Spatiotemporal Analysis of the Formation of Informal Settlements in a Metropolitan Fringe: Seoul (1950–2015)

sustainability

Article Spatiotemporal Analysis of the Formation of Informal Settlements in a Metropolitan Fringe: Seoul (1950–2015)

Yiwen Han 1,2, Youngkeun Song 1,2,*, Lindsay Burnette 3 and David Lammers 4 1 Interdisciplinary Program in Landscape Architecture, Seoul National University, Seoul 08826, Korea; [email protected] 2 Graduate School of Environmental Studies, Seoul National University, Seoul 08826, Korea 3 Department of Landscape of Architecture and Regional Planning, University of Pennsylvania, Philadelphia, PA 19104, USA; [email protected] 4 CDP Europe, Potsdamer Platz-Kemperplatz 1, Berlin 10785, Germany; [email protected] * Correspondence: [email protected]; Tel.: +82-10-8007-2939

Received: 3 May 2017; Accepted: 29 June 2017; Published: 6 July 2017

Abstract: In many metropolitan areas, the urban fringe is defined by highly sensitive habitats such as forests and wetlands. However, the explosive growth of urban areas has led to the formation of informal settlements in the urban fringe, subsequently threatening these sensitive habitats and exaggerating several social and environmental problems. We seek to improve the current understanding of informal settlements and their formation in the metropolitan fringe through a comprehensive spatiotemporal analysis of the Guryong Area (GA) in the Gangnam District, Seoul, South Korea. We measured the land-use and land-cover (LULC) changes in the entire GA from 1950 to 2015, and then analyzed the changes in one specific land-use type defined as “spontaneous settlements”. We then combined these changes with landform and slope data in 600-m-wide bands along the gradient of urbanization. The results showed spontaneous settlements distributed in small clusters in 1975, and the growth of this distribution into larger, more condensed clusters beginning in 1985. Between 1950 and 2015, the total area of spontaneous settlements decreased, while the settlement locations shifted from the urban core to the marginal area of the GA. Meanwhile, the locations selected for spontaneous settlements moved from plain areas with slopes of 2–7%, to more steeply sloped, remote areas such as the mountain foothills with slopes of 15–30%. These results suggest that the spatial characteristics of informal settlements are shown in the degree of aggregation and marginalized trend indicated from the analysis of spontaneous settlements. Finally, we hope the spatial analysis can be used as a basis and starting point for the evaluation process of informal settlement redevelopments in other areas of Seoul, as well as in other Asian cities.

Keywords: land use and land cover; hillside neighborhoods; transition analysis; gradient analysis; Gangnam district

1. Introduction

1.1. Informal Settlements in the Urban Fringes Urban fringes are seen as unique land-use areas because of their geographic location, soil type, and topography [1]. In these areas, the complex mosaic of land use and land cover (LULC) produces sprawling settlements characterized by low-density residential areas, neighbored with agricultural plots and farmlands. These areas are often deﬁned by highly sensitive habitats such as forests, wetlands, and rivers [2,3]. These existing natural habitats are worth being conserved because they can generate diverse ecosystem functions for cities, such as crop production, biodiversity, and carbon

Sustainability 2017, 9, 1190; doi:10.3390/su9071190 www.mdpi.com/journal/sustainability Sustainability 2017, 9, 1190 2 of 18 storage. However, the explosive growth of Asian mega-cities in the post-war decades has created a chaotic mixture of urban and rural land use in metropolitan fringes. It has provoked the formation of several informal settlements in such areas, which has resulted in heightened social and environmental problems [4,5]. Informal settlements—which are variously referred to as autonomous urban settlements, slums, barrios, bidonvilles, shantytowns, squatter settlements or favelas—have generally sprung up without, or in deﬁance of, government approval [6–12]. These settlements tend to share some common features globally [13], such as limited economic activities, difﬁcult living conditions, lack of adequate housing, and residential infrastructure that tends to be unsafe and unhygienic. This living environment not only causes a social divide whereby settlement dwellers easily become impoverished and face social exclusion, but it also impacts the natural environment in often harsh and irreversible ways.

