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Volume 49 (1996 - 199･･･
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Volume 49, Issue 4
Displaying 1-13 of 13 articles from this issue
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[in Japanese]1996 Volume 49 Issue 4 Pages 1-2
Published: November 15, 1996
Released on J-STAGE: April 30, 2010
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Hideaki MIZUNO, Takahisa MIZUYAMA1996 Volume 49 Issue 4 Pages 3-8
Published: November 15, 1996
Released on J-STAGE: April 30, 2010
JOURNAL FREE ACCESSWhen installing grid dams to trap debris flow, it is important to select the interval of steel pipes of the grids with consideration for characteristics of debris flow such as grain size, sediment concentration, and so on. Since the front of debris flow contains coarse grains, the sediment concentration there increase most, while the other sections of debris flow that follow the front contains fine grains, their sediment concentration decreases. The grids for trapping debris flow have such an effect that the front of debris flow is trapped by the lower grids while the following debris flow is trapped by the upper grids. However, since the interval of steel pipes of both the upper and lower grids are conventionally made the same, we thought it might be better to narrow the existing steel pipe interval of the upper grids.
To this end, we carried out flume experiments using grid dam models to examine whether or not the upper grids having a narrow pipe interval is more capable of trapping debris flow. As a result of the experiments, we found that the grid dam models designed to have narrow pipe intervals of the upper grids are capable of trapping more volume of sediment transported by debris flow.View full abstractDownload PDF (2420K) -
Tetsuya KUBOTA1996 Volume 49 Issue 4 Pages 9-14
Published: November 15, 1996
Released on J-STAGE: April 30, 2010
JOURNAL FREE ACCESSNot only matching Sabo facilities to surroundings but also making them suave to the human sense of vision becomes very important these days. In this point of view, here the focus is put on the reflection pattern of stream surface at torrents or at channel works. They were investigated by means of spacial frequency fluctuation, questionnaire, and multi-discriminant analysis. Natural flow or stone made dam used to be felt as having “bland surfce pattern” for the sense of vision, therefore they are supposed to have “bland fluctuation i. e. 1/f fluctuation (f: frequency) ”. In this aspect, it is found consequently that the stream with 1/f fluctuation have suave surface pattern that means “the human touch bland pattern”.View full abstractDownload PDF (5370K) -
Seiji YANAI, Mitsuhiro NAGATA, River Joint Research Group1996 Volume 49 Issue 4 Pages 15-21
Published: November 15, 1996
Released on J-STAGE: April 30, 2010
JOURNAL FREE ACCESSThe influence of channel works on spawning habitat of masu salmon (Oncorhynchus mason BREVOORT) was studied in the Shakotan River of Central Hokkaido, Northern Japan. The meandering channel was straight-ened by enbankment and the river bed was protected by gabion works about 20 years ago. The spawned sites were widely distributed throughout the artificial altered section and natural tributary with density of 0. 5 per 100 m distance. The spawned sites were densely made in the transition from pool to rapid riffle. The gravel used for spawning in altered section were larger than natural river (mode 8-10 cm in diameter), and the velocity was relatively faster than natural (mean 50-60 cm/sec) . Vegetation cover was also additional factor to be chosen for spawn. These facts indicates that the masu salmons were forced to spawn in worse condition in altered section than natural. However, there was remarkable difference on the spawning density depending on the protection ratio of river bed. The spawning sites in altered section were limited in the downstream of falling works with 1 m height where the gravel layer with favorable water depth and velocity was provided. For reproduction of masu salmon in artificially altered river, it is important to allow minor gravel scouring and sedimentation along channel. They can be revived by creating variable stream flow and gravel deposition place.View full abstractDownload PDF (4771K) -
Michiya IRASAWA, Takao TAGUCHI1996 Volume 49 Issue 4 Pages 22-27
Published: November 15, 1996
Released on J-STAGE: April 30, 2010
JOURNAL FREE ACCESSEstablishment of timely warning and refuge system for debris flow is an urgent matter in the mountainous streams. Providing accurate information of rainfall for residents is also imperative. However a number of existing rain-gauges for that are still insufficient. Moreover, systematic methodology for layouts of telemeters aimed at the operation of timely warning and refuge system for debris flow from the viewpoint of sabo has not yet been established. On account of that, more rain-gauges should be installed immediately here. In this study, we examine characteristics of rainfall in the river basin and effecive layouts of telemeters based on existing rain-gauges and an areal concentration of mountainous steams threatened by debris flow. As a result, installations of 21 telemeters are proposed here.View full abstractDownload PDF (2395K) -
Katumi SENOO, Toshio MORI, Yasumasa MARUYAMA, Okichika KUROKAWA1996 Volume 49 Issue 4 Pages 28-33
Published: November 15, 1996
Released on J-STAGE: April 30, 2010
JOURNAL FREE ACCESSThere was a difference in human damage regardless of the scale of the sediment disaster, though the disaster occurred throughout the country in 1993. Then, to understand the actual state of sediment disaster warning and evacuation, a questionnaire carried out to cities, towns, and villages and regional inhabitants where the disaster orrurred. This is a report suggested to a warning and evacuaion system in the future based on this result.View full abstractDownload PDF (9717K) -
Takahisa MIZUYAMA, Michinobu NONAKA, Nobuhisa NONAKA1996 Volume 49 Issue 4 Pages 34-37
Published: November 15, 1996
Released on J-STAGE: April 30, 2010
JOURNAL FREE ACCESSIn order to elucidate how the riverbed elevation or the depositional gradient of sabo dams varies from moment to moment, it is necessary to observe the temporal variation of the sediment discharge rate. Due to technical difficulties, however, no means were available for measuring changes in sediment discharge rate. A hydrophone that can record the numbers of collisions between sand particles and special pipes or board installed along a riverbed is one of the promising methods for measuring how the sediment discharge rate varies from moment to moment. We actually installed a hydrophone made of steel pipe in the bed of a torrent in the Hachisu-dani Valley of Mount Rokko. Although no large-scale flood occurred during two years of observation after the hydrophone was installed, the records obtained from the hydrophone prove that the sediment discharge rate is qreater in the former half of a flood than in the later half of a flood. Since the occurrence of the Hanshin-Awaji earthquake in January, 1995, the observed sediment discharge rate has shown a better correspondence with the water discharge rate.View full abstractDownload PDF (2652K) -
Takio SANO, Atsushi KATAGIRI, Ryouichi KATOU1996 Volume 49 Issue 4 Pages 38-41
Published: November 15, 1996
Released on J-STAGE: April 30, 2010
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Takuya TSURUKI1996 Volume 49 Issue 4 Pages 42-46
Published: November 15, 1996
Released on J-STAGE: April 30, 2010
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Goichiro TAKAHASHI1996 Volume 49 Issue 4 Pages 47-48
Published: November 15, 1996
Released on J-STAGE: April 30, 2010
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Masahiro KAIBORI1996 Volume 49 Issue 4 Pages 49-51
Published: November 15, 1996
Released on J-STAGE: April 30, 2010
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Hideaki MARUI1996 Volume 49 Issue 4 Pages 52-53
Published: November 15, 1996
Released on J-STAGE: April 30, 2010
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Katsuo TAKEZAWA1996 Volume 49 Issue 4 Pages 54-56_2
Published: November 15, 1996
Released on J-STAGE: April 30, 2010
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