Realistic Sedimentary Bedform Prediction: Incorporating Physical and Biological Cohesion (COHBED)

英国是一个沿海国家，大多数人口居住在离河口或海洋几英里的范围内。海岸线的性质取决于当地的地质和水流条件。岩石海岸线是在海水能量高的地方发现的，而泥浆和沙子是在能量低的地方发现的，这些沉积物可以沉积下来。这些低能量的泥质和砂质（沉积）栖息地对英国的生态和经济非常重要。它们为许多鸟类和鱼类提供食物，但也保护海岸线免受海洋的侵蚀。此外，它们还起到了“过滤器”的作用，从河流中捕获污染物并最终降解。由于这些系统的重要性，随着海平面上升和风暴事件随着气候变化频率增加，它们的自然行为和稳定性日益受到关注。英国海岸周围沉积物的移动具有巨大的经济和生态影响，但令人惊讶的是，我们几乎没有科学信息来帮助我们预测天然泥滩和海滩如何应对不断变化的潮汐、风和海浪的力量。当水流过海底时，水流的能量将沉积物塑造成波浪状的特征，称为河床（如波纹）。这些河床有助于控制沙、泥、营养物和污染物的侵蚀和运移。使我们能够预测河床形状、大小和运动的信息对于环境管理、水利工程、底栖生物栖息地生物学、粒子迁移的计算机模型、沉积地质学和许多其他科学学科都是必不可少的。然而，关于由砂和泥的混合物组成的河床的知识几乎完全缺乏。沙质沉积物被称为“非粘性”沉积物，因为沙粒不会粘在一起，而泥浆是由更小的颗粒组成的，这些颗粒会粘在一起，因此被称为“粘性”沉积物。这个名为COHBED的项目将利用最新的测量技术来产生关于由砂和泥的自然混合物组成的河床的生长、运动和稳定性的信息，这是一种非常常见的自然条件，但以前很少被研究过。在一个新的起点上，这项工作包括一个多学科团队，将这些系统的物理学，数学，沉积学和生物学结合起来，因为我们认识到栖息在自然系统中的生物（从细菌到海草）也会改变侵蚀特征和河床行为。这就是为什么COHBED将包括实验室实验和实地调查。在实验室水流通道中进行的一系列实验将研究控制河床行为和性质的关键因素，例如：系统能量：流速、河床摩擦和水流深度的影响；河床性质：粒度、泥沙比例和生物效应；时间：河床生长的速度和随水流能量变化的变化率；当较小的颗粒被侵蚀掉时，表面形态会发生变化。实验室研究的结果将与自然系统的行为进行比较。将进行实地调查，以验证从实验室研究中得出的预测，使用新技术，首次可以同时测量流量、沉积物和河床性质。COHBED项目将使英国保持在这一研究领域的前沿，并将帮助我们在面对气候变化时管理我们的海岸。

The United Kingdom is a coastal nation with the majority of the population living within a few miles of an estuary or the sea. The nature of the coastline depends on the local conditions of geology and water flow. Rocky coastlines are found where the energy of the sea is high, while mud and sand are found where the energy is lower and these sediments can be deposited. These low energy muddy and sandy (depositional) habitats, are very important for the ecology and economy of the UK. They provide food for many species of birds and fish, but also protect the coastline from the erosive forces of the sea. In addition, they act as a "filter", where pollutants from the rivers are captured and eventually degraded. Because of the importance of these systems, their natural behaviour and stability is of increasing concern as sea levels rise and storm events increase in frequency with climate change. The movement of sediment around the coast of Britain has vast economic and ecological consequences, but surprisingly we have very little scientific information that helps us to predict how natural mudflats and beaches will respond to the changing forces of the tides, wind and waves. When water flows over the sea bottom, the energy of the flow shapes the sediment into wavy features called bedforms (such as ripples). These bedforms help control the erosion and transport of sand, mud, nutrients and pollutants. Information allowing us to predict the shape, size and movement of bedforms is essential for environmental management, hydraulic engineering, benthic habitat biology, computer modelling of particle transport, sedimentary geology, and many other scientific disciplines. However, there is an almost complete lack of knowledge concerning bedforms consisting of mixtures of sand and mud. Sandy sediments are known to be "non-cohesive", because the sand particles do not stick together, whereas muds are made up of smaller particles that do stick together and so are called "cohesive" sediments. This project, COHBED, will take advantage of the latest developments in measurement technologies to produce information about the growth, movement and stability of bedforms that consist of natural mixtures of sands and muds, a natural condition that is very common but has rarely been studied before. In a new departure, this work includes a multidisciplinary team to combine the physics, mathematics, sedimentology, and biology of these systems, since we recognise that the organisms (from bacteria to sea grasses) that inhabit natural systems also change the erosional characteristics and bedform behaviour. This is why COHBED will include laboratory experiments and field surveys. A series of experiments in laboratory flow channels will investigate key factors that control the behaviour and properties of bedforms, such as: - System energy: effects of flow velocity, bed friction and flow depth- Bed properties: particle size, proportion of mud and sand, and biological effects- Time: the speed of bedform growth and rate of change as flow energy changes- Particle erosion: changes in the bedforms as smaller particles are eroded awayThe results of the laboratory studies will be compared with the behaviour of natural systems. Field surveys will be conducted to validate the predictions derived from the laboratory studies, using new techniques that for the first time allow essential simultaneous measurements of flow, sediment and bedform properties. The COHBED project will maintain the UK at the forefront of this research area and will help us to manage our coasts in the face of climate change.