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Mechanisms of upstream migration of knickpoints and rapid riverbed degradation

Research Project

Project/Area Number 23K22872
Project/Area Number (Other) 22H01602 (2022-2023)
Research Category

Grant-in-Aid for Scientific Research (B)

Allocation TypeMulti-year Fund (2024)
Single-year Grants (2022-2023)
Section一般
Review Section Basic Section 22040:Hydroengineering-related
Research InstitutionHiroshima University

Principal Investigator

井上 卓也  広島大学, 先進理工系科学研究科(工), 准教授 (20647094)

Co-Investigator(Kenkyū-buntansha) 内田 龍彦  広島大学, 先進理工系科学研究科(工), 准教授 (00379900)
成瀬 元  京都大学, 理学研究科, 准教授 (40362438)
鳩野 美佐子  広島大学, 先進理工系科学研究科(工), 助教 (40837019)
Project Period (FY) 2022-04-01 – 2026-03-31
Project Status Granted (Fiscal Year 2024)
Budget Amount *help
¥17,550,000 (Direct Cost: ¥13,500,000、Indirect Cost: ¥4,050,000)
Fiscal Year 2025: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2024: ¥3,120,000 (Direct Cost: ¥2,400,000、Indirect Cost: ¥720,000)
Fiscal Year 2023: ¥4,810,000 (Direct Cost: ¥3,700,000、Indirect Cost: ¥1,110,000)
Fiscal Year 2022: ¥8,320,000 (Direct Cost: ¥6,400,000、Indirect Cost: ¥1,920,000)
Keywordsニックポイント / サイクリックステップ / 数値計算 / 水理実験 / 滝 / 岩盤 / 現地調査 / 河床低下 / 岩盤侵食 / 流砂 / 気候変動
Outline of Research at the Start

近年,度重なる豪雨により,砂礫層の下にある基盤岩層が露出する河川が増加している.脆弱な岩盤が露出した河川では,ニックポイントの上流移動により,河床が急激に低下する事例が報告されている.これまでニックポイントは,滝壺の拡大によってオーバーハング部が崩落することで上流へ移動すると考えられてきた.しかし,滝壺は砂礫の堆積によって保護されるため一定以上大きくならず,従来の説では大規模移動を説明できないことが明らかになった.本研究は,ニックポイントの上流側に新しい滝壺が自己形成され,連続的に更新されることにより大規模な上流移動を引き起こすという仮説のもと,その発生条件と物理機構の解明を試みる.

Outline of Annual Research Achievements

近年,度重なる豪雨により,砂礫層の下にある基盤岩層が露出する河川が増加している.脆弱な岩盤が露出した河川では,遷急点またはニックポイントと呼ばれる滝の上流移動により,河床が急激に低下する事例が報告されている.しかし,最新の研究によって,滝壺は砂礫の堆積によって保護されるため一定以上大きくならず,従来の説ではニックポイントの大規模移動を説明できないことが明らかになった.本研究は,ニックポイントの上流側に新しい滝壺が自己形成され,連続的に更新されることにより大規模な上流移動を引き起こすという新たな仮説のもと,その発生条件と物理機構の解明を試みる.
本年度は,ニックポイントの落差が上流移動速度に与える影響について,水理実験により調査した.実験の結果,上流移動速度はニックポイントの落差が小さいときに速くなることが判明した.これは,落差が小さい場合,上流側に新たな滝壺が形成される自己更新型の速い上流移動形態になるのに対し,落差が大きい場合は下流側の滝壺が徐々に大きくなるオーバーハング型の遅い移動形態になるためである.
次に,落差が小さい場合の流量がニックポイントの上流移動速度に与える影響を実験により調査した.この結果,流量が大きいほど移動速度が大きくなる傾向が見られた.これは,流量の減少に伴い,新たな滝壺(ステップ)の形成間隔が短くなること,水流によって流送される砂礫粒子の岩盤への衝突速度が小さくなる(衝突摩耗速度が低下する)ためである.
最後に,阿武隈川流域の河川を対象に岩種,岩盤強度,粒径などを調査し,岩質の異なる河川区間の侵食速度を数値解析により調査した.この結果,平衡状態においては,砂礫被覆の効果が岩質の効果よりも大きく,河川の勾配変化点(ニックポイント)は岩質の変化点よりも流量・土砂供給の変化点で発生しやすい可能性が示唆された.

