著：（美）埃里克·魯索 （美）蒂姆·阿格內洛 譯：張文正 胡一可 校：李正

辛辛那提是一座山地城市，歷史上山體滑坡事故頻發(fā)。市域范圍207km2，其中39km2的土地是坡度不小于20%的山地。

辛辛那提山體的主要基巖地層是科佩組（Kope Formation）和費爾維尤組（Fairview Formation）。這些地層易與水反應，促使頁巖迅速崩解。科佩組頁巖的破壞會產(chǎn)生一種叫崩積層（colluvium）的物質，因此問題最為嚴重。辛辛那提地區(qū)最常見、最具破壞性的滑坡就是由崩積層形成的。

辛辛那提始建于1788年，1810年后開始迅速發(fā)展，至1850年已成為美國第六大城市。在這一發(fā)展高峰期中，其大量山地因伐木而變得荒禿，也因建筑、地基及相關用途需求而成為采石場。這些活動加劇了自然山坡的不穩(wěn)定性問題。隨著20世紀辛辛那提不斷發(fā)展和擴張，大規(guī)模的基礎設施和私人開發(fā)項目不斷增加。當這些開發(fā)位于崩積層地區(qū)時，災難性的山體滑坡往往隨之發(fā)生。

20世紀60年代末公眾開始認識到辛辛那提坡地問題及其復雜性，致使隨后幾年進行了一些定量和定性分析。到1976年，這些研究為辛辛那提市對其近一半山地進行開發(fā)立法管控提供了基礎。

1998年，羅伯特·奧申斯基發(fā)表一篇題為《美國的山地開發(fā)管控》的論文，該文從歷史的角度對山地開發(fā)進行了討論，并探究了不同設計學科如何以不同方式介入這種開發(fā)類型。值得注意的是，他的論文最后總結了包括辛辛那提市在內的美國190個地方政府的山地法規(guī)和條例。

本文作者將從歷史和年代順序的角度更深入地探討辛辛那提的山地法規(guī)。首先，總體介紹研究區(qū)域，舉例說明城市的自然地理和地質條件。然后，追溯辛辛那提的人類定居歷史，以及人類活動對山地的破壞性影響，特別是在城市人口經(jīng)過快速增長的初期階段。這些地理、地質和歷史信息大都引自那些保存于山地信托基金會辦公室的博士論文。在這一歷史概述所提供的背景下，筆者繼續(xù)記述一種行動主義的出現(xiàn)，這種行動主義導致建立市政山地法規(guī)的頒布以及山地信托基金會這一非營利性山地保護組織的創(chuàng)建。這些信息大多來自山地信托基金會過去50年來所存檔的報紙和雜志文章。最后，總結了辛辛那提在山地法規(guī)方面所取得的進步及其尚待改進之處。這些結論是基于1976年以來山地信托基金會與辛辛那提市及其山地區(qū)劃法規(guī)的專業(yè)性互動的軼事經(jīng)驗。

1 研究區(qū)域

辛辛那提市是美國俄亥俄州的一個城市，人口301 301[1]。從美國東海岸到辛辛那提市的距離，占到整個美國東西海岸距離的1/3。該市的中央商務區(qū)建于一個約10.05km2的半圓形高地上，高出河漫灘，地勢安全[2]。

辛辛那提核心區(qū)域（或市中心）通常被稱為盆地（圖1），三面為高出盆底70多m的陡坡（圖2）。一些次級山谷——包括那些屬于米爾溪和鹿溪流域的山谷——分別從西部和東部切割盆地山坡，其他次級山谷則直接切入俄亥俄河谷。這些山谷在通往高地的路上形成更小和更淺的溝谷，在盆地上方形成一條連續(xù)的地平線。

在辛辛那提的207km2土地中，39km2為坡度不小于20%的山地[3]。一般來說，這些坡地上覆蓋著次生和三生林，其間零星散布著一些已開發(fā)區(qū)域，在春季和夏季形成一幅綠色馬賽克圖案。

辛辛那提核心區(qū)對面的俄亥俄河南岸地區(qū)主要由肯塔基州（與俄亥俄州南部交界）的科文頓市和紐波特市組成。 這些城市位于另一個較小的高位盆地上，盆地之上的坡地同樣陡峭。該地區(qū)與辛辛那提市和俄亥俄州西南部具有相似的地質條件和山體滑坡易發(fā)性。本文作者將聚焦辛辛那提市。

辛辛那提的坡地景觀是大陸冰川作用的結果，大約在200萬年前開始。最后一次冰川活動于1900年前在辛辛那提北部開始消退[4]。

1 辛辛那提盆地的示意圖Schematic of Cincinnati basin

辛辛那提坡地的主要基巖地層是科佩組和費爾維尤組。 科佩組由約80%的頁巖和20%的石灰?guī)r組成。費爾維尤組位于科佩組上方，由約50%的頁巖和50%的石灰?guī)r組成。在盆地附近，這些地層分布于海拔400～850英尺（約121～260m）處。辛辛那提大學地質學教授保羅·波特認為，“辛辛那提地區(qū)的所有頁巖都容易與水發(fā)生強烈反應，因為它們很容易迅速分解（或崩解）”?？婆褰M地層問題最嚴重，因為它主要是由崩積層生成的基巖單元[5]。崩積層是一個地質學術語，指主要由黏土顆粒組成的土壤，由科佩組頁巖風化分解而來，在基巖上或沿著山谷兩側發(fā)育。辛辛那提地區(qū)最常見和最具破壞性的滑坡即發(fā)生在崩積層[5]。

除崩積層外，冰川沉積物遍布辛辛那提地區(qū)，包括不穩(wěn)定的湖黏土。這些黏土是冰川融水形成湖泊后的殘余沉積物。湖黏土的問題在于其也非常容易發(fā)生滑坡[6]。辛辛那提的滑坡通常移動較慢，不同于加利福尼亞州等美國其他地區(qū)的迅速而劇烈的滑坡可以轉瞬奪去生命。這些滑坡往往每年僅移動幾厘米，但隨著時間的推移，它們帶來的結構損害和經(jīng)濟損失依然不可小覷。

2 早期土地利用與定居的影響

在美國獨立戰(zhàn)爭（1775——1783年）之后，新成立的聯(lián)邦政府決定將阿勒格尼山脈以西土地用于定居[2]。這些土地包括現(xiàn)在的俄亥俄州西南部和肯塔基州北部，擁有原始木材、肥沃的土壤、淡水和豐富的野生動物資源等豐富的資源。

歐洲移民后裔自1788年開始在現(xiàn)在的辛辛那提定居。他們先沿俄亥俄河建立了3個不同的營地，最終選擇在海拔較高且相對開闊的盆地區(qū)域定居[2]。由于與邁阿密、肖尼、威揚多特和特拉華等堅決捍衛(wèi)家園的土著部落發(fā)生持續(xù)沖突，人口增長緩慢[2]。

2 從普萊斯山向東遠眺辛辛那提市的盆地。注意那些環(huán)繞盆地背景的山坡，其形成一條幾乎相同的地平線View of Cincinnati basin looking east from Price Hill. Note hillsides in the background that encircle the basin and form a nearly uniform horizon line

在1794年和1811年美國政府對美國土著民的決定性戰(zhàn)役勝利之后，辛辛那提的人口開始迅速增長[2]。辛辛那提位于一條主要內陸河畔，既是進入美國西部邊疆的一個門戶，也是那些希望在新土地上開始新生活的人們的一個目的地。 美國人口普查數(shù)據(jù)顯示，辛辛那提的人口在1810——1850年間每10年至少增加1倍。至1850年，它已成為美國第六大城市，人口數(shù)量達115 435[2]。

