📚 Urban Drainage Systems: Challenges and Solutions | 城市排水系统的挑战与应对
Urban drainage systems are the unseen networks that safeguard public health, protect property, and maintain the environmental equilibrium of cities. However, rapid urbanisation, climate change, and ageing infrastructure are pushing these systems to their limits. This article explores the multifaceted challenges facing contemporary urban drainage and evaluates the innovative engineering and policy solutions shaping resilient cities of the future.
城市排水系统是保障公众健康、保护财产安全以及维持城市环境平衡的隐形网络。然而，快速的城市化、气候变化和日益老化的基础设施正将这些系统推向极限。本文旨在探讨当代城市排水所面临的多维度挑战，并评估那些正在塑造未来韧性城市的创新工程与政策解决方案。
1. The Impact of Urbanisation on the Hydrological Cycle | 城市化对水文循环的影响
Natural landscapes, such as forests and grasslands, intercept rainfall, promote infiltration, and slow down overland flow. In contrast, urbanisation replaces permeable surfaces with impermeable materials like concrete and asphalt. This transformation dramatically alters the natural hydrological cycle by reducing infiltration and evapotranspiration while significantly increasing surface runoff. Consequently, the lag time between peak rainfall and peak river or sewer flow is shortened, leading to a higher and more abrupt discharge peak.
森林和草原等自然景观能够截留降雨、促进下渗并减缓地表径流。相比之下，城市化用混凝土和沥青等不透水材料取代了透水面。这一转变显著减少了下渗和蒸散发，同时大幅增加了地表径流，从而彻底改变了自然水文循环。其结果是，最大降雨量与最大河流或污水流量之间的滞时缩短，导致更快速、更陡峭的洪峰流量出现。
The degree of alteration can be expressed using the rational method, which estimates peak runoff discharge. The formula is:
Q = C × I × A
In this equation, Q represents the peak discharge (m³/s), C is the runoff coefficient (reflecting surface permeability), I is the rainfall intensity (m/s), and A is the catchment area (m²). In urban areas, the runoff coefficient C is typically 0.7 to 0.9, compared to 0.1 to 0.3 for natural, vegetated surfaces, signifying the profound impact of urbanisation on runoff generation.
在该方程中，Q 代表洪峰流量（m³/s），C 是径流系数（反映地表渗透性），I 是降雨强度（m/s），A 是集水区面积（m²）。在城市区域，径流系数 C 通常为 0.7 至 0.9，而自然植被表面的径流系数仅为 0.1 至 0.3，这充分表明了城市化对径流产生的深远影响。
2. The Growing Challenge of Urban Flooding | 城市内涝日益严峻的挑战
Urban flooding is the most immediate and visible consequence of overtaxed drainage systems. High-intensity, short-duration storms, often exacerbated by climate change, can quickly exceed the design capacity of drainage networks. When the volume of water entering a sewer system surpasses its carrying capacity, water backs up onto streets, inundates underpasses, and seeps into basements, causing severe disruption to transport, business, and daily life. This is particularly acute in densely built low-lying coastal cities and those located on floodplains.
城市内涝是排水系统超负荷运转后最直接、最明显的后果。高强度、短历时的暴雨（通常因气候变化而加剧）能迅速超过排水管网的工程设计能力。当进入下水道系统的水量超过其输送能力时，水便会倒灌至街道、淹没下穿隧道并渗入地下室，对交通、商业和日常生活造成严重破坏。这在建筑密度高、地势低洼的沿海城市以及位于洪泛平原上的城市中尤为突出。
The shape of the river or sewer hydrograph provides a key indicator of urban flood risk. Impermeable surfaces increase the peak discharge and decrease the lag time, producing a “flashy” hydrograph. This makes urban streams and drainage channels particularly prone to rapid, violent rises in water level following heavy rain, posing a significant threat to public safety and urban infrastructure.
