Impacts of sediment and debris from Natural Flood Management

洪水的影响是广泛的，有许多因素增加了全球的风险，包括城市化、经济增长和气候变化的增加。专家、公众和媒体都提出了一系列应对措施，既有传统的，也有更具创新性的。负责的机构必须在明确证据的基础上平衡这些选择。挑战不在于设计新的措施，而在于如何将各种选择结合起来，并评估整个系统的影响。这需要更好地理解影响，以及各种选择是如何积极或消极地相互作用的。这个建议集中在最近引起越来越多兴趣的一个选择——自然洪水管理。这是通过与自然水文和形态过程合作来管理水和沉积物进入水道的来源和途径，寻求减少峰值并考虑时间安排。然而，人们担心，自然洪水管理将增加该系统中沉积物和碎片的数量。虽然沉积物和碎片对河流和生态系统的可持续性很重要，但它们会增加上游的洪水风险，例如，阻塞小桥/涵洞，或在下游，汇水区堆积的碎片会影响桥梁和建筑物。本项目将探讨这些影响中哪些是最重要的，以及它们的相对重要性是否在空间和时间上有所不同。它还将调查影响城市地区的碎片来自哪里：高地地区、当地支流还是更直接的河岸来源？该项目的成果将是更好地了解沉积物和碎屑过程，以便建立证据基础。对影响的全面分析需要了解多个尺度（河段、河网、集水区）以及它们之间的相互作用。然而，现有的自然系统中沉积物和碎屑的研究大多集中在单一尺度上。仅在河段或洪泛区尺度上进行的详细分析不可能扩展到整个流域，因此在这个项目中，学生将在每个尺度上使用新颖的方法，并通过参数化和信息传递以创新的方式将不同尺度的分析联系起来。博士将专注于Aire流域，并回答以下研究问题：有多少沉积物和碎屑进入该系统？沉积物和碎屑是如何在一个范围内移动的？在沉积物和碎屑方面，不同的尺度是如何联系在一起的？

The impact of flooding is widespread and there are a number of factors increasing risk globally including urbanisation, economic growth and increased climate variability. A range of responses, both traditional and more innovative, are advocated by experts, the public and the media. The agencies responsible must balance these options based on clear evidence. The challenge is less about devising new measures, but more about how to combine various options and to assess the impact across the whole system. This requires greater understanding of impacts and how options positively or negatively interact. This proposal focuses on one option that has recently attracted increased interest - natural flood management. This seeks to reduce peaks and consider timings through working with natural hydrological and morphological processes to manage sources and pathways by which water and sediment enter watercourses. However, there is a concern that natural flood management will increase the amount of sediment and debris in the system. Whilst sediment and debris are important for river and ecosystem sustainability, they can increase flood risk in the upstream with, for example, the blockage of small bridges/culverts or in the downstream with the accumulation of debris from across a catchment impacting bridges and buildings. This project will explore which of these effects is most significant and whether their relative significance varies spatially and temporally. It will also investigate where debris impacting urban areas comes from: upland areas, local tributaries or from more direct riparian sources? The project outcome will be better understanding of sediment and debris processes in order to develop the evidence base. A full analysis of the impact requires understanding at a number of scales (reach, river network, catchment) and understanding of their interaction. However, the existing studies of sediment and debris in natural systems are mostly focused on a single scale. A detailed analysis carried out solely at a reach or floodplain scale cannot feasibly be extended to a whole catchment so in this project the student will use novel approaches at each scale and link the analysis across scales in an innovative manner through parameterisation and transfer of information. The PhD will focus on the Aire catchment and answer the following research questions:How much sediment and debris enters the system?How does sediment and debris move within a single reach?How are the different scales connected in terms of sediment and debris?