Journal of the Japan Society of Erosion Control Engineering

[title in Japanese]

[in Japanese]

1995 Volume 47 Issue 6 Pages 1-2
Published: March 15, 1995
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.11475/sabo1973.47.6_1

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Spatial Change of the Strength of Woody Debris Accompanied with Sediment Storage

Tomomi MARUTANI, Mio KASAI

1995 Volume 47 Issue 6 Pages 3-7
Published: March 15, 1995
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.11475/sabo1973.47.6_3

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On the slope at northern part of Kyushu, many blown-over trees occured by typhoon 19, 1991. The trees, slipped down from the slope at intensive rainfall, often construct woody debris in streams. Woody debris caused sediment storage in the stream (in this case, woody debris is called a “wall”) . Spatial changes of the strength of the wall accompanied with sediment storage was investigated. Relationships between the strength of the wall and the distance from the source of trees, and between the strength of the wall and the volume of sediment storage were analyzed.
Result were as follows. The volume of sediment storage tended to increase according to increment of the strength of the wall (to 550 m³) . Momentum of debris flow stopping by the wall increased along the distance from the source of trees. These analyses lead that the wall of the lower part of stream become more stable against debris flow than the wall of the upper part of stream.

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A Study on a Neural Network System for Critical Rainfall Determination of Debris Flow Warning and Evacuation

Tetsuya KUBOTA, Hirosi IKEYA

1995 Volume 47 Issue 6 Pages 8-14
Published: March 15, 1995
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.11475/sabo1973.47.6_8

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In order to prevent debris flow disaster, warning and evacuation are very crucial in the area where it tends to occur. In this study, a critical rainfall determination method of debris flow warning and evacuation is studied for past disaster in Shimane, Kagawa and Kochi prefectures, and for Unzen Fugendake volcano in Kyusyu Island that has been pretty active recent years, using 3 layer neural network computer system combined with the critical rainfall determination system by debris flow discharge which is similar to the current method “A”. And with this method, the debris flow critical rainfall seems to be determined more easily and precisely than before.

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Application of Transient Flow Model of Storm Water Taking Relationship between the Saturation Ratio and the Groundwater Level into Consideration

Kazuko TERAMOTO, Tatsumi SUZUKI, Takahiro NARUSE, Hiroyuki MATSUYAMA, ...

1995 Volume 47 Issue 6 Pages 15-23
Published: March 15, 1995
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.11475/sabo1973.47.6_15

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Hillside landslides occur frequently in many parts of Japan in the period of heavy rains every year. Hillside landslides are triggered by infiltration of the storm water into the surface soil layer on the mountain slope. Thus, to determine the degree of danger of basin collapse, it is necessary to evaluate the storm water hydrologic process on a hillslope in a realistic manner. In this study the vertical infiltration experiments were excuted using a large scale undisturbed soil sample to understand quantitatively the process of rainfall infiltration, ascent of the groundwater level and the relationship between the groundwater level and the saturation ratio on the soil. Using the result of these experiments, the storm water hydrologic process model was proposed. The effectiveness of this model was confirmed by applying it to the small basin which has experienced hillside landslides. The influence of the initial saturation ratio on the soil was evaluated with this model. The result shows that large initial saturation ratio hasten the appearance time of maximum ground-water level and that it is not so much connected with the value of the maximum groundwater level.

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On Debris Flow Disasters on Steep Slopes Facing the Kagoshima Bay, Caused by the Torrential Rain of August 6, 1993, Kyushu

Seiji TAKAYA

1995 Volume 47 Issue 6 Pages 24-27
Published: March 15, 1995
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.11475/sabo1973.47.6_24

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This paper aims to report a result of the research on debris flow disasters which occurred at Ryugamizu and 11 other spots along 3-kilometer distance between Ryugamizu and Hiramatsu.
On August 6, 1993, Kagoshima area was struck by a record-high torrential rain, which caused a number of slope failures and debris flows on steep slopes facing the Kagoshima Bay. The debris flows destroyed several houses and washed away a part of the Japan Railroad track and flew over with a great volume of massive sediment on the JR track and the road.
It was found that first slope failures occurred at the upper steep slopes, followed by debris flow, which reached down the railroad and the road. The debris flow from the Ryugamizu-kita slope reached down onto the sea.

