為恢復臺灣櫻花鉤吻鮭的歷史棲地，雪霸國家公園管理處自2009年開始於有勝溪上游的羅葉尾溪進行域外放流，卻因下游頻繁發生斷流，直接衝擊國寶魚的生存。為探討有勝溪部分河段發生斷流的機制，本研究利用歷史航照影像以及無人飛行載具（Unmanned Aerial Vehicle，UAV）空拍影像產製出正射影像以及數值地表模型（Digital Surface Model，DSM），比較2010年至2022年間河道變遷情形，並搭配水文資料歸納出斷流的成因。結果顯示：2012年7月的大豪雨事件後使右岸的廢耕地遭受侵蝕，部分河段堆高1公尺，此後斷流頻繁發生，河道堆高導致地下水位遠離地表是斷流的主因，除此之外，本研究河段為失水河段，部分河段因側蝕加寬導致入滲量增加，則間接加劇了斷流的發生。雨量為驅動河道高程變化的主因，當最大時雨量大於47.5毫米時（大事件），則造成河道側蝕且最低點堆積；最大時雨量小於20.5毫米且有地表逕流產生時（小事件），則造成河道最低點下切。從2018年後，本研究區多為小事件造成的下切作用，然而下切程度有限，平均一年僅下切0.08公尺，至今部分河段的河道高程仍與2010年相差1公尺以上，加上每4~5年可能有大事件造成的側蝕與堆積，有勝溪在短期內似乎無法避免斷流的命運。

In order to restore the historical habitat of the Formosan landlocked salmons (Oncorhynchus masou formosanus), the offspring have reintrodueced to the Louyewei Creek which is the upstream of the Yousheng Creek by Shei-pa National Park Headquarters since 2009. However, the habitat expansion was hampered by the frequent flow disruption in the upsteram of the Yousheng Creek. In order to investigate the mechanism of flow disruption, this study used historical aerial photographs and unmanned aerial vehicle (UAV) aerial images to produce orthophotos and digital surface models (DSM) to reveal the morphological changes from 2010 to 2022. Besides, hydrological data were supplemented to summarize the causes of flow disruption. The results showed that after the heavy rainfall event in July 2012, the abandoned agricultural land on the right bank was eroded and part of the channel elevated by more than 1 meter, leading to frequent flow disruption afterwards. The groundwater table under the channel became deeper below the riverbed surface owing to sediment deposition, which was the main cause of the flow disruption. In addition, the study stream reach featured losing reach. Lateral erosion, resulting in wider channel, enhanced the amount of infiltrated stream water to the riverbed and indirectly aggravated the flow disruption. Rainfall intensity was the main driving force of the morphological change. When the maximum hourly rainfall was greater than 47.5 mm (major event), the channel was laterally eroded and the thalweg was elevated. When the maximum hourly rainfall was less than 20.5 mm and surface runoff occurred (minor event), the thalweg was incised. After 2018, the study area was mostly incised by minor events, and the extent of incising was around 0.08 m per year. However, the channel elevations of flow disruption reaches were still >1 m higher than that in 2010. At the given condition that major events might occur every 4 to 5 years, it seems difficult to incise the channel to the condition in 2010 and therefore to avoid flow disruption of the Yousheng Creek in the near future.

參考文獻
李宗祐（2003）。氣候變遷對櫻花鉤吻鮭棲地水溫及族群數量之影響。國立臺灣大學生物環境系統工程學研究所碩士論文，台北市。
李宗祐、黃誌川、邱永嘉（2017）。106年評估水文條件改變及河床-河水交互作用對七家灣溪河川流量與溪流棲地之影響。雪霸國家公園管理處委託研究報告（編號：10612）。
許貿傑（2019）。結合季長期天氣預報與標準化降雨指標建立有勝溪斷流預警系統。國立臺灣師範大學地理學系碩士論文，台北市。
張瑀宬（2021）。以鹽水示蹤劑試驗與數值模式探討高山一級河川之地表水及地下水交互作用 ─ 以七家灣溪為例。國立臺灣海洋大學地球科學研究所碩士論文，基隆市。
葉昭憲（2015）。武陵地區七家灣溪及有勝流域壩體改善後溪流物理棲地調查監測。雪霸國家公園管理處委託研究報告（編號：10405）。
葉昭憲（2020）。武陵地區溪流環境及放流棲地監測。雪霸國家公園管理處委託研究報告（編號：10908）。
廖林彥、陳建均、陳瑀訢、藍智鴻（2020）。2020年臺灣櫻花鉤吻鮭族群監測與放流。雪霸國家公園管理處自行研究報告（編號：10914）。
潘彥維（2022）。以HFLUX模式模擬亞熱帶山區間歇性河段熱收支情形。國立臺灣師範大學地理學系碩士論文，台北市。
盧奕穎（2021）。未管理廢耕農地對河川水質與河岸侵蝕之影響 ─ 以有勝溪為例。國立臺灣師範大學地理學系碩士論文，台北市。
Agüera-Vega, F., Carvajal-Ramírez, F., & Martínez-Carricondo, P. (2017). Assessment of photogrammetric mapping accuracy based on variation ground control points number using unmanned aerial vehicle. Measurement, 98, 221-227.
