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A Flume Experiment on Utilizing Time Domain Reflectmetory for Bedload Monitoring
Get PDFTo develop a new bedload monitoring method in pools of mountain streams, we attempted to establish a measurement system of sediment topography in a pool by utilizing TDR (Time Domain Reflectometry). Our measurement system consisted of cable tester, multiplexers and multiple sensor probes that were simply produced from a PCV pipe and two stainless rods. The measurement system was verified by a flume experiment, in which sediment was supplied to a flume and weighed in a container connected to the downstream end of the flume. Eight TDR probes were also installed in the container to measure sediment surface topography. Relative errors of sediment volume measured by TDR were around 10%, suggesting that our measurement system was useful even under running water conditions.To develop a new bedload monitoring method in pools of mountain streams, we attempted to establish a measurement system of sediment topography in a pool by utilizing TDR (Time Domain Reflectometry). Our measurement system consisted of cable tester, multiplexers and multiple sensor probes that were simply produced from a PCV pipe and two stainless rods. The measurement system was verified by a flume experiment, in which sediment was supplied to a flume and weighed in a container connected to the downstream end of the flume. Eight TDR probes were also installed in the container to measure sediment surface topography. Relative errors of sediment volume measured by TDR were around 10%, suggesting that our measurement system was useful even under running water conditions
Application of Time Domain Reflectometry (TDR) on Bedload Monitoring
Get PDFToward a novel approach of bedload monitoring in mountainous streams, we attempted to measure height and porosity of sediment layer below water surface by applying TDR. A column experiment was conducted to validate accuracies of estimated sediment height and porosity for a probe (0.75 mm in length). The probe was inserted into a container filled with water and, then, TDR waveforms were measured during a procedure of supplying the sand until the probe was totally covered by sediment layer. TDR waveforms were analyzed and used for calculating height and porosity of sediment layers. Experimental results show good agreements of calculated heights of sediment layer. Calculated porosities ranged from 0.32 to 0.46, which were consistent with general porosity of deposited sand (about 0.4). Comparisons between calculated and observed cumulative sediment volumes suggested that the method proposed in this study is applicable of monitoring sediment in water and bedload in the field.Toward a novel approach of bedload monitoring in mountainous streams, we attempted to measure height and porosity of sediment layer below water surface by applying TDR. A column experiment was conducted to validate accuracies of estimated sediment height and porosity for a probe (0.75 mm in length). The probe was inserted into a container filled with water and, then, TDR waveforms were measured during a procedure of supplying the sand until the probe was totally covered by sediment layer. TDR waveforms were analyzed and used for calculating height and porosity of sediment layers. Experimental results show good agreements of calculated heights of sediment layer. Calculated porosities ranged from 0.32 to 0.46, which were consistent with general porosity of deposited sand (about 0.4). Comparisons between calculated and observed cumulative sediment volumes suggested that the method proposed in this study is applicable of monitoring sediment in water and bedload in the field
Application of X-band Radar and Runoff Model to Debris Flow Frequently Occurred Creeks in Sakurajima Island
