Experimental Study of River Incision
Experimental Study of River Incision
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河流下切实验研究
DOI：
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发表时间：
1974
期刊：
影响因子：
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通讯作者：
S. Schumm
中科院分区：
文献类型：
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作者：
R. Shepherd;S. Schumm
在一个60英尺长的倾斜，再循环水槽实验进行了研究模拟基岩，这是砂和高岭石的混合物中的河流切口。在四条河槽的发育过程中，坡度、输沙量和流量均受到控制。在恒定流量下坡度增加后，发生以下侵蚀顺序：（1）纵向线理、波纹和坑洞的发展;（2）线理扩大成突出的凹槽;（3）凹槽合并成一个单一的、狭窄的、深的内槽。内水道在基准面以下被切割，形成了一系列基岩低点和高点。基岩冲刷低点有一个弱规则的间距在切割和随机聚集的间距以下淤积。在弯曲的沙床通道中，围绕稳定的交替沙坝的切口导致沙坝的破坏和局部水流收缩处的最大冲刷。在一个最初弯曲的基岩渠道，冲刷深度是在弯曲比在交叉点。如果所有可用的泥沙都被夹带，弯曲的凸岸比凹岸的河床侵蚀更严重。但淤积发生后，最大冲刷量向凹岸转移。这些结果表明，横向或垂直切割弯曲的切割河流弯曲的控制量的可用泥沙夹带的通道形成放电。研究结果还表明，如果造陆倾斜导致了切割，那么自然界中很少会出现下切曲流，这些曲流是由前一种模式叠加在后一种平原上形成的。内水道代表基岩河流冲刷最深的位置，可能是重矿物集中的位置，也可能是砾石沉积的位置。实验结果有助于解释在坝址发现的内部通道，为加州和南非的一些古通道提供了解释，并表明，像达勒夫妇类型的河道，基岩底部的山谷将是不均匀的横向和纵向截面。
Experiments in a 60-ft-long tilting, recirculating flume were conducted to study river incision in simulated bedrock, which was a mixture of sand and kaolinite. Slope, sediment feed, and water discharge were controlled during the development of four channels. After an increase of slope at constant discharge, the following sequence of erosion occurred: (1) development of longitudinal lineations, ripples, and potholes; (2) enlargement of the lineations into prominent grooves; (3) coalescence of the grooves into a single, narrow, and deep inner channel. The inner channel was incised below base level and a sequence of bedrock lows and highs formed. Bedrock scour lows had a weakly regular spacing during incision and a randomly clustered spacing following aggradation. Incision around stabilized alternate bars in a sinuous sand-bed channel resulted in destruction of the bars and maximum scour where the flow was locally constricted. In an initially sinuous bedrock channel, scour depth was greater at bends than at crossings. Provided all of the available sediment load was entrained, the bed was eroded more at convex banks of bends than at concave banks. However, after deposition occurred, the maximum erosion shifted to the concave bank. These results indicate that lateral or vertical incision at bends of incised meandering streams is controlled by the amount of available sediment load entrained by channel-forming discharges. The results also suggest that incised meanders superposed from an earlier pattern on a peneplain should rarely occur in nature, if epeirogenic tilting caused the incision. Representing the locus of deepest scour by a bedrock stream, inner channels may be the locations of heavy mineral concentrations as well as gravel deposits. The experimental results help to explain inner channels discovered at damsites, provide an explanation for some paleochannels in California and South Africa, and suggest that, like the Dalles type of river channel, bedrock floors of valleys will be uneven in both transverse and longitudinal sections.