隨著生態保育意識高漲，於近自然工法中利用天然石材加工排列堆疊，以人為方式營造階梯深潭，可防止河床掏刷、增加水流動能消耗及穩定河床。目前國內外有許多案例及研究可以參考，但多以經驗法則評估進行現地施作，缺乏學理上的佐證，每逢強降雨事件發生，伴隨大量土砂運移，將影響砌石結構的穩定及整體河道的穩定性，仍有安全存疑，因此研究其階梯深潭之水力特性與河相特性，為砌石工法之初期重要工作。
為了解階梯深潭的形成機制、水力特性及上游來砂對河道穩定性之影響，本研究建置一長度為2.9m、寬度0.15m、深度0.3m之實驗渠槽，針對河道坡度、流量及不同砂源(混合粒徑Ａ(D50=12.4mm)與Ｂ(D50=2.9mm))等控制變因設計15組實驗，透過渠槽側面拍攝，量測河道地形、流速場分佈及泥砂出流量，探討階梯深潭形成方式、流體型態及階梯深潭河道破壞現象等，以河相學為基礎、水力學分析為依據，進行階梯深潭學理驗證。
由結果可知，階梯深潭發育過程中，河道中出現關鍵性礫石，其粒徑大小約為渠槽寬度的1/3～1/10倍，透過顆粒間相互緊密鍵結，形成一肋骨狀之橫向結構物；當流量由0.0012cms調整至0.0060cms時，福祿數大於一，流況由舌流轉換為滑移流，階梯處平均流速與深潭處平均流速差異降低30%；加砂實驗中，上游分別加入兩種砂源後，由實驗結果可知，階梯深潭河道依破壞方式可分為土砂掩埋與階梯結構破壞兩種。本研究透過實驗現象與砌石工法連結，以定性定量方式說明階梯結構的組成為階梯深潭河道穩定之重要關鍵。
本研究所建立階梯深潭之概念性實驗現象與現地案例結合，可提供未來國內外砌石工法設計之參考依據。

Longitudinal stair-like structures, such as alternating steps and pools, are found commonly in steep mountain streams. As a way to mimic natural characteristics, artificial step structures have long been used in Taiwan and abroad to stabilize streambeds and enhance aquatic systems but many of these projects lack theoretical verification and evidence. When typhoons come, accompanied by extreme rainfall, large amounts of sediment is taken downstream, making step-pool channels unstable. Previous research has not investigated the effect of sediment load on stability, therefore, this research explores the relationships between hydraulic and geomorphic factors so that future research can have a better understanding of the role of sediment in channel stability. To conduct experiments, a 2.7-m-long, 0.15-wide, and 0.3-m-high acrylic walled recirculating channel was constructed. Fifteen different scenarios were created to understand the formation, hydraulic features, and channel stability of step-pools with different channel slopes, discharges, feeding different source of sediments (mix A(D50=12.4mm), mix B (D50=2.9mm)). We analyzed these factors through the measurement of the lateral images, riverbed elevation, surface velocity and sediment transport ratio. The results indicated that the keystones played a crucial role in stabilizing step-pool structures. The grain sizes of keystones from the experiments ranged approximately from one-third to one-tenth of channel width. In the flow regime, the Froude number was greater than 1 when the flow discharge adjusted from 0.0012cms to 0.0060cms, the flow regime would transform from nappe flow to skimming flow, and the average velocity reduced 30% at steps and pools. In the sediment feeding experiment, we found that feeding both mix A or mix B caused the step-pool channels to be destroyed. Step-pool destruction was divided into two specific types: The first being sediment burying the step-pools, and the second being the destruction of the step-pool keystone structures. By connecting these results with flume experiments and field observations, we can verify the constitution of the step structure is key to step-pools stability. In this study, the combination with the flume experiment and field observation can provide the design method of the artificial step-pools not only in Taiwan but around the world.

1. Allen, J. R. L. (1983), A simplified Cascade Model For Transverse Stone-ribs
In Gravelly Streams, Proc. R. Soc. London, Ser. A, 385, 253–266.
2. Billi, P., D’Agostino, V., Lenzi, M.A., and Marchi, L., (1998). Bedload, Slope and Channel Processes in a High-Altitude Alpine Torrent. Gravel-Bed Rivers in the Environment, ed. P.C. Klingeman et al., Water Resources Publications, LLC, Highlands Ranch, CO.
3. Chin, A., (1998). On the stability of step-pool mountain streams. Journal of geology Vol. 106 , p.59-69. 3.
4. Chin, A., (1999). The morphologic structure of step-pool in mountain streams. Geomorphology 27(3–4), 191–204.
5. Chartrand, S.M., Whiting, P.J., (2000). Alluvial architecture in headwater streams with special emphasis on step-pool topography. Earth Surf. Processes Landforms 25(6), 583–600.
6. Cereghino, R., Giraydel, J. L., Compin, A., (2001). Spatial analysis of stream invertebrates distribution in the Adour-Garonne drainage basin (France), using Kohonen self-organizing maps. Ecol. Modell. 146(1–3), 167–180.
7. Chanson, H. (2001), The Hydraulics of Stepped Chutes and Spillways, 384
pp., A. A. Balkema, Brookfield, Vt.
8. Chin, A., (2003). The geomorphic significance of step-pools in mountain streams. Geomorphology 55(1–4), 125–137.
9. Comiti, F. (2003). Local scouring in natural and artificial step pool systems. Univ Degli Studi Di Padova, Legnaro, Italy.
