三角洲適應(yīng)性轉(zhuǎn)型
——基于景觀的區(qū)域設(shè)計方法

（荷）斯特芬·奈豪斯 熊亮 （意）丹尼艾勒·坎納特拉

處于城市化進程中的三角洲地區(qū)是世界上最富希望且動態(tài)十足的區(qū)域之一。其在世界生態(tài)系統(tǒng)和全球經(jīng)濟中的地位舉足輕重[1]293,[2]，為水系統(tǒng)主導(dǎo)的多種敏感性環(huán)境中的種群聚集提供了條件。同時，由于集約型城市土地利用和經(jīng)濟活動在敏感性水環(huán)境中難以維持，這些三角洲極其脆弱，面臨多重威脅[3-4]。如果缺乏有效的管治就嘗試維持這些活動，將造成生態(tài)系統(tǒng)的破壞和社會—文化價值的損失，也將削弱三角洲抵御自然災(zāi)害和氣候變化的能力。其結(jié)果將影響三角洲地區(qū)的環(huán)境、經(jīng)濟以及生活在這些水系統(tǒng)中居民的健康和繁榮[5]2-3。

城市化三角洲可視為一系列復(fù)雜社會—生態(tài)系統(tǒng)的集合。這些系統(tǒng)包含的各子系統(tǒng)具有獨立的動態(tài)特征和速率變化（圖1）?？臻g戰(zhàn)略可以保障這類區(qū)域的可持續(xù)發(fā)展，增強其韌性、協(xié)助各系統(tǒng)修復(fù)漏洞，并增強這些系統(tǒng)應(yīng)對自然和人工威脅的能力。這些空間戰(zhàn)略應(yīng)能協(xié)調(diào)各系統(tǒng)間的關(guān)系，減少破壞性的系統(tǒng)間矛盾，例如城市發(fā)展引起的洪澇風險增加。生態(tài)敏感型的城市開發(fā)具有保障經(jīng)濟社會增長的潛力，而空間戰(zhàn)略應(yīng)關(guān)注這方面的潛力，并為增強自然系統(tǒng)和水安全提供契機[5]3-4。同時，其也應(yīng)包含廣泛的社會和經(jīng)濟參與者，以支撐當?shù)氐纳鐣⒔?jīng)濟和文化。有說服力的溝通方式能使這類空間戰(zhàn)略得到廣泛的理解和支持，并產(chǎn)生影響[6-7]。

除了改善三角洲地區(qū)的生存條件之外，空間戰(zhàn)略還能通過應(yīng)對氣候變化來降低氣候相關(guān)的風險等級。為創(chuàng)造更有韌性的三角洲區(qū)域，城市規(guī)劃和管理需要有一定的適應(yīng)能力?？臻g戰(zhàn)略應(yīng)該識別出生態(tài)動力設(shè)計的可能。在這些設(shè)計中，自然與城市的發(fā)展有機會得到整合，確保水安全的適應(yīng)性設(shè)計導(dǎo)則也能得以實現(xiàn)。此外，對空間規(guī)劃、設(shè)計和災(zāi)害管理中的各種轉(zhuǎn)型性過程的整合也十分必要。由此可以改善土地利用、機構(gòu)間協(xié)調(diào)和機制間關(guān)系，促成有效、可持續(xù)和全納的城市發(fā)展[5]6。

1 廣州市琶洲典型的漁村與新城開發(fā)反映了長短期發(fā)展之間的矛盾Confrontations between incremental long-term and fast short-term developments indicated by fisherman villages and new urban development in Pazhou, Guangzhou

2 大部分城市化區(qū)域位于洪澇易泛的低地（+10 m地區(qū)，深藍部分），增加了洪澇風險Most of the urbanization takes place in the flood prone lowland (+10 m zone, indicated in dark blue), which increases the flood risk in PRD

自21世紀以來，在城市化三角洲地區(qū)規(guī)劃設(shè)計領(lǐng)域出現(xiàn)了一系列旨在發(fā)展適應(yīng)性系統(tǒng)的研究。包括荷蘭的萊茵—馬斯—斯海爾德河三角洲[8-9]，美國的密西西比河三角洲[10-11]以及越南的湄公河三角洲[12-13]。研究表明，與傳統(tǒng)規(guī)劃戰(zhàn)略相比，在國土治理中采用城市景觀動態(tài)的視角能獲得更大的潛在收益[1]293-312,[14-15]。本文闡明了在城市化三角洲中，通過基于景觀的區(qū)域設(shè)計實現(xiàn)適應(yīng)性城市轉(zhuǎn)型的方法。對珠江三角洲進行案例分析的同時，也著重闡述這一城市景觀規(guī)劃設(shè)計一體化方法。該方法強調(diào)城市景觀的規(guī)劃和設(shè)計須根據(jù)適應(yīng)性城市轉(zhuǎn)型的要求，對自然和城市動態(tài)的適應(yīng)性節(jié)奏和性質(zhì)進行調(diào)節(jié)[5]6。

適應(yīng)性城市轉(zhuǎn)型采用了基于景觀的區(qū)域設(shè)計方法，將其作為整合性、多尺度的規(guī)劃設(shè)計途徑。如此可以結(jié)合多部門活動，促進城市和鄉(xiāng)村多種轉(zhuǎn)型性過程的發(fā)展，以取得更協(xié)調(diào)的可持續(xù)性成果?；诰坝^的區(qū)域設(shè)計是塑造區(qū)域形態(tài)的重要戰(zhàn)略，其以景觀為基礎(chǔ)產(chǎn)生可持續(xù)的城市化三角洲，也通過空間規(guī)劃和設(shè)計為長期可持續(xù)的城市景觀發(fā)展提供途徑。一言以蔽之，區(qū)域設(shè)計是一種跨學(xué)科的嘗試，不但保障可持續(xù)和連續(xù)性發(fā)展，也指導(dǎo)和塑造由社會—經(jīng)濟和環(huán)境過程引起的改變，同時通過有形的關(guān)系為區(qū)域建立當?shù)靥厣玔16]43-46。

1 珠江三角洲

在過去40年間，珠江三角洲（簡稱珠三角）是世界上發(fā)展最快速的三角洲地區(qū)。2014年，其超越東京灣地區(qū)，成為世界上面積最大、人口最多的城市區(qū)域[17]。20世紀80年代起，珠三角一直處于中國城市化和社會經(jīng)濟轉(zhuǎn)型改革的前沿陣地[18]。然而，由于氣候變化和環(huán)境惡化，珠三角的遠期經(jīng)濟發(fā)展需要應(yīng)對巨大挑戰(zhàn)，包括紅樹林生態(tài)系統(tǒng)消失[19]、農(nóng)田流失[20]、空氣和水污染[21]、水資源短缺[22]、社會治安問題[23]等。

一方面，由于洪澇易泛區(qū)的城市化（圖2），使珠三角暴露在持續(xù)增長的洪水風險之中。海平面的持續(xù)上升、夏季臺風等極端性熱帶風暴的加劇對區(qū)域內(nèi)的基礎(chǔ)設(shè)施持續(xù)施壓。另一方面，珠三角的生態(tài)系統(tǒng)日趨破碎和脆弱[24]，表現(xiàn)為生態(tài)系統(tǒng)服務(wù)[25]和環(huán)境承載力[26]的降低。宏觀尺度的干預(yù)使千篇一律的單一性空間在微觀尺度上取代了多樣的歷史性環(huán)境和文化遺產(chǎn)[27]。雖然有關(guān)部門積極推進一體化規(guī)劃設(shè)計方法，但仍未進行大范圍的有效施行[28]。例如“海綿城市”的建設(shè)難點之一就是整合不同部門之間的多種規(guī)劃[29]。

為了珠三角的可持續(xù)發(fā)展，急需在其城市發(fā)展中采用新的規(guī)劃設(shè)計方法。針對經(jīng)濟發(fā)展和環(huán)境修復(fù)之間的矛盾，以及氣候變化帶來的相關(guān)風險，區(qū)域設(shè)計提供了一種解決之道，即發(fā)展基于景觀的概念和實踐。珠三角的高速發(fā)展使其成為一個尤有價值的案例，在此案例中可以探索和驗證這些更具適應(yīng)性的整體規(guī)劃方法的潛力，而基于景觀的區(qū)域設(shè)計就是這類整體規(guī)劃方法中的一種。

3 基于景觀的區(qū)域設(shè)計的4個重要階段Four important phases in landscape-based regional design