人口的迅速增長導致對自然資源特別是木材的需求增加。著名醫(yī)生及自然主義者丹尼爾·德雷克于1815年指出，木材是“主要燃料且來自周圍山丘”[7]。此外山地還被用于農業(yè)生產(chǎn)，被犁耕以種植農作物，以及被開墾為梯田以種植葡萄[8]。19世紀辛辛那提的山坡上普遍進行放牧活動[9]，這可能是造成植被破壞、梯田形成和水土流失加劇的一個因素。辛辛那提和漢密爾頓公共圖書館的主要分館收藏了由豐泰納和波特拍攝于19世紀中期的一系列全景式銀版照片，這些照片描繪了辛辛那提山地植被遭到改變和伐毀的場景（圖3）。

采石是嚴重影響山地的另一個產(chǎn)業(yè)。石灰石是建筑、地基和擋土墻的首選建材[10]，也是石灰砂漿、路基和路面的重要材料[11-12]。除了河床采石場，山地采石場是辛辛那提石灰?guī)r的另一個主要來源[11-12]。山地采石場的最理想位置是費爾維尤組上部50英尺（約15m）處[13]，這一地層位于山地谷壁的最上部。1826年德雷克將辛辛那提山頂附近的區(qū)域描述為“裸露的垂直懸崖”，在費爾維尤組石灰?guī)r的上部因采石活動而變成垂直地形（圖4）。包括砍伐森林和采石活動在內的早期土地利用導致辛辛那提發(fā)生大規(guī)模的山體滑坡[14-15]。

在19世紀最后1/3的時間里，斜坡鐵路、有軌電車和鐵路線的出現(xiàn)使得大量當?shù)厝四軌颉疤与x骯臟而擁擠的盆地”而住在遠離工廠的區(qū)域[2]。從19世紀70年代開始，共5條斜坡鐵路在市中心盆地周邊的各山地上建成（圖4）。這些斜坡鐵路裝載著旅客、建材和貨物穿過陡坡，其規(guī)模是馬車所無法匹敵的。諸如亞當斯山、奧本山、克利夫頓山和普萊斯山這樣的新社區(qū)得以在山地周圍乃至以外地區(qū)發(fā)展起來。

這些斜坡鐵路為辛辛那提首次提供了來往于盆地和山坡之間的廉價便捷通道，從而革命性地帶動了城市發(fā)展[2]。這也使該市土地面積得以最大限度地擴張，在1869——1918年間，辛辛那提向外擴張和吞并了超過168km2的土地，整個城市的人口接近50萬[2]。斜坡鐵路的建造和持續(xù)運營也導致了山體滑坡。

在20世紀20年代末，一條被稱為哥倫比亞林蔭大道的現(xiàn)代公路開始施工。哥倫比亞林蔭大道是美國州際公路系統(tǒng)的先驅，其目的是建立一條連接市中心和東部郊區(qū)的汽車導向型交通走廊，大量的工程和土方作業(yè)需要沿著一片平行于俄亥俄河的陡峭盤旋山地的中部展開。這條公路所造成的地質影響一直持續(xù)到21世紀，下文將就此進行討論。

3 人類與山地互動的影響

早在人類到來之前，大辛辛那提地區(qū)就發(fā)生過大規(guī)模山體滑坡[16]。然而，1788年辛辛那提城市建成以來的高強度土地利用加劇了山地的不穩(wěn)定性。歷史證據(jù)表明，森林砍伐、農業(yè)耕作、采石和放牧活動都對該地區(qū)山地的自然坡度和排水模式產(chǎn)生了負面影響。19世紀上半葉以來滑坡一直都是困擾辛辛那提的問題，而一些深層滑坡（超過1.5m深度）可能未被發(fā)現(xiàn)[14-15]。

隨著城市的發(fā)展和成熟，大型基礎設施和私人開發(fā)項目也在增加，其中許多涉及山地區(qū)域。當這些開發(fā)位于脆弱的基質區(qū)域（崩積層）時，結果往往是災難性的。以下概要重點介紹其中一些災難性事件[14-15]。

·1926年，市中心盆地以西發(fā)生一起大面積基礎坍塌型山體滑坡，原因是坡腳挖方[17]。該斜坡底部的挖方達到600m寬和12m高，導致其上450多m山坡發(fā)生移位，并導致梯形切割面以下的地面被擾動而隆起約4.5m。該滑坡的總體表面積超過350 000m2。

·1930年，在哥倫比亞林蔭大道的施工時發(fā)生了一起重大滑坡，原因是在拓寬狹窄的哥倫比亞路時開挖了路面以上的山地，并將土方傾倒下去。哥倫比亞林蔭大道自竣工以來持續(xù)發(fā)生山體滑坡。它是一條主干道，每天承載成千上萬的車輛。每年林蔭大道上方過陡的斜坡都會沖破擋土墻。這些山體滑坡有時嚴重到每次足以使部分（或全部）的東西向交通要道關閉數(shù)小時（圖5）。

·1972年，一起大規(guī)模山地滑坡在盆地正北方的克利夫頓高地形成了一個55m長、9m高的懸崖，起因是幾年前建造的一座公寓樓及毗鄰的停車場（圖6）。大約12個公寓單元、1座加油站以及滑坡下方工廠的相關人員被撤離[18]。至今，從卡魯塔樓——市中心最高的建筑之一——還可以看到該滑坡的左右兩側。

·1973年，俄亥俄州交通部在亞當斯山山腳下進行了2m高的垂直開挖，為跨俄亥俄河的新471號州際公路大橋建造進出坡道。當天然氣管道和水管開始破裂時，該市下令讓該山地住區(qū)的15家住戶永久撤離[19]。7年后，政府官員批準了一項解決方案，即建造一面長390m、深30m的混凝土墻，使用一種鉆墩和電纜系統(tǒng)來擋住巨大的山坡。在這堵墻的施工期間，打樁引起的震蕩引發(fā)了另一起滑坡，導致大約30家住戶永久撤離[19]。當該混凝土墻在8年后的1981年竣工時，其耗資高達2 220萬美元[20]。當時，這是美國有史以來損失最嚴重的山體滑坡之一。

每年僅因山地滑坡破壞公共基礎設施而付出的代價就已驚人。由辛辛那提大學師生進行的一項滑坡修復研究發(fā)現(xiàn)，辛辛那提市各街道緊急維修的直接費用約為每年50萬美元[5]。1987年辛辛那提各街道滑坡破壞的延期維修費用約為1 850萬美元[21]。這些調查結果是一個更大范圍特別任務的組成部分，該任務于1985年啟動，旨在調查并主動解決辛辛那提基礎設施的維護和保養(yǎng)問題，下文將對此進行更全面的討論。值得注意的是，這些數(shù)字不包括城市內私人財產(chǎn)因滑坡而造成的損失，后者的損失數(shù)字更難量化和獲取。斜坡不穩(wěn)定性及其對辛辛那提山地住宅建設的破壞是普遍存在的問題。

4 激進主義、行動與山地信托基金會的建立

1967年5月4日是辛辛那提實施山地保護措施歷程上的一個里程碑。在這一天，一個“山地論壇”在位于亞當斯山的辛辛那提藝術博物館召開。之所以選中此地可能是因為其如畫的山頂位置，并能俯瞰市中心盆地的景色。

該論壇的一份宣傳單敦促感興趣的公民參與“討論辛辛那提山地的未來”。論壇的演講者包括辛辛那提市各政府部門負責人，以及代表住房、開發(fā)、藝術和環(huán)境等多方面的專業(yè)人士。這個為期一日的活動產(chǎn)生了各種行動步驟，包括對該市山地進行定量和定性分析的計劃。

