Floods encountered around the world are diverse and evolving both in their nature and impact on society. In recent years in Canada, we have seen catastrophic and devastating flood events occurring at all times throughout the year, and not just limited to historically prevalent spring flooding driven primarily by snowmelt and precipitation events. In August 2018, a severe thunderstorm in the downtown area of Toronto, Ontario produced 64 mm of rainfall in a period of 2 hr and resulted in infrastructure damage and basement flooding estimated at $80 million (CAD) (CBC News, 2018). In 2019, the province of Manitoba activated the Red River Floodway (an artificial waterway constructed in 1968 to alleviate downstream flooding in the city of Winnipeg) for the first time ever in the Fall season in response to rising water levels and anticipation of 60–100 mm of rainfall (Kives, 2019). Earlier this year, a 36 hr‐long precipitation event at the end of January produced heavy rainfall over areas in the south coast of the province of British Columbia, with 371 mm of rainfall recorded in an area on western Vancouver Island, leading to widespread flooding, mudslides and landslides (CBC News, 2020). Ice jams occurring along the Athabasca and Clearwater Rivers in the province of Alberta lead to severe flooding in Fort McMurray in April 2020, inundating over 1,000 structures and displacing 13,000 people (Snowdon, 2020). Recently, in July 2020, concern regarding the safety and integrity of the 60 year‐old Rivers Dam along the Little Saskatchewan River in the province of Manitoba mounted following an estimated 1 in 1,000‐year precipitation event that produced 200 mm of rainfall in 72 hr (Gowriluk, 2020).

These examples of recent floods resulted in widespread economic damages and countless social and environmental impacts, including evacuation and displacement of people, loss and damage of homes and businesses, and adverse impacts to ecosystems. The causes and drivers of these flooding events are unique, and require, in many cases, very different approaches to manage and mitigate the adverse impacts. Such measures may include large‐scale reservoirs and stormwater management strategies to divert water from rivers during periods of high flow, structural measures to reduce the impact of rising water levels and ice jams in rivers, landscape stormwater management approaches to promote green infrastructure and more natural drainage in urban environments, and lot‐level strategies homeowners can adopt to reduce the risk of water damage from basement flooding.

Consider, for example, the city of Calgary in the province of Alberta which dealt with an extreme flood event in June 2013 resulting from snowmelt in the mountains combined with a week‐long precipitation event that caused catastrophic damages estimated at $5 billion (CAD). In the years since this flood, the province has been investing $1.47 billion (CAD) towards strategies to mitigate impacts of future destructive floods, including the design of a massive off‐stream reservoir to temporarily detain water during periods of high flow and flood barriers to combat rising water levels (Labby, 2018). Likewise, the city of Toronto, which has faced multiple economically‐devastating catastrophic flood events in recent years, has a commitment from the federal government for an investment of $150 million (CAD) for flood mitigation infrastructure in the region, including expansions and construction of new relief storm sewers to reduce the risk of sewer back‐up and basement flooding as well as water quality improvements (CBC News, 2019). In response to historical ice jam‐induced flooding such as what was experienced earlier this year, the regional municipality encompassing the city of Fort McMurray has invested $150 million towards the construction of berms and flood walls, with further infrastructure and economic investment planned for the coming years (Malbeuf, 2020).

In light of the immense economic investment required for flood mitigation measures around the world, combined with the unique nature of floods requiring targeted strategies, considerable attention into the performance of such strategies and their optimal design under diverse and complex environmental conditions are of the upmost importance. For example, large‐scale structural measures to reduce flood risk have been the focus of recent research including assessment of the effect of simulated detention basins to reduce peak flow from extreme precipitation events and protect downstream areas from flooding (Vieira, Barreto, Figueira, Lousada, & Prada, 2018) and investigation into the performance of emergency measures (e.g., sand bags) for flood prevention and protection (Lendering, Jonkman, & Kok, 2016). Recent research into the performance of green infrastructure, such as low impact development (LID) or best management practices (BMPs), has sought to identify optimal arrangement of BMPs (e.g., vegetative swales and porous pavement) to address water quantity and quality challenges associated with floods (Behroozi, Niksokhan, & Nazariha, 2018) and examine public perception and behaviour surrounding green infrastructure (e.g., bioswales) to evaluate how these measures can be implemented most successfully (Everett, Lamond, Morzillo, Matsler, & Chan, 2018). Further research is seeking to evaluate the performance of combinations of various flood mitigation measures and strategies, such as the application of both engineered approaches and land use approaches to address muddy runoff flooding stemming from soil erosion from agricultural fields (Boardman & Vandaele, 2020), assessing the effectiveness of structural (e.g., new pipes to convey runoff and storage tanks to detain flow) and nonstructural (e.g., early warning systems and deployment of emergency response personnel to close flood prone areas) measures to deal with increased flood risk resulting from extreme precipitation due to climate change (Velasco et al., 2018), and identify optimal arrangements of conventional stormwater management strategies and LID measures for flood mitigation purposes (Zhou, Lai, & Blohm, 2019). Lastly, consideration and promotion of strategies to reduce the risk of urban flooding at the lot‐level (e.g., backwater valves installed in individual homes to reduce the risk of basement flooding from sewer back‐up) and coordination between municipalities and the insurance industry to identify areas at heightened flood risk have been explored and recommended (Sandink, 2016).

Around the world, the diverse nature of floods encountered in any one year poses considerable challenges for flood risk management. Continued efforts to evaluate the performance and interaction of flood prevention, protection and mitigation strategies as we encounter increasingly complex and evolving flood risk from shifts in in climate, increased urbanisation and other factors are needed. This is indeed paramount in order to design and implement optimal flood management strategies to improve resiliency and mitigate the most adverse impacts of floods on people and the environment.

