Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/34944
標題: The Mechanism of Large Woody Debris Initial Entrainment in a Flume Experiment
漂流木初始運動機制之試驗研究
作者: 王啟榮
Wang, Ci-Rong
關鍵字: large woody debris;漂流木;wood stability factor;wood incipient motion prediction model;穩定性因子;漂流木起動預測模式
出版社: 水土保持學系所
引用: 1. 陳樹群、陳佳璜、趙益群 (2010),「漂流木運移特性對河川型態改變之試驗研究」,中華水土保持學報,40(1):。(accepted) 2. 葉昭憲 (2009),「木質殘材對局部河床影響之調查與渠槽試驗研究」,中華水土保持學報,40(1):79~93。 3. 魏曉華、代力民 (2006),「森林溪流倒木生態學研究進展」,植物生態學報,30(6):1018~1029。 4. Abbe, T.B., Montgomery, D.R., Featherston, K., McClure, E. (1993), “A process-based classification of woody debris in a fluvial network; preliminary analysis of the Queets River, Washington,” EOS Transaction of the American Geophysical Union, 74: 296. 5. Abbe, T.B., Montgomery, D.R. (1996), “Large woody debris jams, channel hydraulics and habitat formation in large rivers,” Regulated Rivers: Research and Management, 12: 201~221. 6. Andrus, C. W., Long, B. A., and Froehlich, H. A. (1988), “Woody debris and its contribution to pool formation in a coastal stream 50 years after logging,” Can. J. of Fisheries and Aquatic Sci., 45: 2080~2086. 7. Beschta, R. L., and Platts, W. S. (1986), “Morphological features of small stream: significance and function,” Water Resour. Bull., 22(3): 369~379. 8. Beven, K., Gilman, K., and Newson, M. (1979), “Flow and flow routing in upland channel networks,” Hydrological Sci. Bull., 24(3): 303~325. 9. Bilby, R.E. (1985), “Influence on stream size on the function and characteristics of large organic debris,” West Coast Meeting of the National Council of the Paper Industry for Air and Stream Improvement, p. 1~14. 10. Bilby, R.E., Ward, J.W. (1989), “Changes in characteristics and function of large woody debris with increasing size of streams in western Washington,” Transactions of the American Fisheries Society, 118: 368~378. 11. Bilby, R.E., Ward, J.W. (1991), “Changes in characteristics and function of large woody debris in streams draining old-growth, clear-cut, and second-growth forests in southwestern Washington,” Canadian Journal of Fisheries and Aquatic Sciences, 48: 2499~2508. 12. Bocchiola, D., Rulli, M. C., Rosso, R. (2006), “Flume experiments on wood entrainment in rivers,” Advance in Water Resources, 29: 1182~1195. 13. Bocchiola, D., Rulli, M. C., Rosso, R. (2006), “Transport of large woody debris in presence of obstacles,” Geomorphology, 76: 166~178. 14. Braudrick, C.A., Grant, G.E., Ishikawa, Y., Ikeda, H. (1997) “Dynamics of wood transport in streams: a flume experiment,” Earth Surface Processes and Landforms, 22: 669~683. 15. Braudrick, C.A., Grant, G.E. (2000), “When do logs move in rivers?” Water Resources Research, 36:571~583. 16. Braudrick, C.A., Grant, G.E. (2001), “Transport and deposition of large woody debris in streams: a flume experiment,” Geomorphology, 41: 263~283. 17. Degetto, M., and Righetti, M. (2004), “Dynamic of wood transport in torrents,” Internationales Symposion Interpraevent 2004-RIVA/TRIENT, VII: 73~81. 18. Fetherston, K.L., Naiman, R.J., Bilby, R.E. (1995), “Large woody debris, physical process and riparian forest development in Montane river networks of the Pacific Northwest,” Geomorphology, 13: 133~144. 19. Gippel, C. J., O’Neill, I. C., and Finlayson, B. L. (1992), “The hydraulic basis of snag management,” Ctr. for Envir. Appl. Hydro., Dept. of Civ. and Agric. Engrg., Univ. of Melbourne, Parkvillem Australia. 20. Gippel, C. J. (1995), “Environmental hydraulics of large woody debris in streams and rivers,” Journal of Environmental Engineering, 121(5): 388~395. 21. Gippel, C. J., O’Neill, I. C., Finlayson, B. L., Schnaz, I. (1996), “Hydraulic guidelines for the re-introduction and management of large woody debris in lowland river,” Regulated Rivers: Res Manage, 12: 223~236. 