4 將城市景觀理解為分層的復(fù)雜系統(tǒng)Understanding the urban landscape as a layered and complex system

5 公元前4000年至2015年珠江三角洲景觀的形成Landscape formation of the PRD from 4000 BC to AD 2015

2 基于景觀的區(qū)域設(shè)計

基于景觀的區(qū)域設(shè)計將城市景觀視為全納性的動態(tài)復(fù)雜系統(tǒng)。在此視角下，空間發(fā)展通過生態(tài)區(qū)域的規(guī)劃導(dǎo)則和設(shè)計導(dǎo)則的實施得以實現(xiàn)。這一方法建立在查爾斯·埃里奧特（Charles Eliot）[30]、沃倫·曼寧（Waren Maning）[31]、彼得·維爾哈亨（Pieter Verhagen）[32]、帕特里克·阿伯克羅姆比（Patrick Abercrombie）[33]、弗里茨·舒馬赫（Fritz Schumacher）[34]、伊恩·麥克哈格（Ian McHarg）[35]、菲利普·劉易斯（Philip Lewis）[36]等人的觀點和實踐之上。

區(qū)域設(shè)計采用風景園林、景觀生態(tài)學(xué)、地理學(xué)和建筑學(xué)的原則進行空間導(dǎo)向的研究、設(shè)計和規(guī)劃。同時也利用系統(tǒng)思維和復(fù)雜理論推進更綜合的區(qū)域規(guī)劃設(shè)計，以涵蓋構(gòu)成城市景觀的各種復(fù)雜關(guān)系網(wǎng)絡(luò)[37]13-34?；谶@些目的，區(qū)域設(shè)計為城市轉(zhuǎn)型、生態(tài)多樣性保護、水資源管理、休閑游憩、社區(qū)建設(shè)、文化認同和經(jīng)濟發(fā)展提供了一種模式[38]。

基于景觀的區(qū)域設(shè)計包含2個部分：戰(zhàn)略和干預(yù)。前者辨識并引領(lǐng)對區(qū)域可持續(xù)增長最有利的場所、功能、尺度和相互關(guān)系，后者在微觀尺度創(chuàng)造積極條件[37]22。區(qū)域設(shè)計根據(jù)自然和城市景觀生理和功能塑造區(qū)域的物理形態(tài)，并致力為未來發(fā)展創(chuàng)造條件。這種方法能在區(qū)域到地方之間的不同尺度運作，也能由普遍到特殊，既保持整體連續(xù)性又兼顧局部偶然性。它在各類國土之間提供了多種方式以平衡服務(wù)與質(zhì)量間的關(guān)系[39]。

區(qū)域設(shè)計是著眼于保護和開發(fā)各種資源的開放戰(zhàn)略。通過景觀規(guī)劃和設(shè)計的方式，為空間發(fā)展指導(dǎo)開發(fā)過程并創(chuàng)造前景條件[37]25。區(qū)域設(shè)計也設(shè)置了穩(wěn)健且適應(yīng)能力強的系統(tǒng)，這些系統(tǒng)既有韌性也能根據(jù)變化進行調(diào)整。區(qū)域設(shè)計的組織結(jié)構(gòu)是以水系統(tǒng)和交通系統(tǒng)為代表的“強健”且聯(lián)通的結(jié)構(gòu)，這些組織結(jié)構(gòu)能夠支持區(qū)域發(fā)展，融入當?shù)貙嶋H，經(jīng)受各種挑戰(zhàn)，也足以靈活地邁向未來[40]。

由于這種基于景觀的區(qū)域設(shè)計承認城市肌理的集體性，并允許各類“作者”參與創(chuàng)作，使其成為一種社會全納性的設(shè)計方法[41]，為利益相關(guān)方和其他參與者指明了方向，使各方得以同心協(xié)力。由此，基于景觀的區(qū)域設(shè)計成為一項跨學(xué)科的任務(wù)，工程專業(yè)和生態(tài)專業(yè)通過空間設(shè)計思維在此整合，本地居民的想法和知識也得到重視。因此，區(qū)域設(shè)計可以根據(jù)各要素的時空尺度特征，對自然環(huán)境、個體及信息、治理及其相互關(guān)系進行跨越時空尺度的組織[16]43-46。

基于景觀的區(qū)域設(shè)計的核心是研究與設(shè)計的緊密互動。研究的分析能力與設(shè)計的探索能力密切相關(guān)。在設(shè)計前期，設(shè)計通常會借助一些研究形式來獲得針對空間問題的基本方向和手段，而在這種方法中，設(shè)計過程本身作為視覺化空間問題的推動者，探索多種可能性，生成多樣的解決方案。因此，結(jié)合設(shè)計的研究被視為有力的研究戰(zhàn)略，通過創(chuàng)新型整體化方式來解決復(fù)雜的空間問題。這種目標明確的求索過程是區(qū)域設(shè)計的中心，思考和創(chuàng)作在此攜手并進。研究和設(shè)計的各種機制中融入了想象、創(chuàng)造和創(chuàng)新，結(jié)合設(shè)計的研究將這些機制一一實現(xiàn)。其也可作為通過行動、觀察和求索而獲得洞見的理解方式。因此，圖析和繪圖成為視覺思考和溝通的重要工具[42]。

6 珠三角生態(tài)—農(nóng)業(yè)系統(tǒng)圖The eco-agricultural system of the PRD

3 區(qū)域設(shè)計過程的關(guān)鍵階段

基于景觀的區(qū)域設(shè)計過程包含至少4個迭代階段：收集信息、獲得理解、規(guī)劃發(fā)展和行動展望（圖3）[43]。

3.1 收集信息和獲得理解

在設(shè)計過程開始之前，需要在對場地挑戰(zhàn)和潛力的充分理解之上確立區(qū)域戰(zhàn)略的目標。這不僅意味著收集、創(chuàng)造數(shù)據(jù)及信息，也意味著在多尺度上對區(qū)域進行分析和評價，后者還包括識別利益相關(guān)方。該階段的問題包括：1）一個地區(qū)如何在微觀和宏觀尺度上運作；2）在不同尺度上有哪些決定區(qū)域的空間—視覺、歷史、社會及生態(tài)結(jié)構(gòu)和過程；3）城市和自然各系統(tǒng)如何運轉(zhuǎn)。

上述問題的答案揭示了對設(shè)計要素的描述、選擇和評價，并涵蓋了綜合性城市景觀規(guī)劃設(shè)計中的各個方面。在此過程中，通過設(shè)計者獨自對信息進行解讀、合成和應(yīng)用，數(shù)據(jù)被轉(zhuǎn)化為知識。在該過程中，設(shè)計者通過對數(shù)據(jù)和信息的探索、分析和合成，增進了對區(qū)域（各方面）在空間關(guān)系、結(jié)構(gòu)和格局的理解程度。理解（洞見）是基于評價的認知，使知識提升效益，增加價值[44]。借助理解，設(shè)計者可識別國土的主要挑戰(zhàn)和機遇，并勾勒出多種未來走向。設(shè)計過程不應(yīng)該局限于聽取專家咨詢，也應(yīng)通過交互工作坊、訪談、觀察和問卷等形式，采納政府官員和當?shù)鼐用竦绕渌嫦嚓P(guān)方的意見。

3.2 規(guī)劃發(fā)展和行動展望

在分析和評價階段結(jié)束后，區(qū)域設(shè)計的主要挑戰(zhàn)和機遇已經(jīng)確定，繼而是發(fā)展和探索眾多整體性、多尺度的設(shè)計戰(zhàn)略和導(dǎo)則，尤其需要關(guān)注這些戰(zhàn)略和導(dǎo)則的潛力。需要解答的問題如下：1）如何應(yīng)對該地區(qū)的挑戰(zhàn)；2）如何通過多個尺度上的眾多項目來開發(fā)區(qū)域的潛能；3）在區(qū)域尺度上有哪些需要注明和整體協(xié)調(diào)的空間關(guān)鍵結(jié)構(gòu)和過程；4）在區(qū)域尺度上有哪些戰(zhàn)略點，可安排哪些對其有利的條件；5）這些戰(zhàn)略點和有利條件如何與區(qū)域內(nèi)進行中的項目相聯(lián)系；6）哪些重要的利益相關(guān)方能夠保障社會經(jīng)濟和生態(tài)的扎根；7）是否具有借鑒意義的國際先例；8）如何使長期戰(zhàn)略和短期設(shè)計干預(yù)互相關(guān)聯(lián)、彼此扶持。