1.2. Spatial Analysis for Informal Settlements To identify potential strategies and plans for the future management of informal settlements in the urban fringe, the process of spatial transformation must first be elucidated. Comprehensive spatiotemporal analyses of LULC offer a powerful tool for uncovering historical relationships between human activities and the environment [14–17]. This is useful for improving our understanding of informal settlement development in Asian cities. There have been many studies on informal settlements, which have used LULC change detection as a decision-making tool for urban planners and policy makers. The previous studies primarily concentrated on: (1) the impact of scale on land-cover fractions in informal settlements [18]; (2) the advantages of using high-resolution satellite images to identify informal settlements [19,20]; and (3) the detection of spatial and temporal patterns of informal settlement growth to inform future planning [21–23]. However, few studies have analyzed informal settlement formation through the LULC shifts for a specific urban region along the gradient of urbanization, for example, the urban fringe. In this study, examination at the local scale of small urban areas can provide more accurate information on the local characteristics of a specific targeted area [18,19,24–26].

1.3. Informal Settlements in the Seoul Metropolitan Fringe In the late 1960s and 1970s, South Korea experienced immense economic growth, which was accompanied by expansive rural to urban migration across the country. During this time, due to the difficulty in accommodating the massive influx of people to urban areas, an estimated 20–30% of housing developments across South Korea were informal and deficient in adequate space and basic facilities [27]. In response, the city of Seoul began to focus primarily on controlled urban development [28]. As part of this planning, slum clearance projects were implemented in the 1970s. However, these projects led to further deterioration of the housing situation—leaving the poor with nowhere to go and forcing informal settlements to develop in the marginal areas of Seoul. In the early 1980s, after the ineffective slum clearance of the 1970s, communities labeled as, “newly built slum settlements,” “vinyl house communities,” or “hillside informal neighborhoods” began to spring up on vacant hillsides and in public open green spaces. These communities were characterized by poor housing conditions, overcrowding and a lack of land ownership and building permits [10]. One of the remaining settlements from that period, and the largest until 2015, is now known as the Guryong Slum Village (GSV). The formation of the GSV resulted from the demolition of informal settlements near the stadiums built for the 1988 Olympic Games in the Gangnam District. To make space for the Olympic venues, the government demolished several illegal settlements near the stadiums. The former residents of these areas were not given alternative living spaces, and subsequently were forced to squat in illegal housing areas on the outskirts of Seoul [27]. This gave rise to the beginnings of the GSV, which is one of the few remaining informal settlements in the Seoul urban area, and is located on the outskirts of one of its wealthiest districts, Gangnam. In addition to the GSV, several other informal settlements, Sustainability 2017, 9, 1190 3 of 18

