研究者データベース
Last Updated :2024/10/10
研究者情報
マスター
アカウント（マスター）
氏名
桂 真也(カツラ シンヤ), カツラ シンヤ
所属（マスター）
所属（マスター）
独自項目
syllabus
- 2021, 森林緑地調査解析学特論Ⅰ, Advanced Field Research and Data Analysis on Forest-landscape Management I, 修士課程, 農学院, 修士論文、景観、種、DNA、微地形、斜面崩壊
- 2021, 砂防工学, Erosion Control Engineering, 学士課程, 農学部, 水土砂災害・山地砂防・火山砂防・治山砂防技術・ソフト対策・流域総合土砂管理
- 2021, 森林測量学, Forest Surveying, 学士課程, 農学部, 森林測量，距離測量，角測量，水準測量，トラバース測量，誤差論，最小二乗法，最新の測量技術，測量データの処理，測量データの応用，地形判読
- 2021, 森林測量学実習, Training on Forest Surveying, 学士課程, 農学部, 森林測量，距離測量，角測量，水準測量，トラバース測量，誤差論，最小二乗法，最新の測量技術，測量データの処理，測量データの応用，地形判読
- 2021, 英語演習, English Seminar, 学士課程, 全学教育, 森林生態系の管理・保全、樹木の構造と性質、木質バイオマスの利活用
- 2021, 一般教育演習(ﾌﾚｯｼｭﾏﾝｾﾐﾅｰ), Freshman Seminar, 学士課程, 全学教育, 組織構造、環境応答、強度、木質バイオマス、樹木の化学成分、オゾン・酸性雨、保全管理、森林管理、生物多様性、生態系サービス、国土保全、森林政策
- 2021, 森林保全実習, Practical Field Work on Silviculture and Forest Conservation, 学士課程, 農学部, 流域保全、資源利用、森林と地域社会、自然災害の軽減・修復
- 2021, 流域保全論, Watershed Conservation, 学士課程, 農学部, 流域の認識手法、「流域住民」としての意識形成手法、合意形成、流域環境・生態系保全、防災、地域振興、土地利用
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プロフィール情報
所属
学位
プロフィール情報
姓
桂名
真也ID各種
201501030111678083
所属
業績リスト
研究キーワード
研究分野
経歴
- 2019年04月 - 現在 北海道大学 広域複合災害研究センター
- 2015年07月 - 現在 北海道大学 大学院農学研究院
- 2013年04月 - 2015年06月 独立行政法人（国立研究開発法人）土木研究所
- 2011年07月 - 2013年03月 国土交通省 水管理・国土保全局
- 2009年04月 - 2011年07月 国土交通省 国土技術政策総合研究所
学歴
受賞
論文
- Takamasa Matsunaga, Shin’ya KatsuraJournal of Hydrology 644 131898 2024年11月 [査読有り][通常論文]
- Shin'ya Katsura, Yuko Suzuki, Takahiko YoshinoJournal of Hydrology 632 130889 2024年03月 [査読有り][通常論文]
- Takahiko Yoshino, Shin’ya KatsuraWater 14 19 3122 2022年10月 [査読有り][通常論文]
Groundwater zone formation in the soil layers of a headwater catchment is an important factor that controls volumetric and chemical changes in streamflow; it also induces shallow landslides. Previous studies have suggested that the groundwater zone in soil layers generally forms transiently atop low-permeability layers in response to rainfall. This study focused on an unchanneled hollow in a serpentine headwater catchment, where a semi-perennial to perennial groundwater zone was observed in thin organic soil layers (OSLs) overlying thick clay mineral soil layers (CMLs), even during dry periods. We conducted detailed observations in this catchment to clarify the formation processes of the semi-perennial to perennial groundwater zone. The results showed that water is supplied from the CMLs to the OSLs as unsaturated upward flow in areas where the OSLs are dry. This water then accumulates in the downslope hollow, which sustains the groundwater zone in the OSLs during dry periods. The frequent and long-term occurrence of upward flow can be attributed to differences in the hydraulic properties of OSLs and CMLs. This process prevents the OSLs in the hollow from drying, presumably causes volumetric and chemical changes in streamflow, and reduces the stability of OSLs. - Toshiya Aoki, Shin’ya Katsura, Takashi Koi, Yasutaka Tanaka, Takashi YamadaLandslides 19 8 1813 - 1824 2022年08月 [査読有り][通常論文]