世界各地遇到的洪水是多种多样的，其性质和对社会的影响都在不断发展。近年来，在加拿大，我们一年四季都发生灾难性和破坏性的洪水事件，而不仅限于历史上主要由融雪和降水事件驱动的春季洪水。2018年8月，安大略省多伦多市区发生严重雷暴，在2小时内产生了64毫米的降雨，造成基础设施损坏和地下室洪水，估计价值8000万加元（CBC新闻，2018年））。2019年，马尼托巴省首次在秋季开通了红河洪道（1968年修建的人工水道，以缓解温尼伯市的下游洪灾），以应对水位上升和60-100的预期毫米的降雨量（Kives，2019）。今年早些时候，1月底发生了长达36小时的降雨事件，导致不列颠哥伦比亚省南海岸地区出现大量降雨，温哥华西部岛地区录得371毫米降雨，导致洪水泛滥，泥石流和滑坡（CBC新闻，2020年）。阿尔伯塔省阿萨巴斯卡河和克利尔沃特河沿岸发生的冰堵导致2020年4月麦克默里堡发生严重洪灾，淹没了1,000多个建筑物，使13,000人流离失所（Snowdon，2020年）。最近，在2020年，曼尼托巴省Little Saskatchewan河沿岸已有60年历史的Rivers大坝的安全性和完整性受到关注，原因是估计有1,000年的降水事件中有1次在72小时内产生了200 mm的降雨（Gowriluk，2020年）。

这些近期洪水的例子造成了广泛的经济损失以及无数的社会和环境影响，包括人员疏散和流离失所，房屋和企业的损失和破坏以及对生态系统的不利影响。这些洪灾事件的原因和驱动因素是独特的，并且在许多情况下，需要非常不同的方法来管理和减轻不利影响。这些措施可能包括大型水库和雨水管理策略，以在高流量期间将水从河流中引出；结构性措施，以减少河流中水位上升和冰堵的影响；景观雨水管理方法，以促进绿色基础设施和更自然的发展。城市环境中的排水，

以阿尔伯塔省的卡尔加里市为例，该市在2013年6月处理了一场特大洪水事件，该事件是由山区融雪和为期一周的降雨事件造成的，灾难性损失估计为50亿加元（CAD）。自洪灾发生以来的几年中，该省一直在投资14.7亿加元用于缓解未来破坏性洪灾影响的战略，包括设计大型下游水库，以在高流量和洪灾屏障期间临时滞留水源。应对水位上升（拉比，2018年）。同样，多伦多市近年来也面临着多次经济灾难性的特大洪灾，联邦政府已承诺投资1.5亿加元用于该地区的减灾基础设施，包括扩建和建设新的救济风暴下水道，以减少下水道后备和地下室洪水以及水质改善的风险（CBC News，2019）。为了应对历史悠久的冰堵引发的洪水（例如今年早些时候所经历的洪水），包括麦克默里堡市在内的地区市政当局已投资1.5亿美元用于修建护堤和防洪墙，并计划在未来进行更多基础设施和经济投资年（Malbeuf，2020年）。

鉴于世界范围内采取防洪措施所需的巨大经济投资，再加上洪水需要针对性策略的独特性质，因此对于此类策略的性能及其在多样化和复杂的环境条件下的最佳设计的关注尤为重要。 。例如，减少洪水风险的大规模结构措施已成为近期研究的重点，包括评估模拟滞留盆地的作用，以减少极端降水事件造成的峰值流量并保护下游地区免受洪水侵害（Vieira，Barreto，Figueira，Lousada ，＆Prada，2018）以及对防洪和防洪应急措施（例如沙袋）的性能进行调查（Lendering，Jonkman，＆Kok，2016）。最近对绿色基础设施性能的研究，例如低影响力开发（LID）或最佳管理实践（BMP），已寻求确定BMP的最佳布置（例如，植物繁茂的草丛和疏松的人行道），以解决相关的水量和水质挑战与洪水（Behroozi，Niksokhan，＆Nazariha，2018）并研究公众对绿色基础设施（例如生物交换）的看法和行为，以评估如何最成功地实施这些措施（Everett，Lamond，Morzillo，Matsler和Chan，2018年））。进一步的研究寻求评估各种减灾措施和策略的组合的性能，例如应用工程方法和土地利用方法来解决由农田水土流失引起的泥泞径流洪水（Boardman＆Vandaele，2020年），评估结构性（例如，用于输送径流的新管道和储水罐以阻止水流）和非结构性（例如，预警系统以及部署应急人员以关闭易受洪灾地区的措施）的有效性，以应对极端天气导致的洪水风险增加气候变化造成的降水（Velasco等，2018），并确定用于缓解洪水的常规雨水管理策略和LID措施的最佳安排（Zhou，Lai和Blohm，2019年）。最后，考虑并推广降低地段级城市洪灾风险的策略（例如，在单个房屋中安装回水阀，以减少下水道后备引起的地下洪灾风险），以及市政当局与保险业之间的协调，以期确定并建议发现洪灾风险较高的地区（Sandink，2016）。

在世界范围内，任何一年中遇到的洪水的多样性对洪水风险管理构成了巨大的挑战。由于气候变化，城市化进程加快以及其他因素，我们遇到越来越复杂和不断演变的洪水风险，因此需要继续努力评估洪水预防，保护和减灾策略的性能和相互作用。为了设计和实施最佳的洪水管理策略以提高抗灾能力并减轻洪水对人类和环境的最不利影响，这确实是至关重要的。