With up to 3,000 millimetres of annual rainfall, Hong Kong is one of the wettest cities in the Pacific Rim. The rains come in May with fog and mist blanketing the ceramic tiles and window frames of the city’s shoebox homes, soaking the densely packed city for the following five months. 香港年降水量多达3000毫米，是环太平洋地区最湿润的城市之一。雨季在每年五月到来，在接下来的五个月中，这个人口稠密的城市每个月都会迎来超过300毫米的降雨，雨雾令居民狭小房间的瓷砖和窗棂都覆上水珠。
Flooding and landslides are a major risk, particularly during typhoons and torrential rains, which happen at least ten times a year. Such extreme weather events are expected to become more frequent and of greater intensity in future. To prepare, the city is improving what is already one of the world’s most developed underground drainage systems. However, because climate change is making existing weather data and models redundant, planning new drainage infrastructure is especially challenging because the frequency and intensity of storms and floods cannot be accurately predicted. 雨水也带来了洪水和山体滑坡，尤其是在台风或暴雨肆虐时，而香港每年都要经历十次以上这种天气。预计未来此类极端天气将更为频繁，强度也更大。虽然香港有着堪称世界上最完善的地下排水系统，但为应对未来风险，香港正在对这一系统进行强化。
Concrete roots
When it pours in Hong Kong the city is protected from flooding by a large network of underground tunnels and storage tanks. Richard Leung Wah-ming, senior engineer at the Land Drainage Division of the Drainage Services Department (DSD), explains that the city’s flood control system has three major systems designed to protect it from events that happen once every 200 years.
排水系统：城市的地下根系
香港庞大的地下管道和蓄水池网络可以保护城市免受水灾之患。香港渠务署（DSD）地面排水处高级工程师梁华明（音）解释说，香港的防洪系统由三套主要系统组成，设计能力可防御200年一遇的洪水。
Stretching beneath the city’s roads, pavements and crowded concrete buildings are four rain tunnels, each 5-7 metres in diameter, nestled into the mountain slopes. These tunnels divert heavy rainfall on the upland surface away from low-lying areas downstream. The waters are collected and reused in the city’s water system or drained into the sea. 在地势高的马路、人行道和鳞次栉比的混凝土建筑下面，埋着4条直径5到7米的排水管道。这些管道疏解了地势高地区的地表降水，避免雨水顺着地势流向低洼地区，并将这部分雨水收集利用，或者排入大海。
Where population density is higher (in the “Mid Level”), three underground storm-water storage tanks collect rainwater. The largest, at Tai Hang Tung in West Kowloon, is over 10-metres deep and can hold 100,000 cubic metres of storm water, equivalent to about 40 standard swimming pools. 中间地势是人口最稠密的地区，这些地区的地下有3个收集暴雨的蓄水池。西九龙大坑东的地下蓄水池是其中最大的，深度超过10米，可储存超过10万立方米降水，相当于40个标准游泳池的水量。
The storage tank beneath the Happy Valley racecourse is still under construction but once it’s completed in 2018, it will have a capacity of 60,000 cubic metres, enough to drain the 130 hectares of Wan Chai, Causeway Bay and Happy Valley, even in a 1-in-50 year weather event. 跑马地马场地下的蓄水池仍在建设中，2018年建成之后将具备6万立方米的蓄水能力，足以处理总面积达130公顷的湾仔、铜锣湾和跑马地的降水，甚至可以承受50年一遇的极端降水冲击。
The storage tanks contain water level sensors, culverts and tide gauges that operate automatically based on real-time data of water flow and tidal levels. When the rainfall intensity is low, the weirs of the tank are kept closed and storm-water flows along the culvert. When it rains heavily, the weirs lower to allow storm water to overflow into the tank for temporary storage. After the flood has passed, the weirs are lowered further to allow the stored water to flow back, while the remaining storm water is pumped out. 蓄水池安装了水位探测装置，并设有暗渠和验潮仪，根据水流和潮量的实时数据自动运行。当降水强度低时，蓄水池闸门紧闭，降水沿暗渠排走。当降水强度大时，闸门打开，使过多的暴雨降水流入蓄水池暂时储存。暴雨过后，排出池中蓄水，难以排放的蓄水则通过排水泵排出。
在城市的低洼地带和乡村地区，加粗排水管道，并疏通拉直下水道，形成了长达360公里的排水网络——相当于从华盛顿特区到纽约之间的距离。At the lower levels of the city and in rural areas, drainage channels have been enlarged and dredge sewers straightened, stretching out in a web 360 kilometres long – equivalent to the distance from Washington, DC to New York.