- Takashi Koi, Norifumi Hotta, Yasutaka Tanaka, Shin’ya KatsuraFrontiers in Earth Science 9 769061 2022年03月 [査読有り][通常論文]
The earthquake that occurred on 6 September 2018, in the eastern part of the Iburi region of Hokkaido, Japan (the Hokkaido Eastern Iburi Earthquake) caused thousands of shallow landslides in mountain areas. In areas where many landslides occurred, the trees on the slope became large woody debris (LWD) and were supplied to the catchment. Understanding the properties of LWD during the earthquake and its subsequent movement after the earthquake are important to manage the produced LWD and implement disaster prevention measures. This study evaluates the risk of future LWD disasters based on the sequence of LWD generation, its spatial distribution, and LWD relocation linked to temporal fluctuations in rainfall events. The study site is the upper Habiu River catchment (0.37 km2), where multiple shallow earthquake-related landslides occurred. Orthophotos and elevation data acquired before and after the earthquake were used to detect the properties of LWD. To evaluate the risk of an LWD disaster, we examined the correspondence between the hydraulic quantities, including the precipitation for 2 years after the earthquake and the water depth. It was estimated that approximately 7,000 LWD pieces (9,119 m3 km−2) were produced during the earthquake. Orthophoto interpretations indicate that over 80% of the LWD produced at the time of the landslide moved from the slope to the channel accompanied by the landslide debris; some of that then flowed down, accumulated, and formed logjams. In the river channel approximately two years after the earthquake, the destruction of logjams and the clear and drastic movement of LWD could not be confirmed. In this catchment, the uneven LWD distribution and the formation of logjams were fixed almost immediately after the landslide at the time of the earthquake; these characteristics are important when considering future actions. The water depth evaluation based on the difference in the excess return period indicate that the degree of risk differs depending on the deposition location in the channel. This suggests that not all LWD in the catchment are dangerous and that a risk assessment focusing on the LWD location can be effective. This study also makes it possible to determine high priority areas for LWD treatment. - 松永隆正, 桂真也日本地すべり学会誌 58 4 1 - 16 2021年07月 [査読有り][通常論文]
- Toshiya Aoki, Shin’ya Katsura, Takahiko Yoshino, Takashi Koi, Yasutaka Tanaka, Takashi YamadaVilímek, V., Wang, F., Strom, A., Sassa, K., Bobrowsky, P. T., and Takara, K. (eds.) Understanding and Reducing Landslide Disaster Risk, Vol.5 Catastrophic Landslides and Frontiers of Landslide Science 81 - 86 2021年01月 [査読有り][通常論文]
- 融雪土砂災害に対する融雪を考慮した土砂災害警戒情報の適用性の検討桂真也第10回土砂災害に関するシンポジウム論文集 187 - 192 2020年09月 [査読有り][通常論文]
- 多数の短期・長期降雨指標を用いた平成28年熊本地震後の土砂移動現象発生時の降雨規模評価松永一慶, 桂真也第10回土砂災害に関するシンポジウム論文集 7 - 12 2020年09月 [査読有り][通常論文]
