Natural Flood Management in urban river catchments

自然洪水管理（NFM）技术旨在通过实施保护、恢复和模拟河流集水区自然功能的措施来减少洪水的风险。通常，英国的NFM计划侧重于中等规模河流集水区的农村源头，并通过政府、慈善部门和农业部门之间的合作来实现。国家自然资源管理技术对农村集水区的关注很可能源于对空间可用性的认识。城市环境的局限意味着土地价值按比例比农村地区高得多。在某些情况下，城市河流由于邻近地区的发展而被涵养或变直。相反，在城市集水区工作的潜在好处是，面临洪水风险的人口密度要高得多（增加了成功干预措施的潜在效益-成本比），小集水区的径流水文测量量相对较低，最重要的是，公共开放空间（公园）的存在，这些空间通常位于过去设计的水道周围，以便将洪水快速输送到下游。在城市地区，洪水风险管理的“自然”方法的重点是可持续排水（SuDS），它同样旨在通过减缓新开发地点的径流来模拟自然过程。然而，SuDS领域并没有考虑水道网及其相关洪泛平原对洪水风险管理的影响：它只涉及更广泛的集水区内个别土地的径流。该研究要解决的关键问题是：1)在较小的城市化集水区实施NFM措施的挑战和障碍是什么？为什么从业者不被吸引到城市地区，因为城市地区靠近大量面临洪水风险的财产？2) NFM技术在更城市化的集水区降低洪水风险的潜力是什么？这些技术如何针对这部分河流集水区进行优化？在农村集水区发现的挑战，如洪水同步性，如何适用于城市河流？3) NFM和SUDS的研究领域是否可以统一为一个更全面的流域管理方法，消除城乡洪水管理之间的鸿沟。

Natural Flood Management (NFM) techniques aim to reduce the risk of flooding through the implementation of measure which protect, restore and emulate the natural functions of a river catchment. Typically, NFM schemes in the UK are focused on the rural headwaters of medium scale river catchments and delivered through partnership work between government, the charity sector and the agricultural sector. It is probable that the focus of NFM techniques on rural catchments derives from a perceived availability of space. The confines of the urban environment mean that land values are proportionately much higher than rural areas. In some cases urban rivers have been culverted or straightened with development in close proximity. Conversely, the potential benefits of working in urban catchments are a much higher density of population at risk of flooding (increasing the potential benefit-cost ratio of successful interventions), comparatively lower runoff hydrograph volumes on small catchments and, crucially, the presence of public open space (parkland) which is often sited around watercourses that have been engineered in the past to convey flood flows rapidly downstream.In urban areas, the focus of 'natural' approaches to flood risk management is on sustainable drainage (SuDS) which similarly aims to mimic natural processes by slowing down runoff from new development sites. However, the field of SuDS does not consider the effect of the watercourse network and its associated floodplains on the management of flood risk: it relates only to the runoff from individual pockets of land within the wider catchment. The key questions to be addressed by the research are:1) What are the challenges and barriers to implementation of NFM measures in smaller, urbanised catchments: why are practitioners not drawn towards urban areas given the proximity of high numbers of property at risk of flooding?2) What is the potential for NFM techniques to reduce flood risk in more urbanised catchments and how can these techniques be optimised for this sub-set of river catchments? How do the challenges identified in rural catchments, such as flood synchronicity, apply to urban streams?3) Can the research areas of NFM and SUDS be unified into a more holistic approach to river catchment management that removes the divide between urban and rural flood management.