1969年，辛辛那提規(guī)劃委員會發(fā)布《山地研究》，該報告針對于該市范圍內的23處山地，這些山地具有自然群落分隔、植被綠化背景和住宅區(qū)中心等特征[22]。3年后，辛辛那提規(guī)劃委員會聘請理查德·A·加德納公司編制了《辛辛那提山地——推薦的設計流程和行動計劃》。這份報告的主題包括一個未來幾年需要遵循的循序漸進過程，以確保合適的山地開發(fā)[22]。報告中有一項值得注意的建議，即成立一個非營利性組織來負責征購尚未開發(fā)的山地，并在該土地被出售再開發(fā)時進行設計控制[23]。

從20世紀60年代末至70年代，科爾曼教皇成為城市和社區(qū)圈子中知名的藝術、環(huán)境和城市問題倡導者。他是1967年山地論壇的9位發(fā)言人之一，還曾擔任辛辛那提規(guī)劃委員會的山地咨詢委員會主席，1971年成立了非營利性的以提高城市生活質量為使命的辛辛那提研究所。

在科爾曼教皇的領導下，辛辛那提研究所與辛辛那提規(guī)劃委員會密切合作，開展山地研究和保護工作。1973年，國家藝術基金會在“城市邊緣”計劃下授予辛辛那提研究所40 000美元，以幫助后者保護和改善該市的山地。辛辛那提是367個申請者中獲得這項撥款資助的37個城市之一[3]。該撥款部分被用于分析研究以確定辛辛那提的山地特征及制定設計導則。

辛辛那提研究所聘請了法律顧問來制定臨時管控措施，并為處理該問題的最終土地分區(qū)法規(guī)起草文件。撥款被用于采訪100位辛辛那提市民，記錄他們對該市山地的印象。這些訪談的記錄提供了關于山地對當?shù)鼐用裥睦斫】档姆e極影響的寶貴認識[24]。剩余撥款則被用于建立一個非營利的山地組織，正如加德納公司在1971年研究報告中所建議的。這個非營利組織成立于1976年10月，名為“山地信托基金會”。

辛辛那提研究所在1973年和1974年組織和總結了多次山地研究。1975年，與舊金山規(guī)劃師岡本簽訂合約，進行最終的實地調查、攝影記錄和其他山地分析。這項工作以一份1975年底為辛辛那提城市規(guī)劃委員會準備的題為《辛辛那提山地——開發(fā)導則》的創(chuàng)新性報告而宣告結束。該文件提供了關于地質、土壤特征、植被類型、公私用途、視覺特征和其他城市規(guī)劃因素的詳細研究。隨著山地信托基金會開始發(fā)展，辛辛那提研究所在20世紀70年代末停止運營。

5 山地保護措施建立

1976年6月，辛辛那提規(guī)劃委員會正式采納了一份題為《辛辛那提山地——開發(fā)指南》的文件。當時，該規(guī)劃委員會正在敲定被稱之為“環(huán)境質量區(qū)”（EQD）的特殊規(guī)章。EQD是一種疊加分區(qū)，旨在“協(xié)助土地和建筑開發(fā)以使其與環(huán)境和諧，并保護一些特定地點的城市環(huán)境品質，這些地點具有重要公共價值，以及易被那些傳統(tǒng)分區(qū)和建筑規(guī)章所允許的開發(fā)活動所破壞的環(huán)境特征”[25]。EQD共分4類，包括公共投資區(qū)、城市設計、社區(qū)振興和山地。

然而，正是這些特殊疊加分區(qū)的山地成分才是一開始制定環(huán)境治理區(qū)的背后驅動力。該市意識到其山地易遭滑坡的特性，并認為有必要通過山地法規(guī)來防止這一問題因無序開發(fā)而加劇。1969年《山地研究》所識別的23處山地均被劃入了“環(huán)境質量——山地區(qū)”（EQ-HS）。《山地研究》認為這些坡地極為重要，因為其至少50%面積位于23處山地中的1處或多處之內，且包含以下6個要素中的至少4個：1）大于等于20%的坡度；2）科佩組的存在；3）顯眼的山地（可從辛辛那提山地系統(tǒng)內某被指定山地的下方山谷中的公共街道上看到）；4）擁有觀賞某主要溪流或山谷視野的山地；5）作為社區(qū)分隔或社區(qū)邊界的山坡（已在城市規(guī)劃委員會批準的某社區(qū)規(guī)劃中被識別）；6）樹木茂密的山地。

盡管經(jīng)過多年的努力，EQ-HS所劃定的23處山地中僅有不足一半獲得了城市土地分區(qū)立法。每個社區(qū)理事會有責任向市議會提出建議，在其社區(qū)內采納已有的EQ-HS。也許是因為缺乏緊迫感，其他社區(qū)未能成功采納EQ-HS。盡管如此，自1976年以來，包括東普萊斯山、奧本山、克利夫頓山和亞當斯山在內的所有盆地區(qū)域的山地社區(qū)均通過立法采納了EQ-HS分區(qū)。這些山地社區(qū)不僅可以俯瞰市中心盆地，他們本身也成為從盆地底部仰視所看到的引人注目的自然地標（圖7）。具有諷刺意味的是，在該市開始采取措施積極管理其山地的同時，20世紀70年代辛辛那提地區(qū)的滑坡人均損失創(chuàng)下了美國城市區(qū)的歷史最高紀錄[26]。

在20世紀80年代中期，辛辛那提商界和學界領袖組成一個委員會，就改善和保護城市資產(chǎn)的方法獻計獻策，包括為改進建議提供資金的措施。1987年，在當時寶潔公司董事長兼首席執(zhí)行官約翰·斯梅爾主持下，該委員會完成了《斯梅爾基礎設施委員會報告》。該報告列出的100多項建議中有4項與山地相關，其中最為重要者于1989年被辛辛那提市采納。

第一個建議是提供資金為該市的所有擋土墻編制清冊，包括為該清冊的更新而分配未來預算。截至2018年，該市范圍內約80km長的擋土墻被記錄[27]。這一初步努力的成功發(fā)展為《擋土墻和滑坡穩(wěn)定計劃》，該計劃的目標是“使所有現(xiàn)有擋土墻處于良好狀態(tài)，并穩(wěn)定那些影響城市道路的滑坡”[27]。每面城市擋土墻每6年檢查一次，這有助于確定某墻是否需要被替換或修復。該計劃的資金每年都經(jīng)過精心分配，重點是先解決最迫切的需求以防止對城市街道和設施造成嚴重破壞。值得注意的是，該計劃并沒有減少該市擋土墻上方或下方的滑坡，而僅僅減緩和減輕了滑坡對距離城市街道和公共設施最近處的直接影響。

3 1848年亞當斯山的毀林區(qū)域（7號底片）。俄亥俄河位于前景Deforested hillsides - Mt. Adams, 1848 (Plate No. 7). Ohio River is in the foreground

4 1900年前后的貝爾維尤住宅及斜坡（克利夫頓）。注意建筑群下面的因采石活動而形成的高聳懸崖Bellevue House and incline (Clifton) circa 1900. Note the high vertical cliffs below the complex from quarrying activity

第二個得到實施的建議是在該市交通和工程部內設立一個地質技術處。自1989年以來，該市一直雇傭1名受過工程培訓的全職工程地質學家和1名全職地質技術工程師。這2個職位的主要職責是在公共通行權及該市所控制的其他財產(chǎn)范圍內提供關于滑坡穩(wěn)定和防治的地質技術評價。地質技術人員還與城市規(guī)劃部門、建筑和檢查部門等所有其他市政府職能部門交換意見。具體來說，他們在建筑方案檢查員對位于滑坡敏感地區(qū)的項目進行審查時提供協(xié)助?！端姑窢柣A設施委員會報告》原本建議在地質技術辦公室的兩名雇員中包含1名地質學家，因為地質學家更易發(fā)現(xiàn)先前存在的滑坡狀況，并參考那些易被忽略或遺忘的當?shù)鼗職v史記錄。就其本身而言，山地信托基金會在這個問題上發(fā)揮了重要的核實作用，為歷史滑坡、山地利用及倡導相關記憶提供了一份機構記錄。