Akay, S. S., Özcan, O., Şanlı, F. B., Görüm, T., Şen, Ö. L., & Bayram, B. (2020). UAV-based evaluation of morphological changes induced by extreme rainfall events in meandering rivers. Plos one, 15(11), e0241293.
Baggs Sargood, M., Cohen, T. J., Thompson, C. J., & Croke, J. (2015). Hitting rock bottom: morphological responses of bedrock-confined streams to a catastrophic flood. Earth Surface Dynamics, 3(2), 265-279.
Baynes, E. R., Lague, D., Steer, P., Bonnet, S., & Illien, L. (2020). Sediment flux‐driven channel geometry adjustment of bedrock and mixed gravel–bedrock rivers. Earth Surface Processes and Landforms, 45(14), 3714-3731.
Boulton, A. J., Rolls, R. J., Jaeger, K. L., & Datry, T. (2017). Hydrological Connectivity in Intermittent Rivers and Ephemeral Streams. In Intermittent Rivers and Ephemeral Streams (pp. 79-108).
Bowen, Z. H., & Waltermire, R. G. (2002). Evaluation of light detection and ranging (lidar) for measuring river corridor topography 1. JAWRA Journal of the American Water Resources Association, 38(1), 33-41.
Bull, W. B. (1979). Threshold of critical power in streams. Geological Society of America Bulletin, 90(5), 453-464.
Carling, P. A. (2009). Geomorphology and sedimentology of the Lower Mekong River. In The Mekong (pp. 77-111).
Chiu, Y. C., Lee, T. Y., Hsu, S. Y., & Liao, L. Y. (2020). The effect of hydrological conditions and bioactivities on the spatial and temporal variations of streambed hydraulic characteristics at the subtropical alpine catchment. Journal of Hydrology, 584, 124665.
Church, M. (2002). Geomorphic thresholds in riverine landscapes. Freshwater biology, 47(4), 541-557.
Coleman, J. M. (1969). Brahmaputra River: channel processes and sedimentation. Sedimentary geology, 3(2-3), 129-239.
Costa, J. E. (1974). Response and recovery of a Piedmont watershed from tropical storm Agnes, June 1972. Water Resources Research, 10(1), 106-112.
Cowie, P. A., Whittaker, A. C., Attal, M., Roberts, G., Tucker, G. E., & Ganas, A. (2008). New constraints on sediment-flux–dependent river incision: Implications for extracting tectonic signals from river profiles. Geology, 36(7), 535-538.
Croke, J., Todd, P., Thompson, C., Watson, F., Denham, R., & Khanal, G. (2013). The use of multi temporal LiDAR to assess basin-scale erosion and deposition following the catastrophic January 2011 Lockyer flood, SE Queensland, Australia. Geomorphology, 184, 111-126.
Davis, W. (1902). Baselevel, grade and peneplain. The Journal of Geology, 10(1), 77-111.
Dietrich, J. T. (2016). Riverscape mapping with helicopter-based Structure-from-Motion photogrammetry. Geomorphology, 252, 144-157.
Flener, C., Vaaja, M., Jaakkola, A., Krooks, A., Kaartinen, H., Kukko, A., Kasvi, E., Hyyppä, H., Hyyppä, J., & Alho, P. (2013). Seamless mapping of river channels at high resolution using mobile LiDAR and UAV-photography. Remote Sensing, 5(12), 6382-6407.
Fortugno, D., Boix‐Fayos, C., Bombino, G., Denisi, P., Quinonero Rubio, J. M., Tamburino, V., & Zema, D. A. (2017). Adjustments in channel morphology due to land‐use changes and check dam installation in mountain torrents of Calabria (southern Italy). Earth Surface Processes and Landforms, 42(14), 2469-2483.
Ghose, B., Kar, A., & Husain, Z. (1979). The lost courses of the Saraswati River in the Great Indian Desert: new evidence from Landsat imagery. Geographical Journal, 446-451.
Gracchi, T., Rossi, G., Stefanelli, C. T., Tanteri, L., Pozzani, R., & Moretti, S. (2021). Tracking the Evolution of Riverbed Morphology on the Basis of UAV Photogrammetry. Remote Sensing, 13(4), 829.
