Quantifying sediment pathways in anthropogenic floodplains during extreme flooding

最近在英国发生的特大洪水对城市和农村社区造成了广泛而昂贵的影响。大部分损失来自于水中沉积物造成的财产损失。例如，2015/16年冬季极端洪水（Desmond， Eva和Frank风暴）造成的总经济损失的最佳估计在13 - 19亿英镑之间，其中包括住宅财产损失的3.08 - 3.92亿英镑（环境署，2018年1月）。洪泛平原上沉积物的积累是一个自然过程，但在与人类活动相交的地方，清理成本高昂，对农作物和财产造成损害。更好地管理泥沙洪水是政府基于流域的解决方案和自然洪水管理政策的一个关键目标。同样，农业政策和最佳实践正越来越多地寻求保持土壤在土地上，以帮助减少通常远远超过降雨侵蚀的现场影响的场外损害。为了支持这些政策，这些政策目前正在与英国退出欧盟的决定进行修订，需要提高对沉积沉积物在上游产生的位置的理解，以便以具有成本效益的方式进行干预，以及沉积物是如何沉积在复杂的人为改造洪泛平原上的。这一提议将第一次把对洪泛区复杂性的新测量方法与对沉积物来源、数量和形态的可靠估计结合起来。我们将探讨洪泛区的发展和与农业相关的基础设施对城市景观的影响，在极端洪水中，淤积物通过汇水区被洪泛区处理。我们将利用最近受到严重影响的塞文河和怀河集水区的实地地点，与利益相关者组织合作产生新的数据。这些新数据将用于发展新的理论和证据，以支持英国更大的低地洪泛平原未来的洪水和侵蚀风险管理。

Recent extreme floods in the UK have created extensive and expensive impacts on urban and rural communities. Much of the costs result from property damage caused by sediment in the water. Here, for example, the best estimate of total economic damages resulting from extreme flooding in the winter of 2015/16 (storms Desmond, Eva and Frank) ranges between £1.3-1.9 billion, including £308-392M for damage to residential properties (Environment Agency, January 2018). Accumulation of sediment on floodplains is a natural process but creates expensive clean up and damage to crops and property where it intersects with human activities. To better manage sediment laden flooding is a key aim of government policy for catchment-based solutions and natural flood management. Similarly, agricultural policy and best practice are increasingly seeking to keep soil on the land to help reduce off-site damage which typically far outweighs the on-site impacts of rain-driven erosion. To support these policies, which are currently undergoing revision in connection with the decision of the UK to depart the EU, requires improved understanding of where the deposited sediment is generated upstream for targeting interventions in a cost-effective manner, and how that sediment is deposited in complex human-modified floodplains. This proposal will for the first time, combine novel measures of floodplain complexity with robust estimates of sediment source, quantity and morphology. We will explore how floodplain development and infrastructure associated with farming to urban landscapes influence the processes by which mobilised sediment passing down the catchment in extreme floods is processed by the floodplains. We will use field sites in the recently heavily impacted River Severn and River Wye catchments, to generate new data in collaboration with stakeholder organisations. This new data will be used to develop new theory and evidence to support future flood and erosion risk management on the larger lowland floodplains in the UK.