6 山地信托基金會確立其山地倡導角色

當1976年山地信托基金會成立時，人們就清楚該基金會缺乏資金來實施其綱領中的一個目標，即成為一個購買并持有山地的土地銀行，然后以負責任的方式監(jiān)督其未來發(fā)展。于是該基金會只能強調其綱領中的其他目標：1）研究和教育； 2）土地資源保護；3）倡導負責任的土地利用。

在1987年《斯梅爾基礎設施委員會報告》和1988年山地信托基金會主辦名為“美元和理性——辛辛那提和漢密爾頓縣山體滑坡的經(jīng)濟影響”的會議之后，該基金會在1989年啟動了一項雄心勃勃的研究工作。該研究于1991年完成，成果為《大辛辛那提的山地保護策略》。該研究的第二卷包括詳細的山地分析，以及一系列關于視覺質量、滑坡易發(fā)性、環(huán)境生態(tài)質量、易遭開發(fā)性、視覺和環(huán)境敏感性、需優(yōu)先保護的坡地等問題的地圖?；诘?卷的信息和分析，該研究的第3卷包含了145條針對山地開發(fā)的導則。第1卷包括1篇關于該研究的簡短介紹。

這項研究的300多份復印本已經(jīng)按成本價出售給美國和加拿大的各個市政規(guī)劃部門和私人規(guī)劃設計公司。山地信托基金會在1992年舉辦一個研討會，與辛辛那提市區(qū)內的地方政府進行溝通，建議他們采用山地開發(fā)導則。最終，辛辛那提市和其他地方政府均未采納這些導則。不過，1997年辛辛那提市認可了山地信托基金會在山地和滑坡問題上的專業(yè)聲譽，開始向基金會通報其EQ-HS區(qū)內的山地開發(fā)建議，并邀請其就這些建議公開發(fā)表評論。在1997——2003年間，山地信托基金會就這些EQ-HS區(qū)內的至少28項開發(fā)建議提供了書面或口頭證言。雖然基金會并不反對開發(fā)，它會在必要時與當?shù)鼐用窈献?，揭露那些其認為會對周邊環(huán)境造成負面影響的方案，或指出任何缺乏工程遠見的方案。山地信托基金會之所以能扮演這種角色，是因為其受托人、技術顧問和執(zhí)行董事所具有的專業(yè)知識。

2004年初，辛辛那提市公布了一項新的分區(qū)法規(guī)。所有EQ-HS分區(qū)都被新的類別取代，即“山地疊加區(qū)”（HOD）。之前的EQ-HS僅有不到一半被編入法規(guī)，而新的HOD可被應用于全市范圍。一個地產(chǎn)被劃作HOD的依據(jù)是其任何部分的坡度等于或大于20%，或其任何部分在1980年由索爾斯和達爾林普爾為該市繪制的《滑坡易發(fā)性圖》中被指定為中高或高滑坡易發(fā)。1969年的《山地研究》和1975年的《辛辛那提山地開發(fā)導則》均作為支持文件被納入HOD分區(qū)中。

HOD分區(qū)包括一系列基礎開發(fā)要求，根據(jù)這些要求，必須滿足任何建筑許可證的請求?！缎列聊翘釁^(qū)劃法》第1433-19節(jié)列出了這些要求：1）任何新建筑或舊建筑改造必須限制在最大建筑圍護結構之內（相關參數(shù)由城市定義）；2）山頂上的建筑物高度必須長于寬度，以強調垂直維度；3）位于山脊之下或之上的建筑必須在進深和面寬上采用交錯或階梯式布局，以符合地形；4）屋頂公用設施和機械設備要么完全不用，要么采取屏蔽和聲控措施；5） 建筑竣工后剩下的所有透水面必須用喬木、灌木、草本或其他地被植物進行綠化，以穩(wěn)固坡地和減少過多徑流；6）挖填方的累積高度不超過8英尺（約2.4m），明確禁止與特定開發(fā)無關的任何高度或累積量的挖填方；7）一個初步地質技術評估應考慮相對的山地穩(wěn)定性。

這些基本要求中如有任何一項沒有被滿足，申請人必須在一個市政府所指定的聽審員面前說明為何其應該被豁免1項或多項要求。在2004——2014年間，聽審員是從城市規(guī)劃部門的不同等級人員中選出的。自2014年起，聽審員改從市法務局挑選。山地信托基金會認為，來自市法務局的代表會對HOD條款進行更為嚴格的解讀。自2004年HOD被立法以來，山地信托基金會已就至少43個山地開發(fā)案例表達了意見 。

7 總結和結論

21世紀初的辛辛那提是一座繼承了各種山地債務的城市，這些債務并不只是山地本身不穩(wěn)定性造成的損失。此前幾個世紀的資源開發(fā)性和破壞性土地使用活動，以及不嚴謹?shù)墓こ探鉀Q方案（其中不少先于EQ-HS分區(qū)），都成為該市及其居民要長期（如果不是永久）負責的歷史遺留問題。

近年來辛辛那提在保護其公共基礎設施方面變得更加積極主動，但在監(jiān)督私人地產(chǎn)上的山地開發(fā)方面可以也應該做得更多。來自私營部門的山地開發(fā)壓力是巨大的，而且會在未來變得更大。在非常理想的社區(qū)中，僅存的未開發(fā)土地往往是山地。許多山地還擁有俯瞰盆地和（或）俄亥俄河的壯觀視野，其盈利潛力備受青睞。因為其坡度陡峭，這些山地的開發(fā)風險通常更高。

雖然之前的EQ-HS分區(qū)是朝正確方向邁出的一步，但它并非萬無一失。據(jù)傳聞，在2003年EQ-HS管控下獲批的私人山地開發(fā)項目中，至少有一個于2012年發(fā)生了大面積坍塌，導致花費了幾十萬美元的維修費用（圖8）。幸運的是，公寓業(yè)主可以根據(jù)俄亥俄州關于開發(fā)商責任的10年時效法規(guī)起訴開發(fā)商。山地信托基金會在分區(qū)審批過程中曾公開評論過這一案件。當災難發(fā)生時，基金會發(fā)現(xiàn)其建議中至少有一條未被開發(fā)商采納，就是建筑應該遠離山脊線。到目前為止，由當前HOD分區(qū)下批準的開發(fā)項目尚未發(fā)生崩塌問題。

即便如此，該市最好能遵循以下方面來強化其山地開發(fā)要求的傳遞和效力。第一，在房地產(chǎn)界，許多房地產(chǎn)經(jīng)紀人并不知道HOD區(qū)域的分布情況，特別是其與現(xiàn)有或現(xiàn)建住房之間的關系。該市可以通過在其市政網(wǎng)站上提供一張基于地理信息系統(tǒng)的具體地塊邊界圖來解決這個問題，在圖上突出標記被HOD覆蓋的區(qū)域。每當光標移動到計算機屏幕上的HOD地塊時，就會彈出一個下拉框解釋該HOD的性質和要求。這將有助于使各專業(yè)人士和廣大公眾了解這些地區(qū)的山地開發(fā)和居住相關風險。

第二，該市還可以實施更嚴格的HOD分區(qū)，要求開發(fā)商聘請一名地質技術工程師對該開發(fā)項目的所有土地平整和土方工程階段進行現(xiàn)場監(jiān)督，確保其按照建議遵循相關工程報告。對于已經(jīng)得到市政府授權的初步地質技術工程報告，可以進一步要求開發(fā)商咨詢1位地質學家，該地質學家能夠在現(xiàn)場發(fā)現(xiàn)和記錄任何可能被土木或地質技術工程師忽視的現(xiàn)存滑坡情況。