7 珠三角基礎(chǔ)設(shè)施系統(tǒng)圖A map summarizing the infrastructural system of the PRD

解答此類問題所采取的重要方式包括：先例研究、愿景建設(shè)、結(jié)合設(shè)計的研究等。設(shè)計性思維對探索設(shè)計戰(zhàn)略和導(dǎo)則在空間上應(yīng)用的可能性大有裨益。這部分的關(guān)鍵包括創(chuàng)新、創(chuàng)造和想象。設(shè)計戰(zhàn)略和導(dǎo)則通過視覺化方式探索，其可行性由設(shè)計師、專家和利益相關(guān)方評價。計算機模型、現(xiàn)場試驗、模擬等都是這個過程的組成部分，尤其是涉及產(chǎn)生觀點、視覺化和測試的時候。該步驟涉及的問題包括：1）有哪些有用的空間規(guī)劃設(shè)計戰(zhàn)略和導(dǎo)則；2）這些戰(zhàn)略和導(dǎo)則如何在區(qū)域應(yīng)用，可能的結(jié)果如何；3）在空間、社會和生態(tài)視角上，有哪些優(yōu)化方案；4）是否能在設(shè)計中包含某些歷史層面；5）如何使規(guī)劃適應(yīng)并增強區(qū)域的認知度；6）設(shè)計能否在長時間內(nèi)進行變更并具備靈活度；7）如何構(gòu)成土地利用格局、植被、水、城市類型和其他要素，使其能夠促進生態(tài)系統(tǒng)服務(wù)及文化表達。

區(qū)域設(shè)計不僅僅通過規(guī)劃和設(shè)計技巧來優(yōu)化、整合和組織物理結(jié)構(gòu)，也體現(xiàn)了相關(guān)部門政策發(fā)展下的長期戰(zhàn)略。通常需要在政府治理上做出新的配置來為區(qū)域設(shè)計創(chuàng)造條件，例如開發(fā)一系列微觀項目。因此在規(guī)劃早期，納入相關(guān)決策者、政府部門和其他利益相關(guān)方就顯得十分重要。

4 理解珠三角：一個復(fù)雜系統(tǒng)

珠三角的城市景觀可以理解為一個復(fù)雜系統(tǒng)，其包含著多個子系統(tǒng)，各子系統(tǒng)具有獨立的動態(tài)特征和速率變化[14]160-191。作為一個系統(tǒng)，城市景觀是在網(wǎng)絡(luò)和場所的交織中形成的物質(zhì)空間，其中的網(wǎng)絡(luò)和場所所屬的組織層次繁多，具有顯著的時空維度[45-47]。長時段（longue durée）的概念在此十分必要，因為其將城市景觀視為一種持續(xù)變化的長期性結(jié)構(gòu)。第一級動態(tài)與自然環(huán)境相連，其特征是幾乎難以覺察的慢速過程，包括轉(zhuǎn)型、重復(fù)和自然演替等；第二級動態(tài)與長期社會、經(jīng)濟和文化歷史相連；第三級動態(tài)則是短期的人類和政治事件[48]。簡而言之，在生態(tài)、社會文化和政治因素影響下，自然與人類在結(jié)構(gòu)、格局和過程等層面進行持續(xù)不斷的相互作用，進而產(chǎn)生了不斷發(fā)展的城市景觀。

4.1 圖析景觀系統(tǒng)

圖析（mapping）是制圖探索，可用于研究自然與人類互動所產(chǎn)生的空間關(guān)系，識別重要條件、關(guān)鍵驅(qū)動力和各顯著性動態(tài)帶來的影響。這種對景觀系統(tǒng)進行的圖析與麥克哈格[49]倡導(dǎo)的可持續(xù)性地圖有所分別。圖析著重于理解眾多空間關(guān)系及動態(tài)的變化，這些關(guān)于空間條件的知識并不一定能推導(dǎo)出適建地區(qū)，但是能夠協(xié)助形成適應(yīng)性規(guī)劃戰(zhàn)略和設(shè)計導(dǎo)則。根據(jù)動態(tài)的變化對城市景觀進行逐層分解是理解城市景觀系統(tǒng)的有效方法[50]10-22（圖4）。低速動態(tài)變化的層面是基質(zhì)（如地形、水文、土壤）和氣候（如降水類型、溫度、風）。這些環(huán)境條件對土地利用最具影響力，因此稱為第一級條件。位于中速動態(tài)變化層面中的第二級條件包括交通、水利、能源等基礎(chǔ)設(shè)施網(wǎng)絡(luò)，這些條件對土地利用影響顯著。相對于一級條件，二級條件的增長和變化更快，為農(nóng)業(yè)土地利用和城市定居鋪平了道路，產(chǎn)生了高速動態(tài)變化轉(zhuǎn)型的層面[50]19。

4.2 圖析珠三角的自然和城市系統(tǒng)

為了理解珠三角的自然和城市系統(tǒng)，本文筆者制作了一組地圖以掌握國土各動態(tài)層面、自然和城市系統(tǒng)及其相互作用。總結(jié)了描繪珠三角特征的主要物理結(jié)構(gòu)和格局，包括生態(tài)-農(nóng)業(yè)系統(tǒng)、城市系統(tǒng)、基礎(chǔ)設(shè)施網(wǎng)絡(luò)和城市肌理及其相互關(guān)系。

8 1950—2015年城市發(fā)展Urban development from 1950 to 2015

9 珠三角城市肌理結(jié)構(gòu)圖A map summarizing the structure of the urban tissue in the PRD

自然系統(tǒng)取決于氣候、地貌、水和巖型。這些自然要素驅(qū)動土壤形成，確定水文，生態(tài)系統(tǒng)、農(nóng)業(yè)土地利用、歷史聚落和城市的分布。珠三角可根據(jù)地貌特征分為2個部分：西部是經(jīng)歷數(shù)千年來淤積和沉積過程形成的河控型三角洲，東部河口則為潮控型三角洲（圖5）[51]156，珠三角80%以上的土地是平原，有160余個島丘，另有187個島嶼分布在近海[51]155。其三角洲低地的特點是2個次級三角洲和一個潮控河口。西江、北江和東江主導(dǎo)著珠三角，其流域面積453 690 km2，干流總長2 200 km。西江是最重要的水沙來源（占80%徑流量和90%輸沙量）。西江和北江次級三角洲的洪水期在4—9月。7—9月間，河口區(qū)域受到臺風等熱帶風暴所帶來的風暴潮威脅。

珠三角濕潤平坦，這樣的自然氣候和地理條件是濕地生態(tài)、城市發(fā)展和農(nóng)業(yè)生產(chǎn)的重要基礎(chǔ)。此地的農(nóng)業(yè)活動可以追溯到4 000多年以前。在這個由頻繁的洪水和持續(xù)的泥沙沉積所形成的不斷變化的濕地環(huán)境中，人與自然形成了可持續(xù)發(fā)展的關(guān)系[52-53]。濕潤和平坦的地形特征使當?shù)鼐用窠?jīng)過長年累月形成了一套復(fù)雜的多尺度水敏性途徑——種植業(yè)與水產(chǎn)養(yǎng)殖相結(jié)合。該途徑長久以來作為當?shù)亟?jīng)濟生產(chǎn)的基礎(chǔ)。其中最值得一提的是產(chǎn)生于14世紀的次級三角洲中的基塘系統(tǒng)：四周堤圍種果樹，中間水塘養(yǎng)魚[54]。17世紀早期，這種模式發(fā)生改變，桑樹和四大家魚的組合振興了當?shù)氐慕z綢和漁業(yè)經(jīng)濟。從此，這種種植業(yè)與水產(chǎn)養(yǎng)殖業(yè)結(jié)合的模式延續(xù)到了20世紀20年代[55]。如今，大部分種植業(yè)與水產(chǎn)養(yǎng)殖業(yè)結(jié)合地區(qū)發(fā)生了轉(zhuǎn)化，或成為單一的漁業(yè)養(yǎng)殖，或成為工業(yè)片區(qū)和城市。

珠三角的自然植被由重要的海灣帶和河岸帶主導(dǎo)，在這些區(qū)域中包括了多種紅樹林、濕地和濕潤森林類型。在山區(qū)以多種干旱森林類型為主，一些地區(qū)的原生植被遭到砍伐，并在近期得到再植。坡腳地區(qū)擁有能夠提供淡水和灌溉的淡水集水區(qū)（圖6）。