- Nobutomo Osanai, Takashi Yamada, Shin-ichiro Hayashi, Shin'ya Katsura, Takahisa Furuichi, Seiji Yanai, Yasuhiro Murakami, Tomoyoshi Miyazaki, Yuichiro Tanioka, Shigetaka Takiguchi, Mayumi MiyazakiLANDSLIDES 16 8 1517 - 1528 2019年08月 [査読有り][通常論文]
The 2018 Hokkaido Eastern Iburi Earthquake struck the eastern Iburi region (epicenter: 42.691 degrees N, 142.007 degrees E, depth: 37.0 km) of Hokkaido, Japan, at 3:07.59 JST, September 6, 2018 (18:07.59, September 5, 2018 UTC). Many shallow landslides were triggered by this Mw 6.6 (Mj 6.7) earthquake. The basement complex in the affected area (sedimentary rocks) is covered with thick pyroclastic fall deposits derived from the Tarumae Volcano, etc., and the strong seismic shocks triggered shallow landsliding of them. Shallow landslides moving along valley type topography traveled greater distances than those moving along planar slope topography. Some shallow landslides occurred on relatively gentle slopes (< 30 degrees). The earthquake also induced several large-scale deep- seated landslides, including one that has formed a landslide dam in the Hidaka-horonai River. Landslides were densely distributed over hilly regions (elevation: 200-400 m) within an area of approximately 400 km2 in Atsuma (landslides caused 36 deaths), Abira, and Mukawa, and the number of landslides and the total area of the landslides were the largest in Japan ever since the Meiji Era (1868- 1912). The catchments where shallow landslides were concentrated were severely devastated. - 小山内 信智, 藤浪 武史, 村上 泰啓, 伊波 友生, 佐藤 創, 中田 康隆, 阿部 友幸, 大野 宏之, 武士 俊也, 田中 利昌, 小野田 敏, 海堀 正博, 本間 宏樹, 柳井 一希, 宮崎 知与, 上野 順也, 早川 智也, 須貝 昂平, 山田 孝, 笠井 美青, 林 真一郎, 桂 真也, 古市 剛久, 柳井 清治, 竹林 洋史砂防学会誌 71 5 54 - 65 公益社団法人 砂防学会 2019年01月 [査読有り][通常論文]
On 6th September 2018, a large earthquake (the 2018 Hokkaido Eastern Iburi Earthquake) with the magnitude of 6.7 struck the eastern Iburi region, Hokkaido and triggered numerous landslides. The landslides were distributed densely over hilly areas (400 km2) in Atsuma, Abira, and Mukawa Town, the total area of which reached 13.4 km2. All landslides were shallow landslides except a large-scale deep-seated one generated in midstream area of the Hidaka-Horonai River. The area is covered by thick pyroclastic fall deposits derived from the Tarumae Volcano etc., and the strong seismic shock triggered shallow landsliding of them. Some shallow landslides occurred at a relatively gentle slope (<15°). Shallow landslides moving along a valley topography tended to travel longer than those moving along a non-valley topography. In catchments where shallow landslides densely occurred, the ratio of landslide area to the total catchment area was very large compared with past earthquake events, suggesting that the catchments became highly devastated. Based on these survey results, we propose viewpoints for preventing secondary disasters in the damaged area and for promoting countermeasures against and studies on earthquake-induced landslide disasters in volcanic regions.