Get PDFTo examine effects of spatial distributions of rainfall on local occurrence of debris flow and flash flood, we observed stream discharge by interval cameras and conducted hydrological simulations with X-band rainfall radar data in four catchments in Sakurajima Island. Hydrological processes were simulated for two rainfall data; rainfall data in downstream areas (Case 1) and upstream areas (Case 2) of each catchment was applied for whole area of the catchments. Debris flows generally occurred when very strong rainfall intensity was observed in upstream areas of the study catchments. Simulated stream discharges of Case 2 were more consistent with occurrence of debris flows than those of Case 1. The simulation results also suggested that concentrations of overland flow into gullies were essential for occurrences of debris flow.To examine effects of spatial distributions of rainfall on local occurrence of debris flow and flash flood, we observed stream discharge by interval cameras and conducted hydrological simulations with X-band rainfall radar data in four catchments in Sakurajima Island. Hydrological processes were simulated for two rainfall data; rainfall data in downstream areas (Case 1) and upstream areas (Case 2) of each catchment was applied for whole area of the catchments. Debris flows generally occurred when very strong rainfall intensity was observed in upstream areas of the study catchments. Simulated stream discharges of Case 2 were more consistent with occurrence of debris flows than those of Case 1. The simulation results also suggested that concentrations of overland flow into gullies were essential for occurrences of debris flow
Characteristics of Sediment Disaster in 2010 comparing with Recent Years
No full text公開されている土砂災害および気象の統計情報を用いて近年の土砂災害の傾向と2010年の土砂災害の特徴および傾向について検討した。多雨年においては, 台風の上陸や前線によって広範囲において大規模なものを含む土砂災害が発生していた。2010年の6-10月の降雨量は平年並みであるものの, 多雨年と同様に広範囲にわたって土砂災害が分布し, 比較的小規模な災害が発生し, 期間も複数にわたったことが特徴的であった。また, 非常に局所的かつ短時間の集中豪雨による災害事例が見られた。将来の気候変動によっては豪雨日数が増加することから, 2010年のような小規模ではあるものの高頻度かつ広範囲にまたがる土砂災害が懸念され, 対応するような減災手段を検討していく必要があると考えられる。We investigated trend of sediment disasters in recent years and characteristics of sediment disasters in 2010, using opened database of sediment disaster and rainfall. Because of typhoons and front, many sediment disasters, including large ones, occurred in broad areas in years with heavy rainfall. Precipitation from June to October, 2010 was within the normal range. However, sediment disasters in 2010 distributed in broad areas as similar to the years with heavy rainfall and were distinguished by relatively small ones occurred in several periods. Sediment disasters caused by local intensive storms were also characteristic of 2010. Because number of days in which precipitation is greater than 50 mm/d may increase due to climate change, sediment disasters potentially occur more frequently and in broader areas. New methodology for reduce damages is required for such situation.公開されている土砂災害および気象の統計情報を用いて近年の土砂災害の傾向と2010年の土砂災害の特徴および傾向について検討した。多雨年においては, 台風の上陸や前線によって広範囲において大規模なものを含む土砂災害が発生していた。2010年の6-10月の降雨量は平年並みであるものの, 多雨年と同様に広範囲にわたって土砂災害が分布し, 比較的小規模な災害が発生し, 期間も複数にわたったことが特徴的であった。また, 非常に局所的かつ短時間の集中豪雨による災害事例が見られた。将来の気候変動によっては豪雨日数が増加することから, 2010年のような小規模ではあるものの高頻度かつ広範囲にまたがる土砂災害が懸念され, 対応するような減災手段を検討していく必要があると考えられる。We investigated trend of sediment disasters in recent years and characteristics of sediment disasters in 2010, using opened database of sediment disaster and rainfall. Because of typhoons and front, many sediment disasters, including large ones, occurred in broad areas in years with heavy rainfall. Precipitation from June to October, 2010 was within the normal range. However, sediment disasters in 2010 distributed in broad areas as similar to the years with heavy rainfall and were distinguished by relatively small ones occurred in several periods. Sediment disasters caused by local intensive storms were also characteristic of 2010. Because number of days in which precipitation is greater than 50 mm/d may increase due to climate change, sediment disasters potentially occur more frequently and in broader areas. New methodology for reduce damages is required for such situation
