COMPACT: The role of soil management in mitigating catchment flood risk

洪水风险在英国是一个越来越大的挑战，有240万处房产容易受到河流洪水的影响。这种类型的洪水是由于河流排出的径流量超过了河道的能力而引起的。这导致水被转移到泛滥平原，这可能会产生严重的经济和社会影响。从景观流向河流的径流的数量和速度是产生洪水的一个主要因素。因此，景观管理的方式可能会对这一过程产生重大影响。在过去50年左右的时间里，通过增加牧场中的牲畜数量和使用更大、更重的耕作机械来集约化农业，被认为对洪水的严重程度和频率产生了影响。这些土地管理措施导致土壤紧实，从而降低了降雨入渗率和地下可储存的水量。这导致更多的降雨被分配到更快的地表径流进入河流的途径，并可能导致下游洪水泛滥。然而，土壤压实程度在空间和时间上是高度不均匀的。这是因为不同的动物，如牛、羊和马，对土壤施加不同的负荷，并以不同的密度饲养。此外，众所周知，农场动物表现出的行为是，田地的某些部分比其他部分移动得更频繁。在耕地耕作实践中也是如此，耕作形成了更紧凑的踩踏线或轮子。从免耕到常规耕作，不同形式的管理实践在一年中的不同时间对土壤施加不同的压力。然而，人们对不同管理措施下土壤压实水平的这种差异知之甚少。本研究旨在通过使用新的探地雷达(GPR)技术来量化这种子场压实程度和深度的变化，并评估这种变化对土壤物理性质的影响，水与土壤的相互作用，以及这种影响对流域尺度洪水风险的重要性。这将通过结合实地实验、土壤样本的实验室测试和数值水文模型的多种方法来实现。首先，将使用探地雷达识别高压实度和低压实度区域，并使用传统的基于现场的方法进行验证。这些将通过GPS空间数据与动物和机器转移到哪里的负载相关。然后将进行广泛的现场和实验室测试，以量化诸如体积密度、孔隙率、饱和水力传导性和颗粒大小等特性。此外，X射线CT扫描将揭示压实对土壤结构的细微影响。这些数据将形成一个基于物理的、降低复杂性的、空间分布的水文模型CRUM3的输入。可行的“如果？”将与项目伙伴共同制作情景，包括环境署、Trent Rivers Trust、可持续土地信托、自然英格兰和全国农民联盟通过Soar流域伙伴关系。这将把当地土地管理和土壤特性的变化提升到集水区的洪水规模。这项研究将与一组集水区管理者、土地所有者和当地居民一起进行。这既有利于研究范围的扩大，也有利于研究结果的影响。针对行业、监管机构、政府机构、慈善机构以及当地土地所有者和居民的建议和传播将为基于证据的自然洪水管理政策提供信息。这将通过指导小组会议、英国水文学会全国会议、项目离开日、项目河边野餐结束以及社交媒体的使用来实现。传播也将通过更传统的学术途径进行。

Flood risk is an increasing challenge in the UK, with 2.4 million properties being susceptible to fluvial flooding. This type of flooding is caused by the quantity of runoff being discharged by a river exceeding the capacity of the river channel. This results in water being transferred to the floodplain, which can have severe economic and social impacts. The quantity and speed of runoff from the landscape into rivers is a major factor in generating flooding. The way in which the landscape is managed therefore can have a significant impact on this process. The intensification of agriculture, through increasing the number of animals in pasture, and the use of larger, heavier machinery for arable farming, over the past 50 years or so is hypothesised to have had an impact on the severity and frequency of flooding. These land management practices cause soil compaction, which reduces the rate of rainfall infiltration and the volume of water that can be stored within the sub-surface. This results in more rainfall being partitioned into the faster surface runoff pathway into rivers and potentially causing flooding downstream.However, the level of soil compaction is highly heterogeneous over space and time. This is because different animals i.e. cattle, sheep and horses, exert different loads on the soil and are kept at different densities. Furthermore, farm animals are known to exhibit behaviour whereby certain parts of the field are moved over more frequently than others. The same is the case in arable farming practices, whereby ploughing forms tramlines or wheelings, which are more compacted. Different forms of management practice ranging from zero-tillage to conventional cultivation exert different pressures on the soil at different times of year. However, very little is known about this variability of soil compaction levels at the sub-field level and land under different management practices.This research aims to quantify this sub-field variation in compaction severity and depths through using novel Ground Penetrating Radar (GPR) technology, and assess the impact on the physical soil properties, how water interacts with the soil and ultimately how important this effect is on catchment scale flood risk. This will be achieved through using a multi-methods approach combining field experiments, laboratory tests on soil samples and numerical hydrological modelling. First areas of high and low compaction will be identified using GPR and validated using traditional field based approaches. These will be related to loadings through GPS spatial data on where animals and machinery have moved over. A wide range of field and laboratory tests will then be carried out to quantify properties such as bulk density, porosity, saturated hydraulic conductivity, and particle size. Furthermore, X-Ray CT scanning will reveal the fine scale impacts of compaction on soil structure. This data will form the input to a physically based, reduced complexity, spatially distributed hydrological model, CRUM3. Feasible "what if?" scenarios will be co-produced with the project partners, including the Environment Agency, Trent Rivers Trust, Sustainable Land Trust, Natural England, and National Farmers Union through the Soar Catchment Partnership. This will upscale local changes in land management and soil characteristics to catchment scale flooding.This research will be undertaken with a group of catchment managers, land owners and local residents. This will both benefit the research scope and impacts of the findings. Recommendations and dissemination for industry, regulators, governmental bodies, charities and local land owners and residents will inform evidence based policy on Natural Flood Management. This will be achieved through steering group meetings, a British Hydrological Society national meeting, Project Away day, end of project riverside picnic, and the use of social media. Dissemination will also occur through more traditional academic routes.