Current Status of Research Progress
Current Status of Research Progress

2: Research has progressed on the whole more than it was originally planned.

Reason

当初計画において,2年目は体系的な水理実験によるニックポイントの更新型移動条件の把握と,現地調査と数値解析によるニックポイントの初期形成条件の把握を目的としていた.
本年度は,滝の落差や水深を変えることにより,砂礫粒子の掃流速度を変化させ,これがニックポイントの移動形態・移動速度に与える影響を調査した.また,岩質が縦断的に異なる阿武隈川流域の支川を対象に現地調査と数値解析を行い,岩盤強度と砂礫被覆が勾配変化点(ニックポイント)の形成に与える影響を分析した.
以上のことから研究は当初計画通り順調に進展している.

Strategy for Future Research Activity

現在構築した数値解析モデルは,ニックポイント(勾配変化点)の形成を巨視的にとらえることが出来るが,滝壺が連続的に形成される更新型移動の再現はできない.そこで, 3次元解析によりニックポイント周辺の流れ場を詳細に分析する.ただし,3次元モデルを河川の全延長に適用することは計算負荷から困難である.そこで,非静水圧急変流場を考慮した水深積分モデル(GBVC法)により,ニックポイント周辺の底面流速を評価できるか,常住の3次元モデルによる計算結果と比較し確認する.

Report

(2 results)
  • 2023 Annual Research Report
  • 2022 Annual Research Report
  • Research Products

    (32 results)

All 2024 2023 2022 Other

All Int'l Joint Research (2 results) Journal Article (19 results) (of which Int'l Joint Research: 3 results,  Peer Reviewed: 19 results,  Open Access: 4 results) Presentation (11 results) (of which Int'l Joint Research: 9 results,  Invited: 1 results)

  • [Int'l Joint Research] University of Nevada, Reno/University of Texas, Austin(米国)

    • Related Report
      2023 Annual Research Report
  • [Int'l Joint Research] Jawaharlal Nehru University, New Delhi(インド)

    • Related Report
      2023 Annual Research Report
  • [Journal Article] EFFECT OF THE AMOUNT OF SEDIMENT SUPPLY ON THE UPSTREAM PROGRESS OF WATERFALLS2024

    • Author(s)
      YOKOTA Keiji、IZUMI Norihiro、INOUE Takuya、HIRAMATSU Yuki
    • Journal Title

      Japanese Journal of JSCE

      Volume: 80 Issue: 16 Pages: n/a

    • DOI

      10.2208/jscejj.23-16050

    • ISSN
      2436-6021
    • Related Report
      2023 Annual Research Report
    • Peer Reviewed
  • [Journal Article] UPSTREAM MIGRATION PROCESS OF WATERFALL ON MILD SLOPE CHANNEL2024

    • Author(s)
      HIRAMATSU Yuki、INOUE Takuya、TAKAHASHI Kazutaka、YONEDA Naohiro、UCHIDA Tatsuhiko、IZUMI Norihiro
    • Journal Title

      Japanese Journal of JSCE

      Volume: 80 Issue: 16 Pages: n/a

    • DOI

      10.2208/jscejj.23-16049

    • ISSN
      2436-6021
    • Related Report
      2023 Annual Research Report
    • Peer Reviewed
  • [Journal Article] EFFECTS OF CHANGE IN RIVER WIDTH ON KNICKPOINT RETREAT IN BEDROCK RIVERS2024

    • Author(s)
      SUMNER Tamaki、INOUE Takuya、IZUMI Norihiro、SHIMIZU Yasuyuki
    • Journal Title

      Japanese Journal of JSCE

      Volume: 80 Issue: 16 Pages: n/a

    • DOI

      10.2208/jscejj.23-16015

    • ISSN
      2436-6021
    • Related Report
      2023 Annual Research Report
    • Peer Reviewed / Int'l Joint Research
  • [Journal Article] STUDY ON TRANSPORT AND DEPOSITION OF MIXED SEDIMENT IN BEDROCK RIVERS2024

    • Author(s)
      MASUYA Shigekazu、INOUE Takuya、HIRAMATSU Yuki、SUMNER Tamaki、DENPO Jyunya
    • Journal Title