- A method for estimating maximum damage caused by sediment disaster by surveying with artificial satellite SAR imageryHayashi, S, Katsura, S, Kasai, M, Osanai, N, Yamada, T, Marutani, T, Noro, T, Kamiyama, JSymposium Proceedings of the INTERPRAEVENT 2018 in the Pacific Rim 401 - 407 2018年10月 [査読有り][通常論文]
- A study on criteria of warning and evacuation for large-scale sediment disasters considering the relationships with sediment movement and damageSuzuki, Y, Hayashi, S, Katsura, S, Kasai, M, Osanai, N, Marutani, TSymposium Proceedings of the INTERPRAEVENT 2018 in the Pacific Rim 387 - 393 2018年10月 [査読有り][通常論文]
- Geologic and topographic features of slope failure sites in the Aso caldera wall induced by the 2016 Kumamoto earthquakeSaitou, H, Katsura, S, Umetani, R, Kasai, M, Marutani, TSymposium Proceedings of the INTERPRAEVENT 2018 in the Pacific Rim 117 - 122 2018年10月 [査読有り][通常論文]
- 平成28年熊本地震前後の阿蘇地域における土砂移動現象発生時の各種降雨指標値の比較渡邊輝嗣, 桂真也, 林真一郎, 梅谷涼太, 齋藤はるか, 野呂智之, 村田郁央第9回土砂災害に関するシンポジウム論文集 151 - 156 2018年09月 [査読有り][通常論文]
- M. Touhei, T. Toriumi, S. Katsura, Y. IshiiLandslides and Engineered Slopes. Experience, Theory and Practice 1921 - 1924 2018年04月17日 [査読有り][通常論文]
- 桂真也, 丸山清輝, 池田慎二, 石田孝司日本地すべり学会誌 54 3 25 - 31 2017年05月 [査読有り][通常論文]
- 林真一郎, 内田太郎, 桂真也, 笠井美青, 小山内信智, 丸谷知己日本地すべり学会誌 54 2 18 - 25 2017年03月 [査読有り][通常論文]
- 小山内 信智, 笠井 美青, 林 真一郎, 桂 真也, 古市 剛久, 伊倉 万理, 高坂 宗昭, 藤浪 武史, 水垣 滋, 阿部 孝章, 布川 雅典, 吉井 厚志, 紅葉 克也, 渡邊 康玄, 塩野 康浩, 宮崎 知与, 澤田 雅代, 早川 智也, 松岡 暁, 佐伯 哲朗, 稲葉 千秋, 永田 直己, 松岡 直基, 井上 涼子砂防学会誌 69 6 80 - 91 砂防学会 2017年03月 [査読有り][通常論文]
- 石川芳治, 久保田哲也, 青戸一峰, 飯島康夫, 井川寿之, 池上忠, 池田誠, 植弘隆, 上原祐治, 内村雄一, 江川佳苗, 大石博之, 岡野和行, 海堀正博, 桂真也, 加藤誠章, 川原慎一郎, 古賀省三, 坂島俊彦, 相楽渉, 地頭薗隆, 篠原慶規, 清水収, 下田義文, 鈴木滋, 鈴木正美, 瀬戸康平, 田方智, 寺田秀樹, 寺本行芳, 堂ノ脇将光, 飛岡啓之, 鳥田英司, 中濃耕司, 西川友章, 花田良太, 平川泰之, 福塚康三郎, 藤澤康弘, 藤田正治, 正木光一, 宮田直樹, 山口和也, 山下伸太郎, 山根誠, 横尾公博砂防学会誌 69 3 55 - 66 2016年09月 [査読有り][通常論文]
- 桂真也, 木村誇, 丸山清輝, 石田孝司日本地すべり学会誌 53 3 11 - 20 2016年05月 [査読有り][通常論文]
- 桂真也, 畠田和弘, 木村誇, 丸山清輝, 池田慎二, 秋山一弥日本地すべり学会誌 53 1 1 - 12 2016年01月 [査読有り][通常論文]
- Distribution patterns of long-runout landslides triggered by the northern Nagano Prefecture earthquake of 2011Kimura, T, Hatada, K, Katsura, S, Maruyama, K, Akiyama, K, Noro, TProceedings of the INTERPRAEVENT2014 in the Pacific Rim O-9 2014年11月 [査読有り][通常論文]
- Topographic features of snowmelt-induced landslide locations with long travel distances in JapanKatsura, S, Kimura, T, Hatada, K, Maruyama, K, Akiyama, KProceedings of the INTERPRAEVENT2014 in the Pacific Rim O-13 2014年11月 [査読有り][通常論文]
- Shin'ya Katsura, Ken'ichirou Kosugi, Yosuke Yamakawa, Takahisa MizuyamaJOURNAL OF HYDROLOGY 511 703 - 718 2014年04月 [査読有り][通常論文]
The controls on the rapid mobilization and runoff of pre-event water are an important issue in hillslope hydrology. One of the mechanisms involved is groundwater ridging, based on the capillary fringe effect. The typical conditions for groundwater ridging to occur are as follows: (1) the slope consists of fine- to medium-textured materials with a large extent of the tension-saturated zone, (2) the slope gradient is low, and (3) the initial groundwater level is high. Where these three conditions are met, a further condition, (4) a small amount of rainwater, would then be enough to trigger groundwater ridging. In this study, we detail groundwater ridge formation in the bedrock layers of Akakabe Watershed (Japan) as recorded by detailed field observations using tensiometers and bedrock boreholes under conditions violating the above. The study site consisted of materials showing almost no tension-saturated zone and had a relatively high gradient (22). Moreover, the initially high groundwater level did not always generate a groundwater ridge, and a large total rainfall (>160 mm) was required to trigger groundwater ridging. Hence the conventional mechanism cannot explain the groundwater ridging at the field site studied here. It seems that the smaller distance from the groundwater table to the ground