Optimising NFM in headwater catchments to protect downstream communities

自然洪水风险管理（NFM）描述了通过改变景观来恢复限制下游洪水风险的自然水文行为来改变山坡和集水区径流的方法。该提案是针对NFM与英国高地上正在进行的更广泛的生态系统恢复工作相关的利益进行集中研究。源头占大多数水系长度的60-80%，高坡度和高降雨量意味着它们是山坡径流生产的重要区域。在英国各地，有一些社区容易因陡峭的高地集水区而遭受山洪暴发。这些水源集水区是相对较小的集水区，是正在进行广泛高地恢复的地区，因此它们是可能观察到NFM措施积极影响的地方。源头的脆弱社区往往规模小且分散，其土地价值很少证明通过标准成本效益方法进行硬工程防洪是合理的。如果成本相对较低的高地恢复方法可以减轻这样的社区的风险，那么就有可能为那些资金排除了硬工程方法的社区提供一些保护。该项目将与项目合作伙伴Moors for Future以及大曼彻斯特、默西塞德郡和柴郡环境局合作，他们已经在南奔宁山脉资助了NFM工作，以进行一系列现场实验。这些研究将评估各种形式的沟壑阻塞、泥沼植被的恢复以及高地林地的建立对山坡径流产生和河道流动的潜在影响。它还将通过对成熟林地和完善的沟壑阻塞系统的研究来评估林地和沟壑阻塞方法的长期演变。这是一个重要的考虑因素，因为NFM工程的投资需要对修复径流的长期影响有信心，并了解干预措施的任何持续维护成本。安装NFM计划以减轻洪水风险，需要仔细规划和预测潜在影响。该项目将开发概念复杂但计算简单的模型，可以运行多种场景，以评估在各种设计和各种空间配置中实施的NFM措施对流域径流的影响。该模型将在项目合作伙伴CH2M和潜在用户（如EA）的支持下开发，并使用德比郡Glossop Brook集水区的数据进行验证，该集水区曾发生过严重的山洪暴发，影响了Glossop镇的家庭。然后，建模方法将用于评估在大曼彻斯特东部边缘有风险的21个社区的高地集水区可能的NFM干预措施。在这些集水区中，我们将为NFM效益的最佳旱地恢复措施配置建模。该项目还将与合作伙伴（环境署、威尔士自然资源部、苏格兰环境保护局、国际自然保护联盟）合作，确定英国各地与重要高地恢复地区有关的现有水源流量记录。在这些地点，我们将模拟预期的影响，并询问现有的流量数据，以证明这些影响对径流的影响。该项目将与横跨英格兰、威尔士和苏格兰的项目合作伙伴合作，包括监管机构、土地管理者和行业，共同制定指导方针，以优化未来在英国高地水源集水区实施NFM措施。

Natural flood risk management (NFM) describes methods of modifying hillslope and catchment runoff through the modification of landscapes to restore natural hydrological behaviour which limits downstream flood risk. This proposal is for a focussed study of NFM benefits associated with wider ecosystem restoration work which is under way across the uplands of the UK. Headwaters comprise 60-80% of the length of most river systems and high slopes and high rainfall mean that they are important areas of hillslope runoff production. Across the UK there are communities which are prone to flash flooding from steep upland catchments. These headwater catchments are relatively small catchments and are areas where extensive upland restoration is occurring and so they are locations where positive impacts of NFM measures are likely to be observed. Vulnerable communities in headwaters are often small and dispersed with land values that rarely justify hard engineering flood defences through standard cost-benefit approaches. If relatively low cost upland restoration approaches can mitigate risk to communities such as this then it will be possible to provide some protection to communities where funding precludes hard engineering approaches.This project will work with project partners Moors for the Future and Greater Manchester, Merseyside and Cheshire Environment Agency who have existing funded NFM work in the southern Pennines to undertake a series of field experiments. These will assess the potential impact of various forms of gully blocking, restoration of Sphagnum cover on moorlands, and establishment of upland woodlands on hillslope runoff production and channel flow. It will also assess the longer term evolution of woodland and gully blocking approaches through the study of mature woodland and well established gully blocked systems. This is an important consideration since investment in NFM works requires confidence in the long term impact of the restoration on runoff and knowledge of any ongoing maintenance costs for the interventions.Installation of NFM schemes to mitigate flood risk requires careful planning and prediction of potential impacts. This project will develop conceptually sophisticated but computationally simple models which can run multiple scenarios in order to assess the catchment wide impacts on runoff of NFM measures implemented to a variety of designs and in a variety of spatial configurations.The model will be developed (with input from project partner CH2M and input from potential users such as EA) and validated using data from the Glossop Brook catchment in Derbyshire which has a history of major flash flooding impacting households in the town of Glossop. The modelling approach will then be used to assess possible NFM interventions in the upland catchments draining to 21 communities at risk on the eastern edge of Greater Manchester. In each of these catchments we will model the optimum configuration of upland restoration measures for NFM benefit.The project will also work with partners (Environment Agency, Natural Resources Wales, Scottish Environmental Protection Agency, International Union the Conservation for Nature) to identify existing headwater flow records across the UK which relate to areas of significant upland restoration. At these sites we will model expected impacts and interrogate the available flow data for evidence of these effects on runoff.The project will work with its range of project partners which span England, Wales and Scotland and which comprise regulators, land managers and industry to develop guidelines to optimise future implementation of NFM measures in headwater catchments across upland Britain.