今年夏天雨水特別多，全國(guó)各地普遍降雨量比較大。不論對(duì)老城區(qū)還是新城市來(lái)說(shuō)，這些雨水都是個(gè)挑戰(zhàn)。許多城市因降雨出現(xiàn)內(nèi)澇，開(kāi)啟了“看海模式”。這背后，有許多悲慘而無(wú)奈的故事。城市雨水管理逐步成為了一個(gè)關(guān)系到人民群眾生命財(cái)產(chǎn)安全的重大問(wèn)題，也逐步成為大家關(guān)注的熱點(diǎn)。鑒于此，記者采訪了亞洲開(kāi)發(fā)銀行東亞區(qū)域開(kāi)發(fā)部城市發(fā)展專(zhuān)家Kristina N. Katich，希望能找到大家關(guān)注的問(wèn)題的答案。

Kristina N. Katich的專(zhuān)業(yè)研究領(lǐng)域是氣候適應(yīng)性城市。去年在珠海舉辦的 “第十屆中國(guó)城鎮(zhèn)水務(wù)發(fā)展國(guó)際研討會(huì)與新技術(shù)設(shè)備博覽會(huì)”上，她曾做了題為《推進(jìn)中國(guó)城市雨水管理》的發(fā)言。今天，她將以國(guó)際視角，通過(guò)成功的案例，從政策、技術(shù)、前景等方面分析探討雨水管理的未來(lái)。

(左一：Kristina N. Katich）

記者：您從何時(shí)開(kāi)始城市雨水管理研究的？在您的職業(yè)生涯中，有沒(méi)有遇到過(guò)讓您印象深刻的事？可否和我們分享您的故事？

Kristina N. Katich: 有趣的是，我工作在城市雨水管理領(lǐng)域是因?yàn)槲覍?duì)整體規(guī)劃與社會(huì)公平感興趣。起初，我學(xué)習(xí)建筑，因?yàn)槲腋杏X(jué)建筑有其內(nèi)在的社會(huì)和實(shí)用價(jià)值——?jiǎng)?chuàng)造美麗、有用、安全的空間。隨著職業(yè)的發(fā)展，我轉(zhuǎn)向了城鎮(zhèn)環(huán)境規(guī)劃與管理，也就開(kāi)始了災(zāi)難管理與城市雨水管理。對(duì)我個(gè)人來(lái)講，我不太喜歡防洪的硬派工程；渠化、涵洞、堤壩會(huì)破壞維護(hù)城鎮(zhèn)環(huán)境的自然進(jìn)程。這些技術(shù)把洪水的風(fēng)險(xiǎn)轉(zhuǎn)移到了抵御洪水能力更差的下游社區(qū)，卻把大量快速流動(dòng)的洪水涌向那里。相反，我更喜歡盡可能多的采用軟工程的辦法，因?yàn)榛诃h(huán)境和景觀的洪水管理可以在很多方面極大的有益于城市。盡管我總是喜歡基于自然的方案，我對(duì) “日光”的辦法，即打開(kāi)20世紀(jì)七八十年代鋪設(shè)、下挖的水道，以形成自然的城鎮(zhèn)水道很感興趣。我的研究生論文研究的是氣候適應(yīng)性城市，我研究了首爾的昌溪川項(xiàng)目。除了輔助城市雨水管理，這個(gè)項(xiàng)目通過(guò)建立公園，使城市更具活力。盡管開(kāi)始當(dāng)?shù)鼐用穹磳?duì)，這個(gè)項(xiàng)目不僅大大的改善了生活環(huán)境，也提高了當(dāng)?shù)氐耐恋貎r(jià)值。該項(xiàng)目已獲得國(guó)際認(rèn)可，并被認(rèn)定為最佳范例廣泛在美國(guó)等國(guó)家采用。

記者：在您看來(lái)，城市雨水管理的最終目標(biāo)是什么？為了達(dá)到這一目標(biāo)，需要哪些方面共同努力？

Kristina N. Katich:城市雨水管理的最終目標(biāo)是確保所有的居民——富人、窮人、年輕人、老年人——每個(gè)人都有一個(gè)安全的環(huán)境。城市開(kāi)發(fā)尊重環(huán)境并與自然環(huán)境共生很重要。亞洲的很多快速開(kāi)發(fā)的城市忽略了低劣規(guī)劃的基礎(chǔ)設(shè)施對(duì)自然環(huán)境的影響，隨著時(shí)間的推移，這些影響將挑戰(zhàn)城市的可持續(xù)發(fā)展。鋪裝路面、管道化城市河流意味著城區(qū)吸收的雨水越來(lái)越少。正如我之前談到的，這增加了下游洪水泛濫的風(fēng)險(xiǎn)，同時(shí)也危及城市水供給，通過(guò)地面沉降破壞建筑物的基礎(chǔ)；世界上的城市，例如墨西哥城、雅加達(dá)、北京，因?yàn)殇佈b路面阻止了含水層的回水，正在慢慢的下沉。