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Sediment Production and Storage Processes Associated with Earthquake-induced Landslides in Okushiri Island, 1993

Masami SAITO, Tohru ARAYA, Futoshi NAKAMURA

1995 Volume 47 Issue 6 Pages 28-33
Published: March 15, 1995
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.11475/sabo1973.47.6_28

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On July 12 in 1993, an earthquake (magnitude 7. 8) occurred at a depth of 34 km, off the shore of southwest Hokkaido. Weather Bureau (1993) named it “Hokkaido-nanseioki earthquake”. It triggered many landslides over the southwest Hokkaido district. Especially, the Okushiri Island experienced numerous landslidings. Sediment produced by landslides still remains at footslopes, and might be re-mobilized by debris flow.
We clarified general characteristics of landslides by this earthquake, and estimated sediment volume remaining on hillslopes of the landslides in each watershed of the Okushiri Island. The results are as follows;
1. The number of earthquake-induced landslides recognized by aerial-photographs was 997 including 336 recurring landslides and 71 landslides occurring around roadcuttings or dam sites. Areal ratio of landslides to the distribution area was 0. 74 %, which is the average ratio in comparison with the previous earthquakes in Japan.
2 . Landslides could be classified into 4 types, such as rock-fall, rock-slide, shallow soil-slide and debrisavalanche. Especially, debris-avalanche initiated by this earthquake was rarely observed as opposed to rainfall-induced landslides.
3. Most landslides occurred at convex slopes cross-sectionally such as ridges, terrace cliffs and break lines of slopes.
4, We estimated sediment volume left on hillslopes after landsliding. It was predominantly higher than rainfall-triggered cases. This remaining sediment is hazardous as secondary source for succeeding mass movements from the disaster-prevention point of view.

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The Critical Rainfall Condition Inducing the Debris Flow in Yotagiri River, Central Japan

Shoichi UEMURA, Yuichi ONDA, Yasuo TAKEDA

1995 Volume 47 Issue 6 Pages 34-37
Published: March 15, 1995
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.11475/sabo1973.47.6_34

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[title in Japanese]

Kiyoshi HONDA

1995 Volume 47 Issue 6 Pages 38-41
Published: March 15, 1995
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.11475/sabo1973.47.6_38

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[title in Japanese]

[in Japanese]

1995 Volume 47 Issue 6 Pages 42-43
Published: March 15, 1995
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.11475/sabo1973.47.6_42

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[title in Japanese]

[in Japanese]

1995 Volume 47 Issue 6 Pages 44
Published: March 15, 1995
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.11475/sabo1973.47.6_44

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[title in Japanese]

[in Japanese], [in Japanese]

1995 Volume 47 Issue 6 Pages 45-48
Published: March 15, 1995
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.11475/sabo1973.47.6_45

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[title in Japanese]

[in Japanese]

1995 Volume 47 Issue 6 Pages 49-50
Published: March 15, 1995
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.11475/sabo1973.47.6_49

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[title in Japanese]

[in Japanese]

1995 Volume 47 Issue 6 Pages 51
Published: March 15, 1995
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.11475/sabo1973.47.6_51

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[title in Japanese]

[in Japanese]

1995 Volume 47 Issue 6 Pages 51a-53
Published: March 15, 1995
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.11475/sabo1973.47.6_51a

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[title in Japanese]

[in Japanese]

1995 Volume 47 Issue 6 Pages 54-56_2
Published: March 15, 1995
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.11475/sabo1973.47.6_54

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[title in Japanese]

Masaaki HANAOKA

1995 Volume 47 Issue 6 Pages 57-58
Published: March 15, 1995
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.11475/sabo1973.47.6_57

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