Shear strength and erosion resistance of salt marsh substrates: Which method to use?
Shear strength and erosion resistance of salt marsh substrates: Which method to use?
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DOI：
10.1016/j.ecss.2023.108452
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发表时间：
2023-07
期刊：
影响因子：
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通讯作者：
H. Brooks;Iris Moeller;T. Spencer;K. Royse
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文献类型：
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作者：
H. Brooks;Iris Moeller;T. Spencer;K. Royse
盐沼提供各种生态系统服务，包括提供栖息地、污染物储存以及波浪和水流的衰减。然而，由于波浪或水流施加的剪切力和冲击力以及重力破坏，沼泽边缘、表面和内部侵蚀在许多海岸上很常见。为了预测这些生态系统服务的未来提供，必须确定湿地基质的阻力水动力强迫。目前，存在多种方法来测量抗破坏性（如剪切仪、托氏仪和内聚强度计; CSM），但这些不同的方法测量的是什么，因此，使用不同的方法所产生的差异，往往是很差的规定-甚至被忽视。虽然剪切叶片和torvane设备，直到最近，在盐沼研究中被互换使用，所收集的数据在各个数据集内、在使用相同技术的站点之间以及在各个站点处的技术之间是高度可变的。在英国沼泽地，我们发现，剪切叶片装置记录了更高的不排水剪切强度比torvane在同一基板上，可能是由于更大的相互作用之间的根和较大的叶片的剪切叶片仪器我们的结果还表明，基于叶片的装置和CSM装置测量两种不同的过程，其中叶片量化基板对剪切和质量运动的体电阻，而CSM记录了从基底表面开始的逐粒侵蚀过程。这两个不同的测量是不相关的，所以我们的研究挑战的共同假设，即具有较高的抵抗散装故障过程的基板也有一个高的侵蚀阈值。
Salt marshes provide a variety of ecosystem services, including habitat provision, pollutant storage and attenuation of waves and currents. However, marsh edge, surface and interior erosion is common on many shores due to shear and impact forces applied by waves or currents, as well as gravitational failure. To forecast the future provision of these ecosystem services, the resistance of marsh substrates to hydrodynamic forcing must be determined. At present, a variety of methods exist to measure resistance to failure (e.g. shear vane, torvane and Cohesive Strength Meter; CSM), but what these different methods are measuring, and therefore the differences that result from using different methods, are often poorly specified – or even ignored.While shear vane and torvane devices have, until recently, been used interchangeably in salt marsh studies, the data collected is highly variable within individual datasets, between sites using the same technique, and between techniques at an individual site. In UK marshes, we find that the shear vane apparatus records a higher undrained shear strength than the torvane on the same substrate, possibly due to greater interaction between roots and the larger blades of the shear vane instrument (compared to the torvane).Our results also show that the vane-based and CSM devices measure two different processes, with vanes quantifying the bulk resistance of the substrate to shear and mass movement, while the CSM records the process of grain-by-grain erosion from the substrate surface. These two distinct measurements were not related, so our research challenges the common assumption that substrates with a higher resistance to bulk failure processes also have a high erosion threshold.