Effect of Soil Moisture on Landslide Occurrences by the Earthquake : Tohoku Pacific Ocean Earthquake
No full text2011年3月11日，東北太平洋沖地震が発生，地震に伴い発生した津波により，東北太平洋側地域に甚大な被害をもたらした。また，福島県白河市葉ノ木平地区等では，人的な被害を伴う土砂災害が発生した。被害は決して小さなものばかりではなかったが，全体的に見ると，地震の規模や記録された地震動の加速度の大きさにもかかわらず，山地部における斜面崩壊等の土砂災害は少数であり，規模も小さかった。また，人的被害を伴う土砂災害は，福島・栃木県に限定されていた。この原因について検討するために，地震発生時の土壌水分状態と地震の加速度を考慮した静的な斜面安定解析を行い，土壌水分状態が斜面安定性に与える影響を検討した。その結果，地震発生時期の先行降雨が少なかったことで，斜面安定性は大きく低下しなかったことが判明，仮に夏季の降雨イベント後に地震が発生していたら，実際よりも大きな被害がもたらされたと結論付けられた。The pacific side of Tohoku region, Japan was suffered by a devastating earthquake on 11th March, 2011. Several hillside slopes were collapsed due to the earthquake in inland region, and a number of people were also killed by the sediment related disaster. Contrasting with the devastating earthquake which suffered wide area, the landslides were limited in its number, area, and size. To understand the reasons of this limited landslide occurrences, distribution of the maximum earthquake acceleration was investigated. The effects of the slope topographical properties such as slope gradient, direction, and bedrock geomorphology were also investigated by the field observation. Numerical experiments were also conducted to demonstrate the effects of the slope topographical properties and soil moisture conditions on the landslide occurrences. From the field investigations and numerical simulations, it is elucidated that the reasons of the limited landslide occurrences are 1) limited suffering area of strong acceleration by the earthquake and 2) relatively dry soil moisture condition of slopes at the earthquake occurrence.2011年3月11日，東北太平洋沖地震が発生，地震に伴い発生した津波により，東北太平洋側地域に甚大な被害をもたらした。また，福島県白河市葉ノ木平地区等では，人的な被害を伴う土砂災害が発生した。被害は決して小さなものばかりではなかったが，全体的に見ると，地震の規模や記録された地震動の加速度の大きさにもかかわらず，山地部における斜面崩壊等の土砂災害は少数であり，規模も小さかった。また，人的被害を伴う土砂災害は，福島・栃木県に限定されていた。この原因について検討するために，地震発生時の土壌水分状態と地震の加速度を考慮した静的な斜面安定解析を行い，土壌水分状態が斜面安定性に与える影響を検討した。その結果，地震発生時期の先行降雨が少なかったことで，斜面安定性は大きく低下しなかったことが判明，仮に夏季の降雨イベント後に地震が発生していたら，実際よりも大きな被害がもたらされたと結論付けられた。The pacific side of Tohoku region, Japan was suffered by a devastating earthquake on 11th March, 2011. Several hillside slopes were collapsed due to the earthquake in inland region, and a number of people were also killed by the sediment related disaster. Contrasting with the devastating earthquake which suffered wide area, the landslides were limited in its number, area, and size. To understand the reasons of this limited landslide occurrences, distribution of the maximum earthquake acceleration was investigated. The effects of the slope topographical properties such as slope gradient, direction, and bedrock geomorphology were also investigated by the field observation. Numerical experiments were also conducted to demonstrate the effects of the slope topographical properties and soil moisture conditions on the landslide occurrences. From the field investigations and numerical simulations, it is elucidated that the reasons of the limited landslide occurrences are 1) limited suffering area of strong acceleration by the earthquake and 2) relatively dry soil moisture condition of slopes at the earthquake occurrence
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Meltwater-driven sediment transport dynamics in two contrasting alpine proglacial streams