河流或下水道系统的水文过程线形态是判断城市洪涝风险的关键指标。不透水面增加了洪峰流量并缩短了滞时，形成“陡峭”的洪水过程线。这使得城市河流和排水渠道在暴雨后极易出现快速且猛烈的水位上涨，对公共安全和城市基础设施构成重大威胁。
3. The Problem of Combined Sewer Overflows (CSOs) | 合流制溢流（CSO）问题
Many older cities, particularly in Europe and North America, utilise combined sewer systems that transport both stormwater runoff and domestic sewage in the same pipe network. During dry weather, these systems convey all wastewater to treatment plants. However, during intense rainfall, the volume of mixed water can exceed the capacity of both the sewer and the treatment plant. To prevent sewage from backing up into homes and streets, these systems are designed to discharge the excess mixture—combining raw sewage, industrial waste, and stormwater—directly into rivers, lakes, or coastal waters. This is known as a Combined Sewer Overflow (CSO).
许多历史悠久的城市，尤其是欧洲和北美的城市，采用合流制排水系统，即在同一管网中同时输送雨水径流和生活污水。在干旱天气，这些系统将所有废水输送到处理厂。然而，在强降雨期间，混合水量可能超过下水道和处理厂的处理能力。为了防止污水倒灌进入住宅和街道，这些系统被设计为将多余的混合物（包括未经处理的原生污水、工业废水和雨水）直接排放到河流、湖泊或近海水域。这就是所谓的合流制溢流（CSO）。
CSOs are a major environmental and public health concern. They contribute to eutrophication, introduce pathogens into recreational waters, and deposit harmful pollutants into aquatic ecosystems. For instance, in London, the discharge of CSOs into the River Thames has historically been a significant source of pollution, harming wildlife and limiting recreational use of the river. Managing CSOs is therefore a critical priority for cities seeking to improve water quality and meet stringent environmental regulations.
合流制溢流是一个重大的环境和公共健康问题。它会导致水体富营养化，将病原体引入休闲水域，并向水生生态系统沉积有害污染物。例如，在伦敦，合流制溢流对泰晤士河的排放历来是重要的污染源，危害了野生动物并限制了河流的休闲娱乐功能。因此，管理合流制溢流是那些致力于改善水质、满足严格环境法规要求的城市所面临的关键优先事项。
4. Water Quality Degradation and the ‘First Flush’ Effect | 水质恶化与“初次冲刷”效应
Urban stormwater runoff is not simply clean rainwater; it acts as a mobile solvent, collecting a wide array of pollutants as it travels over roofs, roads, and parking lots. These pollutants include heavy metals, oils, lubricants, microplastics, fertilisers, pesticides, and animal waste. The phenomenon known as the ‘first flush’ occurs when the initial period of storm runoff carries an exceptionally high concentration of these accumulated pollutants, delivering a toxic shock to receiving water bodies.
城市雨水径流并非单纯干净的雨水；它在屋顶、道路和停车场表面流动时，充当了流动的溶剂，收集了各种污染物。这些污染物包括重金属、油类、润滑油、微塑料、化肥、杀虫剂和动物粪便。所谓的“初次冲刷”现象，发生在暴雨径流的初始阶段，此时水流携带了异常高浓度的累积污染物，对受纳水体造成毒性冲击。
Unlike sewage, which is typically treated before discharge, stormwater runoff is often released into the environment with little or no treatment. This non-point source pollution makes it difficult to regulate and manage. The consequence is the degradation of urban river ecosystems, the closure of bathing beaches, and the contamination of groundwater aquifers. Furthermore, thermal pollution occurs when runoff from sunheated impervious surfaces enters rivers, raising water temperatures and threatening temperature-sensitive aquatic species.
与通常经过处理后才排放的污水不同，雨水径流往往在很少或未经处理的情况下直接排入环境。这种非点源污染使得监管和管理变得十分困难。其后果是城市河流生态系统退化、海滨浴场关闭以及地下含水层受到污染。此外，当来自被阳光加热的不透水表面的径流进入河流时，还会引发热污染，从而提升水温并威胁到对温度敏感的水生生物。
5. Ageing Infrastructure and Limited Capacity | 基础设施老化与能力不足
The drainage infrastructure in many established cities was designed and constructed decades, or even over a century, ago. These ageing underground networks are often under-sized for current population levels and are deteriorating due to age, ground movement, and root intrusion. The original design parameters, based on historical rainfall patterns, are becoming increasingly obsolete as climate change intensifies the frequency and intensity of extreme precipitation events.