第三，該市可以補充立法，對任何故意向市政府提交關于建筑許可和變更的錯誤或虛假信息的HOD申請人（開發(fā)商、設計師或房主）進行罰款。山地信托基金會曾目睹了一些此類情況，即申請人以超過其所提交的設計方案規(guī)模進行建造，或未能按照承諾采取適當?shù)挠旰榭刂拼胧?/p>

最后，該市要填補任何使坡地開發(fā)者得以完全繞過HOD流程的漏洞。在2016年，1個申請建造19套住房的人找到了一種合法繞過HOD分區(qū)要求的方式，即在城市規(guī)劃委員會的土地細分法規(guī)下直接獲得項目批準。最終，政府并未根據(jù)HOD流程舉行公眾聽證，使山地信托基金會或其他人能夠問詢提出疑慮或討論案件細節(jié)。該項目在土地平整和土方工程階段就出現(xiàn)了問題，住宅在一場暴雨后被洪水沖下了山坡。

總之，辛辛那提建在一個極為美麗卻敏感的景觀之上，有著一段長時間且代價巨大的滑坡破壞、修復和緩解危害的經(jīng)歷。本文作者強調了與這些山地相關的損失，以及辛辛那提為減少其未來損失和代價而做出的努力。

注釋：

圖1由科爾曼教皇提供；圖2、7、8由埃里克·魯索提供；圖3為1948年Charles Fontayne和William Porter拍攝的《銀版攝影術記錄的辛辛那提》，由辛辛那提和哈密爾頓公共圖書館提供；圖4～6由辛辛那提大學圖書館提供。

（編輯/王一蘭）

Cincinnati is a city of hillsides with a history of slope instability. Of the 207 square kilometers that comprise the incorporated area of the city, 39 square kilometers consist of hillsides defined by slopes of 20 percent or greater.

The predominant bedrock strata underlying Cincinnati’s hillsides are the Kope and Fairview Formations. These formations are known to be very reactive to water whereby the shale disintegrates and weakens quickly. It is the Kope Formation that is the most problematic, because the breakdown of its shale results in a material called colluvium. The most common and most destructive landslides in the Cincinnati area are those formed in colluvium.

Cincinnati was settled in 1788 and began to grow rapidly after 1810. By 1850, it was the sixth largest city in the United States. During this growth spurt, many of its hillsides were stripped bare for lumber, and quarried for buildings, foundations,and other related uses. These activities exacerbated natural slope instability problems. As Cincinnati continued growing and expanding into the 20th century, large-scale infrastructure and private development projects increased. When these developments located in zones of colluvium,catastrophic landslides often resulted.

During the late 1960s, public awareness of the problems and complexities of Cincinnati’s hillsides led to concrete action steps that resulted in quantitative and qualitative analyses over the next several years. By 1976, these studies provided a basis for Cincinnati legislating development controls on nearly half of its hillsides.

In 1998, Robert Olshansky published a paper entitled Regulation of Hillside Development in the United States. The paper discusses hillside development from a historical perspective, and it explores how different points of view among design disciplines are likely to approach this type of development in different ways. Notably,his paper concludes with a summary of hillside regulations and ordinances gathered from 190 local governments across the United States, including the City of Cincinnati.

This paper will explore in greater depth,Cincinnati’s hillside regulations from a historical and chronological view point. It will begin with an overview of the study area, illustrating the city’s physical geography and its geology. It will continue with a history of Cincinnati’s settlement and the destructive impacts of human interaction on its hillsides, especially as the city’s population went through initial stages of rapid expansion. Much of this geographical, geological and historical information are referenced from Ph.D. dissertations and thesis research stored in the offices of The Hillside Trust. This historical overview provides context for the following sections of the paper which chronicle the emergence of activism that lead to the establishment of municipal hillside regulations, and to the creation of The Hillside Trust, a non-profit hillside advocacy organization.Much of the information collected in this section is derived from archived newspaper and magazine articles spanning 50 years that are stored with The Hillside Trust. In conclusion, the paper summarizes where Cincinnati has made strides in its hillside regulations, and where it still has room for improving upon them. These conclusions are based on the anecdotal experiences of The Hillside Trust interacting professionally with the city and its hillside zoning regulations since 1976.

1 Study Area

Cincinnati, Ohio is a city in the United States,with a population of 301,301[1]. It is located along the northern banks of the Ohio River in the eastern third of the country. Its central business district (CBD) is built upon an approximately 10.05 square-kilometer, semi-circular plateau elevated safely above the river’s flood plain[2].

This central core (or downtown) is commonly known as the basin (Fig. 1). It is flanked on three sides by steep slopes towering well-over 70 meters above the basin floor (Fig. 2). Secondary valleys,including those belonging to the Mill Creek and the Deer Creek cut through the basin hillsides on the west and east, respectively. Other secondary valleys cut directly into the Ohio River valley. These secondary valleys lead to smaller and shallower troughs on the way up to a plateau, forming a continuous horizon line above the basin.

Of the 207 square kilometers that comprise the incorporated area of Cincinnati, 39 square kilometers consist of hillsides defined by slopes of 20 percent or greater[3]. Generally, these hillsides are wooded with secondary and tertiary forest cover,interspersed with pockets of development, forming a green mosaic during the months of spring and summer.

The region opposite the central core of Cincinnati, along the southern banks of the Ohio River, is comprised principally of the cities Covington and Newport, in the Commonwealth of Kentucky, which is a state directly south of Ohio.These cities are located upon a smaller elevated basin of their own, with hillsides that rise no less dramatically above the basin. This region shares a similar geology and landslide susceptibility to that of Cincinnati and southwestern Ohio. This paper will focus exclusively on the City of Cincinnati.

Cincinnati’s hillside landscape is the result of continental glaciation, which began approximately two million years ago. The last glacial advance began receding just north of Cincinnati around 19,700 years ago[4].

5 哥倫比亞林蔭大道工程所導致的1930年滑坡
Landslide in 1930 resulting from development of Columbia Parkway

The predominant bedrock strata underlying Cincinnati’s hillsides are the Kope and Fairview Formations. The Kope Formation is comprised of approximately 80 percent shale and 20 percent limestone. The Fairview Formation is located above the Kope Formation and is comprised of approximately 50 percent shale and the remainder limestone. Around the basin, these formations are located between elevations that are 400 and 850 feet above sea level. University of Cincinnati Geology professor, Paul Potter explains that “all of the shales of these Cincinnati Series are very reactive to water, as they are prone to disintegrating(or slaking) quickly.” It is the Kope Formation that is the most problematic, because it is the principal colluvium-producing bedrock unit[5]. Colluvium is the geologic term for soil, that is composed primarily of clay particles. It develops on top of bedrock, along valley walls, from Kope shale that breaks down from weathering. The most common and most destructive landslides in the Cincinnati area are those formed in colluvium[5].

In addition to colluvium, glacial deposits are scattered throughout the Cincinnati region,including unstable lake clays. These clays are remnant deposits from lakes that formed from glacial melt water. Lake clays are problematic in that they are also highly susceptible to landslides[6].Unlike other parts of the United States, such as California, where landslides are often swift,dramatic, and can result in sudden loss of life,Cincinnati’s landslides are usually slower moving.Often, they creep at a rate of a few centimeters per year but are no less significant when it comes to structural damages and economic losses over time.

Following American’s war for independence from Britain (1775——1783), the newly-formed United States was determined to settle lands west of the Allegheny Mountains[2]. These lands, including what are now known as southwestern Ohio and northern Kentucky, possessed an abundance of resources, including virgin timber, fertile soil, fresh water, and a rich population of game animals.

2 Impacts of Early Land Use and Settlement

People of European descent settled the land which is now Cincinnati in 1788. After establishing three different camps along the Ohio River, they eventually settled on the higher elevation and relatively expansive opening offered by the basin area[2]. The population was slow to expand due to ongoing skirmishes with indigenous tribes such as the Miami, Shawnee, Wyandot and Delaware, who fiercely defended their homelands[2].

