Understanding Runoff and Erosion Dynamics

水对土壤的侵蚀正在导致世界粮食生产用地的加速丧失，威胁到全球粮食安全。模型是试图了解农业过程、土地利用和气候变化对土壤侵蚀影响的重要组成部分。然而，目前的方法来模拟土壤侵蚀，尽管有很长的遗产，并没有表现出整体改善其预测能力。所有的模型都受到其所依赖的实验基础的限制，对于土壤侵蚀来说，其中大部分都来自一代人以前的实验和技术。到目前为止，技术上的局限性限制了实验工作，以稳态测量实际上是一个高度动态的过程。例如，推导土壤侵蚀模型参数的实验通常使用恒定强度的降雨，然后将这些参数应用于随时间变化的自然降雨下的侵蚀模型，尽管我们现在有证据表明，以这种方式推导的参数将对随时间变化的自然降雨做出错误的预测。走出这一僵局的一种方法是使用机械工程领域开发的光学诊断技术，该技术能够研究高度动态的多相流。脉冲激光照明光源和数码相机技术的最新发展允许以高达每秒20，000帧的速率记录颗粒/流动相互作用。利用这些技术，现在有可能使我们对土壤侵蚀过程的动力学的理解发生一步变化。这项研究将（一）改进现有的高速、高分辨率成像和粒子图像测速技术，以便同时跟踪代表土壤侵蚀的浅层漫流中0.063毫米至2.0毫米的沉积物颗粒; ㈡利用这些完善的技术开发高分辨率和高准确度的数据集，以说明脱离接触的不同组成部分的动态特征，浅层地表水流中的迁移和沉积过程; ㈢向更广泛的土壤侵蚀界提供这些数据集，供其自行开发和测试模型;（iv）利用获得的数据在现有土壤侵蚀模型中开发子模型（MAHLERAN），我们以前开发的，能够代表动态特性的侵蚀过程，而不是稳态条件下;和（v）测试修订版的MAHLERAN对现有的数据集不稳定的条件。这项工作将为NERC的关键战略领域做出重要贡献，例如与环境变化共存，分析环境变化对生态系统服务的影响，以及可持续性、全球贫困和碳固存方面的后果。这项研究还将导致为环境管理人员制定更有效的工具，以根据欧盟水框架和硝酸盐指令等现行立法的要求实施综合流域管理做法。

Soil erosion by water is leading to an accelerated loss of the world's food-producing lands, threatening global food security. Models are a vital component of attempts to understand the impact of agricultural processes, land-use and climate change on soil erosion. However, current approaches to modelling soil erosion, despite a long heritage, have shown little overall improvement in their predictive capability. All models are constrained by the experimental base upon which they rests, much of which, for soil erosion, dates from experiments and technologies of a generation ago. Thus far, technological limitations have constrained experimental work to steady-state measurements for what is actually a highly dynamic process. For example, experiments to derive the parameters of soil-erosion models typically use constant-intensity rainfall and then apply these parameters to model erosion under temporally varying natural rainfall, although we now have evidence that parameters derived in this way will make incorrect predictions for temporally varying natural rainfall. A way out of this impasse is to use optical diagnostic techniques, developed in the field of mechanical engineering, which enable the study of highly dynamic multiphase flows. Recent developments in pulsed laser-illumination sources and digital camera technology allow the recording of particle/flow interactions at rates up to 20,000 frames per second. Using these techniques it is now possible to make a step change in our understanding of the dynamics of processes of soil erosion. This research will (i) refine existing high-speed, high-resolution imaging and PIV techniques to track sediment particles of 0.063 mm to 2.0 mm simultaneously in shallow overland flows that typify soil erosion; (ii) use these refined techniques to develop datasets of high resolution and high accuracy that will characterize the dynamics of the different components of the detachment, transport and deposition processes in shallow overland flows; (iii) make these datsets available to the wider soil-erosion community for their own model development and testing; (iv) use the data obtained to develop submodels within an existing soil-erosion model (MAHLERAN) which we have previously developed that are capable of representing dynamic properties of erosion processes, rather than steady-state conditions; and (v) test the revised version of MAHLERAN against existing datasets for unsteady conditions. The work will provide an important contribution to key NERC Strategy areas such as Living with Environmental Change and the analysis of the impact of environmental change on ecosystem services, with consequences in terms of sustainability, global poverty and carbon sequestration. The research will also lead to the production of more effective tools for environmental managers to implement practices of integrated river-basin management as required under current legislation such as the EU Water Framework and Nitrates Directives.