Sustainability 2017, 9, 1190 3 of 18 hosting approximately 2000 households, continued to exist as “hillside informal neighborhoods” near informal settlements, hosting approximately 2000 households, continued to exist as “hillside the fringe of the Gangnam District until 2011. informal neighborhoods” near the fringe of the Gangnam District until 2011. Seoul’s metropolitan area and its surrounding districts are encompassed by mountains on all Seoul’s metropolitan area and its surrounding districts are encompassed by mountains on all sidessides [29 ].[29]. As As a result, a result, the the urban urban fringe’s fringe’s informal informal settlementssettlements have impacted, impacted, and and are are impacted impacted by, by, ecologicalecological characteristics characteristics of of mountains. mountains. Previous studies studies on on the the “hillside “hillside informal informal neighborhoods” neighborhoods” of of SeoulSeoul havehave focusedfocused primarilyprimarily onon socioeconomicsocioeconomic factors, including including policy policy alternatives alternatives [30], [30 ],housing housing regenerationregeneration [11 [11,28],,28], living living conditions conditions [ 10[10].]. However,However, nonenone ofof thesethese studies have have investigated investigated the the spatiallyspatially explicit explicit characteristics characteristics of of informal informal settlements settlements thatthat resultresult from specific specific site site selections selections and and theirtheir relationship relationship with with the the topography, topography, particularly particularly in in a a marginal marginal urban urban area.area. In thisIn this study, study, we we propose propose to to improve improve understanding understanding ofof informalinformal settlements’ formation formation at at the the metropolitanmetropolitan fringe fringe through through a a comprehensive comprehensive spatiotemporalspatiotemporal analysis that that considers considers the the role role of of topographicaltopographical characteristics. characteristics. We We have have conducted conducted thisthis studystudy using the the Guryong Guryong Area Area (GA) (GA) in in the the GangnamGangnam District, District, Seoul, Seoul, Korea, Korea, as a caseas a study.case study. Through Through this study, this westudy, wish we to wish answer to theanswer following the fourfollowing questions: four What questions: was the What historical was the development historical development of LULC from of 1950 LULC to 2015?from 1950 What to characteristics 2015? What of informalcharacteristics settlement of informal formation settlement were formation revealed bywere the revealed changes by in the LULC? changes How in LULC? is the formationHow is the of informalformation settlements of informal related settlements to the topographicalrelated to the to characteristicspographical characteristics of the marginal of the area? marginal And area? finally, whatAnd are finally, the potential what are future the potential implications future of theimplications historical of and the ecological historical researchand ecological for urban research planning for urban planning and informal settlement redevelopments? We measured the changes in the LULC and informal settlement redevelopments? We measured the changes in the LULC for a specific for a specific land-use type defined as “spontaneous settlements.” This allowed us to interpret land-use type defined as “spontaneous settlements.” This allowed us to interpret autonomous features autonomous features of the targeted areas, considering the formation of informal settlements at two of the targeted areas, considering the formation of informal settlements at two scales: the entire GA, scales: the entire GA, and 600-m-wide bands of the area along the gradient of urbanization. In and 600-m-wide bands of the area along the gradient of urbanization. In addition, we identified addition, we identified patches of spontaneous settlement that were gained or lost during four patchessuccessive of spontaneous periods. We settlement then examined that were the relati gainedonship or lost between during informal four successive settlement periods. formation We and then examinedtopographical the relationship characteristics. between informal settlement formation and topographical characteristics. 2. Materials and Methods 2. Materials and Methods 2.1. Study Area 2.1. Study Area The study area, the GA, extends from Guryongsan Mountain (Figure1A) and Deamansan The study area, the GA, extends from Guryongsan Mountain (Figure 1A) and Deamansan MountainMountain (Figure (Figure1B) to1B) the to Yangjacheonthe Yangjacheon River River (Figure (Fig1ureD). 1D). The areaThe area is approximately is approximately 825 ha.825 The ha. GSVThe is locatedGSV is located in a valley in a valley at the at base the base of Guryongsan of Guryongsan Mountain Mountain and and Deamansan Deamansan Mountain,Mountain, facing facing the the YeongycheonYeongycheon stream. stream.

FigureFigure 1. 1.Map Map showing showing thethe location of of the the Guryong Guryong Area Area on onthe theoutskirts outskirts of Gangnam of Gangnam District. District. This Thisincludes includes the the units: units: Dogok Dogok 1 Dong, 1 Dong, Dogok Dogok 3 Dong, 3 Dong, Daechi Daechi 1 Dong, 1 Dong, Gaepo Gaepo 4 Dong, 4 Dong, Gaepo Gaepo 1 Dong, 1 Dong,and andGaepo Gaepo 2 2Dong. Dong. Sustainability 2017, 9, 1190 4 of 18

2.2. Date Collection A series of LULC maps were assembled using ﬁve historical maps with land-cover information from 1950 to 1994, and a contemporary digitized land-use map from 2015 [31–34] (Table1). The topographical characteristics (landforms, slopes, and soil characteristics), were obtained using soil data from the Korean Rural Development Administration (RDA, 2010) [35].