有許多案例，低劣規(guī)劃的城鎮(zhèn)化以及城市雨水管理給無(wú)法承受洪水的物理、經(jīng)濟(jì)影響的貧窮地區(qū)造成不必要的負(fù)擔(dān)。例如，洪水泛濫地區(qū)或邊緣地區(qū)的土地、建筑成本可能更低，導(dǎo)致窮人聚集在這些地區(qū)。洪水來(lái)臨的時(shí)候，他們不僅可能失去家園、財(cái)產(chǎn)，他們的安全都將會(huì)有危險(xiǎn)。

城鎮(zhèn)雨水管理有三大障礙。一是洪水并不認(rèn)行政區(qū)的邊界，上游活動(dòng)極大的影響著下游的社區(qū)。這將導(dǎo)致城市間協(xié)作以及城鎮(zhèn)開(kāi)發(fā)、雨水管理的基礎(chǔ)設(shè)施和實(shí)踐的管理變得困難。另外，這也導(dǎo)致行政層面的雨水管理融資變得困難。

第二，同一個(gè)城市內(nèi)，政府機(jī)構(gòu)間的協(xié)作通常很差。許多政府機(jī)構(gòu)的行為——包括環(huán)境保護(hù)、應(yīng)急管理、固體廢物管理、交通、城市開(kāi)發(fā)等等——將會(huì)影響城市的抗洪能力。政府機(jī)構(gòu)間通常有不清晰、重疊的職責(zé)，缺乏理解和信息共享。

最后，不是每天可見(jiàn)的問(wèn)題，政客們也沒(méi)有興趣去改進(jìn)。除非一個(gè)城市近期經(jīng)歷了洪水，城市雨水管理通常在政府的日程中處于較低的優(yōu)先級(jí)——尤其是在官員變更頻繁的國(guó)家和城市。許多政府愿意構(gòu)建居民一年365天可見(jiàn)的基礎(chǔ)設(shè)施；雨水管理設(shè)施大都在地下，而且施工對(duì)居民交通和日常生活也有影響。除非有大量降雨或者河水泛濫，雨水管理設(shè)施的投資會(huì)被忽視或者被低估。城市雨水管理需要協(xié)作、資金、綜合規(guī)劃、以及構(gòu)建安全、環(huán)境友好的城鎮(zhèn)環(huán)境的遠(yuǎn)見(jiàn)。

記者：城市建設(shè)對(duì)雨水自然循環(huán)有哪些影響？如何實(shí)現(xiàn)人和自然的和諧管理？

Kristina N. Katich:城鎮(zhèn)建設(shè)的形式和速度對(duì)雨水自然循環(huán)有巨大的影響。在中國(guó)，城鎮(zhèn)規(guī)劃通常沒(méi)有包含足夠多的雨水管理規(guī)范。許多城市開(kāi)發(fā)較快，有向外擴(kuò)張而不是增加密度的趨勢(shì)。城市開(kāi)發(fā)增加了不透水路面，減少了儲(chǔ)存區(qū)，從而增加了城市地區(qū)的徑流。

為服務(wù)原有地區(qū)設(shè)計(jì)的排水系統(tǒng)無(wú)法承受從新鋪裝地區(qū)聚集的多余雨水。上游地區(qū)新增的雨水充滿了下游現(xiàn)有的管道，導(dǎo)致雨水無(wú)處可去。

隨著城市的擴(kuò)張，原來(lái)農(nóng)村或城市周邊的河流變成了市內(nèi)河流。這樣，由于淤積、城市廢物管理較差導(dǎo)致的垃圾，以及新建筑、高架、橋梁的占用，這些河流的排水量和蓄水能力會(huì)降低。高強(qiáng)度的土地開(kāi)發(fā)，改變了周?chē)淖匀坏匦蔚孛?，改變了河流系統(tǒng)、河漫灘、湖泊的自然流動(dòng)。

