Reconnaissance study of erosion and deposition produced by the flood of August 1955 in Connecticut
Reconnaissance study of erosion and deposition produced by the flood of August 1955 in Connecticut
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对 1955 年 8 月康涅狄格州洪水造成的侵蚀和沉积的勘察研究
DOI：
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发表时间：
1958
期刊：
影响因子：
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通讯作者：
Jack P. Eiler
中科院分区：
文献类型：
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作者：
M. Wolman;Jack P. Eiler
1955年8月，康涅狄格州谷底的大片地区被洪水淹没。相对于被淹没的总面积，被水流永久改变的部分出奇地小。虽然在某些地方很大，这些永久性的修改渠道和洪泛平原的分布是参差不齐的。
在狭窄陡峭的山谷中，河道和谷底的侵蚀似乎最为严重。沉积环境是多种多样的。它们似乎与水流的速度和方向、当地沉积物的数量和大小有关，在某些情况下还与植被的存在有关。大多数沉积在山谷中的粗沉积物似乎来自当地的来源，例如由冰川沉积物和含有大量砾石的冰碛和泛滥平原组成的谷壁和阶地。沉积的大部分沉积物中以细砂为主。
考虑到径流量的大小，洪水输移或沉积的细泥沙量很小。在斯堪的纳维亚河布罗德布鲁克观测到的最高浓度为百万分之473。在许多山谷的洪泛平原上，新沉积的细粒沉积物很薄或不存在，这些山谷位于缓慢流动的洪水沃茨以下20英尺。在这种理想的沉积环境中，沉积物的缺乏也表明水流中没有高浓度的细沉积物。一些直径为5至7英尺的巨石被洪水沃茨冲走，而较小的砾石则未受影响。
高地的严重侵蚀很轻微。在这次勘察中，我们几乎没有看到新形成的冲沟，也没有看到严重的片蚀区。林地和牧场的情况都是如此。大量的地下水流和相对不易侵蚀的地面被认为是没有侵蚀的原因。
A large area in the valley bottoms in Connecticut was inundated by the flood of August 1955. Relative to the total area flooded that part permanently modified by the flow was surprisingly small. Although great in some places, the distribution of these permanent modifications of channel and flood plain was spotty.
Erosion of the channel and valley bottom appears to have been most severe in narrow, steep valleys. Environments of deposition were diverse. They appeared to be related to rate and direction of flow, quantity and size of sediments locally available, and in some cases to the presence of vegetation. Most of the coarse sediment deposited in the valley appears to have been derived from local sources such as valley walls and terraces composed of glacial outwash and till and flood plains containing considerable gravel. Fine sand predominated in most of the sediment deposited.
Considering the magnitude of the runoff, the quantity of fine sediment transported or deposited by the flood was small. The maximum observed concentration was 473 parts per million in Scantic River at Broad Brook. Newly deposited fine sediments are thin or absent on the flood plains of many valleys which were beneath 20 ft of slow-moving flood waters. The paucity of deposition in such ideal depositional environments also indicates that the flow did not have a high concentration of fine sediments. A number of boulders five to seven feet in diameter were moved by flood waters in reaches in which smaller gravels were undisturbed.
Severe erosion in the uplands was minor. In this reconnaissance we saw little evidence of newly formed gullies and no areas of severe sheet erosion. This was the case in both woodland and pasture land. Large amounts of subsurface flow and relatively unerodible ground are presumed to be responsible for the absence of erosion.