7.1 結論
本研究分三年進行，最終目的為有效評估主槽沖刷、高灘地淤積及考量底床 變動情形下之洪水位與定床時之差異，並分析高灘地糙度改變於洪水位上升程度 與上升百分比之影響。從模式研發、測試、檢定到實際案例應用，經由嚴謹之檢 定與驗證，已研發一套應用於水庫洩洪沖淤河床之水平二維動床模式，可歸納以 下幾點研究結論：
1. 本研究發展的數值模式與 所 收 集 之 實 驗 水 槽 動 床 資 料 進 行 率 定 比 較 之 下 ， 率 定 結 果 與 實 驗 資 料 除 定 性 之 趨 勢 一 致 外 ， 定 量 上 亦 達 相 當 之 準 確 度 。
2. 以Suryanarayana(1969) 報 告 中 之 水 槽 動 床 實 驗 模 擬 單 槽 淤 積 案 例 ， 上 游 以409ppm濃 度 固 定 入 砂 ， 考 慮 單 一 粒 徑 0.45mm， 在流量 增大的條件下，底床越刷越深，使得洪水位可以相對降低；另外於加大粒徑 2倍及3倍的情況下，其底床沖刷越緩和，底床變化程度逐漸變小，故水面線 高程逐漸抬高。另外依序加大上游入流懸浮值濃度值，底床高程也將越高，
水面線高程也將逐漸抬高。
3. 於 Suryanarayana(1969)報 告 中 之 沖 刷 案 例 ， 假 設 上 游 以 0ppm 濃 度 清 水 沖 刷，在流量增大的條件下，其底床沖刷越激烈，導致底床相對下 降，故水面線高程相對下降；另於標準案例之流量下，依序加大粒徑大小，
其底床沖刷越緩和，底床變化程度逐漸變小，水面線高程逐漸抬高。
4. 經由 Suryanarayana(1969)單 槽 斷 面 假設之實驗室複式斷面案例模擬後 發現，主槽與高灘地間之交換機制影響著底床之變化，進而也影響著水位的 變化，主深槽底床與高灘地淤高時，水位隨之壅高；沖刷時，水位隨之下降。
5. 於實驗室複式斷面案例中，高灘地的寬度對於底床之淤積與沖刷程度有著相 關性存在，高灘地越寬，淤積與沖刷的程度越明顯；但對於水位而言，高灘 地的寬度則並不具有絕對的影響性。
6. 正交與非正交格網分析方面，從 Babarutsi (1989)之定床實驗案例可知，在特 定之流場條件下，應有一定程度疏密且符合流場形狀之格網點才能將該流場 特性完全展現，而該案例正交與非正交之差異在格網點大於21x11 時即非常 小。
7. 在曾文溪納莉颱洪實際模擬案例中，模擬範圍玉田至二溪大橋段呈現淤積趨 勢，二溪大橋至麻善大橋段呈現沖刷情形，整體沖淤範圍約在-0.6m~+0.6m。
8. 比較計算斷面 I=123 水平方向之水面線，高灘地水位相較主深槽區域來的 高，且越靠近高灘地岸邊壅高程度越大。
9. 在模擬 5、50、100、200 不同頻率年洪水案例中，藉由改變高灘地糙度之量 化圖分析其對洪水位上升之影響，發現高灘地糙度越高，上升程度越大，流 量越大，上升程度亦越大，顯示高灘地糙度與流量大小對於洪水位升高具有 影響性存在。
7.2 建議
1. 二維模擬格網點高程之建構僅由實測斷面資料內差換算，對於斷面與斷面間 實際地形變化仍有所誤差，若能有更精準之河道數值高程資料，將有助模擬 成果精度之提升。
2. 水位上升值、水位上升百分比與糙度關係圖，其中各項變數之相互關係可否 藉由無因次化使其更具通用性，後續仍有許多研究價值。
參考文獻
1. Anderson, M. G., Bates, P. D., and Walling, D. E. (1996). “The general context for floodplain process research.” Floodplain Process, 1-14.
2. Bhallamudi, S.M., and Chaudhry, M.H. (1991). “Numerical modeling of aggradation and degradation in alluvial channels.” J. Hydr. Engrg., ASCE, 117(9), 1145-1164.
3. Bousmar, D. and Zech, Y. (1999). “Momentum transfer for practical flow computation in compound channels.” J. Hydr. Eng., ASCE, 125(7), 696-706.
4. Cokljat, D. and Younis, B. A. (1995). “Compound-cannel flows: a parametric
study using a Reynolds-stress transport closure.” J. Hydr. Res., 33(3), 307-320.
5. Cunge, J. A. et al. (1980). “Chapters 2 and 4.” Practical aspects of computational river hydraulics, Pitman Pub., London.
