High resolution mapping of fine sediment and pollutants throughout large river cross sections with innovative uncrewed survey boats; supporting improv

除了14%的英国河流外，其他所有的河流都没有达到环境署对“良好生态状况”的定义，没有一条河流被评为“良好化学状况”。因此，细沉积物（沙粒和细颗粒）和其他污染物通过河流系统的数量和运输仍然是研究人员和流域利益相关者的主要兴趣，因为对污染物和养分转移的过程理解和量化具有根本重要性。泥沙的搬运和沉积是河流地貌和由此产生的生境的关键，进而决定了生物多样性。此外，了解沉积物通量对于确定基础设施的可持续性（水电、防洪）、洪水风险、农业土壤流失和洗澡水安全非常重要。传统上，最可靠的细沉积物通量估计和污染物测量来自连续的河岸监测或现场采样。然而，在具有大断面和/或复杂和动态水文形态的河流中，各断面的通量变化很大。虽然细颗粒通常被认为是相对均匀地分布在整个流动截面上，但这些颗粒的聚集可能意味着沉积物浓度会发生显著变化。鉴于这些变化难以量化，理解不足，并且可能对沉积物和污染物通量的估计很重要，因此这是一个优先研究领域。该项目的目的是首次解决细沉积物和污染物运输的这些横截面变化，从而实现沉积物预算估算、栖息地适宜性评估和洪水风险影响的逐步变化。拟议的项目侧重于使用新型仪器以前所未有的分辨率解决沉积物和其他污染物通量。首先，将使用先进的无人船，同时对河流水力学、悬浮沉积物和污染物进行测量。其次，将研究观测到的变化，以阐明沉积物/污染物运移的横截面变化及其控制。通过对各种集水区设置和一系列流动条件的观察，可以获得知识。最先进的ADCP（声学多普勒电流分析器）仪器和多参数水质传感器将用于小溪流量、河流水力学、细沉积物和其他污染物的测量。这些仪器将通过配备差分全球定位系统的无线电控制船（ARCboat和arcboatite）远程部署，以便对通常难以进入的大型河流和洪泛平原进行安全调查（见图）。ADCP反向散射数据将根据原位物理水样（粒径和质量）和独立的直接测量（浊度和粒径）进行评估，以提供稳健的校准。这种复杂的校准程序特别适合于研究项目，并将有助于提供优化的技术方案。多频ADCP传感器可以对沉积物粒度及其空间分布有新的认识，而高分辨率的河流水力学数据将有助于说明沉积物移动和沉积的环境、过程和条件。无人船在一系列地点和时间进行的测量将有助于了解在一系列流量条件下影响水质的空间和时间因素。这将提供更准确的下游通量定量，使人们能够更好地了解控制沉积物和其他污染物运输的因素和过程，从而了解化学、生物和生态状况以及洗澡水安全。

All but 14% of UK rivers fail to meet the Environment Agency definition of Good Ecological Status, and none are rated good for Chemical Status1. Therefore the amount and transportation of fine sediment (sand particles and finer) and other pollutants through river systems remains of major interest to researchers and catchment stakeholders because of the fundamental importance for the process-understanding and quantification of contaminant and nutrient transfer. Sediment transport and deposition is a key to in-stream geomorphology and the resultant habitat which in turn determines biodiversity. Furthermore, knowledge of sediment fluxes is important in determining infrastructure sustainability (hydropower, flood defences), flood risk, agricultural soil loss and bathing water safety.Traditionally, the most robust fine sediment flux estimates and pollutant measurements have been from continuous bank-side monitoring or spot sampling. However, in rivers with large cross sections and/or complex and dynamic hydromorphology, fluxes will vary greatly over cross sections. Although fine particles are often assumed to be relatively evenly distributed throughout flowing cross sections the aggregation of these particles can mean that significant variations in sediment concentration can occur. Given that these variations are challenging to quantify, poorly understood and are likely to be important in the estimation of sediment and pollutant fluxes this represents a priority research area. The aim of this project is to resolve, for the first time, these cross-sectional variations in fine sediment and pollutants transport, to enable a step-change in sediment budget estimation, habitat suitability assessment, and implications for flood risk.The proposed project focusses on the use of novel instrumentation to resolve sediment and other pollutant fluxes at previously unprecedented resolution. Firstly, simultaneous, co-located measurements of river hydraulics, suspended sediment and pollutants will be obtained using advanced uncrewed survey boats. Secondly, observed variations will be investigated to elucidate cross-sectional changes in sediment/pollutants transport and their controls. Knowledge will be gained by making observations in a variety of catchment settings and across a range of flow conditions. A state of the art ADCP (Acoustic Doppler Current Profiler) instrument and multi-parameter water quality sensors will be used to make streamflow, river hydraulics, fine sediment and other pollutants measurements. The instruments will be deployed remotely using Differential GPS equipped, radio-controlled boats (ARCboat and ARCboatlite) to allow the safe survey of large and often inaccessible river and floodplain flows (see photo). The ADCP backscatter data will be evaluated against in situ physical water samples (particle size and mass) and independent direct measurements (turbidity and particle size) to provide robust calibration. This sophisticated calibration procedure is particularly well suited to a research project and will contribute to the delivery of an optimised techniques protocol. The multi-frequency ADCP sensor should allow new insights into sediment particle sizes and their spatial distribution, while the high-resolution river hydraulics data will help illustrate the settings, processes and conditions in which sediments are mobilised and deposited.Measurements undertaken with the uncrewed boats at a range of locations and times will help inform understanding of the spatial and temporal factors influencing water quality across a range of flow conditions. This will provide a more accurate quantification of downstream fluxes, enabling improved understanding of the factors and processes that control sediment and other contaminant transport, and hence chemical, biological and ecological status and bathing water safety.