Table 1. Maps used for land-use and land-cover (LULC) reclassiﬁcation.

Year Scale Description Topographic map of Doonjeon; National Geographic Information Institute of the 1950 1:50,000 Republic of Korea. Topographic map of Doonjeon; based on aerial photos with 10 m and 5 m resolution 1975 1:25,000 and field survey; National Geographic Information Institute of the Republic of Korea. Land cover map of Doonjeon; based on topographic map of Doonjeon in 1975, 1975 1:25,000 National Construction Research Institue Ministry of Construction. Topographic map of Doonjeon, based on aerial photos with 10 m and 5 m resolution 1985 1:25,000 and field survey; National Geographic Information Institute of the Republic of Korea. Topographic map of Suwon, based on aerial photos with 10 m and 20 m resolution and 1994 1:50,000 field survey; National Geographic Information Institute of the Republic of Korea 2015 1:1000 Vector data of land use, Seoul Metropolitan Government.

2.3. Date Processing

2.3.1. Mapping and Re-Classifying the LULC The first step in data processing involved standardizing and transforming the significant LULC types in each map into a common LULC classification with a unified legend covering the study periods (Figure2). The LULC classifications were based on significant information interpreted from the historical maps [36]. They were then mapped as polygons in a vector-based geographical information system (GIS) using ArcGIS 10.2.2. Each LULC type was quantified to identify the nature of land cover and its transitions. Because historical maps differ in details, survey techniques, accuracy, and map content, there are some shortcomings of these maps. However, the transformation of specific map categories into a generic type is a common technique used in historical landscape analysis to make comparisons between time periods [36,37]. The study periods were selected to represent key periods in South Korea’s history. Given the available historical data, five different years have been used to analyze the changes in the LULC: 1950, 1975, 1985, 1994, and 2015. Until the late 19th century, the original network of Seoul’s primary streets remained unchanged [28]. The Korean War, a major historic turning point for the Korean Peninsula, lasted from 1950 to 1953, during which many natural habitats were destroyed. Following the war, the concentration of South Korea’s population in Seoul accelerated the development of roads and residential land due to rapid industrialization. The Gangnam District developed rapidly during this time, as can be seen from the 1975 map [31]. The maps from 1985 and 1994 represent the periods before and after the Olympic Games, respectively [33,34]. Finally, the map from 2015 was chosen to represent the current status of the area [32]. A spatial-temporal database including the five time periods of 1950, 1975, 1985, 1994, and 2015 was created using the historical topographic maps and historical land use maps for the Gangnam districts. LULC patches in 1950 were digitized from a georegistered digital map, scanned from a hard copy of the 1950 topographic map of the Doonjeon area (Gangnam district’s old name). The 1975 (Doonjeon area), 1985 (Doonjeon area) and 1994 (Suwon area) maps were paper works created from aerial photos, with a spatial resolution of 5 m, by the National Geographic Information Institute of the Republic of Korea. LULC patches in 2015 were digitized from aerial photos by the Seoul Metropolitan Government, SustainabilitySustainability2017 2017, 9, ,9 1190, 1190 5 of 518 of 18 with a spatial resolution of 5 m. Each map from 1950 to 1994 was digitized using image-to-image georeferencing methods in order to match the scales at a 5 m spatial resolution.

Figure 2. Reclassiﬁed maps of land use and land cover (LULC) in 1950, 1975, 1985, 1994, and 2015; (a) is the location of the Guryong Slum Village (GSV).