地下世界宛若一个混凝土筑成的植物根系，维护着地表城市的健康和长远发展。1700公里的下水道和2300公里的泄洪渠遍布香港全城。根据DSD的介绍，全部主要的防洪“盲点”都得到了解决，风险等级不同的各类危险点的数量已经从1995年的90个减少至今年的8个。This underground concrete root system is meant to maintain the health and longevity of the city above ground. The sewers and storm-water drains extend as far as 1,700 kilometres and 2,300 kilometres, respectively. All major flood “blackspots” have been neutralised, and the number of danger points, posing varying degrees of risk, have been reduced from 90 in 1995 to just eight this year, according to the DSD.
How Hong Kong manages heavy rainfall 香港如何管理暴雨
移除点击此处添加图片说明文字
Accelerating climate change
Even with its “world-class system”, Leung said that climate change poses a major challenge as extreme weather events increase.
气候变化加剧带来挑战
然而，梁华明表示，即便香港已经有了世界级的排水网络，但在气候变化的背景下，极端气候事件的增多还是给香港带来了巨大的挑战。
Data from the Hong Kong Observatory shows that rainfall records are regularly broken. Previously, the maximum hourly precipitation record in the period between the 1880s and the late 1970s would stand for 40 years on average. This has fallen to less than 20 years between the late 1970s and the 1990s. From the 1990s to 2014, the records were broken every ten years. 香港天文台的数据显示，近年来香港降水量不断突破记录。从19世纪80年代到20世纪70年代，每小时雨量的最高纪录平均能够保持40年。20世纪70年代到20世纪90年代，这一纪录平均能够保持不到20年。而20世纪90年代到2014年间，这一纪录则每10年就被打破一次。
“Climate change is really accelerating,” said Leung. “这意味着气候变化确实在加速。”梁华明表示。
According to the Hong Kong climate change report released in November 2015, the number of extremely wet years is expected to quadruple, from three during 1885 to 2005 to about 12 from 2006 to 2100. Leung said the DSD is using the combined data from the Intergovernmental Panel on Climate Change (IPCC) under the United Nations, and the Hong Kong Observatory to review Hong Kong’s flood prevention system. 根据2015年11月发布的香港气候变化报告，极端湿润年份的数量预计将从1885年到2005年之间的三个增长到2006年到2100年之间的12个。梁华明表示，DSD正在结合联合国政府间气候变化专门委员会（IPCC）和香港天文台的数据，重新评估香港的防洪系统。
“The capacities of the current rainstorm tanks and channels may not be able to hold heavy rainstorms in the future. Together with the changing land use and new urban design, we need to update the current systems,” Leung said. “目前蓄水池和泄洪管道的能力难以应对未来更大的降水。再加上土地用途的变更，以及新的城市设计，我们需要对现有系统进行升级换代。”梁华明表示。
Landslides and debris
“The most significant thing to consider for the future of flood prevention in Hong Kong, especially in urban areas threatened by climate change, is how to prevent floods caused by landslides and debris that leads to blockage of drainage systems,” said Chen Ji, associate professor at the Department of Civil Engineering at the University of Hong Kong (HKU).
山体滑坡和杂物淤塞排洪渠
2016年10月19日，“黑色”暴雨预警发布。这是1998年暴雨预警系统启动以来首次在十月份发布“黑色”预警。
On October 19, 2016, a “black” rainstorm warning was issued; the first during an October since the warning system was put in place in 1998.
The Hong Kong Observatory said the hourly rainfall exceeded 100 millimetres, far above the threshold of 70 millimetres for the black warning. The day’s total rainfall reached 223 millimetres. This is remarkable given that annual rainfall in the city is between 1,400 and 3,000 millimetres, depending on the district. 香港天文台表示，每小时降水量可能超过100毫米，远远高于70毫米的黑色预警门槛。当日总降水量达到223毫米。考虑到香港年降水量不过在1400毫米到3000毫米之间（依区域不同而有所差异），这一降水量确实十分惊人。
The downpour struck suddenly and caused floods in 14 areas. The waters were muddy and clay-coloured. This was history repeating itself, said Chen, recalling that heavy rainfall and floods six years earlier had resulted in a landslide that blocked the drainage system. Preliminary findings by the DSD confirmed that blocked drains cause major damage. 暴雨突然而至，造成14个地区发生洪涝。香港大学土木工程系副教授陈骥指出，洪水混浊并呈现黏土的颜色。陈教授认为，这与六年前造成山体滑坡和排水道淤塞的强降水情况相似，是历史重演。 “香港未来防洪工作——特别是受到气候变化威胁的市区——需要考虑的最重要的一点，就是如何避免山体滑坡和杂物造成的排水系统阻塞而引发的洪涝。”陈教授表示。
Responding to the Legislative Council on November 23, 2016, Secretary for Development Paul Chan Mo-po said, “[Tree branches and leaves] were washed down into the catch basins and storm-water drainage systems downstream by the severe rainstorm on October 19, resulting in blockage of the drainage systems, and hence undermining the overall flood-relieving capacities.” Further inspections and practical solutions to the problem are under review. DSD的初步研究发现证实了陈教授的判断。11月23日，香港发展局局长陈茂波在回答立法会质询时说：“大量被强风刮掉的树枝和树叶堆积在上游的山坡上。10月19日的暴雨将这些东西冲刷进下游的滤污器和排水系统，造成排水系统阻塞，导致系统的整体防洪能力下降。” 针对这一问题的进一步调查和解决方案还在审议之中。DSD的梁华明说：“我们需要关于降水时间和降水量的详细数据，还需要测试类似的情况是否会再次发生。”
Problem forecasts
The problem with existing flood prevention standards that guide the planning and design of storm-water drainage systems is that they’re based on analysis of historical data.