许多成熟城市中的排水基础设施是在几十年前甚至一个多世纪前设计和建造的。这些老化的地下管网往往无法满足当前的人口规模，并且由于老化、地层移动和树根侵入而不断恶化。最初基于历史降雨模式的设计参数，正随着气候变化加剧极端降水事件的频率和强度而变得越来越过时。
The cost of replacing or upgrading this underground infrastructure is astronomically high, involving significant social and economic disruption. Concrete pipes have a finite lifespan, typically 50 to 100 years, and their failure can lead to sinkholes, sewer collapses, and localised flooding. Consequently, cities face a difficult choice: invest enormous sums in replacing conventional systems, or pivot towards distributed, nature-based solutions that complement existing networks and enhance their resilience.
更换或升级这些地下基础设施的成本极其高昂，并且会带来巨大的社会和经济干扰。混凝土管道有其有限的使用寿命，通常为 50 至 100 年，其失效可能导致地陷、下水道坍塌和局部内涝。因此，城市面临着一个艰难的选择：是投资巨额资金更换传统系统，还是转向采用分布式的、基于自然的解决方案，以补充现有管网并增强其韧性。
6. Sustainable Urban Drainage Systems (SuDS) | 可持续城市排水系统（SuDS）
In response to the limitations of conventional drainage, Sustainable Urban Drainage Systems (SuDS) have emerged as a paradigm shift in urban water management. SuDS aim to manage rainfall as close to where it falls as possible, mimicking natural drainage processes. They are designed to achieve multiple objectives: controlling the quantity of runoff, improving the quality of water, enhancing biodiversity, and creating amenity spaces for communities.
为了应对传统排水的局限性，可持续城市排水系统（SuDS）作为城市水管理的范式转变应运而生。SuDS 旨在尽可能在降雨落地处就近管理雨水，模拟自然排水过程。它们旨在实现多重目标：控制径流总量、改善水质、提升生物多样性并为社区创造休闲娱乐空间。
Common SuDS components include permeable pavements, which allow water to infiltrate into the ground beneath; green roofs, which intercept and store rainfall; swales (vegetated channels), which convey water slowly; and basins or ponds, which store and treat runoff. By intentionally redesigning the urban landscape to absorb and slow water, SuDS reduce the burden on downstream sewer systems and mitigate the risk of urban flooding. For example, the use of permeable pavements in parking lots can reduce surface runoff by up to 50-80%.
常见的 SuDS 组成部分包括：允许水渗透到地下层的透水铺装；能够截留和储存雨水的绿色屋顶；用于缓慢输水的植草沟（植被渠道）；以及用于储存和处理径流的洼地或池塘。通过有意地重新设计城市景观以吸收和减缓水流，SuDS 减轻了下游下水道系统的负担，并降低了城市内涝的风险。例如，在停车场使用透水铺装可以减少高达 50% 至 80% 的地表径流。
7. Green and Blue Infrastructure | 绿色与蓝色基础设施
Green and Blue Infrastructure (GBI) is a closely related concept that integrates natural elements—such as parks, woodlands, and wetlands (green)—with water-based features—such as rivers, canals, and ponds (blue)—into the urban fabric. Unlike single-purpose grey infrastructure (pipes and concrete channels), GBI provides multiple ecosystem services. These services include carbon sequestration, air pollution absorption, urban heat island mitigation, and wildlife habitat provision, alongside water management benefits.
绿色与蓝色基础设施（GBI）是一个紧密相关的概念，它将自然元素（如公园、林地和湿地，即“绿色”）与水体元素（如河流、运河和池塘，即“蓝色”）整合到城市肌理中。与功能单一的传统灰色基础设施（管道和混凝土渠道）不同，GBI 提供多种生态系统服务。这些服务包括碳封存、吸收空气污染、缓解城市热岛效应以及提供野生动物栖息地，同时具备水管理效益。
Urban river restoration is a prominent example of GBI. Many cities are now “daylighting” buried rivers—removing the concrete culverts that confined them and restoring natural, meandering channels with vegetated banks. This not only increases the flood storage capacity of the floodplain but also transforms sterile concrete channels into vibrant natural corridors that enhance the quality of urban life. The Cheonggyecheon stream restoration in Seoul, South Korea, is a world-renowned example of how removing urban infrastructure (an elevated highway) and restoring a riverine ecosystem can bring profound environmental, social, and economic benefits to a city.