10. Curran, J.H., and Wohl, E.E., (2003). Large woody debris and flow resistance in step-pool channels, Cascade Range, Washington. Geomorphology, 51, 141–157, doi: 10.1016/S0169-555X (02)00333-1.
11. Church, M., and Zimmermann, A., (2007). Form and stability of step-pool channels: Research progress. Water resources research, Vol. 43, W03415, doi:10.1029/2006WR00
12. Curran, J. C., (2007). Step-pool formation models and associated step spacing. Earth Surf. Processes Landforms 32(11), 1611–1627.
13. Comiti, F., Cadol, D., Wohl, E., (2009). Flow regimes, bed morphology, and flow resistance in self-form step-pool channels. Water resources research, Vol. 45, W04424, doi: 10.1029/2008WR007259.
14. Grant, G.E., Swanson, F.J., and Wolman, M.G., (1990). Pattern and Origin of Stepped Bed Morphology in High-Gradient Streams. Western Cascades, Oregon.
15. Heede, B.H., (1981). Dynamics of Selected Mountain Streams in the Western United States of America. Zeitschrift fur Geomorphologie, 25(1): 17-32.
16. Judd, H.E., (1964). A Study of Bed Characteristics in Relation to Flow in Rough, High-Gradient Natural Channels. PhD Thesis, Utah State University, pp. 182.
17. Keller, E.A., Swanson, F.J., (1979). Effects of large organic material on channel form and fluvial processes. Earth Surf. Processes Landforms 4(4), 361–380.
18. Leopold, L.B., and Wolman, M.G., (1957). River Channel Patterns: Braided, Meandering, and Straight. United States Geological Society Professional Paper 282B.
19. Morris, S., Moses, T., (1998). Channel and streambank stabilization in a steep colluvial valley. Lake Oswego OR Proc. 29th Conf. Winning Solutions for Risky Problems, 367–371, Intl Erosion Control Association, Reno, NV, Denver, CO, USA.
20. Maxwell, A.R., Papanicolaou, A.N., (2001). Step-pool morphology in high-gradient stream. International Journal of sediment research, Vol. 16, No. 3, pp.380-390.
21. Newson, M.D., and Harrison, J. G., (1978). Channel Studies in the Plynlimon Experimental Catchments. Rep. 47, Wallingford.
22. Petts, G. and Foster, I., (1985). Rivers and Landscape. Edward Arnold, London.
23. Parker, G., (1991). Selective sorting and abrasion of river gravel. II: Applications. Journal of the Hydraulic Engineering, 117(2):150-171.
24. Wertz, J.B., (1966). The Flood Cycle of Ephemeral Streams in the South-Western United States. Association of American Geographers Annals, 56: 598-633.
25. Whittaker, J.G., (1987). Sediment Transport in Step-pool Streams. Sediment Transport in Gravel-bed Rivers, eds. C.R. Thorne, J.C. Bathurst and R.D. Hey, John Wiley & Sons, Ltd., pp. 545-579.
26. Whittaker, J. G., and Jaeggi, M. N. R. (1982), Origin of Step–Pool Systems in Mountain Streams, Journal of the Hydraulic Division, 108(6): 758-773
27. Wohl, E.E., and Grodek, T., (1994). Channel Bed Steps Along Nahal Yael, Negev Desert, Israel. Geomorphology, 9: 117-126.
28. Wang, Z.Y., Melching, C.S., Duan, X. H., Yu, G. A., (2009). Ecological and hydraulic studies of step-pool systems. Journal of hydraulic research, dio: 10.1061/ (ASCE) 0733-9429 135:9(705).
29. Yang, C.T., (1971). Formation of Riffles and Pools. Water resources research, 7(6): 1567-1574.
30. Yu, G.A., Wang, Z.Y., Zhang K., Duan, X., Chang. T.C., (2010). Restoration of an incised mountain stream using artificial step-pool system. Journal of hydraulic research, Vol. 48, No. 2, pp. 178–187 doi: 10.1080/00221681003704186.
31. Zimmermann, A., Church, M., (2001). Channel morphology, gradient stresses and bed profiles during flood in a step-pool channel. Geomorphology 40(3–4), 311–327.
32. 王筱雯，2010，「七家灣溪一號壩壩體及棲地改善工程-泥砂衝擊物理模型及數值分析」，內政部營建署雪霸國家公園管理處。
33. 徐江、王兆印，2004，「階梯-深潭的形成及作用機理」，水利學報，10 : 1-11。
34. 陳樹群、鄒青穎，2005，「溪流階梯深潭型態分類及能耗率變化之渠槽實驗」，中華水土保持學報， 36(3): 267-280。
35. 莊志宏 譯，2003，「近自然工法之石組技術」，行政院農業委員會特有生物研究保育中心。
36. 梁文盛，2006，「后番子坑溪整治」，水庫集水區生態工法諮詢成果研討會。
37. 莊明德、周文杰、廖光正、李德旺、陳伊昱，2008，「河川砌石固床工之技術推廣與應用案例介紹」，自然保育季刊，第六十三期。
38. 張家豪，2012，「七家灣溪壩體移除對河相演變之探討」，國立成功大學水利與海洋學系。
39. 福留脩文、山脇正俊訳監脩，1994，「近自然工法の思想と技術／人と自然にやさしい地域づくりのコンセプト」，近自然河川工法研究会。
40. 鄒青穎，2005，「山區河流階梯-深潭之渠槽實驗研究」，國立中興大學水土保持學系。