Statistical characterization of erosion and sediment transport mechanics in shallow tidal environments – Part 1: Erosion dynamics

IF 2.8 2区 地球科学 Q2 GEOGRAPHY, PHYSICAL
Andrea D'Alpaos, Davide Tognin, Laura Tommasini, Luigi D'Alpaos, Andrea Rinaldo, Luca Carniello
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Abstract

Abstract. Reliable descriptions of erosion events are foundational to effective frameworks relevant to the fate of tidal landscape evolution. Besides the rhythmic, predictable action of tidal currents, erosion in shallow tidal environments is strongly influenced by the stochastic wave-induced bottom shear stress (BSS), mainly responsible for sediment resuspension on tidal flats. However, the absence of sufficiently long, measured time series of BSS prevents a direct analysis of the combined tide- and wave-driven erosion dynamics and its proper representation in long-term morphodynamic models. Here we test the hypothesis of describing erosion dynamics in shallow tidal environments as a Poisson process by analysing, with the peak-over-threshold theory, the BSS time series computed using a fully coupled, bi-dimensional numerical model. We perform this analysis on the Venice Lagoon, Italy, taking advantage of several historical surveys done in the last 4 centuries, which allow us to investigate the effects of morphological modifications on spatial and temporal erosion patterns. Our analysis suggests that erosion events on intertidal flats can effectively be modelled as a marked Poisson process in different morphological configurations because the interarrival times, durations, and intensities of the over-threshold exceedances are always well described by exponentially distributed random variables. The resulting statistical characterization allows a straightforward computation of morphological indicators, such as the erosion work, and paves the way for a novel synthetic, yet reliable, approach for the long-term morphodynamic modelling of tidal environments.
浅海潮汐环境中侵蚀和沉积物迁移力学的统计特征 - 第 1 部分:侵蚀动力学
摘要。对侵蚀事件的可靠描述是与潮汐景观演变命运相关的有效框架的基础。除了潮汐流有节奏、可预测的作用外,浅潮汐环境中的侵蚀还受到波浪引起的随机底部剪应力(BSS)的强烈影响,BSS 是潮滩沉积物再悬浮的主要原因。然而,由于缺乏足够长的 BSS 测量时间序列,因此无法直接分析潮汐和波浪共同驱动的侵蚀动态,也无法在长期形态动力学模型中对其进行适当表述。在此,我们利用峰值过阈值理论,对利用完全耦合的二维数值模型计算出的 BSS 时间序列进行了分析,从而检验了将浅潮汐环境中的侵蚀动力学描述为泊松过程的假设。我们对意大利威尼斯泻湖进行了分析,利用过去 4 个世纪中进行的几次历史调查,研究了形态变化对空间和时间侵蚀模式的影响。我们的分析表明,潮间带滩涂上的侵蚀事件可以有效地模拟为不同形态配置下的明显泊松过程,因为超阈值侵蚀的到达时间、持续时间和强度总是可以用指数分布的随机变量很好地描述。由此产生的统计特征可以直接计算侵蚀作用等形态指标,并为潮汐环境的长期形态动力学建模铺平了一条新颖、可靠的合成之路。
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来源期刊
Earth Surface Dynamics
Earth Surface Dynamics GEOGRAPHY, PHYSICALGEOSCIENCES, MULTIDISCI-GEOSCIENCES, MULTIDISCIPLINARY
CiteScore
5.40
自引率
5.90%
发文量
56
审稿时长
20 weeks
期刊介绍: Earth Surface Dynamics (ESurf) is an international scientific journal dedicated to the publication and discussion of high-quality research on the physical, chemical, and biological processes shaping Earth''s surface and their interactions on all scales.
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