這就是海綿城市的概念在中國(guó)如此重要的原因之一。海綿城市試點(diǎn)將展示投資基于生態(tài)設(shè)計(jì)的雨水管理應(yīng)該應(yīng)用于中國(guó)所有的城市。西方知名的“綠色設(shè)施”、“低影響開(kāi)發(fā)(LID)”，基本原則是減少人工系統(tǒng)，如排水管道、泵站的開(kāi)發(fā)和建設(shè)，對(duì)自然和生態(tài)系統(tǒng)的影響。低影響開(kāi)發(fā)旨在通過(guò)儲(chǔ)存，滲透，蒸發(fā)，保留，減少地表徑流，模擬自然生態(tài)環(huán)境，以增加地下水補(bǔ)給。通過(guò)去中心化、小范圍源頭控制機(jī)制和相關(guān)技術(shù)，減少由暴雨導(dǎo)致的徑流。目的是盡可能多的維護(hù)開(kāi)發(fā)前的自然環(huán)境和水生態(tài)循環(huán)。

記者：在城市雨水管理領(lǐng)域，世界上有哪些城市做的比較好，有哪些經(jīng)驗(yàn)可以學(xué)習(xí)和借鑒？

Kristina N. Katich:我最近剛從荷蘭回來(lái)，荷蘭的水管理經(jīng)驗(yàn)給我留下了深刻的印象。眾所周知，荷蘭通過(guò)堤壩、堤岸的使用，開(kāi)墾大片土地，以及傳統(tǒng)荷蘭風(fēng)車(chē)的使用，在管理他們的國(guó)家與海洋的關(guān)系方面有著悠久的歷史。不那么廣為人知的是，這個(gè)國(guó)家本質(zhì)上是默茲河、萊茵河、斯海爾德河沖積的大三角洲。另外，超過(guò)80%的人口住在城市里，有很高的年均降水，城市雨水管理、控制河面高度以防止洪水泛濫極其重要。

雨水管理最有創(chuàng)意的是鹿特丹。位于萊茵河與默茲河的三角洲地帶，鹿特丹采取了積極的總體規(guī)劃管理，不僅使他們免于洪水災(zāi)害，而且免于受到潛在的氣候變化的影響。通常，氣候變化不僅會(huì)影響降雨的頻率，而且會(huì)影響降雨的密度。氣候變化對(duì)本地的影響已經(jīng)被感知，但是很少有城市有應(yīng)對(duì)潛在影響的意愿和資源。從2013年開(kāi)始，鹿特丹有了自己的氣候適應(yīng)策略：找出當(dāng)?shù)卮嗳觞c(diǎn)，創(chuàng)建用于未來(lái)彈性規(guī)劃和投資的框架。

意識(shí)到傳統(tǒng)的抗洪措施不足以應(yīng)對(duì)未來(lái)的風(fēng)險(xiǎn)，鹿特丹開(kāi)始嘗試其他辦法，收集并疏導(dǎo)雨水以防地區(qū)泛洪。鹿特丹的干預(yù)從小規(guī)?！缰С志G色屋頂、雨水收集的開(kāi)發(fā)——到大規(guī)模，例如重新設(shè)計(jì)現(xiàn)有的堤壩，用作多種用途。

鹿特丹減少洪水風(fēng)險(xiǎn)的創(chuàng)新項(xiàng)目，例如Benthemplein水上廣場(chǎng)，已經(jīng)贏得眾多國(guó)際城市規(guī)劃師的認(rèn)可。集成了公共娛樂(lè)空間、溫室、蓄水，Benthemplein水上廣場(chǎng)是世界上第一個(gè)大規(guī)模的水廣場(chǎng)。有不同座位、活動(dòng)場(chǎng)所的多層次空間，廣場(chǎng)在降雨量大的時(shí)候，成為了水庫(kù)。寬闊的排水溝收集雨水，并導(dǎo)向公園的深層盆地。盆地會(huì)24小時(shí)吸收雨水；超大降雨的時(shí)候，吸收的雨水會(huì)被抽到附近的水道，從而減輕鹿特丹污水處理系統(tǒng)的負(fù)擔(dān)。公園包含大量的綠色空間和公共空間，可用于運(yùn)動(dòng)和社交活動(dòng)，給周邊帶來(lái)了生機(jī)，很受本地學(xué)生和居民的歡迎。