22. Gomi, T., Sidle, R. C., Bryant, M. D., and Woodsmith, R. D. (2001), “The characteristics of woody debris and sediment distribution in headwater streams, southeastern Alaska,” Canadian Journal of Forest Research, 31: 1386~1399. 23. Gregory, S.V. (1991), “Spatial and temporal patterns of woody debris retention and transport,” North American Benthological Society, p. 75. 24. Gurnell, A.M., Petts, G.E., Hannah, D.M., Smith, B.P.G., Edwards, P.J., Kollman, J., Ward, J.V., Tockner, K. (2000), “Wood storage within the active zone of a large European gravel-bed river,” Geomorphology, 34: 55~72. 25. Gurnell, A.M., Petts, G.E., Harris, N., Ward, J.V., Tockner, K., Edwards, P.J., Kollman, J. (2000), “Large wood retention in river channels: the case of the Fiume Tagliamento, Italy,” Earth Surface Processes and Landforms, 25: 255~ 275. 26. Hinze, J. O. (1975), “Turbulence,” (2nd Ed.), Mc Graw Hill. 27. Hogan, D.L. (1987), “The influence of large organic debris on channel recovery in the Queen Charlotte Islands, British Columbia, Canada,” Proceedings of the Corvallis Symposium: Erosion and Sedimentation in the Pacific Rim, p. 342~353. 28. Keller, E.A., Swanson, F.J. (1979), “Effects of large organic material on channel form and fluvial processes,” Earth Surface Processes and Landforms, 4: 361~380. 29. Lienkaemper, G.W., Swanson, F.J. (1987), “Dynamics of large woody debris in old-growth Douglas-fir forests,” Canadian Journal of Forest Research, 17: 150~156. 30. MacDonald, A., and Keller, E. A. (1987), “Stream channel response to the removal of large woody debris, Larry Damm Creek, northwestern California,” Erosion and sedimentation in the Pacific Rim; Proc., Corvallis Symp.; IAHS Publ.,165:406~406. 31. Montgomery, D. R., Collins, B. D., Buffington, J. M., Abbe, T. B. (2003), “Geomorphic effects of wood in river,” American Fisheries Society Symposium, p. 1~27. 32. Nakamura, F., Swanson, F.J. (1994), “Distribution of coarse woody debris in a mountain stream, western Cascades Range, Oregon,” Canadian Journal of Forest Research, 24: 2395~2403. 33. Petryk, S., and Bosmajian III, G. (1975), “Analysis of flow through vegetation,” J. Hydr. Div., ASCE, 101(7): 871~884. 34. Shaw, T. L. (1971), “Effect of side walls on flow past bluff bodies,” J. Hydr. Div., ASCE, 97(1): 65~79. 35. Shields Jr., F. D., Gippel, C. J. (1995), “Prediction of effects of woody debris removal on flow resistance,” J. Hydr. Engrg., ASCE, 121(4): 341~354. 36. Smith, R. D., Sidle, R. C., and Porter, P. E. (1993), “Effects on bedload transport of experimental removal of woody debris from a forest gravel bed stream,” Earth Surface Processes and Landforms, 18: 455~468. 37. Toews, D.A.A., Moore, M.K. (1982), “The effects of three streamside logging treatments on organic debris and channel morphology in Carnation Creek,” Proceedings: Carnation Creek Workshop, p. 129~153. 38. Wallerstein, N., Thorne, C. R., Doyle, M. W. (1997), “Spatial distribution and impact of large woody debris in northern Mississippi,” In Management of Landscapes Disturbed by Channel Incision, Wang SSY, Langendoen EJ, Shields FD (eds). University of Mississippi: Mississippi, USA; p. 145~150. 39. Wallerstein, N. P., Alonso, C. V., Bennett, S. J., Thorne, C. R. (2002), “Surface wave forces acting on submerged logs,” ASCE J Hydraul Eng, 128(3):349~353. 40. Wooster, J., Hilton, S. (2004), “Large woody debris volumes and accumulation rates in cleaned streams in redwood forests in Southern Humboldt county, California,” USDA Forest Service Research Note, PSW-RN-426. 41. Young, M.K. (1994), “Movement and characteristics of stream bourne coarse woody debris in adjacent burned and undisturbed watersheds in Wyoming,” Canadian Journal of Forest Research, 24: 1933~1938.