Grant, G. E. (2012). The geomorphic response of gravel‐bed rivers to dams: perspectives and prospects. Gravel‐bed Rivers: Processes, tools, environments, 165-181.
Gumiero, B., Rinaldi, M., Belletti, B., Lenzi, D., & Puppi, G. (2015). Riparian vegetation as indicator of channel adjustments and environmental conditions: the case of the Panaro River (Northern Italy). Aquatic sciences, 77(4), 563-582.
Hartshorn, K., Hovius, N., Dade, W. B., & Slingerland, R. L. (2002). Climate-driven bedrock incision in an active mountain belt. Science, 297(5589), 2036-2038.
Hemmelder, S., Marra, W., Markies, H., & De Jong, S. M. (2018). Monitoring river morphology & bank erosion using UAV imagery–A case study of the river Buëch, Hautes-Alpes, France. International Journal of Applied Earth Observation and Geoinformation, 73, 428-437.
Heritage, G. L., & Milan, D. J. (2009). Terrestrial laser scanning of grain roughness in a gravel-bed river. Geomorphology, 113(1-2), 4-11.
Hooke, J. M. (1980). Magnitude and distribution of rates of river bank erosion. Earth Surface Processes and Landforms, 5(2), 143-157.
Howard, A. D. (1998). Long profile development of bedrock channels: Interaction of weathering, mass wasting, bed erosion, and sediment transport. Geophysical Monograph-American Geophysical Union, 107, 297-319.
Ielpi, A., & Lapôtre, M. G. (2020). A tenfold slowdown in river meander migration driven by plant life. Nature Geoscience, 13(1), 82-86.
Jansen, J. D. (2006). Flood magnitude–frequency and lithologic control on bedrock river incision in post-orogenic terrain. Geomorphology, 82(1-2), 39-57.
Johnson, J. P., Whipple, K. X., & Sklar, L. S. (2010). Contrasting bedrock incision rates from snowmelt and flash floods in the Henry Mountains, Utah. Geological Society of America Bulletin, 122(9-10), 1600-1615.
Johnson, J. P., Whipple, K. X., Sklar, L. S., & Hanks, T. C. (2009). Transport slopes, sediment cover, and bedrock channel incision in the Henry Mountains, Utah. Journal of Geophysical Research: Earth Surface, 114(F2).
KANO, T. (1940). Zoogeographical studies of the Tsugitakayama Mountains of Formosa. Shibusawa Institute for Ethnographical Research, Tokyo. 145p.
Keesstra, S., Van Huissteden, J., Vandenberghe, J., Van Dam, O., De Gier, J., & Pleizier, I. (2005). Evolution of the morphology of the river Dragonja (SW Slovenia) due to land-use changes. Geomorphology, 69(1-4), 191-207.
Lague, D., Hovius, N., & Davy, P. (2005). Discharge, discharge variability, and the bedrock channel profile. Journal of Geophysical Research: Earth Surface, 110(F4).
Leopold, L. B., & Langbein, W. B. (1966). River meanders. Scientific American, 214(6), 60-73.
Hoover Mackin, J. (1948). Concept of the graded river. Geological Society of America Bulletin, 59(5), 463-512.
Mertes, L. A. (2002). Remote sensing of riverine landscapes. Freshwater biology, 47(4), 799-816.
Meshkova, L. V., & Carling, P. A. (2012). The geomorphological characteristics of the Mekong River in northern Cambodia: A mixed bedrock–alluvial multi-channel network. Geomorphology, 147, 2-17.
Messager, M. L., Lehner, B., Cockburn, C., Lamouroux, N., Pella, H., Snelder, T., Tockner, K., Trautmann, T., Watt, C., & Datry, T. (2021). Global prevalence of non-perennial rivers and streams. Nature, 594(7863), 391-397.
Montgomery, D. R., & Buffington, J. M. (1997). Channel-reach morphology in mountain drainage basins. Geological Society of America Bulletin, 109(5), 596-611.
Muste, M., Yu, K., & Spasojevic, M. (2004). Practical aspects of ADCP data use for quantification of mean river flow characteristics; part I: moving-vessel measurements. Flow measurement and instrumentation, 15(1), 1-16.
Özcan, O., & Özcan, O. (2021). Multi-temporal UAV based repeat monitoring of rivers sensitive to flood. Journal of Maps, 17(3), 163-170.
Parsons, D. R., Best, J. L., Orfeo, O., Hardy, R. J., Kostaschuk, R., & Lane, S. N. (2005). Morphology and flow fields of three‐dimensional dunes, Rio Paraná, Argentina: Results from simultaneous multibeam echo sounding and acoustic Doppler current profiling. Journal of Geophysical Research: Earth Surface, 110(F4).