surface and the higher hydraulic conductivity in the downslope areas compared to the upslope areas caused a more rapid and larger groundwater level rise in the downslope areas, which accounted for the observed groundwater ridging. This study demonstrated that a groundwater ridge can be formed in the absence of the capillary fringe effect and that bedrock groundwater can contribute to storm runoff generation in headwater catchments under the influence of groundwater ridging. (C) 2014 Elsevier B.V. All rights reserved. - 権田豊, 秋山一弥, 桂真也, 畠田和弘, 秦雅之, 高橋幸彦, 桐生理, 澤陽之, 大曽根啓介, 小泉良彦, 川邉洋砂防学会誌 66 6 60 - 67 2014年03月 [査読有り][通常論文]
- Yosuke Yamakawa, Ken'ichirou Kosugi, Shin'ya Katsura, Naoya Masaoka, Takahisa MizuyamaVADOSE ZONE JOURNAL 11 1 vzj2011.0029 2012年02月 [査読有り][通常論文]
Electrical resistivity imaging (ERI) as an effective method to evaluate water flow processes through bedrock in a hillslope in a headwater catchment was validated by invasive hydrometric observations. Distributions of increases and decreases in electrical resistivities rho relative to a reference rho profile (Delta rho) corresponded well with the increases and decreases in volumetric water content theta (Delta theta) calculated from the directly observed pressure head psi using tensiometers and borehole wells. This demonstrates the applicability of time-lapse ERI measurement for qualitatively evaluating the spatial and temporal variations in theta (i.e., wetting and drying processes) for not only soil mantles but also for bedrock in a natural hillslope. There was a reasonable correlation (R-2 = 0.69 to 0.77) between each average theta and rho in regions assumed to have different degrees of weathering, indicating the potential of ERI for quantitatively evaluating moisture conditions within an en tire natural hillslope, including bedrock, based on field-scale calibrations with invasive methods. Fluctuations in groundwater tables in boreholes within bedrock along the survey line and discharge from two differently sized catchments including the study slope were both successfully reflected in the temporal variation in mean rho in the regions located just above and below the groundwater tables. This indicates the potential of ERI for estimating groundwater levels and runoff from a watershed based on temporal rho monitoring within an en tire slope, including the bedrock; such estimations may be more difficult to achieve with invasive methods in many mountain slopes. - Mizuno, M, Sato, T, Hayashi, S, Nishi, M, Katsura, S, Nakagawa, KInternational Journal of Erosion Control Engineering 4 2 48 - 56 2011年12月 [査読有り][通常論文]
- Ken&apos, ichirou Kosugi, Masamitsu Fujimoto, Shin&apos, ya Katsura, Hiroyuki Kato, Yoshiki Sando, Takahisa MizuyamaWATER RESOURCES RESEARCH 47 W07530 2011年07月 [査読有り][通常論文]
Understanding a discharge hydrograph is one of the leading interests in catchment hydrology. Recent research has provided credible information on the importance of bedrock groundwater on discharge hydrographs from headwater catchments. However, intensive monitoring of bedrock groundwater is rare in mountains with steep topography. Hence, how bedrock groundwater controls discharge from a steep headwater catchment is in dispute. In this study, we conducted long-term hydrological observations using densely located bedrock wells in a headwater catchment underlain by granitic bedrock. The catchment has steep topography affected by diastrophic activities. Results showed a fairly regionalized distribution of bedrock aquifers within a scale of tens of meters, consisting of upper, middle, and lower aquifers, instead of a gradual and continuous decline in water level from ridge to valley bottom. This was presumably attributable to the unique bedrock structure; fault lines developed in the watershed worked to form divides between the bedrock aquifers. Spatial expanse of each aquifer and the interaction among aquifers were key factors to