6. Dai, W. (1994). “Numerical solutions of unsteady Navier-Stokes equations using explicit finite analytic Scheme.” Ph.D. Thesis, the Univ. of Iowa, Iowa City, Iowa.
7. Fathi-Maghadam, M. and Kouwen, N. (1997). “Nonrigid, nonsubmerged, vegetative roughness on floodplains.” J. Hydr. Eng., ASCE, 123(1), 51-57.
8. Falconer, R. A. and Chen, Y. (1996). “Modelling sediment transport and water quality processes on tidal floodplains.” Floodplain Processes, 361-398.
9. Hardy, R. J. et al. (2000), “Development of a reach scale 2-D finite element model for floodplain sediment deposition.” Water and Martime Eng., 142(3), 141-156.
10. Holly, F.M. Jr., and Rahuel, J.L. (1990). “New numerical/physical framework for mobile-bed modeling.” J. Hydr. Research, 28(4), 401-416.
11. Hsu, C. T., Yeh, K. C., and Yang, J. C. (2000). “Depth-averaged 2-D curvilinear explicit finite analytic model for open-channel flows.” Inter. J. for Numerical Methods in Fluids, 33, 175-202.
12. James, C. S. (1985). “Sediment transfer to overbank sections.” J. Hydr. Res., 23(5), 435-452.
13. Jia, Y. and Wang, S. S. Y. (1999). “Numerical model for channel flow and morphological change studies.” J. Hydr. Eng., ASCE, 125(9), 924-933.
14. Knight, D. W., and Brown, F. A. (2001). “Resistance studies of overbank flow in rivers with sediment using the flood channel facility.” J. Hydr. Res., 39(3), 283-302.
15. Knight, D. W., and Demetriou, J. D. (1983). “Flood-plain and main channel flow iteration.” J. Hydr. Engrg., ASCE, 109(8), 1073-1092.
16. Knight, D. W. and Hamed, M. E. (1984). “Boundary shear in symmerrical compound channels.” J. Hydr. Engrg., ASCE, 110(10), 1412-1430.
17. Knight, D. W. and Sellin, R. H. J. (1987). “The SERC flood channel facility.” J.
Instin. Water aand Envir. Mgmt., 1(2), 198-204.
18. Lai, C. J., Lin, C. L., and Lin, Y. Z. (2000). “Experiments on flood-wave propagation in compound channel.” J. Hydr. Eng., ASCE, 126(7), 492-501.
19. Lambert, M. F. and Sellin, R. H. J. (1996). “Discharge prediction in straight compound channel using the mixing length concept.” J. Hydr. Res., 34(3), 381-394.
20. Lambert, M. F. and Sellin, R. H. J. (2000). “Estimating the discharge capacity of doubly sinuous compound channels.” Water and Martime Eng., 142(2), 103-112.
21. Lin, B. and Shiono, K. (1995). “Numerical modeling of solute transport in compound channel flows.” J. Hydr. Res., 33(6), 773-788.
22. Myers, R. C. and Lyness, J. F. (1997). “Discharge ratios in smooth and rough compound channels.” J. Hydr. Eng., ASCE, 123(3), 182-188.
23. Myers, W. R. C. et al. (2000). “Geometrical and roughness effects on compound channel resistance.” Water and Martime Eng., 142(3), 15-166.
24. Myers, W. R. C., Lyness, J. F., and Cassells, J. (2001). “Influence of boundary roughness on velocity and discharge in compound river channels.” J. Hydr. Res., 39(3).
25. Naot, D., Nezu, I. and Nakagawa, H. (1993). “Calculation of compound-channel flow.” J. Hydr. Eng., ASCE, 119(12), 1418-1426.
26. Narinesingh, P. et al. (1999), “Floodplain sedimentation along extended river reaches.” J. Hydr. Res., 37(6), 827-846.
27. NERC. (1975). Flood Studies Rep., Vol. III: Flood routing studies, National Environment Research Council, London, U. K.
28. Nokes, R. I. and Hughes, G. O. (1994), “Turbulent mixing in uniform channels of irregular cross-section.” J. Hydr. Res., 32(1), 67-86.
29. Onishi, Y., and Trest, D.S. (1985). “Three-dimensional simulation of flow, salinity, sediment, and radionuclide movements in the Hudson River estuary.”
Proceedings of the Specialty Conference, Hydraulics and Hydrology in the Small Computer Age, ASCE, Orlando, 12-17 August, 1095-1100.
30. Pavlovic, R. N., Varga, S., and Misic, B. (1985). “Two-dimensional depth-averaged model for the calculation of sediment transport and riverbed deformation. ” Proceedings of International Symposium on Refined Flow Modeling and Turbulence Measurements, Iowa, U.S.A., September.
