Gravel barrier resilience in a changing climate (#gravelbeach)

含有大量砾石的海滩和屏障系统，包括“纯砾石”、“复合砾石”和“混合砂砾”，在全球中高纬度地区很常见。这些地貌特征，在此统称为“砾石屏障”，代表了英国波浪暴露海岸线的20%。它们提供自然保护，防止沿海洪水和侵蚀，并支持独特的生态系统。然而，我们预测它们形态动力学的能力大部分来自对桑迪海岸的研究，这在翻译上是有缺陷的。具体来说，我们的理解和能力，包括砂砾石混合物的障碍物的形态动力学建模是显着lacked.Fundamental的差异，砂和砾石沉积物输运过程和形态的反应排除直接应用桑迪海岸模型砾石障碍。在混合砂砾系统中，一种粒度组分的存在通过选择性夹带和级联扰动影响另一种粒度组分的输运。因此，我们对砾石屏障特性的了解，特别是它们对海平面上升、风暴和与气候变异有关的波浪条件变化的反应，主要是定性的。我们知道，例如，向陆地屏障迁移发生由于风暴引起的过洗，但对迁移率的限制知之甚少。虽然随着海平面上升，移民可能会增加，但不同沉积物等级和容纳空间的影响尚不清楚。同样，主要波向的变化通过海滩旋转和沉积物分选引起沿岸和跨岸响应。这反过来又改变了海岸线的位置，并可能造成侵蚀热点，但在不同的气候变化情景下对这些过程进行可靠预测的能力是不足的。传统上，它们是通过沉积物循环和海滩营养来维持的。然而，有证据表明，其中一些做法对屏障的稳定性产生了负面影响，使其不可持续，特别是在海平面上升的情况下。因此，该项目（#gravelbeach）旨在制定可靠、一致和适当的方法，利用这些自然特征并为其腾出空间，以便能够采取更可持续和适应性更强的全国范围管理做法。

Beach and barrier systems with a substantial gravel fraction, including 'pure', 'composite' and 'mixed sand-gravel', are common globally at mid to high latitudes. These geomorphological features, collectively referred to herein as 'gravel barriers', represent up to 20% of the wave-exposed coastline of Great Britain. They provide natural protection against coastal flooding and erosion, and support unique ecosystems. However, much of our ability to predict their morphodynamics comes from research on sandy coasts, which is flawed in translation. Specifically, our understanding and capability to model the morphodynamics of barriers comprising sand-gravel mixtures is significantly lacking.Fundamental differences in sand and gravel sediment transport processes and morphological response preclude direct application of sandy coastal models to gravel barriers. In mixed sand-gravel systems, the presence of one grain size fraction affects the transport of another through selective entrainment and cascading disturbances. Our understanding of gravel barrier behaviour, especially their response to sea-level rise, storms, and changes in wave conditions related to climate variability, is thus mainly qualitative. We understand, for example, that landward barrier migration occurs due to storm-induced overwash, but the constraints on the migration rate are poorly understood. Whilst migration is likely to increase with sea-level rise, the influence of different sediment grades and accommodation space is unclear. Likewise, changes in the predominant wave direction induce both alongshore and cross-shore response through beach rotation and sediment sorting. This, in turn, changes shoreline position and can create erosion hotspots, but the ability to robustly predict these processes for different climate change scenarios is deficient.Gravel barriers have an important role in providing coastal protection. Traditionally they have been maintained through sediment recycling and beach nourishment. However, evidence indicates that some of these practices negatively impact barrier stability making it unsustainable, particularly under rising sea levels. Thus, this project (#gravelbeach) aims to develop, reliable, consistent and appropriate approaches for working with, and making space for, these natural features, to enable more sustainable and adaptive national-scale management practices.