Following the U.S. government’s decisive victories against the Native Americans in 1794 and again in 1811, the population of Cincinnati began to grow rapidly[2]. With its location along a major inland river, Cincinnati was both a gateway to the western frontiers of the United States, as well as a destination for those seeking new beginnings in a new land. U.S. Census figures show that Cincinnati’s population at least doubled every ten years between 1810 and 1850. By 1850, it was the sixth largest city in the United States with a population of 115,435[2].

The rapid increase in population exerted an increased demand for natural resources, particularly lumber. In 1815, Daniel Drake, a prominent doctor and a naturalist wrote that wood was the “chief article of fuel and that it was obtained from the“surrounding hills.”[7]In addition, the hillsides were used for agriculture, plowed for crops, and terraced for vineyards[8]. Livestock grazing on the “sloping hills of Cincinnati was common in the 1800s”[9]and may have been a factor in the destruction of vegetation, the formation of terraces, and accelerated erosion. A rare mid-nineteenth century panoramic series of daguerreotype photographs by Fontayne and Porter preserved in the main branch of the Public Library of Cincinnati and Hamilton,portrays the Cincinnati hillsides modified and stripped of vegetation (Fig. 3).

Quarrying was another industry by which the hillsides were significantly impacted.Limestone was a preferred construction material for buildings, foundations and retaining walls[10],and to a lesser extent for lime mortar, roadbeds,and pavements[11-12]. Besides river quarry beds,hill quarry beds were another primary source of Cincinnati limestone[11-12]. The most desirable section of the hill quarry beds was the upper 50 feet (about 15m) of the Fairview Formation[13].This formation underlies the uppermost portion of the hillside valley walls. In 1826, Drake described the area near the summit of Cincinnati’s hillsides as “naked perpendicular cliffs,” where the upper Fairview limestone stood in vertical relief from quarrying activity (Fig. 4). Early land use, including deforestation and quarrying activity initiated largescale landslides in Cincinnati[14-15].

During the last third of the 1800s, the advent of inclined railroads (inclines), trolleys and railroad lines made it possible for large numbers of people to “escape the dirty, crowded basin” and live some distance from their work[2]. Beginning in the 1870’s,a total of five inclines would be built on various hillsides rimming the downtown basin (see example Fig.4). These inclines traversed the steep slopes with passengers, building materials, and commercial goods on a scale by which horse-drawn carriages were incapable of matching. New neighborhoods developed around and beyond the hillsides in communities such as Mt. Adams, Mt. Auburn,Clifton and Price Hill.

These inclines revolutionized the city’s growth by providing Cincinnati with cheap and convenient access between the basin and the hillsides for the first time in its history[2]. It also led to the city’s greatest expansion in land area. Between 1869 and 1918, Cincinnati reached out and annexed more than 168 square kilometers of land, and the population of the entire city approached one half million people[2]. The construction and ongoing operation of the inclines also resulted in landslides.

In the late 1920s, construction began on a modern roadway for automobiles that would become known as Columbia Parkway. A forerunner of America’s interstate highway system, Columbia Parkway’s purpose was to create a major caroriented transportation corridor to connect downtown with the eastern suburbs. It required significant engineering and earthworks along the mid-slope of a steep and sprawling hillside system that runs parallel to the Ohio River. The geological impacts of this roadway are still being felt well into this century, as discussed below.

3 Impacts of Human Interactions on the Hillsides

There were mass slope movements in the Greater Cincinnati region, long before humans arrived[16]. However, it is the intensive land use of Cincinnati’s hillsides following its settlement in 1788, that exacerbated slope instability. There is historical evidence that widespread deforestation,farming, quarrying, and livestock grazing all negatively impacted the natural slope and drainage patterns of the region’s hillsides. Landslides have been a problem in Cincinnati since the early to mid-1800’s, with deep landsliding (greater than five feet in depth) probably going unrecognized[14-15].

Large-scale infrastructure and private development projects increased as the city grew and matured. Many of these involved hillside areas. When these developments located in zones of weak substrate (colluvium), the results were often catastrophic. The following summary highlights some of these disasters[14-15].

·In 1926, an extensive base-failure landslide occurred west of the downtown basin from removal of the toe of the slope[17]. A massive cut measuring 600 meters wide by 12 meters high was made into the bottom of a slope. The hillside moved, extending more than 450 meters upslope. Ground disturbance extended below the terraced cut face, as the ground bulged up some four and a half meters. The total surface area of this landslide was over 350,000 square meters.

6 1972年克利夫頓高地滑坡，描繪了滑坡的巨大體積
Clifton Heights landslide in 1972, depicting the shear volume of hillside that failed

·In 1930, a large landslide occurred during construction of Columbia Parkway. This was the result of widening narrow Columbia Road,by cutting the hillside above the roadway and dumping cut material below it. Columbia Parkway has experienced continued landslides since its completion. It is a major arterial roadway, carrying thousands of vehicles per day. Annually, the oversteepened slopes above the Parkway breach the retaining walls that attempt to hold it back. These landslides are significant enough at times to close some (or all) of the eastbound and westbound traffic lanes for several hours at a time (Fig. 5).

·In 1972, a large landslide resulting from the construction of an apartment building and adjoining parking lot several years earlier, created a head scarp 55 meters long and nine meters high in Clifton Heights immediately north of the basin(Fig. 6). About 12 apartment units were temporarily vacated, as were a gas station and manufacturing facility downhill from the slide[18]. The right and left flank of the landslide are still visible today from one of downtown’s tallest buildings, the Carew Tower.

·In 1973, the Ohio Department of Transportation (ODOT) made a two meter vertical cut into the toe of the Mt. Adams hillside, to build entrance and exit ramps for the new Interstate 471 bridge spanning the Ohio River. When gas and water lines began rupturing, the city ordered the permanent evacuation of 15 families in this hillside neighborhood[19]. Seven years later, government officials approved a solution which was to build a concrete wall 390 meters long and 30 meters deep,using a system of drilled piers and cables to retain the massive hillside. During construction of this wall, concussions from pile driving triggered another slope failure, leading to the permanent evacuation of approximately 30 more families[19]. When the wall was finally completed eight years later in 1981, it was at a cost of $22.2 million[20]. At the time, this was one of the costliest landslides in the history of the United States.

The annual costs from landslide damage to public infrastructure alone can be staggering. A study of landslide repairs compiled by students and faculty of the University of Cincinnati, found that the annual direct cost of emergency repairs to local streets in the City of Cincinnati is about $500,000 annually[5]. Deferred repairs of landslide damage to Cincinnati streets amounted to approximately$18.5 million in 1987[21]. These findings were part of a larger special commission established in 1985 to investigate and proactively address the care and maintenance of Cincinnati’s infrastructure,discussed more fully below. It is important to note that these figures do not include the costs of landslide damage to private property within the city, the figures of which are much more difficult to quantify and obtain. Slope instability and damages to residential construction on Cincinnati’s hillsides are widespread problems.

4 Activism, Action and Founding of The Hillside Trust

May 4, 1967 is a benchmark in Cincinnati’s history for establishing hillside protection measures.On that date, a “Hillside Forum” was convened at the Cincinnati Art Museum in Mt. Adams.Presumably, this site was chosen because of its picturesque hilltop location, and its commanding view of the downtown basin.

A flyer advertising the Forum, urged interested citizens to attend to “discuss the FUTURE of Cincinnati’s hillsides.” The Forum’s speakers included City of Cincinnati Department directors, and other professionals representing housing, development, the arts, and the environment. This daylong event produced various action steps, including plans to conduct quantitative and qualitative analyses of the city’s hillsides.