該區(qū)域在各歷史時期非常依賴水上交通。從20世紀50年代起，土地所有權(quán)從私有變?yōu)閲谢蚣w所有，這使得珠三角在區(qū)域尺度發(fā)展基礎(chǔ)設(shè)施成為可能。大尺度堤圍的改造[51]156、（高速）鐵路網(wǎng)絡(luò)的鋪開和公路里程的持續(xù)增長成為城市快速擴張的重要條件。在廣州—深圳（香港）和廣州—珠海（澳門）的廊道上均有優(yōu)良的公路鐵路基礎(chǔ)設(shè)施。重要的交通樞紐包括香港和南沙的海港，以及香港和廣州的空港（圖7）。

包括廣州、佛山和澳門等在內(nèi)的歷史名城可以追溯到2 000多年之前。以廣州為例，考古發(fā)現(xiàn)的規(guī)?？捎^的王宮御苑，展示了南越國在公元前約203年左右豐富的文化[56]。值得一提的是，廣東省的嶺南園林和傳統(tǒng)建筑適應(yīng)了特殊的氣候條件，在選址、朝向、布局和實際建造方面都主動營造微氣候。由于戰(zhàn)略和交通原因，這些歷史城市的核心地區(qū)都與河流和海洋相連。

自20世紀50年代起，歷史城市開始受到基礎(chǔ)設(shè)施建設(shè)的影響。從20世紀80年代起，中國在珠三角建立特別經(jīng)濟區(qū)以吸引外資，珠三角也開始成為世界上城市化最快速的三角洲區(qū)域（圖8）[50]。該區(qū)域在關(guān)稅、金融和稅收上獲得了一定程度的自主權(quán)。制造業(yè)公司開設(shè)工廠，創(chuàng)造了富有活力的經(jīng)濟區(qū)域。在城市化過程中，大面積的圩田地區(qū)由農(nóng)業(yè)用地轉(zhuǎn)為城市用地。根據(jù)廣東省2016統(tǒng)計年鑒，珠三角擁有6 000萬人口，并將在2030年增長到8 000萬。

城市發(fā)展的空間模式因地而異。北部的城市化呈現(xiàn)出圍繞歷史城鎮(zhèn)中心的同心圓模式。東部的城市化以線性模式沿著海岸線發(fā)展并受山脊限制。西部由圩田城市化產(chǎn)生了分散模式。目前城市化集中于廣州—深圳的城市廊道，南沙作為連接口岸具有重要的地位（圖9）。

綜合圖（圖10）展示了在環(huán)境條件（如基質(zhì)和氣候）和基礎(chǔ)設(shè)施網(wǎng)絡(luò)（交通、水管理和能源）相互作用下的城市景觀。這些條件為農(nóng)業(yè)用地和城市定居點的發(fā)展鋪平了道路，而后者則帶來了最高級別的變化和轉(zhuǎn)型動態(tài)層面。然而，快節(jié)奏的城市化與氣候變化在城市中產(chǎn)生了嚴重問題。除了海平面上升之外，臺風引起的空前風暴潮和增長的河流徑流量導(dǎo)致了城市區(qū)域頻繁的洪澇。渠化的河流失去蓄洪空間，水安全受到威脅。相當一部分農(nóng)業(yè)用地轉(zhuǎn)型成工業(yè)用地及城市區(qū)域，失去了調(diào)蓄雨水的能力。原生紅樹林的消失使得海岸線更易遭受洪水威脅。除了洪澇之外，珠三角還遭受著一系列威脅：流失的生態(tài)和文化—歷史價值、地層下陷、咸潮入侵、用于食物生產(chǎn)的農(nóng)業(yè)用地流失，以及眾多社會—經(jīng)濟問題等。

5 邁向珠三角可持續(xù)發(fā)展的未來

基于景觀的區(qū)域戰(zhàn)略，以適應(yīng)性城市轉(zhuǎn)型作為基礎(chǔ)來正視珠三角的主要挑戰(zhàn)和潛力。在這種戰(zhàn)略中，針對從多系統(tǒng)分析中提煉出的多種自然和城市動態(tài)，必須調(diào)節(jié)其適應(yīng)性的節(jié)奏和性質(zhì)。規(guī)劃發(fā)展和行動展望將聚焦在尺度的角度以連接經(jīng)濟和生態(tài)發(fā)展的潛力，使規(guī)劃得以順利開展。目標是為舊工業(yè)（居住區(qū)）和受到建成區(qū)擴張限制之下的區(qū)域農(nóng)業(yè)景觀提供可持續(xù)的轉(zhuǎn)型，使其能夠容納經(jīng)濟和人口的增長。這些地區(qū)具有特別的空間條件，適于長期的經(jīng)濟發(fā)展。與此同時，這些地區(qū)通常位于三角洲河口的新圍墾之地，該地河網(wǎng)密集，魚塘密布，濕地和農(nóng)業(yè)為高敏感的生態(tài)系統(tǒng)，易受洪澇威脅。在這一階段識別出區(qū)域藍綠基礎(chǔ)設(shè)施和城市級水網(wǎng)的發(fā)展可能性，以提升區(qū)域的適應(yīng)能力、生態(tài)系統(tǒng)服務(wù)功能和水安全。

10 珠三角城市景觀The urban landscape of the PRD

5.1 愿景研究

筆者進行了愿景研究來調(diào)查珠三角可能的未來發(fā)展。通過結(jié)合現(xiàn)實和想象，識別關(guān)鍵位置、驅(qū)動力和未來事件的預(yù)期影響，這些既是機遇，也是挑戰(zhàn)（圖11）[1]293-312。愿景作為有用的工具，可以解決未來發(fā)展趨勢的不確定性，并理解各種發(fā)展趨勢及其之間的聯(lián)系、新的挑戰(zhàn)和政策以及政策成效，也能建立并促進各利益相關(guān)方參與戰(zhàn)略性對話[57],[58]11-13。目前為止各種愿景都是在學(xué)術(shù)環(huán)境下制定的，政府機構(gòu)和水務(wù)局也包含在內(nèi)。愿景的完善需借助制定假設(shè)集合的方式。這個包含多條假設(shè)條件的集合根據(jù)已發(fā)現(xiàn)的各種主要相互作用關(guān)系而制定，且必須自洽和自相干。在這些假設(shè)之上，可以依據(jù)現(xiàn)有愿景系統(tǒng)地進行選擇性描述，并識別決定空間發(fā)展走向的最顯著外部變量[58]11-13。

11 探索珠三角空間發(fā)展的未來愿景Exploring future scenarios for the spatial development of the PRD

12 使用電腦制圖桌共同思考珠三角的未來Thinking together about the future of the PRD using a digital map table

5.2 發(fā)展區(qū)域的戰(zhàn)略視野

珠三角戰(zhàn)略視野的雛形由主導(dǎo)未來發(fā)展的因素決定，這些因素通過2種評價相結(jié)合：1）隨時間推移的城市景觀增長評價，2）區(qū)域現(xiàn)有空間發(fā)展項目評價。這個戰(zhàn)略視野需要根據(jù)以下基本設(shè)想進一步深化：珠三角將成為中國的硅谷，擁有交通便捷的城市品質(zhì)，健全的藍綠框架，鄉(xiāng)土的文化—歷史資產(chǎn)，以及水敏型社會—生態(tài)全納的城市性。根據(jù)東翼（廣州—香港一線）現(xiàn)有規(guī)劃，珠三角將繼續(xù)發(fā)展成為連接通達的“紅—綠項鏈”，山海之間將形成強有力的城市口岸和港口以及健全的綠色廊道。西翼則將受益于濕潤平原的特征，發(fā)展成結(jié)合水敏性生態(tài)農(nóng)業(yè)—水產(chǎn)業(yè)和蓄洪區(qū)域的藍色軸線，并以交通導(dǎo)向發(fā)展形成的強健的城市口岸為補充。