explain gentle and considerable variations in the base flow discharge and triple-peak discharge responses of the observed hydrograph. A simple model was developed to simulate the discharge hydrograph, which computed each of the contributions from the soil mantle groundwater, from the lower aquifer, and from the middle aquifer to the discharge. The modeling results generally succeeded in reproducing the observed hydrograph. Thus, this study demonstrated that understanding regionalized bedrock aquifer distribution is pivotal for explaining discharge hydrograph from headwater catchments that have been affected by diastrophic activities. - 小山内信智, 桂真也, 冨田陽子, 小川紀一朗, 中田慎砂防学会誌 63 5 22 - 32 2011年01月 [査読有り][通常論文]
- Katsura, S, Tomita, Y, Osanai, N, Inaba, C, Arai, M, Saguchi, OJournal of Disaster Research 5 3 315 - 323 2010年06月 [査読有り][通常論文]
- Shin'ya Katsura, Ken&apos, ichirou Kosugi, Tasuku Mizutani, Takahisa MizuyamaVADOSE ZONE JOURNAL 8 3 557 - 573 2009年08月 [査読有り][通常論文]
Recent studies have emphasized the importance of bedrock in hydrologic processes occurring in headwater catchments. To understand water flow processes through variously weathered bedrock, we measured the saturated hydraulic conductivity, K(s), and water retention characteristics of weakly to highly weathered Tanakami granite and Rokko granite core samples. On the basis of these core-scale properties, along with the core shape and in situ K(s) measurements, we defined two groups of bedrock: C(M) class (weakly weathered) and C(L) to D(L) class (moderately to highly weathered). The C(M) class bedrock cores had almost no effective porosity (i.e., the amount of porosity that effectively contributes to water flow) and therefore extremely small core-scale K(s), indicating that the matrix could be regarded as essentially impermeable. The in situ K(s) was much larger than the core-scale values, however, and the core shape showed apparent fractures, suggesting that water did flow preferentially through the fractures. The volumetric water content of the C(L)-to D(L)-class bedrock water retention curves changed little in the dry range but changed gradually in the wet range, resulting in a moderate core-scale K(s) of 10(-5) to 10(-3) cm s(-1). The core-scale K(s) values were well explained by the parameters characterizing the water retention curve. The similarity of the in situ K(s) to the core-scale values, and the lack of fractures in the core shape, suggested that water flow could be characterized as matrix flow. The hydraulic properties of weathered granite at other sites followed the trends observed at our sites, implying wide applicability of the findings in this study to various types of weathered granite. - Two different processes of groundwater generation in soil layers observed in a granitic headwater catchment in central JapanKatsura, S, Kosugi, K, Okunaka, S, Mizutani, T, Mizuyama, TIAHS publication 326 133 - 138 2009年03月 [査読有り][通常論文]
- K. Kosugi, S. Katsura, T. Mizutani, H. Kato, T. Mizuyama, K. Goto, K. IshioFROM HEADWATERS TO THE OCEAN: HYDROLOGICAL CHANGES AND WATERSHED MANAGEMENT 341 - + 2009年 [査読有り][通常論文]
This study showed that two different components of groundwater were combined within a single well excavated in a soil mantle. One component (EG) showed an ephemeral-type response, and the other component (SPG) showed a semi-perennial-type response. The generation and cessation of SPG were well explained by the antecedent precipitation index, which represents the long-lasting effects of antecedent rainfall. Hydrogeochemical observations of soil mantle groundwater and bedrock groundwater indicated that the sources of EG were storm rainwater and preevent solum water, whereas the source of SPG was deep bedrock groundwater. SPG led to considerably high antecedent soil moisture conditions between storms, which may affect base flow discharge and biogeochemical processes in the soil mantle, and also facilitate an increased peak runoff and shallow landslides during a later storm event. Thus, this study showed that deep bedrock groundwater plays important roles in surface hydrological processes in headwater catchments. - Shin'ya Katsura, Ken&apos, ichirou Kosugi, Tasuku Mizutani, Suemi Okunaka, Takahisa MizuyamaWATER RESOURCES RESEARCH 44 9 W09430 2008年09月 [査読有り][通常論文]