The new LULC classification patches were interpreted and digitized based on a series of criteria that were defined for land cover delineation (Table2). These were identified as the following LULC categories: agriculture, woodland, transportation, open field, water, planned settlements, and spontaneous settlements. The most significant LULC type for this study was the category “spontaneous settlements” (Table2-01) (Figure3A). This LULC type is useful for examining changes The new LULC classification patches were interpreted and digitized based on a series of criteria in settlements that form spontaneously during urbanization. As mentioned in the introduction, that were defined for land cover delineation (Table 2). These were identified as the following LULC “autonomous urban settlements” were generally occupied through the processes of informal occupation categories: agriculture, woodland, transportation, open field, water, planned settlements, and ratherspontaneous than through settlements. formal planningThe most orsignificant construction LULC [12 ].type This for in turnthis manifestedstudy was into the spontaneouscategory spatial“spontaneous patterns. settlements” However, due(Table to 2-01) the limited (Figure accuracy 3A). This ofLULC historical type is data, useful some for examining of the unidentifiable changes autonomouslyin settlements formed that form settlements spontaneously were included during (Figureurbanization.3c). Therefore, As mentioned we use thein the term introduction, “spontaneous settlements”“autonomous to denoteurban thesettlements” characteristics were ofgenerally informal occupied settlements through (Figure the3b). processes of informal occupation rather than through formal planning or construction [12]. This in turn manifested into spontaneous spatial patterns.Table 2. However,Reclassification due ofto LULCthe limited types usedaccuracy in the of analysis. historical data, some of the unidentifiable autonomously formed settlements were included (Figure 3c). Therefore, we use the termNo. “spontaneous Land Cover settlements” Class to denote the characteristics Class of Descriptioninformal settlements (Figure 3b). Autonomous urban settlements, informal settlements including slums or 01 Spontaneous settlementTable 2. Reclassificationsquatter settlements of LULC and types unplanned used in settlementsthe analysis. ; other unidentifiable settlements with spontaneously formed characteristics. No. Land Cover Class Urban residential, commercialClass or Description industrial areas according to official 02 Planned settlements Autonomousurban planning. urban settlements, informal settlements including slums or squatter 0301 SpontaneousTransportation settlement settlements Roads, and large unplanned scale/public settlements parking ; other lots. unidentifiable settlements with spontaneously formed characteristics. 04 Agriculture Cultivated field, open agricultural land. 02 Planned settlements Urban residential, commercial or industrial areas according to official urban planning. 0503 TransportationWoodlands Roads, Forest large or scale/public parks with parking clustering lots. trees. 0604 AgricultureWater Cultivated River, stream,field, open pool, agricultural canal. land. 0705 Open Woodlands field Forest Planned or parks or with designed clustering green trees. spaces; Un-developed or unused lands, heath. 06 Water River, stream, pool, canal. 07 Open field Planned or designed green spaces; Un-developed or unused lands, heath. Sustainability 2017, 9, 1190 6 of 18 SustainabilitySustainability2017 2017, 9,, 11909, 1190 6 of6 of 18 18

