Rollover, drowning, and discontinuous retreat: Distinct modes of barrier response to sea-level rise arising from a simple morphodynamic model
Rollover, drowning, and discontinuous retreat: Distinct modes of barrier response to sea-level rise arising from a simple morphodynamic model
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DOI：
10.1002/2013jf002941
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发表时间：
2014-04-01
影响因子：
3.9
通讯作者：
Ashton, Andrew D.
中科院分区：
文献类型：
--
作者：
Lorenzo-Trueba, Jorge;Ashton, Andrew D.
我们建立了一个简单的形态动力学模型，探讨了经历海平面上升的海岸屏障系统的长期动态演变。使用简化的障碍物几何形状，该模型包括一个动态的滨面轮廓，可以是不平衡的，并明确地将障碍物沉积物过洗作为一个通量。障碍物的行为主要由最大潜在的过洗通量和滨面响应率控制，模拟的障碍物系统表现出四个主要行为：高度淹没，宽度淹没，不断向陆地撤退，和定期撤退。当过洗通量不足以维持与海平面上升同步所需的向陆地迁移速率时，就会发生高度淹没。另一方面，宽度淹没发生时，滨面响应率不足以维持障碍物的几何形状在过冲驱动的向陆迁移。在周期性的障碍撤退，障碍的经验振荡期的快速过洗，然后是相对稳定的时期，作为滨面resteepens。这种周期性的撤退，即使发生在一个恒定的海平面上升率，出现时，过洗率和滨面响应率是大的，类似的幅度。我们探讨了这些行为的发生在很大范围的参数值，并发现，除了最大的过洗通量和滨面响应率，障碍响应可以是特别敏感的海平面上升率和后障泻湖坡度。总体而言，我们的研究结果与以前的研究相比，主要与复杂的障碍行为与外部强迫的变化，如海平面上升速率，沉积物供应，或后障碍的几何形状。
We construct a simple morphodynamic model to investigate the long-term dynamic evolution of a coastal barrier system experiencing sea-level rise. Using a simplified barrier geometry, the model includes a dynamic shoreface profile that can be out of equilibrium and explicitly treats barrier sediment overwash as a flux. With barrier behavior primarily controlled by the maximum potential overwash flux and the rate of shoreface response, the modeled barrier system demonstrates four primary behaviors: height drowning, width drowning, constant landward retreat, and a periodic retreat. Height drowning occurs when overwash fluxes are insufficient to maintain the landward migration rate required to keep pace with sea-level rise. On the other hand, width drowning occurs when the shoreface response rate is insufficient to maintain the barrier geometry during overwash-driven landward migration. During periodic barrier retreat, the barrier experiences oscillating periods of rapid overwash followed by periods of relative stability as the shoreface resteepens. This periodic retreat, which occurs even with a constant sea-level rise rate, arises when overwash rates and shoreface response rates are large and of similar magnitude. We explore the occurrence of these behaviors across a wide range of parameter values and find that in addition to the maximum overwash flux and the shoreface response rate, barrier response can be particularly sensitive to the sea-level rise rate and back-barrier lagoon slope. Overall, our findings contrast with previous research which has primarily associated complex barrier behavior with changes in external forcing such as sea-level rise rate, sediment supply, or back-barrier geometry.