城市河流修复是 GBI 的一个突出例子。许多城市正在“重见天日”那些被埋藏的河流——移除限制河道的混凝土暗渠，恢复自然蜿蜒的河道和植被茂密的河岸。这不仅增加了洪泛区的蓄洪能力，还将了无生机的混凝土渠道转变为充满活力的自然廊道，提升了城市生活质量。韩国首尔的清溪川河流修复工程就是一个举世闻名的例子，展示了如何通过移除城市基础设施（高架桥）并恢复河流生态系统，为城市带来深远的环境、社会和经济利益。
8. Smart Technologies and Real-Time Control | 智能技术与实时控制
The advent of the Internet of Things (IoT) and artificial intelligence is revolutionising the management of urban drainage. By equipping sewer networks with a vast array of sensors that monitor water levels, flow rates, and water quality, municipalities can now obtain a real-time, granular view of their system’s performance. This data is transmitted to centralised control platforms, where predictive algorithms and digital twin models can simulate various rainfall scenarios and optimise system operations.
物联网（IoT）和人工智能的到来正在彻底改变城市排水系统的管理方式。通过在排水网络中部署大量监测水位、流量和水质的传感器，市政部门现在可以获得关于系统运行状况的实时、精细的视图。这些数据传输到中央控制平台，在那里，预测算法和数字孪生模型可以模拟各种降雨情景，从而优化系统运行。
Real-time control (RTC) takes this a step further by allowing operators to actively manage the system in response to dynamic conditions. For instance, remote-controlled gates and valves can be adjusted to store stormwater in specific parts of the sewer network during peak rainfall, or to divert flow to areas with spare capacity. This proactive water management maximises the utilisation of existing infrastructure, significantly reducing flooding and CSO events, all at a fraction of the cost of building new storage tunnels. For example, the city of Copenhagen uses real-time control to anticipate cloudbursts and pre-emptively drain its sewer systems to create additional storage headroom.
实时控制（RTC）则更进一步，允许操作员根据动态条件主动管理整个系统。例如，在峰值降雨期间，可以通过远程控制的闸门和阀门将雨水储存在下水道网络的特定区域，或者将水流引导至有空余容量的区域。这种主动式水管理最大化了对现有基础设施的利用，显著减少了内涝和合流制溢流事件的发生，而其成本仅为新建蓄水隧道的一小部分。例如，哥本哈根市利用实时控制来预测暴雨，并预先排空下水道系统以创造额外的蓄水空间。
9. Policy, Governance and Community Engagement | 政策、治理与社区参与
Technological and engineering solutions alone are insufficient to address the complex challenges of urban drainage. Effective policy and governance frameworks are essential for implementing large-scale changes. This includes adopting integrated urban water management (IUWM) plans, enforcing strict stormwater regulations for new developments, and securing long-term funding for infrastructure investment. Policy instruments such as stormwater utility fees and tax incentives can encourage property owners to implement on-site rainwater harvesting or green infrastructure which eases the strain on the drainage network.
仅靠技术和工程方案不足以应对城市排水的复杂挑战。完善的政策和治理框架对于实施大规模变革至关重要。这包括采用城市水资源综合管理计划、对新开发项目严格执行雨水管理规定以及为长期基础设施投资提供持续的资金保障。通过征收雨水公用事业费或提供税收减免等政策工具，可以鼓励业主实施雨水收集或绿色基础设施，从而减轻排水网管的压力。
Furthermore, community engagement is a vital cornerstone of urban water resilience. Public education campaigns can raise awareness about the impact of disposing of wet wipes and cooking oil down drains, which are major causes of sewer blockages. Community-based initiatives, such as adopting a drain or installing rain barrels and rain gardens on residential properties, empower citizens to actively participate in managing urban waters. These hyper-local projects, like the sustainable drainage systems built into Portland’s residential streets, collectively contribute significantly to reducing runoff volume and improving local water quality.