气候变化加大灾害预测难度
目前，指导暴雨排洪系统规划和设计的现有防洪标准的主要问题在于，它们是以历史数据为基础建立起来的。
“Due to the uncertainty of climate change, or even the natural system, the frequency and intensity of rainfall are hard to predict. It is highly possible that a 1-in-200 year rainstorm could become a 1-in-100 or 1-in-50 year event,” Chen said. “由于气候变化乃至自然系统存在不确定性，降水的频度和强度难以预测。200年一遇的暴雨可能会变成百年一遇或者50年一遇。”陈教授说。
Rainstorms usually strike Hong Kong between May and September but last year there were successive typhoons and heavy rainfall in October, which is normally a dry month.This abnormal weather, Chen explained, was due to a strong occurrence of La Niña, an atmospheric phenomenon that increased the number of tropical cyclones and brought above-average rainfall to Hong Kong. 暴雨通常在五月到九月之间光临香港，但去年在通常是旱季的十月份却接连碰上台风和强降水。陈教授解释说，这种反常的天气是受拉尼娜效应的强烈影响。拉尼娜效应是一种气候现象，它增加了热带飓风的数量，并造成香港高于平均值的降水。
It is possible this phenomenon could become more frequent under the impact of climate change, Chen said. “So it is important to enhance the accuracy of seasonal forecasting of heavy rainfall in the dry season so that the DSD can take all precautions to mitigate the impact of floods.” 陈教授认为，在气候变化的影响下，这种现象可能会更加频繁发生。“因此必须提高旱季强降水预测的准确度，帮助DSD更好地采取一切预防措施，减轻洪涝灾害的影响。”一方面，科学家正在研究提升洪涝预报准确度的方法，而另一方面，建筑专家也开始将洪涝灾害作为建筑设计中的常规假设条件。
移除Hong Kong drainage master plan review
Living with floods
While scientists are working on ways to improve the accuracy of flood forecasting, architects are beginning to work on the assumption that flooding will happen regardless.
与洪灾共生
“未来，洪涝灾害是不可避免的。我们应该考虑如何适应，”香港中文大学建筑学院助理教授廖桂贤表示。解决的办法在于设计出可涝区域，保证公共区域特别是城区公共区域的多功能性，在强降水发生时可以储水。
“Flooding is inevitable in the future. It is time to think about how to adapt to it,” said Liao Kuei-Hsien, assistant professor in the School of Architecture of the Chinese University of Hong Kong. The solution is to design areas that are floodable and ensure that public space, especially in urban areas, is multi-functional so it can be used at times of heavy rain to store water. Flooding is a natural phenomenon argues Liao so city planners and architects should be focused on reducing flood hazards, the threat of flooding to human beings, and flood disasters, which cause damage to residents and the economy.廖教授认为，洪涝是正常现象，因此城市规划者和建筑师应该致力于减轻洪水险情的应对工作，降低其对人类的威胁并避免可能对居民安全和经济发展造成重大伤害。
It is important “to increase the resilience of the city and to prevent flood hazards from becoming flood disasters,” said Liao, explaining that resilience means a flooded city can recover quickly. 廖教授认为，“增加城市防洪能力、避免洪水险情发展成为洪涝灾害”是十分重要的，而城市的防洪能力意味着被淹之后可以迅速恢复。
“We’ll be living in an environment where flooding is natural. So we need to get used to it. Just let it flood.” “我们将生活在一个洪涝频发的环境当中。所以我们只能顺其自然，尽力适应。” 廖说。