We investigated processes of soil mantle groundwater generation in a granitic headwater catchment in central Japan. Two types of groundwater were observed: ephemeral-type groundwater (EG), which developed in response to rainfall events and disappeared rapidly after the events ceased, and semiperennial-type groundwater (SPG), which remained formed for more than several months. The groundwater level, chemistry, and temperature within the soil and bedrock layers indicated that the source of EG was rain or soil water, whereas the source of SPG was deep bedrock groundwater. The generation processes of soil mantle groundwater varied both spatially and temporally under the influence of the underlying bedrock. Whereas only EG was generated in upslope areas, bedrock groundwater continuously seeped into the soil layers in downslope areas to generate SPG. In middle-slope areas, an increase in the bedrock groundwater level generated SPG in soil layers, but the SPG disappeared when the bedrock groundwater level fell. Our results indicate that bedrock is important in controlling soil mantle groundwater generation and water flow processes in headwater catchments and that direct measurements of bedrock conditions are vital for clarifying the roles of bedrock in these processes. - Shin'ya Katsura, Ken&apos, ichirou Kosugi, Takahisa MizuyamaHYDROLOGICAL PROCESSES 22 6 750 - 763 2008年03月 [査読有り][通常論文]
As a first step toward describing water flow processes in bedrock, a coil-type time domain reflectometry (TDR) probe capable of measuring volumetric water content, theta, in weathered bedrock at three depths was prepared, Because the coil-type TDR probe is large in diameter (19 mm), it can be installed even in highly weathered bedrock more easily and appropriately than conventional TDR probes that consists of two or three rods of small diameter (5-8 mm). The probe calibrations suggest that the values measured by the probe are very sensitive to changes in theta. Using the calibrated probe together with commercially available profile soil moisture sensors, the theta profile was monitored for I year. Even rainfall events with relatively small cumulative rainfall of 15 mm increased the bedrock theta, and the increments were comparable to those in the soil. After the end of the rainfall events, the bedrock theta displayed a more rapid drop than the soil, and varied little during the period of no rainfall. The water storage showed similar tendencies. These observations suggest that the bedrock theta is controlled by clearly distinguishable macropores and micropores within the bedrock. It is concluded that the coil-type TDR probe is very effective in determining theta in weathered bedrock, and that bedrock, conventionally defined by conducting cone penetration tests and treated as impermeable. does conduct and hold substantial amounts of water, and therefore contribute greatly to hydrological processes in headwater catchments. Copyright (C) 2007 John Wiley & Sons, Ltd. - Ken&apos, ichirou Kosugi, Shin'ya Katsura, Takahisa Mizuyama, Suemi Okunaka, Tasuku MizutaniWATER RESOURCES RESEARCH 44 1 W01407 2008年01月 [査読有り][通常論文]