In 1969, the Cincinnati Planning Commission published a “Hillside Study.” It identified 23 hillsides within the city possessing such qualities as natural community dividers, backdrops of vegetated greenery, and focal points for housing areas[22]. Three years later, the Cincinnati Planning Commission hired Richard A. Gardiner &Associates to produce “The Cincinnati Hillsides:Recommended Design Process and Action Program.” The main theme of this report included a step-by-step process to be followed in the next several years to insure proper hillside development[22]. A noteworthy recommendation in the report included the establishment of a nonprofit organization that would buy up undeveloped hillside land and impose design controls when the land was sold for redevelopment[23].

During the late 1960s to 1970s, Pope Coleman was known in city and community circles as an advocate for the arts, the environment, and urban issues. He was one of nine speakers at the 1967 Hillside Forum. He also served as chairman of the Cincinnati Planning Commission’s Hillside Advisory Committee, and in 1971 he established the non-profit Cincinnati Institute, whose mission was to enhance urban quality-of-life issues.

Under Coleman’s leadership, the Cincinnati Institute worked closely with the Cincinnati Planning Commission on hillside research and preservation efforts. In 1973, the National Endowment for the Arts awarded the Cincinnati Institute a $40,000 grant, under its “City Edges”Program, to help preserve and enhance the city’s hillsides. Cincinnati was one of only 37 applicants out of 367 to receive this funding[3]. A portion of this grant went towards analytical research to define the characteristics of Cincinnati’s hillsides, and to create design guidelines.

The Institute hired legal counsel to establish interim control measures and to draft language for eventual zoning ordinances dealing with this issue. Grant funding was used to interview 100 Cincinnatians to record their impressions of the city’s hillsides. The transcripts of these interviews provided invaluable insights into the positive impact that hillsides have upon the psychological wellbeing of the city’s residents[24]. The remainder of the grant served as seed money to establish a non-profit hillside organization, as recommended in the 1971 study by Gardiner & Associates. This non-profit was founded in October, 1976 as “The Hillside Trust.”

The Cincinnati Institute organized and summarized the multitude of hillside research conducted in 1973 and 1974. In 1975, it contracted with San Francisco planner, Rai Y. Okamoto to perform final field surveys, photographic documentation, and additional hillside analysis.This work culminated in a seminal report,“Cincinnati Hillsides: Development Guidelines”prepared for the Cincinnati City Planning Commission in late 1975. The document provided detailed research into geology, soil characteristics,vegetation, tree patterns, public and private uses,visual characteristics and other urban planning considerations. By the late 1970s, the Cincinnati Institute ceased operations as The Hillside Trust began to grow.

5 Hillside Protection Measures Established

In June, 1976, the Cincinnati Planning Commission formally adopted a document known as “Cincinnati Hillsides: Development Guidelines.”At the time, the Planning Commission was finalizing special regulations called Environmental Quality Districts (EQD). EQD was an overlay zoning designed to “assist the development of land and structures in order to be compatible with the environment, and to protect the quality of the urban environment in those locations where the characteristics of the environment are of significant public value and are vulnerable to damage by development permitted under conventional zoning and building regulations”[25]. EQD classified four categories: public investment areas, urban design,community revitalization, and hillsides.

It is the hillside component of these special zoning overlay districts, however, that was the driving force behind drafting EQD in the first place.The city recognized the landslide-prone nature of its hillsides and understood that hillside regulations were needed to prevent unregulated development from exacerbating this problem. All 23 hillsides identified in the 1969 “Hillside Study” were designated as Environmental Quality-Hillside Districts (EQ-HS).The “Hillside Study” had considered these hillsides critically important based on having at least 50 percent of their area within one or more of the 23 designated hillsides, and containing at least four of the following six elements: 1) Slopes of 20 percent or greater; 2) Existence of Kope formation;3) Prominent hillsides viewable from a public thoroughfare located in a valley below a hillside identified within the Cincinnati Hillside System;4) Hillsides that possess views of a major stream or valley; 5) Hillsides that function as community separators or community boundaries as identified in a community plan accepted and approved by the City Planning Commission; and 6) Hillsides which support a substantial wooded cover.

Despite years of effort, less than half of the 23 hillsides designated under the EQ-HS were legislated under city zoning. Individual community councils had the responsibility of recommending to City Council the adoption of established EQ-HS districts within their own neighborhoods. Perhaps a lack of urgency led to the failure to adopt EQHS districts in these neighborhoods. Nevertheless,all basin hillside communities including East Price Hill, Mt. Auburn, Clifton and Mt. Adams adopted and legislated EQ-HS zoning, beginning as early as 1976. Not only do these hillside communities possess commanding views of the downtown basin, they also provide striking natural landmarks when viewed from the basin floor (Fig.7). Ironically,at the same time the City began enacting measures to proactively manage its hillsides, landslide losses in the Cincinnati area during the 1970s, were the highest per capita ever documented for a U.S. urban area[26].

In the mid-1980s, a blue-ribbon group of Cincinnati business and academic leaders was formed to recommend ways to improve and protect the city’s assets, including measures needed to finance the suggested improvements. In 1987,this committee produced what is known as the Smale Infrastructure Commission Report, headed by John Smale, then chairman and chief executive officer of the Proctor & Gamble Company. More than 100 recommendations were listed in the report, four of which pertained to hillsides. The most important of these hillside recommendations were adopted by Cincinnati in 1989.

The first recommendation involved funding an initial inventory of all the city’s retaining walls,including future budget allocations to keep the inventory current. As of 2018, nearly 80 linear kilometers of retaining walls were documented within the city[27]. The success of this original effort has grown into the Retaining Wall and Landslide Stabilization Program, which has the goal of“bringing all existing walls into good condition,and stabilizing landslides that impact the City’s roadways”[27].

Each City wall is inspected on a six-year cycle, which assists in determining whether a wall needs to be replaced or rehabilitated, if necessary.Funding for this program is carefully allocated each year with a focus on addressing the most urgent needs first, to prevent serious damage to city streets and utilities. Of note, this program has not curtailed landslides either above or below the City’s retaining walls. It has simply slowed and lessened immediate impacts closest to city streets and utilities.

7 從盆地向北仰望克利夫頓山坡的主要街道
Main Street from the basin floor looking north towards the Clifton hillside

The second recommendation implemented was the establishment of a Geo-Technical Office within the City’s Department of Transportation and Engineering. Since 1989, the City has maintained a full-time engineering geologist (a geologist trained with an engineering background),and a full-time geo-technical engineer. Together,the primary duties of these positions are to provide geo-technical expertise concerning landslide stabilization and prevention within the public rightof-way, and on any other property controlled by the city. The geo-technical staff also consult with all other city departments, including the Departments of City Planning and Buildings and Inspections.Specifically, they assist building plan examiners in their review of projects in landslide-sensitive areas.The Smale Report originally recommended that a geologist be one of the two professionals employed within the Geo-Technical Office. A geologist is more inclined to recognize pre-existing landslide conditions, and to reference the historical record of local landsliding, which otherwise is more easily ignored or forgotten. For its part, The Hillside Trust serves as a valuable check on this issue and provides an institutional record of memory for historical landslides, hillside use, and advocacy.

6 The Hillside Trust Establishes its Hillside Advocacy Role

8 2012年普賴斯山某區(qū)域的修復工作，該區(qū)域在鄰近盆地西邊公寓的位置發(fā)生嚴重塌方
Remediation work on a hillside in 2012 that collapsed perilously close to condominiums west of the basin in Price Hill

When The Hillside Trust was formed in 1976,it became clear early on that it lacked the financial resources to implement one of its charter purposes,which was to be a land bank that purchased and held hillside land, then supervised its future development in a responsible manner. Instead, The Hillside Trust emphasized its other charter purposes of: 1) research and education; 2) land conservation; and 3) advocacy of responsible land use.

