Sediment transport process in mountain streams has been studied theoretically and experimentally in the first place, which resulted in various experimental bed load equations. Field sediment transport observation such as direct sediment sampling in mountain streams has been circumvented by many obstacles such as the inherent brevity of its observation. Since direct sampling is indispensable in the calibration of bed load equations, however, it has been undertaken by various means. The sampling and observation efforts led to the development of more indirect but stable sediment transport monitoring methods (hereafter “indirect method") in recent years. One of the indirect methods, a hydrophone sediment discharge measuring system (hereafter “hydrophone system"), has been intensely studied for the development of practical sediment transport monitoring. Hydrophone systems have been tested quantitatively in relation to bed load equations as well as to directly sampled sediment discharge in 100 and 200 km²-scale river basins. The reliability of sediment discharge estimation made by hydrophone systems has been quantitatively assessed in comparison to direct sampling results obtained by sediment traps. The tests were carried out on a unit width basis and have not been expanded to full-scale river width thus far. The results of the tests were also limited by the brevity of sample observations, which lasted not more than a few days.
In this study, the scope of reliability analysis concerning hydrophone systems was expanded both in space and in time. Unit width sediment discharge was observed and analyzed in 2 river basins in Hokuriku region, and then converted to full scale by multiplying their discharge ratios. Observation periods in the basins were extended to more than a year. Combined, the observation results constituted sets of basin-wide sediment discharge estimated on a yearly basis. Basinwide sediment discharge has long been studied as a subject of reservoir sedimentation. Quality observation data of reservoir sedimentation are available in Hokuriku region. Estimated sediment discharge in observed basins was converted to total load quantity over unit area, so that it became comparable to corresponding reservoir sedimentation,which consisted of a wider range of sediment particles.
Reservoir sedimentation was statistically analyzed in terms of regional and geological characteristics. Sample frequency distributions of yearly unit area sedimentation used for comparative analysis were formed from sedimentation samples with similar basin-wide geologic properties. The spread of the frequency distributions were analyzed by classifying reservoir service periods. Unit area total load sediment discharge estimation fell in large part within a normal range of yearly unit area reservoir sedimentation at 5% statistical significance. The results of the verification were thought to become more rigorous by further examining the ratio between bed load and total load discharge based on simultaneous total load observation and analysis in the basins.

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In erosion control engineering field, various kinds of new techniques have been developed and briskly put into practical uses. Among these techniques, it is said that non-structural measures have been in demand lately. These measures contain many kinds of techniques and the terminology “non-structural measures" that are still not clear. Therefore, in this study, various kinds of non-structural measures which have been developed so far are reviewed, and the present technological development measures are analyzed in relation to social demands. As a result, practical needs on these measures, today and in the future, will be clarified. This paper's distinctive feature is its analysis based on the quantity of patent right registration, while in many preceding papers, major analyses used to be conducted based on the quantity of academic papers. Additionally, the questionnaire survey or the hearing investigation was executed to extract the problem that the erosion and torrent control field had, and it listened to engineer's opinion and manager's opinion at the technology development. From the result of this investigation, it turned out to be felt that the entrepreneurial strategy and the advantage of making to the patent are different.

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One of the causes of debris flow is fluidization of deposits. Although it is generally estimated that the deposits of riverbed are saturated when the debris flow occurs, no observations have been conducted of moisture changes of debris flows. Thus, in this study, we observed moisture changes of deposits in the field just before the occurrence of debris flow. The study site was located in uppermost part of the Hirudani Valley of Mount Yakedake, where thick deposits have formed on a steep stream(34°). We installed nine tensiometers at three depths in three plots across the deposits. The results are summarized as follows. 1) The initial responses were about 20 minutes faster at the deep tensiometers than at the middle-layer tensiometers. This suggests that water flow progressed quickly along the base of the deposit. 2)Although the upper and lower layers were saturated by the heaviest rainfall (24.5 mm/h), the middle layer was unsaturated. This suggests that water flowed not only vertically downward but also parallel to the stream.

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In this report, characteristics of sediment related disasters triggered by the Noto-Hantou Earthquake was described. And theyare summarized as follows. The area where the sediment disasters occurred was almost located within the range of 500-700 gal of the earthquake acceleration except small-scale slope failure disasters. Slope failures which occurred around the surface part of earthquake fault located comparatively high density. As for the slope failures of the inland,damages occurred mainly in the consolidated or semisolid sedimentary layer of Miocene by presumed from the house damage and geological features of the slope failure situation. By the examination of earthquake acceleration and velocity component, the earthquake movement reached to the mountanious slope covered with thin topsoil layer and coastal erosion cliff in Wajima-city and Shika-town estimated at the same level as the earthquake record of Togi observation point.

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The earthquake occurred in the Iwate Prefecture inland southern part at the time at eight forty-three a.m. on June 14 th in 2008. At magnitude 7.2, in the focal region in Iwate Prefecture and Miyagi Prefecture, the large-scale landslide disaster generated this earthquake. As for featuring an earthquake this time, little damage at the building occurs whereas it is in the characteristic that there is much landslide disaster in the upland. The large-scale dirt production phenomenon with the scale which crosses 10,000,000 m³ occurred. Also, a lot of landslide dams emerge and the danger of the burst continues. By the purpose to grasp the disaster actual state this time, it composed an urgent probe squad belong with Japan Society of Erosion Control Engineering sent. This report is the one to have gathered the result.

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The Wenchuan Earthquake occurred at 15 : 07, on May 12, 2008 in China. Its hypocenter was close to the Wenchuan,Sichuan, (North 31°01'05'', East 103°36'05") and its magnitude (M) was 8.0. Many landslides were triggered by the earthquake in the Mts. Longmenshan, west of Chengdu. Field investigation were conducted for the sediment disasters at the end of July - beginning of August. Characteristics of several large landslides and landslide dams are described.

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