5.3 轉(zhuǎn)型視角

區(qū)域戰(zhàn)略視野主要用于確定空間規(guī)劃設(shè)計中的優(yōu)先權(quán)。通過返測（back casting）識別空間轉(zhuǎn)型視角，以協(xié)助完成由戰(zhàn)略規(guī)劃設(shè)定和引導(dǎo)的目標。空間轉(zhuǎn)型視角提供了一套適應(yīng)性設(shè)計戰(zhàn)略，這套戰(zhàn)略是根據(jù)珠三角2個次級三角洲和1個河口的國土上的挑戰(zhàn)和潛力定制而成。每一個轉(zhuǎn)型的視野具有以下視野之一：水敏和社會—生態(tài)全納、多時空尺度下的靈活和多功能。在2個次級三角洲上，轉(zhuǎn)型視野與河流和雨水適應(yīng)性途徑相聯(lián)接。其包含以下設(shè)計導(dǎo)則：韌性河流設(shè)計；農(nóng)業(yè)—水產(chǎn)養(yǎng)殖業(yè)一體化；可持續(xù)城市轉(zhuǎn)型；新城區(qū)、歷史村落整合；工業(yè)轉(zhuǎn)型和生態(tài)旅游等。在河口上，轉(zhuǎn)型視野主要與海水適應(yīng)性途徑相連接。其包含以下設(shè)計導(dǎo)則：多功能防洪；港口和碼頭發(fā)展；圍墾（沉積與侵蝕）；水岸發(fā)展和轉(zhuǎn)型以及紅樹林和其他海岸生態(tài)系統(tǒng)的保護及開發(fā)。

各項轉(zhuǎn)型視角均須深化。設(shè)計導(dǎo)則需要通過對相關(guān)成功國際案例的研究而形成。此外，它們的潛在需求須通過研究結(jié)合設(shè)計的過程來探索。這些設(shè)計導(dǎo)則的可能性可以通過空間和視覺的方式以戰(zhàn)略性地區(qū)作為實驗場進行測試。讀者可在孫傳致等[59]一文中了解農(nóng)業(yè)—水產(chǎn)養(yǎng)殖業(yè)一體化這一設(shè)計導(dǎo)則在珠三角多尺度水敏性設(shè)計中的深化。

5.4 行動展望

為了將獲取的知識和想法轉(zhuǎn)化成行動，需要為新型治理創(chuàng)造條件。因此區(qū)域設(shè)計將猜想也包含在內(nèi)，以促成各利益相關(guān)方之間的互動，完成合作、共同設(shè)計和微調(diào)設(shè)計的過程。如上所述，2種評價對區(qū)域設(shè)計過程至關(guān)重要，包括針對現(xiàn)有城市規(guī)劃戰(zhàn)略和項目的建成后評價，以及針對潛在適應(yīng)性戰(zhàn)略愿景的預(yù)評價。區(qū)域設(shè)計過程必須通過這2種評價，理解城市景觀各動態(tài)并促進其轉(zhuǎn)型[5]3-4。交流是將本地利益相關(guān)方和決策者納入的核心，因此發(fā)展和利用創(chuàng)新型視覺化方法和工具十分關(guān)鍵。針對利益相關(guān)方的訪談和工作坊貫穿于整個過程之中，以探討達成共識的可能性。在工作坊中，利益相關(guān)方圍繞在電腦制圖桌周圍理解各系統(tǒng)的相互關(guān)系（圖12）。除了電腦制圖桌外，其他視覺化手段還包括增強現(xiàn)實技術(shù)和虛擬現(xiàn)實技術(shù)[60]。參與者可以看到其行為在其他系統(tǒng)上可能產(chǎn)生的影響。這些創(chuàng)新型的視覺化手段大大加速了所有利益相關(guān)方關(guān)于各種提議的討論，并將進一步發(fā)展區(qū)域視野和相關(guān)戰(zhàn)略。轉(zhuǎn)型視野將引領(lǐng)三角洲的發(fā)展，使其通向更可持續(xù)的前景。

6 結(jié)語

綜上所述，珠三角的城市景觀是多種過程和系統(tǒng)的產(chǎn)物，這些過程和系統(tǒng)擁有不同的變化動態(tài)且相互影響。相互連接系統(tǒng)及其外在形態(tài)是當今區(qū)域發(fā)展的基礎(chǔ)之一。因此，通過空間設(shè)計將系統(tǒng)聯(lián)系起來的能力變得愈發(fā)重要。

在珠三角的適應(yīng)性轉(zhuǎn)型中，我們提倡將基于景觀的區(qū)域設(shè)計作為一種全納性的規(guī)劃設(shè)計方法。本文不僅描述了其結(jié)果，也闡釋了這一方法。在挑戰(zhàn)接踵而至的時代，此類方法的提出使不同的理解方式、社會—生態(tài)全納性設(shè)計過程以及不同學(xué)科和利益相關(guān)方的合作模式成為可能。基于景觀的區(qū)域設(shè)計促進了設(shè)計學(xué)科間的合作，如建筑、城市規(guī)劃和風景園林等，也通過塑造建成環(huán)境來檢視空間設(shè)計的效果。此外，這種全納性的設(shè)計方法得以建立多對關(guān)系，如生態(tài)與文化、過程與形態(tài)、長期發(fā)展與短期發(fā)展、區(qū)域戰(zhàn)略與本地干預(yù)等。因此，基于景觀的區(qū)域設(shè)計是指導(dǎo)國土轉(zhuǎn)型強有力的媒介，是其兼顧本地認同的產(chǎn)生和區(qū)域關(guān)系的保障，同時將生態(tài)、社會過程與城市形態(tài)聯(lián)系起來。

在這種思路下，基于景觀的區(qū)域設(shè)計提供了新的運作能力，使空間設(shè)計成為一種整體性的創(chuàng)意行為，也將區(qū)域城市景觀作為重要的探索領(lǐng)域。在此之中的探索由文脈而驅(qū)動，以方案為焦點，并且跨越學(xué)科。

致謝：

感謝格利高里·布拉肯博士所作的英文編輯。

圖片來源：

圖1由謝光源攝；圖2基于SRTM（30 m）和Hydropolis由斯特芬·奈豪斯繪；圖3來源于參考文獻[37]；圖4由斯特芬·奈豪斯繪；圖5、8來源于參考文獻[50]；圖6、7、9、10由斯特芬·奈豪斯、丹尼艾勒·坎納特拉、熊亮繪，數(shù)據(jù)來源于SRTM（30 m）、Hydropolis、谷歌地圖、百度地圖、開放街道圖（OSM，2018.4），其中土地利用數(shù)據(jù)源于世界生態(tài)土地單位地圖（250 m，WorldELU，2015）、Globeland30（2010）、港口數(shù)據(jù)源于世界港口指數(shù)數(shù)據(jù)庫（WPI，2018.4），老城區(qū)數(shù)據(jù)源于參考文獻[50]；圖11、12由斯特芬·奈豪斯攝。

Urbanizing deltas are among the most promising and dynamic regions of the world.They play a significant role in both the world’s ecosystems and the global economy[1]293,[2]. They accommodate large concentrations of population in particularly sensitive environments that are dominated by water systems. As a result, these deltas face extreme vulnerability and multiple threats[3-4]. This is because the intensification of urban land use and economic activity within a sensitive water environment is a difficult situation to manage. In the absence of effective governance,the outcomes of this management are often a combination of ecosystem damage and the loss of socio-cultural values. This weakens the capacity of deltas to resist natural hazards, and the risks associated with climate change. These effects have consequences for the environment, the economy of the deltas, and the health and prosperity of citizens that live around these water systems[5]2-3.

Urbanizing deltas can be understood as a set of complex social-ecological systems and subsystems, each with their own dynamics and speed of change (Fig. 1). To ensure a more sustainable future, spatial strategies are needed in order to strengthen resilience, assist systems to cope with their vulnerabilities, and strengthen their capacity to face natural and human-made threats. These strategies will need to address the interrelation of systems by helping to avoid damaging contradictions,such as when urban development increases the risk of flooding. Strategies like these can draw attention to the potential of ecologically sensitive urban development that ensures economic and social growth, while also providing opportunities for the strengthening of natural systems and water safety[5]3-4. Concurrently, a spatial strategy such as this must involve a wide range of social and economic actors, while also supporting the social, economic,and cultural conditions of the local inhabitants.These strategies should be communicated in ways that are persuasive so that they may gain wide understanding, support, and influence[6-7].

At the same time, it is not only necessary for these strategies to improve the living conditions within urban deltas, but to also adapt to climate change in order to decrease the risk level of these areas. The urban planning and management necessary to create more resilient deltas require a certain degree of adaptive capacity. Their strategies must also identify eco-dynamic design options that not only provides opportunities for the integration of nature alongside urban development processes, but also implements adaptive design principles that ensure water safety.In addition to this, there is a need to integrate transformative processes in governance that combine spatial planning, design, and disaster management.Doing so will allow for the optimization of landuse, institutions, and mechanisms for an efficient,sustainable, and inclusive urbanization[5]6.