總的來(lái)說(shuō)，我認(rèn)為鹿特丹可以作為中國(guó)城市雨水管理學(xué)習(xí)的一個(gè)極佳范例，不僅是因?yàn)槁固氐?yīng)對(duì)風(fēng)險(xiǎn)的整體氣候適應(yīng)性規(guī)劃，而且是因?yàn)樗闪讼窬G色屋頂這樣小規(guī)模嘗試。城市重新吸收的每一滴雨水對(duì)當(dāng)?shù)匾约跋掠蔚姆篮槎加杏绊憽?/p>

記者：夏日來(lái)臨，雨水增多，中國(guó)很多城市下了暴雨，有些地區(qū)甚至下了冰雹。暴雨對(duì)城市排水系統(tǒng)是一個(gè)挑戰(zhàn)。在城市排水防澇方面，有哪些行之有效的應(yīng)對(duì)措施？

Kristina N. Katich:中國(guó)最明顯的一大問(wèn)題是大多數(shù)城市只有小型或者管道排水系統(tǒng)。在許多國(guó)家，雨水系統(tǒng)通常包括小型系統(tǒng)和大型系統(tǒng)。小型系統(tǒng)用于應(yīng)對(duì)不密集的雨水，設(shè)計(jì)應(yīng)對(duì)2到10年一遇的暴雨。小型系統(tǒng)通常包括地下管道和溝渠。另一方面，大型系統(tǒng)用于應(yīng)對(duì)嚴(yán)重的暴雨，設(shè)計(jì)應(yīng)對(duì)50到100年一遇的暴雨。大型系統(tǒng)通常包括旁路通道，綠化帶和道路，用來(lái)處理超過(guò)小型排水系統(tǒng)處理能力的徑流。2012年，亞洲開(kāi)發(fā)銀行和住建部支持的一項(xiàng)中國(guó)城市雨水管理研究表明，這是中國(guó)城市最薄弱的問(wèn)題之一(http://www.adb.org/projects/45512-001/main)。這項(xiàng)研究找出了一些優(yōu)秀城市示例，例如亞洲的吉隆坡，以及一些西方城市。

在吉隆坡，一個(gè)“智能通道”被用作多種用途。通道是直徑為12米的三層結(jié)構(gòu)。最底層用于通常降水時(shí)的徑流排放。中間層平時(shí)用于交通，在暴雨的時(shí)候，會(huì)關(guān)閉交通，改為排水通道；設(shè)計(jì)應(yīng)對(duì)5年以上一遇的暴雨。在特大暴雨的時(shí)候，最上層以及整個(gè)通道會(huì)關(guān)閉交通，完全用于排水。

來(lái)源: http://www.tunnelvisions.eu/projects/nieuwe-pagina/

中國(guó)已經(jīng)通過(guò)了一系列的法規(guī)，將改進(jìn)并鼓勵(lì)城市排水和城市防洪設(shè)施的建設(shè)，并且引進(jìn)了海綿城市的概念。

記者：最近在雨水管理方面，是否出現(xiàn)了新的材料、設(shè)備、最新科技產(chǎn)品，能夠大大提升雨水管理的效率？

Kristina N. Katich:雨水管理最明顯的技術(shù)更新可以從透水路面的演變看出來(lái)。過(guò)去的幾年，這一領(lǐng)域有了突飛猛進(jìn)的進(jìn)展。過(guò)去，透水路面意味著鋪石頭或路磚的時(shí)候，留有空隙，讓水可以滲入。這種辦法在小范圍內(nèi)有效?，F(xiàn)在，許多透水路面更復(fù)雜，有多層，不僅吸收水，而且過(guò)濾，導(dǎo)向附近的沼澤或者水道，因此減少了排水和污水處理的負(fù)擔(dān)。透水路面種類(lèi)和復(fù)雜程度不同，給開(kāi)發(fā)人員和管理者在預(yù)算范圍內(nèi)，滿足設(shè)計(jì)要求的更多的選擇。透水路面可以減少?gòu)搅?，防止水體淤積，控制污染物，同時(shí)可以和鋪裝地區(qū)的樹(shù)木共存。

記者：最后，請(qǐng)問(wèn)您對(duì)有志于從事雨水管理領(lǐng)域的人員有哪些建議？或者您有哪些話想對(duì)中國(guó)讀者說(shuō)？