FigureFigure 3.3.The The conceptualconceptual figurefigureof ofthe the relationship relationship between between “spontaneous “spontaneous settlements”settlements” andand “slum“slum settlements”.settlements”.Figure 3. The (A conceptual) SpontaneousSpontaneous figure settlementssettlements of the relationship areare notnot ( (bbetweenb)) informalinformal “spontaneous settlements,settlements, settlements” becausebecause ofof (andc(c)) other other“slum unidentifiableunidentifiablesettlements”. spontaneous spontaneous(A) Spontaneous settlements. settlements. settlements are not (b) informal settlements, because of (c) other unidentifiable spontaneous settlements. 2.3.2.2.3.2. MappingMapping thethe TopographicalTopographical Characteristics Characteristics 2.3.2. Mapping the Topographical Characteristics InIn thethe secondsecond stepstep ofof datadata processing,processing, thethe topographicaltopographical characteristicscharacteristics werewere assessed.assessed. TheThe topographicaltopographicalIn the second characteristicscharacteristics step of wereweredata derivedprocessing,derived fromfrom the soilso iltopographical codescodes fromfrom the the characteristics Korean Korean soil soil information informationwere assessed. system system The (http://soil.rda.go.kr/soil/index.jsp(http://soil.rda.go.kr/soil/index.jsp).topographical characteristics were derivedThis). This included from included so theil codes thetopographical topographical from the Koreanlandscape landscape soil types,information types, slopes, slopes, system and andrecommended(http://soil.rda.go.kr/soil/index.jsp). recommended use usefor each for each soil soilcode. code.This In 1964,included In 1964, the the Korean topographical Korean government government landscape launched launched types, a National a slopes, National Soil and SoilSurveyrecommended Survey Project, Project, testinguse testing for andeach and documenting soil documenting code. In soil1964, soil ty typespesthe throughoutKorean throughout government South South Korea, Korea, launched and increasingincreasinga National the theSoil amountamountSurvey of ofProject, detail detail each eachtesting year. year. and Each Each documenting soil soil type type is is defined soildefined ty bypes by its throughout its physical physical and Southand chemical chemical Korea, properties, properties,and increasing as wellas well asthe itsasamount landscapeits landscape of detail parameters parameters each year. [29]. AlthoughEach[29]. soilAlthough type landforms is definedlandforms and slopesby itsand physical changed slopes and significantlychanged chemical significantly during properties, periods during as well of rapidperiodsas its urbanization, landscapeof rapid urbanization, parameters the primary the[29]. landscapes primary Although landscapes types landforms determined types and determined from slopes the changed soil from characteristics the significantly soil characteristics retained during theirretainedperiods natural theirof rapid status. natural urbanization, Thirty-two status. Thirty-two soil the codesprimary soil were landscapescode identifieds were types identified in the determined GA in and the 10 GA from soil and codesthe 10 soil soil were characteristics codes found were in GSVfoundretained (Table in GSV their3). Using (Table natural the 3). status. topographyUsing Thirty-twothe topography type attached soil codetype tos atta eachwereched ofidentified the to each soil codes ofin the as soilGA an codesand index, 10 as thesoil an soil codesindex, types were the weresoilfound types grouped in GSVwere into (Table grouped eight 3). topographical Usinginto eight the topography topographical types throughout type types atta Seoulched throughout to [29 each]. Five ofSeoul ofthe these soil[29]. codes eight Five topographicalasof anthese index, eight the typestopographicalsoil weretypes foundwere types grouped in were the Gangnam found into eight in the District topographical Gangnam and in District the types GA: and throughout local in the alluvial, GA: Seoul local alluvial [alluvial,29]. Five plain, alluvial of mountainthese plain, eight foothill,mountaintopographical rolling foothill, or types hill, rolling were and mountain foundor hill, in and the or hill. Gangnammountain Similarly, Districtor sixhill. slope andSimilarly, in classifications the GA:six localslope were alluvial, classifications identified: alluvial 0–2%, wereplain, 2–7%,identified:mountain 7–15%, 0–2%, foothill, 15–30%, 2–7%, rolling 30–60%, 7–15%, or andhill,15–30%, 60–100%and 30–60%,mountain (Figure and or4 )[60–100% hill.35]. Similarly, The (Figure landforms six4) [35].slope were The classifications closely landforms related were were to slopecloselyidentified: type, related and 0–2%, someto slope2–7%, landforms type, 7–15%, and included 15–30%, some diverse landforms 30–60%, slopes; and included for60–100% example, diverse (Figure the slopes; local 4) [35]. alluvial for Theexample, included landforms the slopes local were ofalluvialclosely 2–7% and includedrelated 7–15%. to slopes slope of type, 2–7% and and some 7–15%. landforms included diverse slopes; for example, the local alluvial included slopes of 2–7% and 7–15%.

Figure 4. Maps of landforms and slopes based on soil data downloaded from the database of Figure 4. Maps of landforms and slopes based on soil data downloaded from the database of Agricultural and Soil Information of South Korea; (a) shows the location of Guryong Slum Village (GSV). AgriculturalFigure 4. Maps and Soilof landformsInformation and of Southslopes Korea;based (a)on showssoil data the downloadedlocation of Guryong from the Slum database Village of (GSV).Agricultural and Soil Information of South Korea; (a) shows the location of Guryong Slum Village (GSV). Sustainability 2017, 9, 1190 7 of 18

Table 3. Soil types and their description in the Guryong Area (GA).