      Japanese Journal of JSCE

      Volume: 80 Issue: 16 Pages: n/a

    • DOI

      10.2208/jscejj.23-16053

    • ISSN
      2436-6021
    • Related Report
      2023 Annual Research Report
    • Peer Reviewed
  • [Journal Article] DISCUSSIONS OF BAR GROWTH RATE AND DEVELOPMENT OF BAR HEIGHT ESTIAMATION METHOD2024

    • Author(s)
      INOUE Takuya、IWASAKI Toshiki、SUMNER Tamaki、HIRAMATSU Yuki、OZEKI Toshihisa、SASAKI Shunichi、TOMINO Tatsuro、KIDO Riho
    • Journal Title

      Japanese Journal of JSCE

      Volume: 80 Issue: 16 Pages: n/a

    • DOI

      10.2208/jscejj.23-16017

    • ISSN
      2436-6021
    • Related Report
      2023 Annual Research Report
    • Peer Reviewed
  • [Journal Article] Waterfall height sets the mechanism and rate of upstream retreat2023

    • Author(s)
      Inoue T.、Izumi N.、Scheingross J.S.、Hiramatsu Y.、Tanigawa S.、Sumner T.
    • Journal Title

      Geology

      Volume: 51 Issue: 7 Pages: 693-697

    • DOI

      10.1130/g51039.1

    • Related Report
      2023 Annual Research Report
    • Peer Reviewed / Int'l Joint Research
  • [Journal Article] Assessing the impact of climate change on sediment discharge using a large ensemble rainfall dataset in Pekerebetsu River basin, Hokkaido2023

    • Author(s)
      Kido Riho、Inoue Takuya、Hatono Misako、Yamanoi Kazuki
    • Journal Title

      Progress in Earth and Planetary Science

      Volume: 10 Issue: 1 Pages: 54-54

    • DOI

      10.1186/s40645-023-00580-0

    • Related Report
      2023 Annual Research Report
    • Peer Reviewed / Open Access
  • [Journal Article] A Route Search System to Avoid the Danger to Life in Dynamic Inundation2023

    • Author(s)
      Ogawa Kohei、Inoue Takuya、Hiramatsu Yuki、Mishra Jagriti
    • Journal Title

      Water

      Volume: 15 Issue: 7 Pages: 1417-1417

    • DOI

      10.3390/w15071417

    • Related Report
      2023 Annual Research Report 2022 Annual Research Report
    • Peer Reviewed / Open Access / Int'l Joint Research
  • [Journal Article] EXPERIMENTAL STUDY ON EFFECT OF DIFFERENCES IN SANDBAR HEIGHT AND WATER DISCHARGE ON RIVERBANK EROSION2022

    • Author(s)
      HIRAMATSU Yuki、INOUE Takuya、YAMAGUCHI Satomi
    • Journal Title

      Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering)

      Volume: 78 Issue: 2 Pages: I_1231-I_1236

    • DOI

      10.2208/jscejhe.78.2_I_1231

    • ISSN
      2185-467X
    • Related Report
      2022 Annual Research Report
    • Peer Reviewed
  • [Journal Article] A STUDY ON THE DESIGN OF THE INLET SECTION OF A DRIFTWOOD CAPTURE FACILITY INSTALLED IN A RIVER BEND2022

    • Author(s)
      KATO Kazuo、SUMNER Tamaki、CHIBA Kiichi、INOUE Takuya、SHIMIZU Yasuyuki
    • Journal Title

      Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering)

      Volume: 78 Issue: 2 Pages: I_289-I_294

    • DOI

      10.2208/jscejhe.78.2_I_289

    • ISSN
      2185-467X
    • Related Report
      2022 Annual Research Report
    • Peer Reviewed
  • [Journal Article] A PREDICTION METHOD FOR BANK EROSION WIDTH CONSIDERING MULTIPLE CHANNEL CONDITIONS2022

    • Author(s)
      ABE Takaaki、INOUE Takuya、HIRAMATSU Yuki、OGUSHI Hiroya、HAMAKI Michihiro、TOMURA Sho
    • Journal Title

      Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering)