Kristina N. Katich:對(duì)任何有志于從事雨水管理，以及中國(guó)的讀者，我鼓勵(lì)他們?cè)诘陀绊戦_(kāi)發(fā)以及基于自然的城市排水解決方案方面學(xué)習(xí)。氣候變化將會(huì)導(dǎo)致更頻繁更密集的降雨，將會(huì)超過(guò)亞洲城市現(xiàn)有的已疲于應(yīng)對(duì)的降雨量。哪怕城市沒(méi)有采取有效的措施，個(gè)人依然有能力通過(guò)參與雨水收集、綠色屋頂、低仰角綠化帶貢獻(xiàn)自己的力量。最終，多個(gè)個(gè)體的貢獻(xiàn)將會(huì)在城市防洪中發(fā)揮重大作用。

我們感謝Kristina N. Katich和我們分享雨水管理領(lǐng)域的經(jīng)驗(yàn)和看法，首爾的昌溪川項(xiàng)目、鹿特丹的Benthemplein水上廣場(chǎng)、吉隆坡的“智能通道”，都給我們留下了深刻的印象。先進(jìn)的透水路面設(shè)計(jì)，正印證著“科學(xué)技術(shù)是第一生產(chǎn)力”，改變著城市雨水管理與規(guī)劃的未來(lái)。先進(jìn)的理念，先進(jìn)的技術(shù)，加上我們無(wú)數(shù)雨水管理領(lǐng)域內(nèi)孜孜以求的工作者，相信我們的雨水管理會(huì)做得更好，相信我們的城市會(huì)更好。

Interview Outline

Kristina N. Katich

Urban Development Specialist,

East Asia Regional Department (EARD)

Asian Development Bank

Field of Study: Climate adaptation and cities

Interview theme: Urban Storm Water Management

(1st left：Kristina N. Katich）

1. When did you start your study in urban storm water management? There might be something or some technology that impressed you very much in your career, could you share your story with us?

Interestingly, I came to work on urban storm water management out of an interest in holistic planning and social equity. Initially, I trained as an architect, as I felt that architecture had inherent social and utilitarian values – the function to create beautiful, functional, and safe spaces. As my career developed, I moved on to urban and environmental planning and management, which ultimately led the issues of disaster risk and urban storm water management. Personally, I am less of a fan of hard engineering approaches to prevent flooding; channelization, culverts, and dams tend to disrupt the natural processes which are required to maintain the urban environment. These techniques pass the flooding risks to downstream communities which may have even less capacity to absorb and cope with large amounts of fast-moving water. Rather, I prefer to use soft-engineering approaches as often as possible, as environmental and landscape-based flood management can greatly benefit cities in a variety of ways. While I have always preferred nature-based solutions, I was particularly impressed with the practice of, “daylighting,” or the opening up of natural urban waterways which were previously paved over or culverted during the 1970s and 1980s. My graduate school thesis focused on climate adaptation in cities, and through this, I learned of the Cheong Gye Cheon Project in Seoul. In addition to helping manage urban storm water, the project also revitalized the heart of the city through the creation of a public park. Despite initial resistance from area residents, the project has greatly improved not only their living environment but also increased local land-values. The project has gained international recognition and is considered a best-practice which is now being adopted in other countries, such as the United States.

Source: http://inhabitat.com/how-the-cheonggyecheon-river-urban-design-restored-the-green-heart-of-seoul/

(many additional photos available on this website)

2. In your point of view, what’s the finalpurpose of urban storm water management? In order to accomplish this, what parties should be involved and what effort should be devoted?

The final purpose of urban storm water management is to ensure a safe and secure urban environment for all residents – rich, poor, young, old – everyone. It is important that urban development respects and considers its symbiosis with the natural environment. Rapid urban development in many Asian cities has neglected the impact that poorly planned infrastructure has had on the natural environment, and overtime, this neglect is challenging the sustainability of cities. The paving of roads and culverting of urban rivers means that less and less rain water can be reabsorbed in urban areas. As I mentioned before, this increases flood risks downstream, but also threatens the urban water supply and undermines the foundations of buildings through land subsidence;cities around the world, such as Mexico City, Jakarta, and Beijing, are slowly sinking because paved roads prevent water from recharging urban aquifers.

In many cases, poorly planned urbanization and stormwater management practices create an unnecessary burden of poorer communities which cannot absorb the possible physical and economic impacts of floods. For example, land and construction prices may be cheaper in flood- or land slide-prone areas, leading them to live in these areas. In the case of flooding, not only could they lose their home and belongings, but their safety and livelihood could be at risk.

