Sensitivity of Estuaries to Climate Hazards (SEARCH)

居住在英国河口附近的2000万人面临着复合洪水灾害的风险。最近在英国集水区和河口发生的险些发生的洪水(2013年12月至2017年1月)可能会更糟糕，因为激增-降水时间发生了微妙的变化，尽管仍造成了广泛的破坏，造成了5亿英镑的损失。河口群落特别容易受到未来洪水风险变化的影响；通过海平面上升和风暴潮高度的增加，以及降水和温度模式的变化，这将对河流行为产生深远影响。搜索项目将通过开发一种新的方法来评估英国河口的气候洪水危害，从而直接解决这一重要问题。该方法将首次适用于不同时空尺度、不同集水区和河口类型的复合洪涝事件。这种方法将准确地解决所有的水文和海洋过程及其联合概率。它将评估从UKCP18降级到洪水的气候预测如何影响；因此，为EA、NRW和SEPA提供独特和关键的洪水和可能性数据，以确定最容易发生复合洪水的社区，并在突发事件应对期间有效管理它们的资源。重要的是，我们将展示复合洪灾是如何发生的，以及不同的系统对气候变化的不同驱动因素是多么敏感。本世纪全球海平面预计将上升至1米，对于英国等一些地区，降水和温度分布可能会发生变化，随着时间的改变，风暴、热浪和干旱等极端事件变得更加强烈和季节性。洪水驱动强度的变化预计会影响到灾害和风险。然而，我们假设，它们的时间相对于彼此的变化也将对洪水风险至关重要。例如，由于降水和温度的变化影响土壤水分和地下水流动，河流事件的时间可能会发生变化。作为NERC项目箱中的一个概念证明，研究人员确定了河口对潮汐-潮汐-河流事件共同作用的敏感性，将河口内风险增加的不同区域隔离开来，这取决于相对于河口的集水区大小、河口形状以及潮汐和河流事件相对于彼此的时间。因此，气候变化导致的洪水风险变化将因地点而异，灾害驱动因素的相对作用在空间上有所不同。极端事件的长期变化往往是不可预见的，因为我们对综合系统的理解是不完整的。考虑到河口高的社会经济和环境价值，复合灾害的复杂性，驱动因素的预测变化，以及不受监管的土地使用管理，现在是时候开发新的战略来缓解复合洪水，并开发改进的洪水保护风险评估工具。与英国洪水监管机构合作，Search将使用过去和新的观测数据，并将降水、温度、河流流量、风暴潮和海平面的预测应用于快速、测试和开放源代码的水动力-地下水模型，以模拟洪水灾害。我们将模拟14个系统，覆盖英国境内的各种地点和河口。我们迫切需要我们的结果，因为确定洪水风险的概率方法已经过时，因为它们没有捕捉到非线性动态，也不包括未来的变化。这个为期两年的项目汇集了世界领先的从集水区到海岸的环境科学研究人员(与班戈大学和赫尔大学的PDRA)，以解决这个计算上具有挑战性且调查不足的问题。该团队在关键政策和行业合作伙伴的参与和支持下，成功地开展了合作，建立了洪水风险方面的新范式，积累了大量数据。

Twenty million people living near UK estuaries are at risk from compound flooding hazards. Recent near-miss flooding in UK catchments and estuaries (Dec-2013, Jan-2017) could have been much worse with subtle changes in surge-precipitation timings, although still caused extensive damage costing £500M. Estuary communities are especially vulnerable to future changes in flood risk; via sea-level rise combined with increases in storm surge heights - and changing precipitation and temperature patterns that will have profound impacts on fluvial behaviour. The SEARCH project will address this important issue directly by developing a new method to evaluate climate flooding hazards in UK estuaries. For the first time this method will be fit-for-purpose for compound flooding events across different spatial and temporal scales, and for different catchment and estuary types. This method will accurately resolve all hydrological and marine processes and their joint-probabilities. It will evaluate how climate predictions from UKCP18 downscale to flooding impact; hence, providing unique and crucial inundation and likelihood data for the EA, NRW and SEPA to identify the most vulnerable communities to compound flooding and to manage their resources effectively during incidence response. Importantly, we will show how compound flooding occurs and how sensitive different systems are to the different drivers of climate change. Global sea levels are expected to rise up to 1 m this century and for some regions like the UK, precipitation and temperature distributions are likely to change, with extreme events such as storms, heatwaves and droughts becoming more intense and seasonal with altered timings. Changes in the intensity of flood drivers are expected to affect the hazard and risk. However, we hypothesise that changes in their timings relative to one another will also be vital for flood risk. For example, the timings of fluvial events will likely change due to changes in precipitation and temperature affecting soil moisture and groundwater flow. As a proof of concept in the NERC project CHEST, the investigators established the sensitivity of estuaries to tide-surge-fluvial events acting in combination, isolating distinct zones within estuaries of increased risk depending on catchment size relative to the estuary, estuary shape and the timing of surge and fluvial events relative to each other. Changes in flood risk due to climate change will therefore be site specific, with the relative roles of hazard drivers varying spatially. Long-term changes in extreme events are often unforeseeable because our understanding of the integrated system is incomplete. Considering the high socio-economic and environmental value of estuaries, the complexity of compound hazards, the projected changes in drivers, and unregulated landuse management, it is timely to develop new strategies for mitigating against compound flooding and to develop improved risk assessment tools for flood protection.Working with the UK regulators of flooding, SEARCH will use past and new observations with UKCP18 projections of precipitation, temperature, fluvial flows, storm surge and sea level applied to a fast, tested and open-source hydrodynamic-groundwater model to simulate flooding hazards. We will simulate 14 systems that cover the range of locations and estuaries within the UK. Our results are urgently needed, as probabilistic methods of determining flood risk are obsolete because they do not capture the non-linear dynamics and do not include future changes. This two year project brings together world-leading researchers in catchment-to-coast environmental science (with PDRAs at Bangor and Hull Universities) to tackle this computationally challenging and under-investigated issue. This team have worked together successfully, with the involvement and support of key policy and industrial partners, establishing a new paradigm in flood risk and accumulating a vast amount of data.