The formation of groundwater in the soil mantle has a dominant effect on rainwater discharge and shallow landslide occurrence in headwater catchments. Here, we report two completely different groundwater responses within a single well excavated into the soil mantle. One was an ephemeral-type response that is well described by physical hydrology models based on a geographic information system (GIS). The other was a semiperennial-type response, rarely reported in previous studies, which cannot be explained by the existing physical models. The semi-perennial groundwater caused considerably high antecedent groundwater tables between storms, leading to an increased peak in the groundwater level during later heavy storm events and a likely increase in the risk of shallow landslides. Moreover, peaks in the semi-perennial groundwater lagged considerably behind rainstorm events, which probably affected base flow discharge by forming a delayed peak. Geochemical and geothermal observations indicated that the source of the semi-perennial groundwater was deep bedrock groundwater, demonstrating the considerable effects of bedrock groundwater on surface hydrological processes. - K Kosugi, S Katsura, M Katsuyama, T MizuyamaWATER RESOURCES RESEARCH 42 2 W02414 2006年02月 [査読有り][通常論文]
Recent studies have suggested that bedrock groundwater can exert considerable influence on runoff generation, water chemistry, and the occurrence of landslides in headwater catchments. To clarify water infiltration and redistribution processes between soil and shallow bedrock and their effect on storm and base flow discharge processes in a small headwater catchment underlain by weathered granite, we conducted hydrometric observations using soil and bedrock tensiometers combined with hydrochemical measurements and water budget analyses at three different spatial scales. Results showed that in an unchanneled 0.024-ha headwater catchment, saturated and unsaturated infiltration from soil to bedrock is a dominant hydrological process at the soil-bedrock interface. Annual bedrock infiltration ranged from 35 to 55% of annual precipitation and increased as precipitation increased, suggesting a high level of potential bedrock infiltration, partly explained by the high buffering capacity of the soil layer overlying the bedrock. This physical property of the soil layer was an important factor in controlling the generation of bedrock infiltration and saturated lateral flow over the bedrock. In a 0.086-ha watershed including the unchanneled headwater catchment, exfiltration from the bedrock toward the soil layer composed more than half the annual discharge. - S Katsura, K Kosugi, N Yamamoto, T MizuyamaVADOSE ZONE JOURNAL 5 1 35 - 47 2006年02月 [査読有り][通常論文]
As a first step toward describing water flow processes in bedrock, we determined the hydraulic properties of three trimmed samples of weathered granitic bedrock ( referred to as Samples A, B, and C, in order of size) in the laboratory. Silicone rubber was used to fill the space between each sample and the surrounding cylinder wall, ensuring accurate measurement of hydraulic properties of the samples. All samples showed similar saturated hydraulic conductivity values of 1 x 10(-4) cm s(-1), with the saturated water flow in all samples obeying Darcy's Law. Unsaturated hydraulic conductivity and water retention functions of Sample A were determined by means of a multistep outflow experiment. Parameters in both functions were optimized by comparing observed and computed cumulative outflow rates. The resulting computed cumulative outflow rates using the optimized parameters showed a good match to the observed cumulative outflow data. Moreover, the derived water retention function agreed closely with the function measured by the pressure plate method. We conclude that the methods proposed in this study are effective for determining the hydraulic properties of weathered bedrock. The bedrock water retention curve exhibited small changes in volumetric water content throughout the measurement range where the pressure head, psi was greater than -200 cm. The bedrock hydraulic conductivity function showed a small decrease in hydraulic conductivity in the very wet range of psi greater than 230 cm, and then declined gradually with decreasing psi.
MISC
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