There are three huge obstacles to urban storm water management. One is that flooding does not recognize municipal boundaries, and upstream activities hugely affect downstream communities. This can make it difficult for cities to coordinate with each other and other levels of government on urban development and storm water management infrastructure and practices. Additionally, this can make financing storm water management investments very difficult at the municipal level. Secondly, even within cities, there is often poor coordination between government agencies. The individual activities of many agencies – including environmental protection, emergency management, solid waste management, transport, urban development, and others – can affect a city’s ability cope with flood risk. There are often unclear and overlapping responsibilities as well as a lack of understanding and information sharing between agencies. Finally, there is a lack of political will to improve a problem which isn’t visible every day. Unless a city has recently experienced significant urban floods, urban storm water management is usually low on a government’s agenda – particularly in countries or cities with short political cycles. Many governments prefer to build infrastructure that is visible to its citizens 365 days a year; urban storm water infrastructure is largely underground and its construction can be problematic for traffic and other daily activities of city residents. Unless there is a large rainfall or river flooding event, the investment in hard urban storm water infrastructure will go unnoticed and unappreciated. Urban storm water management requires coordination, financing, comprehensive planning, and a vision at creating a safe and environmentally-friendly urban environment.

3. How can urban construction affect natural cycling of storm water? How to accomplish harmonious management between people and nature?

The type and speed of urban construction can have a huge effect on the natural cycling of storm water. In the People’s Republic of China (PRC), urban planning has frequently not included sufficient storm water provisions. Many cities have developed quickly, with a tendency to expand outward rather than by increasing density. City development increases impervious pavement and decreases storage areas, resulting in increased runoff in urban areas.

Drainage systems that were designed to meet the needs of the original service areas are unable to carry extra storm water runoff from newly paved areas in the catchment area. The increase of storm water from the newly developed areas in upstream areas overloads the existing pipelines downstream, leaving storm water with no place to go.

As cities expand outward, rivers that used to be in rural or peri-urban areas become urban rivers. With this, the water-carrying and storage capacity of these rivers decreases due to siltation and possibly garbage if the city has poor solid waste management, as well as the encroachment of development, namely buildings, highways, and bridges. High intensity land development changes the surrounding natural terrain and topography, and alters the natural flows of river systems, floodplains, and lakes.

This is one reason that the Sponge City concept that is being pursued in the PRC is so important. The Sponge City pilots will hopefully demonstrate that investment in ecologically-designed storm water management practices should be used in all Chinese cities. Known as “Green Infrastructure” or “Low Impact Development” (LID) in Western countries, the basic principle is to minimize the impacts on natural and ecological systems caused the development and construction of artificial systems, such as drainage channels and pumping stations. LID aims to simulate natural ecological conditions through the storage, infiltration, evaporation, retention, and reduction of surface runoff, thereby increasing groundwater replenishment. LID minimizes runoff and nonpoint source pollution (NPS) caused by rainstorms by using decentralized and small-scale source control mechanisms and appropriate technologies. The objective is to maintain, as much as possible, the pre-development conditions of the natural environment and hydrological cycle.

4. In the field of urban storm water management, are there any cities that have made great progress?Are there any useful experiences that we could learn from?

I recently returned from a trip to the Netherlands and I was very impressed by the Dutch experiences in water management. It is well known that the Netherlands has a long history in managing the relationship that their country has with the sea, reclaiming large areas of land through the use of dikes, levees, and the traditional Dutch windmills. What is less widely known is that the country is essentially a large delta for the rivers Meuse, Rhine, and Scheldt. Additionally, over 80% of the population is urban and the country has a high average yearly rainfall rate, making it very important for Dutch cities to manage storm water and river levels to prevent flooding.

Of the cities with the most aspirational approach to their storm water management is Rotterdam. Located in the delta of the Rhine and Meuse Rivers, Rotterdam has taken a very active and holistic approach to managing their vulnerabilities to not only flooding by also the potential climate change impacts. Under most models, climate change will affect not only the frequency, but also the intensity of rainfall events. The impacts of climate change on local weather patterns are already being felt, but few cities have had the political will and resources to plan for the potential impacts. Since 2013, Rotterdam has had its own climate adaptation strategy which required the identification of local vulnerabilities and created a framework for future resilience planning and investments.