      Volume: 78 Issue: 2 Pages: I_1171-I_1176

    • DOI

      10.2208/jscejhe.78.2_I_1171

    • ISSN
      2185-467X
    • Related Report
      2022 Annual Research Report
    • Peer Reviewed
  • [Journal Article] EFFECTS OF CHANNEL DEFORMATION ON LONGITUDINAL AND TEMPORAL CHANGES IN CHANNEL GRADIENT2022

    • Author(s)
      INOUE Takuya、SUMNER Tamaki、HIRAMATSU Yuki、YAMAGUCHI Satomi
    • Journal Title

      Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering)

      Volume: 78 Issue: 2 Pages: I_865-I_870

    • DOI

      10.2208/jscejhe.78.2_I_865

    • ISSN
      2185-467X
    • Related Report
      2022 Annual Research Report
    • Peer Reviewed
  • [Journal Article] IMPACT ASSESSMENT OF CLIMATE CHANGE ON SEDIMENT DISCHARGE USING A LARGE-EMSEMBLE CLIMATE DATABASE2022

    • Author(s)
      木戸理歩、井上卓也、鳩野美佐子、山野井一輝
    • Journal Title

      Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering)

      Volume: 78 Issue: 2 Pages: I_55-I_60

    • DOI

      10.2208/jscejhe.78.2_I_55

    • ISSN
      2185-467X
    • Related Report
      2022 Annual Research Report
    • Peer Reviewed
  • [Journal Article] ON THE RISK OF BANK EROSION DOWNSTREAM OF CROSS-SECTIONAL STRUCTURES IN SMALL AND MEDIUM-SIZED RIVERS: CASE STUDY ON THE JULY 2021 FLOOD IN BUTTSUJI RIVER2022

    • Author(s)
      冨山 遼,内田龍彦,井上卓也,鳩野美佐子,小林大祐,永井秀和,松尾大地
    • Journal Title

      Advances in River Engineering

      Volume: 28 Issue: 0 Pages: 127-132

    • DOI

      10.11532/river.28.0_127

    • ISSN
      2436-6714
    • Related Report
      2022 Annual Research Report
    • Peer Reviewed / Open Access
  • [Journal Article] Numerical Study of the Interaction Between Wet‐Dry Weathering and Bedload Induced Abrasion2022

    • Author(s)
      Sumner Tamaki、Mishra Jagriti、Inoue Takuya、Shimizu Yasuyuki
    • Journal Title

      Water Resources Research

      Volume: 58 Issue: 3

    • DOI

      10.1029/2021wr030952

    • Related Report
      2022 Annual Research Report
    • Peer Reviewed / Open Access
  • [Journal Article] Creation of a 3D Flood Hazard Map for a Flood-Prone Area in the Republic of the Philippines and Dissemination of the Mapping Technology2022

    • Author(s)
      Naoko NAGUMO、Miho OHARA、Masakazu FUJIKANE、Takuya INOUE、Yuki HIRAMATSU、Patricia Ann JARANILLA-SANCHEZ
    • Journal Title

      E-journal GEO

      Volume: 17 Issue: 1 Pages: 123-136

    • DOI

      10.4157/ejgeo.17.123

    • ISSN
      1880-8107
    • Related Report
      2022 Annual Research Report
    • Peer Reviewed
  • [Journal Article] 山地斜面における岩盤内と表層地下水の変動特性に関する研究2022

    • Author(s)
      笹谷慎之介・内田龍彦・井上卓也・鳩野美佐子・梶昭仁・小森潤二・宮田英樹・海堀正博
    • Journal Title

      第 11 回土砂災害に関するシンポジウム論文集

      Volume: 11 Pages: 179-184

    • Related Report
      2022 Annual Research Report
    • Peer Reviewed
  • [Journal Article] FRP 側溝とコンクリート側溝による細粒土砂輸送能力の比較2022

    • Author(s)
      杉保生尚・家久侑大・内田龍彦・鈴木啓之・藤岡博邦・西田直也・井上卓也
    • Journal Title

      第 11 回土砂災害に関するシンポジウム論文集

      Volume: 11 Pages: 155-160

    • Related Report
      2022 Annual Research Report
    • Peer Reviewed
  • [Journal Article] DEVELOPMENT OF AN EVACUATION ROUTE SEARCH SYSTEM CONSIDERING THE DANGER TO LIFE IN DYNAMIC INUNDATION2022