Phillips, J. D. (2006). Evolutionary geomorphology: thresholds and nonlinearity in landform response to environmental change. Hydrology and Earth System Sciences, 10(5), 731-742.
Phillips, J. D. (2011). Emergence and pseudo-equilibrium in geomorphology. Geomorphology, 132(3-4), 319-326.
Pollen‐Bankhead, N., & Simon, A. (2009). Enhanced application of root‐reinforcement algorithms for bank‐stability modeling. Earth Surface Processes and Landforms, 34(4), 471-480.
Rango, A., & Anderson, A. T. (1974). Flood hazard studies in the Mississippi river basin using remote sensing 1. JAWRA Journal of the American Water Resources Association, 10(5), 1060-1081.
Rhoads, B. L. (2020). River dynamics: geomorphology to support management. Cambridge University Press.
Righini, M., Surian, N., Wohl, E., Marchi, L., Comiti, F., Amponsah, W., & Borga, M. (2017). Geomorphic response to an extreme flood in two Mediterranean rivers (northeastern Sardinia, Italy): Analysis of controlling factors. Geomorphology, 290, 184-199.
Ruiz, A., González, X., Herms, I., & Bastianelli, L. (2002, March). Flood Risk Mapping Based on Airborne Laser Scanner Data: Case of the Llobregat River. In Proceedings of the Int. Conference on Flood Estimation (pp. 6-8).
Salo, J., Kalliola, R., Häkkinen, I., Mäkinen, Y., Niemelä, P., Puhakka, M., & Coley, P. D. (1986). River dynamics and the diversity of Amazon lowland forest. Nature, 322(6076), 254-258.
Sanchis‐Ibor, C., Segura‐Beltrán, F., & Navarro‐Gómez, A. (2019). Channel forms and vegetation adjustment to damming in a Mediterranean gravel‐bed river (Serpis River, Spain). River Research and Applications, 35(1), 37-47.
Schumm, S. A. (1973). Geomorphic thresholds and complex response of drainage systems. Fluvial geomorphology, 6, 69-85.
Schumm, S. A. (1979). Geomorphic thresholds: the concept and its applications. Transactions of the Institute of British Geographers, 485-515.
Sklar, L. S., & Dietrich, W. E. (2004). A mechanistic model for river incision into bedrock by saltating bed load. Water Resources Research, 40(6).
Sklar, L. S., & Dietrich, W. E. (2006). The role of sediment in controlling steady-state bedrock channel slope: Implications of the saltation–abrasion incision model. Geomorphology, 82(1-2), 58-83.
Surian, N., Righini, M., Lucía, A., Nardi, L., Amponsah, W., Benvenuti, M., Borga, M., Cavalli, M., Comiti, F., & Marchi, L. (2016). Channel response to extreme floods: insights on controlling factors from six mountain rivers in northern Apennines, Italy. Geomorphology, 272, 78-91.
Tomsett, C., & Leyland, J. (2019). Remote sensing of river corridors: A review of current trends and future directions. River Research and Applications, 35(7), 779-803.
Turowski, J. M., Badoux, A., Leuzinger, J., & Hegglin, R. (2013). Large floods, alluvial overprint, and bedrock erosion. Earth Surface Processes and Landforms, 38(9), 947-958.
Turowski, J. M., Hovius, N., Meng‐Long, H., Lague, D., & Men‐Chiang, C. (2008). Distribution of erosion across bedrock channels. Earth Surface Processes and Landforms, 33(3), 353-363.
Watanabe, K., & Saito, N. (2021). Study on the Behavior of Sandbar in a River Channel at the Babamegawa River. GEOMATE Journal, 20(78), 115-120.
Winter, T. C. (1999). Ground water and surface water: a single resource (Vol. 1139). Diane Publishing.
Wobus, C. W., Tucker, G. E., & Anderson, R. S. (2006). Self‐formed bedrock channels. Geophysical Research Letters, 33(18).
Wolman, M. G., & Gerson, R. (1978). Relative scales of time and effectiveness of climate in watershed geomorphology. Earth Surface Processes and Landforms, 3(2), 189-208.
Wolman, M. G., & Leopold, L. B. (1957). River flood plains: some observations on their formation (Vol. 282, pp. 87-109). Washington, DC: US Government Printing Office.
Wolman, M. G., & Miller, J. P. (1960). Magnitude and frequency of forces in geomorphic processes. The Journal of Geology, 68(1), 54-74.
Zhu, L., Chen, D., Hassan, M. A., & Venditti, J. G. (2022). The influence of riparian vegetation on the sinuosity and lateral stability of meandering channels. Geophysical Research Letters, 49(2), e2021GL096346.