29
    発行日: 2008/07/15
    公開日: 2013/09/02
    ジャーナル オープンアクセス
    The area around Mt. Mayon in Albay Province Philippines was affected seriously by large mudflow caused by heavy rainfall of the typhoon 21 in Nov. 2006. The loss of human lives amounted to 1,300 deaths and many houses, infrastructures were damaged. After the disaster, an urgent survey conducted by a research team dispatched by Ministry of Land Infrastructure and Transportation Japan revealed that all of the riverbeds in the mountain foot area where mudflow passed were scoured deeply and widely in spite of the gentle slope, which was around 3-4 degree. Maximum depth of the scouring reached to 10 m, and maximum width reached to 30-50 m. It was remarkable that the gradient of the sections where we found the deep scouring was too gentle to result in such a deep scouring. We tried to clarify this mechanism of the deep scouring by a numerical riverbed fluctuation model to refer to further counter measures. Due to lack of data in detail such as rainfall data in upper stream and the latest map to know the condition of catchment area, it was impossible to know an exact peak discharge and a hydrograph, so it didn't allow us to say anything quantitative. However, our result infers that the very low sediment concentration in the subsequent flow and the fine and loose material of the sediment in riverbed might cause the deep scouring.
研究ノート
  • 井上 公夫, 蒲原 潤一, 本橋 和志, 渡部 康弘
    2008 年 61 巻 2 号 p. 30-35
    発行日: 2008/07/15
    公開日: 2013/09/02
    ジャーナル オープンアクセス
    The Abe River is one of the steepest rivers in Japan (channel length 51 km, drainage area 567 km2), originating from Oya Peak (elev. 1999.7 m) running through the central area of Shizuoka City. Several severe floods occurred in this river, including the floods of 1828 and 1914. When the typhoon struck on Aug. 28, 1914, the upstream area of the Abe River was subject to rainfall of more than 400 mm. This caused a major flood over Shizuoka City area, resulting in severe damage including 45 death, 1,000 houses washed away, and 10,000 houses inundated. It was found that the cause of this flood was not only the heavy rainfall but also river-bet blockage at 23.5 km from the river mouth. This blockage, caused by the large-scale landside (200 m wide, 180 m high) on the right bank, covered more than 2/3 of the river width (500 m) and created a landslide dam with a height 15 m, area 320,000 m2, and volume 1,600,000 m3. This landslide dam burst immediately, triggering a flood surge which attacked the city area downstream. We can see well that the topography of this area has changed over the years if we examine 1/5000 to 1/50,000 scale topographical maps prepared by Geographical Survey Institute in 1889, 1896, 1916, 1948, 1974, and 1978 (including corrective surveys).
  • 和田 孝志, 里深 好文, 水山 高久
    2008 年 61 巻 2 号 p. 36-40
    発行日: 2008/07/15
    公開日: 2013/09/02
    ジャーナル オープンアクセス
    Current numerical models for debris flow simulation usually use one-dimensional models in gullies and two-dimensional models in alluvial fans. However, using different models gives inaccurate results in the boundary areas between gullies and alluvial fans. In this study, we aimed to improve results in the boundary areas by constructing an integrated model. We used one-dimensional models in gullies and two-dimensional models in alluvial fans for each timestep, but the procedure considered the mutual influence between these models at the boundary areas. Using our integrated model, we simulated debris flow on a virtual watershed that had different slope angles between a gully and an alluvial fan. The results demonstrated that our integrated model provided a more rational description of debris flow in the boundary areas. This led to more accurate results in the alluvial fans. Therefore, our integrated model is more effective at numerically simulating debris flow than current models.
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