Recognizing that the city’s traditional flood defenses as being inadequate for future risks, the city began to access other ways to collect and channel storm water to prevent localized flooding. The interventions in Rotterdam range from small scale – such as supporting the development and planting of green roofs and rainwater harvesting– to large scale, such as the redesigning of their existing dikes to allow for multipurpose uses.

Innovative projects related to reducing flood risks in Rotterdam, such as the Benthemplein water plaza, have gained global recognition among urban planners. Integrating public recreational space, greenery, and water storage, Benthemplein water plaza was the world’s first large-scale water square. A multi-level space with different seating and activity areas, the plaza becomes a water reservoir during heavy rains. Wide gutters collect rain water and funnel it towards the deeper basins of the park for collection. The basins allow for the rainwater to be reabsorbed into the ground over a 24-hour period; in cases of extreme rain events, the water is drained to a nearby water way, thereby reducing the load on Rotterdam’s sewage system.The park with its substantial greenspaces and public spaces for sports and socializing has revitalized the area around it and become popular with local students and residents.

Overall, I think that Rotterdam serves at an excellent example of storm water management for cities in the PRC, not only for their holistic climate-aware approach to risk, but also for the integration of small scale efforts such as green roofs. Every drop of water that is reabsorbed in the city can have an impact on local and downstream flood prevention.

5. When summer comes, the rain increases. Recently, it rained heavily in several cities in China, even hail in some district. The torrent rain is a challenge to the drainage system.Are there any effective strategies in drainage and flood prevention?

One of the significant problems in the PRC is that most cities have only minor, or pipeline drainage systems. In many countries, stormwater systems are typically comprised of both minor and major systems. The minor systems are designed to discharge less intensive rainstorms with a design return period of two to ten years. The minor systems commonly consist of underground pipes and ditches. On the other hand, major systems are designed for severe rainstorms with a design return period of 50 to 100 years. Major systems commonly include bypass tunnels, greenbelts, and roads which are used to handle the runoff which exceeds the capacity of the minor drainage system. In 2012, the Asian Development Bank supported a study with the Ministry of Housing and Urban Rural Development on urban storm water management in the PRC which identified this as being one of the biggest weaknesses of Chinese cities (http://www.adb.org/projects/45512-001/main) . The study identified a number of good examples in Asia such as Kuala Lumpur, and as well as many Western cities.

In Kuala Lumpur, a “Smart Tunnel” was constructed with multiple uses. The tunnel is a three-level structure of 12m diameter. The lower compartment is used for discharging runoff during normal rainstorms. The middle compartment is used for traffic in ordinary times and will be closed and utilized as a drainage tunnel in rainstorm events with a five-year return period and above. The upper deck and the whole tunnel will be fully closed from traffic in case of extreme rainstorms for discharge of stormwater.

Source: http://www.tunnelvisions.eu/projects/nieuwe-pagina/

The PRC has since enforced a number of new regulations which will improve and encourage the construction of urban drainage and urban flood-protection facilities, as well as introducing the sponge-city concept.

6. Recently, are there any new materials, devices, or latest technologies which could improve storm water management dramatically?

Some of the most significant technological advances related to storm water management can be seen in the evolution of permeable pavements. Over the past few years, this field has grown significantly. In the past, permeable pavement signified the placement of stones or pavers with gaps between them to allow water to filter through, which works well on a small scale. Now many permeable pavements are more complex, featuring multiple layers which serve to not only absorb water, but also filter and convey it to swales or other nearby waterways, thereby avoiding the overloading of storm drains and sewers. The variety and complexity of permeable pavements vary, giving developers and governments more options to find options within their budget to fit their design requirements. Permeable paving has been shown to reduce run-off, prevent siltation in water bodies, control pollutants, and allow the root systems of urban trees to coexist thrive within paved areas.

7. Finally, do you have any advice to those who are willing to start their career in storm water management? Or anything you would like to say to the Chinese audience?

For anyone interested in starting a career in storm water management, as well as for the Chinese audience, I would encourage them to educate themselves on the concepts of low impact development and nature-based solutions to urban drainage. Climate change will bring more frequent and potential more intense rainfall, which will surpass the rainfall levels that already cripple Asian cities. Even if cities fail to take action, individuals still have the capacity to do their part by engaging is activities such as rainwater harvesting, green roofs, and low-elevation greenbelts. At the end of the day, many individual actions can make a big difference to prevent urban flooding.

編輯：趙凡