31. Pezzinga, G. (1994). “Velocity distribution in compound channel flows by numerical modeling.” J. Hydr. Eng., ASCE, 120(10), 1176-1198.
32. Prinos, P., Townsend, R., and Trvoularis, S. (1985). “Structure of turbulence in compound channel flow.” J. Hydr. Engrg., ASCE, 111(9), 1246-1261.
33. Richmond, M. C, Chen, H.C., and Patel, V. C. (1986). “Equations of laminar and turbulent flows in general curvilinear coordinates.” IIHR Report No. 300, Univ.
of Iowa, Iowa.
34. Shiono, K., and Knight, D. W. (1991). “Turbulent open-channel flows with variable depth across the channel.” J. Fluid Mech., Cambridge, England, 222, 617-646.
35. Shome, M. L. and Steffler, P. M. (1998). “Lateral flow exchange in transient compound channel flow.” J. Hydr. Eng., ASCE, 124(1), 77-80.
36. Simons, D.B., Chen, Y.H., and Ponce, V.M. (1979). “Development of a two-dimensional water and sediment routing model and its application to study lower poor 4 in the upper Mississippi River system.” Engrg. Research Center, Colorado State Univ., Fort Collins, Colorado.
37. Sofialidis, D. and Prinos, P. (1998), “Compound open-channel flow modeling with nonlinear low-Reynolds
k −
ε models.” J. Hydr. Eng., ASCE, 124(3), 253-262.38. Sofialidis, D. and Prinos, P. (1999), “Numerical study of momentum exchange in compound open channel flow.” J. Hydr. Eng., ASCE, 125(2), 152-165.
39. Sofialidis, D. and Prinos, P. (1999), “Turbulent flow in open channels with smooth and routh flood plains.” J. Hydr. Res., 37(5), 615-640.
40. Sturm, T. W. and Sadig, A. (1996). “Water surface profiles in compound channel with multiple critical depths.” J. Hydr., Eng., ASCE, 122(12), 703-709.
41. Suryanarayana, B. (1969). “Mechanics of Degradation and Aggradation in a Laboratory Flume”, thesis presented to Colorado State University, at Fort Collins, Colorado, in 1969.
42. Thomas, W.A., and McAnally, W.H. Jr. (1985). “User’s manual for the generalized computer program system open-channel flow and sedimentation – TABS-2, main text.” Instruction Report HL-85-1, Waterways Experiment Station, U.S. Army Corps of Engineers, Vicksburg, Mississippi, July, 30 Pages.
43. Tingsanchali, T., and Ackermann, N. L. (1976). “Effects of overbank flow in flood computation.” J. Hydr. Div. ASCE, 102(7), 1013-1025.
44. Tingsanchali, T., and Lal, N. K. (1988). “Subsidence of flood waves in overbank flow.” J. Hydr. Res., 26, 585-597.
45. Tominaga, A., and Nezu, I. (1991). “Turbulent structure in open compound channel flows.” J. Hydr. Engrg., ASCE, 117(1), 21-41.
46. Tominaga, A., Nezu, I., and Ezaki, K. (1989). “Experimental study on secondary currents in compound open-channel flow.” Proc., 23
rd
IAHR Congr., A15-A22.47. Tucciarelli, T. and Termini, D. (2000). “ Finite-element modeling of floodplain flow.” J. Hydr. Eng., ASCE, 126(6), 416-424.
48. Usseglio-Polatera, J.M., and Cunge, J.A (1985). “Modeling of polutant and suspended-sediment transport with Argos modeling system.” International Conference on Numerical and Hydraulic Modeling of Ports and Harbors, Birmingham, 23-25 April.
49. Walling, D. E., He, Q., and Nicholas, A. P. (1996). “Floodplains as suspended sediment sinks.” Floodplain Processes, 399-440.
50. Wormleaton, P. R., Allen, J., and Hadjipanos, P. (1982). “Discharge assessment in compound channel flow.” J. Hydr. Div., ASCE, 108(9), 975-993.
51. Wormleaton, P. R., and Merrett, D. (1990). “An improved method of calculation of steady uniform flow in prismatic main/flood channel plain section.” J. Hydr.
Res., 28, 157-174.
52. Yen, C. L. (1987). “Subsidence of peak flow in open channel with storage area.”
J. Hydr. Res., 16(4), 309-326.
53. 葉克家、沈澄宇(2000)，「水庫排放凝聚性沈滓對下游河道之影響研究」，國 科會精簡報告。
54. 經濟部水利處南區水資源局，「曾文水庫淤積清理規劃後續研究報告」，中華 民國88 年 11 月。
55. 鄭育能（1995），「 結構性格點產生的一些進展」，第三屆計算流力研討會，
59-65。