    • Author(s)
      OGAWA Kohei、INOUE Takuya、HIRAMATSU Yuki
    • Journal Title

      Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering)

      Volume: 78 Issue: 2 Pages: I_1009-I_1014

    • DOI

      10.2208/jscejhe.78.2_I_1009

    • ISSN
      2185-467X
    • Related Report
      2022 Annual Research Report
    • Peer Reviewed
  • [Presentation] A morphodynamic model for incised bedrock meanders2024

    • Author(s)
      Takuya Inoue
    • Organizer
      International Conference on Advances in Civil & Environmental Engineering (ICACEE 2024)
    • Related Report
      2023 Annual Research Report
    • Int'l Joint Research / Invited
  • [Presentation] Assessment of Sediment Production by Freezing and Thawing using a Large Ensemble Dataset in Pekerebetsu River Basin in Hokkaido2024

    • Author(s)
      Riho Kido, Takuya Inoue, Shigeru Mizugaki, Sumner Tamaki
    • Organizer
      The 6th Korea -Japan Mini-Symposium on Modeling and Measurement in Hydraulics
    • Related Report
      2023 Annual Research Report
    • Int'l Joint Research
  • [Presentation] Risk assessment method for bar height increase considering flow distribution2023

    • Author(s)
      Tatsuro Tomino, Takuya Inoue, Tamaki Sumner
    • Organizer
      13th Symposium on River, Coastal and Estuarine Morphodynamics(RCEM 2023)
    • Related Report
      2023 Annual Research Report
    • Int'l Joint Research
  • [Presentation] Changes in Sediment Discharge Due to Climate Change Considering Sediment Production Factors2023

    • Author(s)
      Riho Kido, Takuya Inoue, Misako Hatono, Kazuki Yamanoi, Shigeru Mizugaki, Sumner Tamaki
    • Organizer
      20th Annual Meeting of the Asia Oceania Geosciences Society
    • Related Report
      2023 Annual Research Report
    • Int'l Joint Research
  • [Presentation] Development of a route search system considering the risk of being involved in flooded areas2023

    • Author(s)
      Kohei Ogawa, Takuya Inoue, Yuki Hiramatsu
    • Organizer
      9th International Conference on Flood Management
    • Related Report
      2022 Annual Research Report
    • Int'l Joint Research
  • [Presentation] Impact Assessment of Climate Change on Sediment Discharge using d4PDF2023

    • Author(s)
      Riho Kido, Takuya Inoue, Misako Hatono, Kazuki Yamanoi
    • Organizer
      9th International Conference on Flood Management
    • Related Report
      2022 Annual Research Report
    • Int'l Joint Research
  • [Presentation] 滝の更新型移動とフルード数の関係2022

    • Author(s)
      井上卓也、米田 直弘,内田 龍彦,平松裕基,泉典洋
    • Organizer
      土木学会中国支部研究発表会
    • Related Report
      2022 Annual Research Report
  • [Presentation] Formation of steps near a knickpoint due to collisions of moving sediments2022

    • Author(s)
      Kazutaka Takahashi, Takuya Inoue
    • Organizer
      AGU Fall meeting 2022
    • Related Report
      2022 Annual Research Report
    • Int'l Joint Research
  • [Presentation] Development of a Route Search System considering the Risk of being involved in Flooded areas2022

    • Author(s)
      Ogawa, Kohei; Inoue, Takuya; Hiramatsu, Yuki
    • Organizer
      AGU Fall meeting 2022
    • Related Report
      2022 Annual Research Report
    • Int'l Joint Research
  • [Presentation] Effects of Climate Change on the Return Periods of Water and Sediment Discharge2022

    • Author(s)
      Kido, Riho ; Inoue, Takuya ; Hatono, Misako ; Kazuki, Yamanoi
    • Organizer
      AGU Fall meeting 2022
    • Related Report
      2022 Annual Research Report
    • Int'l Joint Research
  • [Presentation] d4PDFを用いた気候変動による土砂流出量への影響評価2022

    • Author(s)
      木戸理歩,井上卓也,鳩野美佐子,山野井一輝
    • Organizer
      土木学会中国支部研究発表会
    • Related Report
      2022 Annual Research Report

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Published: 2022-04-19   Modified: 2024-12-25  

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