No full textSubglacial sediments are a large component of the sediment budget of glacierized catchments but insights into the subglacial origin of sediments (bedload, in particular) linked to proglacial runoff dynamics remain scarce. In this study, we use a tracer-based approach to quantify meltwater proportions related to sediment transport at two proglacial streams, draining glaciers (named debris-covered and clean glacier) of different size, aspect and elevation range with contrasting distribution and thickness of debris cover and lithology of the subglacial sediments (i.e., metamorphic vs. sedimentary), in the Sulden/Solda catchment (Italian Alps). Results indicate that the glacier melt component (75 to 80 %) was associated with bedload concentrations of 1 to 10 kg m−3 at the debris-covered glacier and much lower concentrations of 0.01 to 1 kg m−3 at the clean ice glacier. At the seasonal scale, bedload and suspended sediment concentrations at both sites strongly varied with discharge. While daily bedload concentrations varied by up to two orders of magnitude obscured the seasonal development of bedload concentrations at both sites, a clear seasonality for suspended sediment concentrations was found. At the daily scale, the relationship of discharge, bedload, and suspended sediment was more complex because discharge and sediment transport did not always follow the daily variation of air temperature, or similar daily air temperatures resulted in different discharge and sediment transport responses and vice versa. Glacier size, presence of debris cover, and substrate were identified as the main drivers of meltwater dynamics and sediment transport at both glaciers. This study adds further insights into the interplay of meltwater contributions and sediment transport, which are essential to better assess the impact of climate warming on sediment supply in glacierized catchments
Effects of Snow on Deposition Area of Volcanic Mud Flow
No full text融雪型火山泥流は甚大な物的・人的被害をもたらす現象であるが，その発生メカニズムは明らかとなっていない。本研究では融雪実験をもとに構築した火山噴出・積雪層の熱交換および融雪モデルより得られた泥流ハイドログラフを用い，積雪層，火山噴出物供給範囲などの諸条件が発生泥流量および融雪型火山泥流の流下・堆積に及ぼす影響について北アルプスの焼岳西斜面に位置する足洗谷を対象として検討を行った。熱移動と融雪，融雪水浸透解析の結果，発生泥流ハイドログラフは形状，ピーク流量ともに積雪深と積雪密度に大きく影響を受けることが明らかとなり，従来用いられていたハイドログラフよりも早くピーク流出が発生することが示唆された。二次元河床変動計算による泥流の流下・堆積解析の結果，いずれのケースにおいても発生源から約7km流下した栃尾地点において1-2mの浸水が起こることが示された。Generation process of volcanic mudflow is still unclear although volcanic mudflow induces huge damage and losses. We used newly developed simple heat transfer, snowmelt and infiltration of snowmelt water equations and calculated initial mudflow hydrograph under several depth and density of snow and amount of pyroclastic flow. Our results showed that initial mudflow volume was associated to snow depth and density. The results also suggested initial mudflow increased earlier than that assumed in previous studies. For all cases of the calculated initial mudflow hydrograph, a two dimensional riverbed change simulation showed inundation of 1 - 2 m depth at Tochio approximate 7 km downstream from the source of mudflow.融雪型火山泥流は甚大な物的・人的被害をもたらす現象であるが，その発生メカニズムは明らかとなっていない。本研究では融雪実験をもとに構築した火山噴出・積雪層の熱交換および融雪モデルより得られた泥流ハイドログラフを用い，積雪層，火山噴出物供給範囲などの諸条件が発生泥流量および融雪型火山泥流の流下・堆積に及ぼす影響について北アルプスの焼岳西斜面に位置する足洗谷を対象として検討を行った。熱移動と融雪，融雪水浸透解析の結果，発生泥流ハイドログラフは形状，ピーク流量ともに積雪深と積雪密度に大きく影響を受けることが明らかとなり，従来用いられていたハイドログラフよりも早くピーク流出が発生することが示唆された。二次元河床変動計算による泥流の流下・堆積解析の結果，いずれのケースにおいても発生源から約7km流下した栃尾地点において1-2mの浸水が起こることが示された。Generation process of volcanic mudflow is still unclear although volcanic mudflow induces huge damage and losses. We used newly developed simple heat transfer, snowmelt and infiltration of snowmelt water equations and calculated initial mudflow hydrograph under several depth and density of snow and amount of pyroclastic flow. Our results showed that initial mudflow volume was associated to snow depth and density. The results also suggested initial mudflow increased earlier than that assumed in previous studies. For all cases of the calculated initial mudflow hydrograph, a two dimensional riverbed change simulation showed inundation of 1 - 2 m depth at Tochio approximate 7 km downstream from the source of mudflow
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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