From the 2000s onwards, there have been serious attempts to develop an adaptive systems approach towards the planning and designing of urbanizing deltas. Examples of these attempts include the Rhine-Meuse-Scheldt (RMS) Delta in the Netherlands[8-9], the Mississippi River Delta in the United States[10-11]and the Mekong Delta in Vietnam[12-13]. This paper and the related research suggests that there is a much greater potential benefit in using urban landscape dynamics in territorial governance, as opposed to more traditional planning strategies[1]293-312,[14-15].The paper also elaborates on a landscape-based regional design approach for an adaptive urban transformation of the urbanizing deltas. It not only uses the Pearl River Delta as an example of this, but also focuses on the description of the approach itself. Therefore, this paper outlines an integrative approach towards the planning and designing of urban landscapes, where natural and urban dynamics must set both the pace and nature of adaptation required for adaptive urban transformation (AUT)[5]6.

AUT employs landscape-based regional design methods as an integrative and multiscale design and planning approach. Doing so can steer urban and rural transformative processes through a combination of sector activities aimed towards more coordinated sustainable outcomes.Landscape-based regional design is considered to be an important strategy that shapes the physical form of regions by using landscape as the basic condition to generate sustainable urbanized deltas.It also provides ways for long-term sustainable urban landscape development through both spatial planning and design. In summary, regional design is a transdisciplinary effort that not only safeguards sustainable and coherent development, but also guides and shapes changes that are brought about by socio-economic and environmental processes,while establishing local identity through tangible relationships to a region[16]43-46.

1 Pearl River Delta

The Pearl River Delta (PRD) in China has been the fastest developing delta in the world for the past four decades. In 2014, it even surpassed Tokyo to be the world’s largest urban area in regards to both size and population[17]. The PRD has led to groundbreaking changes in Chinese urbanization and socio-economic transformation changes since the 1980s[18]. In spite of this, the PRD faces immense challenges regarding its long term economic development because of the threats posed by climate change and environmental degradation. These challenges include issues such as mangrove disappearance[19], agriculture land loss[20], air and water pollution[21], water shortage[22],and a decrease in social security[23].

On the one hand, the region is exposed to increasing flood risks due to urbanization in flood prone areas (Fig. 2) due to rising sea levels and extreme typhoons and storms in summer, which put stress on infrastructure systems of the region.On the other hand, the ecosystem is becoming increasingly fragmented and vulnerable[24], which is characterized by a decline in both ecological services[25]and environmental carrying capacity[26].At the local level, large scale interventions have replaced the diverse historical environment and cultural heritage of the PRD, with more uniform space that lacks any sort of distinctiveness[27]. There is, however, an increasing awareness by authorities and authorities of the value in more integrated planning and design approaches, but they have not been so widely introduced yet[28]. For example, the implementation of the so-called national “Sponge City” policy — a concept that focuses on integrated urban water management — has met with delays in the elaboration of both multiple and separate sectoral plans[29].

In order to guide the PRD towards a more sustainable future, there is an urgent need for new ways of planning and design in the practice of its urban development. The emerging concept and practice of landscape-based regional design offers a way to tackle the conflicts and threats between economic development, environmental recovery,and risks associated with climate change. The high speed in which the PRD has developed makes it a particularly valuable case where the potential of more adaptive integrated planning approaches,such as landscape-based regional design, can be experimented and explored.

2 Landscape-based Regional Design

Landscape-based regional design aims to afford spatial development by applying bioregional planning and design principles that regard the urban landscape as an inclusive, dynamic and complex system. Landscape-based regional design builds on ideas developed and applied by Charles Eliot[30], Waren Maning[31], Pieter Verhagen[32],Patrick Abercrombie[33], Fritz Schumacher[34], Ian McHarg[35]and Philip Lewis[36].

Regional design uses principles from landscape architecture, landscape ecology,geography, and architecture for spatial oriented research, design and planning. It also utilizes ideas from both system thinking and complexity theory to promote a more comprehensive type of regional planning and design that addresses the complex relationship webs that make up the urban landscape[37]13-34. For these purposes, regional design offers a mode for urban transformation,preservation of biodiversity, management of water resources, leisure, community building, cultural identity and economic development[38].

Landscape-based regional design identifies and guides the most advantageous places,functions, scales and inter-relationships for a region’s sustainable growth — strategy — and sets the scene for local initiatives — intervention[37]22.Regional design forms the physical shape of regions based on knowledge of the natural and urban landscape physiology and functioning, and focuses on generating circumstances for future development. This type of approach also operates on different scales, ranging from regional to local,and from general to particular, while preserving overall continuity and promoting local contingency.It also offers ways of balancing out the services and qualities between parts of a territory[39].

The regional design is like an open-ended strategy that is aimed at protecting and developing resources. This is achieved by guiding developments and establishing future conditions for spatial development by means of landscape planning and design[37]25. It also sets up robust and adaptive systems that are resilient and open to change. The organizational structures — “strong” and coherent structures such as water and transport systems —provide the backbone for regional development as well as adapt to local circumstances and withstand challenges, but also sufficiently flexible to develop into future situations[40].

Regional design based on landscape is a social-inclusive approach as it acknowledges the collective nature of the urban tissue and enables various “writers” to participate[41]. The regional design generates a directed field where various stakeholders and other participants can contribute to its development. In this regard, landscape-based regional design is a transdisciplinary undertaking where engineering and ecology specializations merge with spatial design thinking, but also involve local residents’ thoughts and knowledge. Regional design can therefore be regarded as an integrative platform that organizes physical environment,individuals and information, governance, and their interaction at distinct scales through space and time[16]43-46.

At the heart of landscape-based regional design exists a strong interaction between research and design. This implies that the analytical capacity of research is closely connected to the explorative power of design. Next to typical forms of research that serve as input for the design, the design process itself is employed as a vehicle to not only frame spatial problems visually,but to explore multiple possibilities and generate various solutions. Therefore, research through design can be regarded as a powerful research strategy in which complex spatial problems are approached in a creative and integrated manner.The targeted search process plays a central role in which thinking and producing go hand in hand.Research through design implements mechanisms of research and design that are combined with imagination, creativity, and innovation. It is also used as a way to understand where action,observation, and searching can be used in order to achieve new insights. Therefore, mapping and drawing are important tools for visual thinking and communication[42].

3 Key Phases in the Regional Design Process

Landscape-based regional design consists of at least four iterative phases: collecting information,gaining understanding, plan development, and action perspective (Fig. 3).

3.1 Collecting Information and Gaining Understanding

Before the start of the design process, the objectives of the regional strategy need to be identified and based on a proper understanding of the site, including its challenges and potentials. Not only does this means the collection and creation of data and information, but it also means the analysis and evaluation of the region at multiple scales,which includes the identification of all relevant stakeholders. The questions one should ask at the beginning of this process includes: 1) How does an area operate on a local scale level, and how does it function in a larger regional context; 2) What are the spatio-visual, historical, social, and ecological structures and processes that determine the region at different scales; 3) How does both the urban and natural systems work.

Answering questions such as the ones mentioned above implies the description, selection,and valuation of the elements, while also including aspects that matter in comprehensive urban landscape planning and design. It is a process where data becomes knowledge in relation to an individual interpreting, synthesising, and applying information.The process is about exploring, analysing, and synthesising data and information in order to increase the level of understanding on (aspects of) the region in terms of spatial relations, structures, and patterns.Understanding (or “insight” ) is the application of knowledge, increasing effectiveness, and adding value by judgement[44]. It enables the application of knowledge to identify the main challenges and opportunities of the territory, while also outlining alternative futures. The design process should also not only just get the consultation of experts, but it should also include the input of other stakeholders,such as governmental officials and people living in the region. This can be done via interactive workshops,interviews, observations, questionnaires, etc.

3.2 Plan Development and Action Perspective

As soon as the analysis and evaluation phase is finalized, and the main challenges and opportunities are determined, various integral and multiscale design strategies and principles need to be developed and explored, especially in regards to their potential.The questions that need to be answered involve the following: 1) What can be done to address the challenges of the area; 2) How can the potential of the region, by means of projects at multiple scales,be exploited; 3) What are spatial key structures and processes that need to be addressed and coordinated integrally at the regional scale; 4) What are strategic locations, and what are the favourable conditions that can be arranged at the regional scale; 5) How does that relate to the on-going projects in the region; 6) Who are the important stakeholders that should be involved to ensure social-economic and ecological embedment; 7) Are there any informative(international) precedents; 8) How can long-term strategies and short-term design interventions interrelate and strengthen each other.