此外，社区参与是城市水韧性的重要基石。公共教育活动可以提高公众意识，让大家了解将湿纸巾和食用油丢弃到下水道所带来的危害，这些都是造成下水道堵塞的主要原因。社区层面的倡议，例如认领排水口、在住宅区安装雨水桶和雨水花园，能够使居民积极参与到城市水管理中来。这些超本地化的项目（例如波特兰住宅街道上建造的可持续排水系统）能够显著降低径流量并改善局部水质。
10. Case Studies: London and Beijing | 案例研究：伦敦与北京
Examining specific cities provides valuable context for how these challenges are being tackled in practice. London, England, represents a classic case of a historical city grappling with an overburdened, combined sewer system. The city’s iconic Victorian sewer network, built in the 19th century, is simply too small for its modern population. To address this, the Thames Tideway Scheme, a “super sewer” currently under construction, is a 25 km tunnel running under the River Thames. Its primary purpose is to capture, store, and transfer the millions of tonnes of untreated sewage that currently overflow into the river each year, significantly reducing CSO pollution and restoring the health of the river.
研究具体城市可以为理解这些挑战的实际应对方式提供宝贵的背景。英国伦敦是一个典型的案例，反映了历史悠久的城市如何努力应对超负荷的合流制排水系统。该市建于 19 世纪的地标性维多利亚式下水道网络已无法适应现代人口的需求。为了解决这一问题，正在建设中的泰晤士河潮道工程（Thames Tideway Scheme），即所谓的“超级下水道”，是一条位于泰晤士河下方、全长 25 公里的隧道。其主要目的是截流、储存和输送目前每年溢流进入河流的数百万吨未经处理的污水，从而大幅减少合流制溢流污染，恢复河流的健康。
Beijing, China, meanwhile, offers a more contemporary example of proactive, landscape-scale planning. In line with its national “Sponge City” initiative, Beijing is implementing a comprehensive strategy to absorb, store, and reuse up to 70% of its rainwater. The approach integrates a vast range of measures, from green roofs and urban wetlands to permeable pavements and rainwater harvesting systems across new and existing developments. This transition from a purely grey “drain-and-convey” approach to a green-blue “infiltrate-and-retain” model is designed to enhance water security, mitigate urban flooding, and restore natural hydrological processes across the city.
与此同时，中国北京则提供了一个更具前瞻性、景观尺度规划的当代案例。根据国家“海绵城市”倡议，北京正在实施一项综合战略，旨在吸收、储存并再利用高达 70% 的雨水。该方法整合了大量措施，范围广泛，从绿色屋顶和城市湿地，到新城建设和既有社区改造中的透水铺装和雨水收集系统。这种从单纯的灰色“快排式”模式向绿色蓝色“渗滞式”模式的转变，旨在增强水安全、缓解城市内涝并恢复城市内自然的水文过程。
In conclusion, the challenges facing urban drainage systems are complex and accelerating, driven by the combined pressures of climate change, urbanisation, and decaying infrastructure. The era of relying solely on vast, buried concrete pipes to convey stormwater away is ending. A resilient, sustainable strategy for the future demands a comprehensive, multi-layered approach: utilising smart real-time controls to breathe intelligence into existing networks; replacing grey infrastructure with green and blue infrastructure wherever possible; implementing robust policies that mandate sustainable drainage; and fostering a culture of community stewardship to protect these vital systems. By embracing this new paradigm of water-sensitive urban design, cities can transform their drainage networks from a hidden liability into a multifaceted asset that delivers social, economic, and environmental value for generations to come.
总而言之，在气候变化、城市化和基础设施老化的多重压力下，城市排水系统面临的挑战日益复杂和紧迫。单纯依靠巨大且深埋于地下的混凝土管道来排走雨水的时代已经结束。未来打造韧性城市的可持续战略需要全面的、多层次的方法：利用智能实时控制为现有管网注入智慧；尽可能用绿色和蓝色基础设施取代灰色基础设施；实施强制采用可持续排水系统的有力政策；并培养社区共同维护这些关键系统的文化。通过拥抱这种全新的“水敏感型城市设计”范式，城市可以将其排水网络从一项隐蔽的负担转变为一项多功能的资产，为子孙后代创造社会、经济和环境价值。
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