Optimising NFM in headwater catchments to protect downstream communities

自然洪水风险管理描述了通过改变景观来改变山坡和集水区径流的方法，以恢复自然的水文行为，从而限制下游洪水风险。这项提议是为了集中研究与更广泛的生态系统恢复工作相关的NFM效益，这项工作正在整个英国的高地进行。水源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产生山坡径流的重要地区。在英国各地，陡峭的高地集水区容易发生山洪暴发。这些源头集水区是相对较小的集水区，正在进行广泛的高地恢复，因此这些地区可能会观察到NFM措施的积极影响。发源地的脆弱社区往往很小，而且分散，土地价值很少证明通过标准的成本效益方法进行艰难的工程防洪是合理的。如果相对低成本的高地恢复方法可以减轻这样的社区的风险，那么就有可能为资金排除了艰难工程方法的社区提供一些保护。该项目将与项目合作伙伴摩尔斯未来和大曼彻斯特、默西塞德和柴郡环境局合作，他们已经在Pennines南部资助了NFM工作，以进行一系列实地实验。这些研究将评估各种形式的沟渠堵塞、沼泽地恢复泥炭覆盖，以及建立旱地林地对山坡产流和渠道径流的潜在影响。它还将通过对成熟林地和成熟的沟渠堵塞系统的研究，评估林地和沟渠堵塞方法的长期演变。这是一个重要的考虑因素，因为对NFM工程的投资需要对恢复对径流的长期影响有信心，并需要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，该模型可以运行多种场景，以评估在各种设计和各种空间布局中实施的NFM措施对流域径流的广泛影响。该模型将开发(来自项目合作伙伴CH2M的输入和来自潜在用户(如EA)的输入)，并使用来自德比郡Glossop Brook流域的数据进行验证，该流域有重大山洪影响Glossop镇家庭的历史。然后，将使用建模方法来评估在向大曼彻斯特东部边缘21个面临风险的社区排水的高地集水区可能进行的NFM干预。项目还将与合作伙伴(环境署、自然资源威尔士、苏格兰环境保护署、国际自然保护联盟)合作，以确定整个英国与重要高地恢复区域相关的现有源头流量记录。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，以寻找这些对径流影响的证据。该项目将与其横跨英格兰、威尔士和苏格兰的一系列项目合作伙伴合作，包括监管机构、土地管理人员和行业，以制定指导方针，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.