Following the 1987 Smale Infrastructure Commission Report, and a 1988 Conference hosted by The Hillside Trust entitled, “Dollars and Sense: The Economic Impact of Landslides in Cincinnati and Hamilton County”, The Hillside Trust embarked upon an ambitious research effort in 1989. Completed in 1991, this research was published as “A Hillside Protection Strategy for Greater Cincinnati.” Volume 2 of the research included detailed hillside analyses and a series of maps pertaining to visual quality,landslide susceptibility, environmental-ecological quality, development susceptibility, visual and environmental sensitivities, and hillsides prioritized for protection. Volume 3 of the research included 145 hillside-specific development guidelines,drawing from the information and analyses produced in Volume 2. Volume 1 consisted of a short introduction to the study.

More than 300 copies of this research were sold (at cost) to various municipal planning departments and private planning and design firms across the United States and Canada. The Hillside Trust hosted a workshop in 1992 and directed communications to local governments within the metropolitan region, recommending that they adopt the hillside development guidelines.Ultimately, neither the City of Cincinnati nor any other local jurisdiction adopted the guidelines.However, in 1997, Cincinnati recognized The Hillside Trust’s growing professional reputation within the region as an expert on hillside and landslide issues. The city began notifying the organization about hillside developments proposed within its EQ-HS districts and invited it to publicly comment on them. Between 1997 and 2003, The Hillside Trust provided either written or oral testimony on at least 28 development proposals within these districts. While The Hillside Trust is not opposed to development, it will cooperate with local residents, when necessary, to expose plans that it believes will have a negative impact on the surrounding environment, or to highlight any plans that lack engineering foresight. The Hillside Trust can undertake this role because of the expertise of its trustees, technical advisors, and its executive director.

In early 2004, Cincinnati unveiled a new zoning code. All EQ-HS zoning was replaced with a new classification called Hillside Overlay Districts(HOD). Whereas less than half of the former EQHS districts were codified into law, the new Hillside Overlay Districts provide city-wide application.Property is zoned under an HOD classification if any portion of it contains a slope of 20 percent or greater, and/or any part of it is designated as moderately high or high in landslide susceptibility,according to a 1980 “Landslide Susceptibility Map produced by Sowers and Dalrymple for the city. Both the 1969 “Hillside Study” and the 1975“Cincinnati Hillsides Development Guidelines”report were incorporated in the Hillside Overlay District zoning as supporting documentation.

Hillside Overlay District zoning includes a set of base development requirements, under which any application seeking a building permit is obligated to meet. Section 1433-19 of the Cincinnati Zoning Code lists these requirements:1) Any new building or building alteration must be contained within the maximum building envelope(the parameters of which are defined by the City);2) Buildings proposed on top of the hillside must be taller than wider to accentuate the vertical dimension; 3) Buildings proposed below or above the brow of the hill must be staggered or stepped in depth and width to match the topography;4) Rooftop utilities and mechanical equipment are either to be avoided altogether, or screened and sound controlled; 5) All pervious surfaces remaining after completion of construction must be landscaped in trees, shrubs, grass, or other ground covers to promote hillside stability and reduce excessive water runoff; 6) Excavation and fills should not exceed eight feet in cumulative height. Excavation and/or fill of any height or cumulative amount that is not tied to a specific development is expressly prohibited; 7) A preliminary geo-technical evaluation should address relative hillside stability.

If any one of these base requirements is not met, the applicant is required to appear before a city-appointed hearing examiner to testify as to why a variance should be granted to exempt one or more of the requirements. Between 2004 and 2014,the hearing examiner was selected from the ranks of the city’s Planning Department. Since 2014, the hearing examiner has been selected from the city’s Law Department. It is The Hillside Trust’s opinion that representation from the city’s Law Department has resulted in stricter interpretation of the HOD language. Since the HOD was legislated in 2004,The Hillside Trust has publicly commented on at least 43 hillside development cases.

7 Summary and Conclusions

Cincinnati of the early 21st century is a city that has inherited various hillside liabilities extending beyond the natural instability of its slopes. Exploitive and detrimental land-use practices from previous centuries, and negligent engineering solutions, many of which pre-date the original EQ-HS zoning, have created a legacy of long-term (if not perpetual) responsibilities for the city and its residents.

Cincinnati has evolved to a point of being more proactive in the protection of its public infrastructure in recent years, but more could and should be done to strengthen oversight of hillside development on private property. Pressures from the private sector to build on hillsides are strong and will only grow stronger in the generations to come. In highly desirable neighborhoods, often the only undeveloped lands remaining are those occupied by slopes. Many hillsides also possess spectacular views of the basin and/or the Ohio River, and are highly prized for their profit-making potential. These hillsides often carry an even higher development risk, because of significantly steeper grades.

While the former EQ-HS zoning was a step in the right direction, it was not foolproof. Anecdotally, at least one private hillside development approved under the former EQ-HS in 2003, failed in 2012 when a massive section of hillside collapsed, resulting in a repair bill in the hundreds of thousands of dollars (see Figure 8).Fortunately, condominium owners were able to sue the developer under the State of Ohio’s 10-year statute of limitations pertaining to developer liability. The Hillside Trust had publicly commented on this case during the zoning approval process.When the failure occurred, it discovered at least one of its recommendations, siting the building further away from the brow of the hill, was not followed by the developer. To date, no known slope failures have occurred involving development projects approved under the current HOD zoning.

That said, the city would be wise to strengthen the delivery and effectiveness of its hillside development requirements with the following improvements. One, within the real estate community, many real estate agents are unaware of Cincinnati’s Hillside Overlay Districts, especially as they relate to existing housing or new construction.The city could remedy this problem by providing a Geographic Information Systems (GIS) parcelspecific boundary map on its municipal website,highlighting the areas covered by HOD zoning.Whenever a cursor goes over an HOD parcel on the computer screen, a drop-down box could appear explaining the nature and expectations of the HOD. This would serve to notify various professionals and the public at-large about the risks associated with hillside development and hillside living in these areas.

Two, the city also could implement stronger enforcement of its HOD zoning by requiring developers to pay for a geo-technical engineer to be on-site during all grading and earthworks stages of the development, ensuring that the engineering report is being followed as advised. The preliminary geo-technical engineering report already mandated by the City, could be strengthened by requiring developers to engage the services of a geologist,who is trained to observe and document any preexisting landslide conditions on site that might otherwise go unnoticed by civil or geo-technical engineers.

Three, the city could add legislation fining any HOD applicant (developer, designer or homeowner) who knowingly submits false or misleading information to the city concerning building permits and variances. The Hillside Trust has witnessed several situations where an applicant either built the project larger than submitted in the design plans or failed to implement appropriate storm water control measures as promised.

Finally, the city could close any loopholes that allow hillside developers to navigate around the HOD process altogether. In 2016, an applicant for a 19-home development found a way to legally maneuver around HOD zoning requirements by gaining project approval directly from the City Planning Commission under its subdivision regulations. Ultimately, there was no public hearing under the HOD, in which The Hillside Trust or others could ask questions, raise concerns, or discuss details of the case. Problems arose during the grading and earthworks phase of the project when residential properties were flooded downhill following a torrential rainstorm.

In closing, Cincinnati is built upon a spectacularly beautiful yet sensitive landscape, with a long and expensive history of landslide damages,repairs and mitigation. This paper highlights the liability side of interacting with these hillsides, and what Cincinnati has done to begin minimizing its exposure to further damages and costs.

Notes:

Fig.1 courtesy of Pope Coleman, Fig.2,7-8 courtesy of Eric Russo, Fig.3 ? Charles Fontayne and William Porter’s Daguerreotype View of Cincinnati, The Cincinnati Panorama of 1848 in the Collection of the Public Library of Cincinnati and Hamilton County, Fig.4-6 courtesy of University of Cincinnati Library.