In order to address these type of questions,precedent study, scenario building, and research through design are important means that can be used to answer them. Design thinking is also useful to explore the spatial possibilities of the application, in regards to various the design strategies and principles. The keywords this part of the process are innovation, creativity, and imagination. Design strategies and principles are also explored in a visual way, while also being evaluated on their feasibility by designers,specialists, and stakeholders. Computer models,field experiments, modelling etc. can also be parts of this process, especially in regards to generating ideas, visualization, and testing. The questions that need to be addressed in this phase include: 1) What are any useful spatial planning design strategies and principles; 2) How can they be applied at multiple scales in the region, and what will be the probable outcome; 3) What is the optimal solution from a spatial, social, and ecological point of view; 4) Is it possible to include any historical aspects in the design; 5) How can the plan adapt to the identity of the region, and strengthen it as well; 6) Does the design allow for change and flexibility over time;7) How can the composition of land use-patterns,vegetation, water, urban typologies, and other elements facilitate ecosystem services, as well as cultural expression.

The regional design is not only a platform that prioritizes, integrates, and organizes physical structures that make use of planning and design skills. It is also an implementation of a longterm strategy that requires policy development by responsible authorities. However, new governance arrangements often need to be developed in order to set conditions, such as the development of local projects, for example. Therefore, it is important to involve relevant policymakers, governmental authorities, and other stakeholders who already need to participate in early stages of the planning process.

4 Understanding the PRD as a Complex System

The PRD’s urban landscape can be understood as a complex system consisting of subsystems.Each of them has its own dynamics and velocity of change[14]160-191. The urban landscape as a system is a material space that is structured as a constellation of networks and places with various organizational levels that address distinct spatial and temporal dimensions[45-47]. Here, the concept of longue durée is essential as it is about understanding the urban landscape as a long-term structure that is constantly changing. The first level of dynamics is connected to the natural environment and is characterized by a slow process of almost imperceptible transformation, repetition, and natural succession.The second level of dynamics is linked to longterm social, economic, and cultural history. The third level of dynamics is that of short-term human and political occurrences[48]. In short, the urban landscape is an ongoing development that is the result of action and interaction between natural and human structures, patterns, and processes that depend on ecological, socio-cultural, economic, and political factors.

4.1 Mapping Landscape Systems

The spatial relationships between environmental circumstances and human reactions and interventions can be studied through cartographic explorations —mapping — to identify important conditions, critical driving forces and the effects of distinct dynamics.Mapping landscape systems as such is different from the suitability maps as proposed by McHarg[49]. This because the mapping is focused on understanding spatial relationships and the dynamic of change,and not necessarily indicating areas where e.g. urban developments can take place. Rather, it reveals the spatial conditions that can inform adaptive planning strategies and design principles. Decomposing the urban landscape in layers according to the dynamic of change is a proven method for gaining understanding the urban landscape system (Fig. 4)[50]10-22. Layers with a low dynamic of change are substratum(e.g. topography, hydrology, soil) and climate (e.g.precipitation patterns, temperature, wind). These environmental conditions are regarded as the most influential conditions for land use and are known as first tier conditions. Infrastructural networks for transportation, water management and energy supply are grouped in another layer and indicated as second tier conditions. These are also significant conditional variables for land use, but their growth and change is quicker than environment the first tier conditions.These conditions together pave the way for the development of agricultural land use and urban settlements, resulting in the layer with the highest change and transformation dynamics[50]19.

4.2 Mapping the Natural and Urban System of the PRD

In order to understand the natural and urban system of the PRD, several maps have been made to get a grip on the dynamic of the territory, the natural and urban system and their interactions. The three maps that were made summarizes the main physical structures and patterns that characterize the PRD which are the eco-agricultural system,the urban system, the infrastructure networks and urban tissue, and their relationships.

The natural system is based on climate,landforms, water and rock type. These physical factors drive the formation of soils, determine hydrology and the distribution of eco-systems,agricultural land-use and historical settlements and cities. The PRD can be divided into two parts which have different types of geomorphology. The western part of the delta is a river-dominated plain that has been formed by natural processes such as siltation and deposition, for over a millennium. The estuary in the east is tide-dominated (Fig. 5)[51]156.Almost 90% of the land in the PRD is a flat terrain comprised of 160 hills and 187 islands that is spread around the coast[51]155. The deltaic lowland is characterized by two sub-deltas and an estuary with tidal influence. The rivers that dominate the PRD are the Xijiang River, the Beijiang River and the Dongjiang River. Together, they cover a drainage area of 453,690 km2and have a total length of 2,200 km. The most important river in terms of water discharge and sediment load is the Xijiang River (80% of the water discharge, 90% of the sediment load). Seasonal flooding is a common characteristic in the Xijiang River and Beijiang River sub-deltas mainly during the period from April to September. The estuary also suffers from extreme tides induced by typhoons or storm surges that mainly occur in typhoon season which ranges from July to September.

In the PRD, the wet and flat characteristics are important conditions for wetland ecology, urban development and agriculture. It is notable that more than 4,000 years of extensive agricultural activities have taken place here. This has proven to be a sustainable human-environment relationship in the ever-changing wetland environment that has resulted from frequent flooding and the continual seaward extension[51-52]. Over the years, due to the wet and flat conditions of the terrain, the inhabitants have developed a sophisticated multiscale water-sensitive approach known as agri-aquaculture in the warm hot plains. This was for a long time the basis for local economic production. One of the most notable approaches is the dike-pond system found in the sub-deltas that was developed from the 14th century onwards with fruit trees planted on dikes with fish ponds in the centre[54]. This changed in the early 17th century where a combination of mulberry and four major fish species were utilized and had created a local silk and fisheries economy. Since then, this type of agri-aquaculture pattern continued to grow and prosper until it hit a peak around the 1920s[55].Nowadays, most of these areas have transformed into fish ponds for only fish production, industrial plots and urban tissue.

The natural vegetation in the PRD are defined by important bays and riparian zones which consists of mangrove forests, wetlands and wet forests. Individual mountains and ridges are home to dry forests. However, many of these have become deforested and in recent events, the process of replanting the trees has started. On the foot of the slopes, fresh water basins have been created for fresh water supply and irrigation (Fig. 6).

In historical times, the region heavily relied on transportation over water. From the 1950’s,the change of land ownership from private to state-owned has enabled large scale infrastructure development in the PRD. Large-scale dike reconstructions[51]156, the development of a vast network of (high-speed) train connections and an increase in road infrastructure has been important conditions for the rapid urban extension in the region. Well-developed road and train infrastructure can be found in the corridors from Guangzhou-Shenzhen/Hong-Kong and Guangzhou-Zhuhai/Macau. Important transportation hubs are the ports of Hong Kong and Nansha and the international airports of Hong Kong and Guangzhou (Fig. 7).

Historical cities such as Guangzhou, Foshan and Macau have a long history that dates back to more than 2,000 years. In Guangzhou for instance,archaeologists discovered the visible remains of a sizeable royal garden and palace showcasing the rich culture of the Nanyue kingdom that dates back to about 203 BC[56]. A notable detail is that the historic Lingnan gardens in the Guangdong province and its traditional architecture have adapted to specific climatological circumstances in terms of allocation, orientation, layout and materialisation that have positively influenced the micro-climate. The historical cities cores are all related to the river and sea for strategic reasons and transportation.

From the 1950’s onwards, the historical cities have been influenced by infrastructural investments.Since the 1980s, China created the PRD Special Economic Zone to attract foreign investment and the delta turned into the fastest urbanizing delta in the world (Fig. 8)[50]. It gave the area a certain degree of autonomy in terms of customs, finance and taxes. Manufacturing companies opened factories and had created a vibrant economic region. During the process of urbanization, large areas inside the polders transformed from farmland into urbanized areas. Presently, there are now 60 million inhabitants according to the Guangdong Statistical Yearbook 2016, and the PRD expects to reach a population of 80 million by 2030.