摘要: 
鑑於吾人對於漂流木在河道中的運動機制瞭解有限;因此,本研究藉由渠槽試驗模擬單根漂流木在定床渠道之初始起動情形,並探討不同漂流木長度、直徑、與水流夾角及底床粒徑對漂流木初始起動水流條件之影響。另外,本研究亦藉由水流作用在單一漂流木的力學平衡,建立漂流木初始起動之預測模式,並以渠槽試驗之結果對預測模式進行驗證。
試驗發現,當漂流木與水流方向平行時,隨著水深逐漸增加,漂流木所受之浮力隨之增加,摩擦阻力則逐漸減小,直至漂流木開始發生運動,此時漂流木會以半浮動半滑動的方式向下游移動;而漂流木與水流方向傾斜及垂直時則皆為滾動之方式向下游移動。綜合試驗與模式預測之結果得知,漂流木能否穩定停留在渠道中,主要跟漂流木與水流之夾角、漂流木密度、直徑、渠道坡度及底床粗糙度等因子有關,而與漂流木長度及拖曳力係數較無關係。雖然在許多漂流木相關研究中皆指出,漂流木長度係影響漂流木穩定性的重要因子,但從試驗結果及預測模式皆顯示,長度因子對於漂流木穩定性並無顯著之影響,是由於本研究之漂流木長度均小於渠寬。
本研究結合漂流木滑動(合力平衡)與滾動(合力矩平衡)兩種不同力學平衡機制,建立漂流木初始起動預測模式:

式中,ρlog、Dlog、Llog及θ分別代表漂流木密度、直徑、長度及與水流夾角, 為漂流木與水流夾角θ相應之摩擦角,ρw及dw分別代表水密度與漂流木初始起動所需之水深,S為渠道坡度(S=tanα),ds為底床粒徑,CD為拖曳力係數。
此預測模式主要適用在漂流木與水流方向之任意夾角;由已知之漂流木性質(水流夾角、密度、直徑及長度)和渠道性質(坡度及底床粒徑),即可預測漂流木初始起動所需之水深。針對預測模式進行驗證之結果顯示,預測模式與試驗結果之誤差範圍佔漂流木直徑之10%,尤其在漂流木與水流方向傾斜及垂直時,其誤差範圍只佔漂流木直徑之5%。上述結果顯示,本研究所提出之漂流木初始起動預測模式之預測能力良好。

There has thus far been relatively little research into large woody debris (LWD) motion. The research was designed as a fixed bed flume experiment to explore the state of LWD critical entrainment, and discussed the initial flow condition was influenced by different length, diameter, orientation and bed roughness. Additionally, the theoretical model was developed to predict wood entrainment and compare predictor with experiment results.
The experiment results show that different orientations of wood will lead to different types of wood movement. For wood parallel to flow, the mechanism of motion features started by semi-floating and semi-sliding, because flow was gradually raised with the buoyant force increased and the friction force decreased until the wood moved to downstream. For wood oblique or perpendicular to flow, the mechanism of motion features started by rolling. Both the models and the experiments indicate that stable wood is significantly associated with wood angle relative to flow direction, the density of wood, wood diameter, channel slope and bed roughness. The wood stability is less sensitive to the choice of the apparent drag coefficient and wood length. Although previously reported as the most important factor in wood stability, wood length did not significantly affect the threshold of movement in the experiments or the model predictions, for wood shorter than channel width.
This research consists of sliding and rolling equilibrium equations to establish a prediction model of wood entrainment:

where dw is the flow depth for wood incipient motion, Llog is the wood length, Dlog is wood diameter, ρlog and ρw are the densities of wood and water, respectively, S is the channel slope (S=tanα), CD is the drag coefficient of the wood in water, ds is the bed grain size, θ is the angle of the wood relative to flow, and is the friction angle between wood and channel bed.
This prediction model is helpfully used for multiple angles of the wood relative to flow, and the flow depth for wood incipient motion could be predicted under the wood and channel characteristics are given. To compare model predictors with experiments, the bias account for about 10% of the wood diameter. Moreover, for wood oblique or perpendicular to flow, the bias only account for about 5% of the wood diameter. According to the results, the prediction model is relative successfully at predicting depths for wood incipient motion.
URI: http://hdl.handle.net/11455/34944
其他識別: U0005-2207201010242700
Appears in Collections:水土保持學系

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