BEACH STEPS - AN EVOLUTIONARY PERSPECTIVE
BEACH STEPS - AN EVOLUTIONARY PERSPECTIVE
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DOI：
10.1016/0025-3227(95)00011-m
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发表时间：
1995-04-01
期刊：
影响因子：
2.9
通讯作者：
ALLEN, JR
中科院分区：
文献类型：
--
作者：
BAUER, BO;ALLEN, JR
在接下来的两天里，当内冲浪区的入射波条件相似时，对卡纳维拉尔国家海岸对比海滩台阶行为的实地观察促使我们重新审视我们对海滩台阶的概念和定量理解。这些低前滨特征比之前假设的更为复杂，通过侵蚀和增生阶段演变，并在几何形式上显示出等值性，但不一定是内部沉积结构。回顾了过去和最近的证据，将海滩台阶与汹涌-骤降过渡时的入射波以及反冲洗涡流的作用联系起来。潮汐和低频波可能对海滩台阶的形成没有直接作用，尽管它们的存在可以对调节近岸流体动力学产生显着影响，从而对海滩台阶的维持和演化产生显着影响。提出了一个概括的概念模型，捕捉海滩台阶动力学的这些方面。海滩阶梯的启动通过“雕刻”、“挖掘”或“建造”步骤进行，具体取决于海滩前滩系统的侵蚀-增生特征。阶梯形式的后续演化可能采取几种替代形态动力学途径之一，包括阶梯面“撤退”、阶梯“拖拽”或阶梯“填充/消除”，具体取决于潮汐阶段/范围或波浪建立/下降。在用实际结果制定海滩台阶存在和演化的定量模型之前，需要有关平衡海滩台阶形式以及相关形态动力学和水动力条件的额外数据。
Field observation of contrasting beach-step behavior at Canaveral National Seashore on two subsequent days when incident-wave conditions in the inner surf zone were similar prompted this re-examination of our conceptual and quantitative understanding of beach steps. These lower-foreshore features are more complex than previously assumed, evolving through erosional as well as accretional phases, and displaying equifinality in geometric form but not necessarily internal sedimentary structure. Past and recent evidence is reviewed that links beach steps to incident waves at the surging-plunging transition and to the action of a backwash vortex. Tides and low-frequency waves likely play no direct role in beach-step initiation, although their presence can have pronounced influences on modulating nearshore hydrodynamics, and thus, on beach-step maintenance and evolution. A generalized, conceptual model capturing these aspects of beach-step dynamics is presented. Beach-step initiation proceeds via step ''carving'', ''excavation'', or ''building'' depending on the erosional-accretional character of the beach-foreshore system. Subsequent evolution of the step form may take one of several alternative morphodynamic pathways including step-face ''retreat'', step ''drag down'' or step ''infilling/elimination'' depending on tidal stage/range or wave set-up/set-down. Additional data on equilibrium beach-step forms and associated morphodynamic and hydrodynamic conditions in the field are necessary before quantitative models of beach-step existence and evolution can be formulated with realistic results.