The urban development followed different spatial patterns. In the North, urbanization occurred in a more concentric pattern around the historic town cores. In the East, urbanization occurred in more linear developments that followed the coast line but has been limited by mountain ridges. Finally, in the West, dispersed patterns have been observed as a result of the polder fields that were used to urbanize. In terms of urbanization,the main focus is now on the urban corridor in Guangzhou-Shenzhen, with an important role for Nansha as connection hub (Fig. 9).

The synthesis map (Fig. 10) shows the urban landscape as the result of the interaction between environmental conditions (e.g. substratum and climate) and the infrastructural networks for transportation, water management and energy.These conditions have paved the way for the development of agricultural land uses and urban settlements which has resulted in the layer with the highest dynamics of change and transformation.However, the fast pace of urbanization and climate change has caused severe problems in the region.Next to sea-level rise, unpreceded storm surges caused by typhoons and increased water discharges by the rivers have resulted in frequent floods in urban areas. Water safety is under threat by the canalization of rivers which also lacks in flood storage. Sizeable stretches of agricultural land have been transformed into industrial sites and urban areas, and thereby lose their absorption/storage capacity for keeping rain water and ability to mitigate abundance and shortage of water. Natural mangrove forests have disappeared while making the coast line more vulnerable to flooding. Besides floods, the PRD also suffers from the loss of ecological and cultural-historical values, subsidence,salt water intrusion, agriculture land loss for food production and socio-economic problems.

5 Towards a Sustainable Future for the PRD

Adaptive urban transformations are the basis for a landscape-based regional strategy to address the main challenges and potentials of the PRD. In this strategy, natural and urban dynamics as derived from the systems analysis must set the pace and nature of adaptation. Plan development and the action perspective on how to make the plan work will focus on the potential of connecting economic and ecological development at multiple scales. The goal is to facilitate sustainable transformations of old industrial/housing areas and the regional agricultural landscape associated with the constraints on the expansion of the built-up area to accommodate economic and population growth. These areas possess specific spatial conditions for long term economic development. At the same time, they are usually located on the newly reclaimed land at the estuaries of the delta, with dense waterways, vast areas of fishing ponds, wetlands and agriculture with highly sensitive ecosystems and are very vulnerable to flooding. In this phase the possibilities for the development of regional green-blue infrastructures and city-level water networks are identified for increasing adaptive capacities, ecosystem services and water safety.

5.1 Scenario Studies

To investigate the PRD’s likely future development, scenario studies are employed.In scenario studies realism and imagination are combined to identify critical key locations, driving forces and prospective impacts of occurrences in the future — both opportunities and threats(Fig. 11)[1]293-312. Using scenarios is an useful instrument to address uncertainty and to generate understanding about trends and their relationships,new challenges and policies, and their effects. It also structures strategic discussions and encourages involvement of various stakeholders[57],[58]11-13. For now the scenarios are conducted in an academic setting, but with involvement of governmental authorities and water boards. Building scenarios involves formulating an internally consistent and coherent set of hypotheses on the primary relationships that are explored. On the basis of these assumptions, a systematic but selective description of the current scenario can be made,as well as identifying the most significant external variables that determine the course of spatial development[56]11-13.

5.2 Developing a Regional Strategic Vision

Together with the assessment of urban landscape growth over time and the evaluation of present spatial development projects in the region,several significant factors of future development are identified which led to an initial strategic vision for the PRD. The vision needs further elaboration on the basic idea that the PRD will develop into China’s Silicon Valley with strong developed and well connected urban qualities, robust greenblue frameworks, have cultural-historical assets connected to the region and water sensitive socioecological inclusive urbanism. According to the initial idea the East-wing (Guangzhou-Hong Kong corridor), the PRD will further develop into a well-connected red-green necklace, with strong urban hubs and marinas, alternated with robust green corridors that connect the mountains to the sea. The West-wing will take benefits from the wet plains developing into a blue axis with water sensitive ecological agri-aquaculture and flood storage, complemented with strong urban hubs that benefit from transit oriented development (TOD).

5.3 Transformation Perspectives

The primary use of the regional strategic vision is to determine priorities in spatial planning and design.Back casting is used to identify spatial transformation perspectives that help to accomplish the objectives as set by the strategic plan and guide actions according to. The spatial transformation perspectives provide a set of adaptive design strategies that are specific to the challenges and potentials of the territories in the subdeltas and the estuary of the PRD. The perspective of each transformation has a spatial dimension and is: water sensitive and socio-ecologically inclusive,flexible and multifunctional and addresses multiple temporal and spatial scales. In the sub-deltas, the transformation perspectives are connected to the river and rain water adaptive approaches and which includes design principles for resilient river design, integrated agri-aquaculture, sustainable urban transformations,new urban districts, integration of (historic) villages,industrial transformation and eco-tourism. In the estuary, the transformation perspectives are mainly connected to sea water adaptive approaches which includes design principles for multifunctional flood protection, harbour and marina development, land reclamation (sedimentation, erosion), development and transformation waterfronts and protection and development of mangroves and other coastal ecosystems.

Each of these transformation perspectives need to be elaborated into more detail. Design principles need to be identified by studying relevant and successful (international) cases. In addition,their potential needs to be explored through a research through design process. Strategic areas can serve as experimentation sites, to test the possibilities of their application in a spatial and visual way. In Sun Chuanzhi’s paper readers can find further elaboration on agri-aquaculture for multiscale water-sensitive design in the PRD[59].

5.4 Action Outlook

In order to put the gained knowledge and ideas into action, it is important to address the question of whether it is possible to create conditions for new governance arrangements. Therefore the regional design involves speculation in order to investigate if and how different stakeholders would be able to find ways of collaborating, agreeing on a design and fine-tuning it. As discussed, the regional design process must facilitate an understanding of urban landscape dynamics and the transformations through an ex-post evaluation of existing urban planning strategies and projects, and an ex-ante evaluation of scenarios of potential adaptation strategies[5]3-4. Communication is a central issue and it is crucial to develop and utilise innovative visualisation methods and tools that permit the involvement of local stakeholders and decision makers. Throughout the process, interviews and workshops with stakeholders are organized to investigate possible agreements between them.During the workshops, stakeholders are brought together around digital map-tables (Fig. 12),where the relationships between different systems can be shown. Augmented Reality and Virtual Reality are also other mediums that are employed[60]. Participants are able to see the possible consequences of their initiatives on other systems.These innovative visualisation methods speed up the discussion on different proposals with all the stakeholders and will form the basis for the further development of the regional vision and related strategy. The transformation perspectives that will guide the development of the delta towards a more sustainable future.

6 Conclusion

As discussed, the PRD’s urban landscape is the result of various processes and systems that have different dynamics of change and influence each other. The ability to interrelate systems through spatial design has become increasingly important,as the interconnection of different systems and their formal expression is a fundamental aspect of contemporary regional development.

Landscape-based regional design is put forward as an inclusive planning and design approach for adaptive transformation of the PRD.The paper outlined an approach rather than the outcomes. In times of complex challenges the development of approaches like offer alternative ways of understanding, socio-ecological inclusive design processes and modes for collaboration amongst disciplines and stakeholders. Landscapebased regional design stimulates design disciplines like architecture, urban planning and landscape architecture to cooperate. It also reviews the agency of spatial design by giving shape to the built environment. In addition, as an inclusive design approach it establishes relationships between ecology and cultural aspects, process and form,long-term and short-term developments, and regional strategies and local interventions. As such landscape-based regional design is a powerful vehicle for guiding territorial transformations in a process of creating local identity and safeguarding regional relationships, and at the same time linking ecological and social processes and urban forms.

In this line of thinking, landscape-based regional design provides a new operational power for spatial design — as an integrative, creative activity— and recognizes the regional urban landscape as a significant field of inquiry that is context-driven,solution-focused, and transdisciplinary.

Acknowledgements:

We would like to thank Dr. Gregory Bracken for English editing.

Sources of Figures:

Fig. 1 ? Xie Guangyuan; Fig. 2 ? Steffen Nijhuis based on SRTM (30m), Hydropolis; Fig. 3 ? reference [37]; Fig.4, 11, 12 ? Steffen Nijhuis; Fig. 5,8 ? reference [50]; Fig.6,7,9,10 ? Steffen Nijhuis, Daniele Cannatella & Xiong Liang, the statistics from SRTM (30m), Hydropolis, google map, baidu map, OpenStreetMap (OSM, 2018.4), land use data from Word ecology land unit (250m, WorldELU, 2015),Globeland30 (2010), port data from the World Port Index Database (WPI, 2018.4), old town data from reference [50].