Soil-Code Soil-Series Soil Order Landforms Slope Recommended Use In GSV SRF2 Songsan Inceptisols Mountain or Hill 60~100 Forest OnD2 Osan Inceptisols Rolling or Hill 15~30 Orchard and mulberry 4 HEC Hoegog Entisols Local alluvial 7~15 Paddy 4 SqD Suam Entisols Mountain foot 15~30 Native Pasture 4 JoB Jigog Inceptisols Local alluvial 2~7 Cultivated upland 4 JiB Jisan Inceptisols Local alluvial 2~7 Paddy 4 NkB Noegog Inceptisols Local alluvial 2~7 Cultivated upland JOC Jigog Inceptisols Local alluvial 7~15 Cultivated upland 4 SuC Sangju Inceptisols Local alluvial 7~15 Cultivated upland SuB Sangju Inceptisols Local alluvial 2~7 Cultivated upland YbC2 Yesan Inceptisols Rolling or Hill 7~15 Cultivated upland SqC Suam Entisols Mountain foothill 7~15 Cultivated upland SfB Sachon Inceptisols Local alluvial 2~7 Paddy SE Seogcheon Inceptisols Alluvial plain 0~2 Paddy OnC2 Osan Inceptisols Rolling or Hill 7~15 Cultivated upland Gt Gangseo Inceptisols Alluvial plain 0~2 Paddy Jd Jungdong Entisols Alluvial plain 0~2 Cultivated upland OnE2 Osan Inceptisols Rolling or Hill 30~60 Native Pasture 4 OcB Ogcheon Inceptisols Local alluvial 2~7 Paddy 4 Np Nampyeong Inceptisols Alluvial plain 0~2 Paddy SNE2 Songsan Inceptisols Mountain or Hill 30~60 Native Pasture 4 YbC2 Yesan Inceptisols Rolling or Hill 7~15 Cultivated upland YbD2 Yesan Inceptisols Rolling or Hill 15~30 Cultivated upland Pt Pyeongtaeg Inceptisols Alluvial plain 0~2 Paddy Nn Nagdong Entisols Alluvial plain 0~2 Cultivated upland HT Hwasu Inceptisols Alluvial plain 0~2 Paddy DsD2 Dosan Entisols Mountain or Hill 15~30 Native pasture AsC2 Asan Entisols Rolling or Hill 7~15 Cultivated upland YcB Yeongog Inceptisols Mountain foothill 2~7 Cultivated upland SRE2 Songsan Inceptisols Mountain or Hill 30~60 Native pasture Ce Cheongweon Inceptisols Alluvial plain 0~2 Paddy 4 DsD2 Dosan Entisols Mountain or Hill 15~30 Native pasture 4: the soil code exists in the location of GSV.

2.4. Date Analysis

2.4.1. Determination of Changes and Transition Analysis The spatial pattern development in the GA over time was analyzed at two spatial scales: the entire GA, and bands extending from the core of the GSV to the upper end of the GA. The analysis of the bands demonstrated the variability in the spatial patterns of the LULC [38–40], especially that of spontaneous settlements, along the gradient of urbanization in the Gangnam District [39]. Six 600-m-wide bands at intervals of 3.3 km were defined, beginning at the core of the GSV and extending out towards the urban core of the GA (Figure5). The size of each distance band was defined using the size of GSV and the average width from the core of the GSV to the border of the GA [38]. To determine changes in spatial pattern, and to identify the “from–to “nature of the transitions in spontaneous settlement land-cover types, changes in land cover were examined using successive periods: 1950–1975, 1975–1985, 1985–1994, and 1994–2015. By overlaying the spontaneous settlement patch layers from two successive periods, we identified trends in land-cover transitions. For example, an area was defined as “lost” if spontaneous settlement cover occurred in the earlier sample period, but not in the later one. Sustainability 2017, 9, 1190 8 of 18 Sustainability 2017, 9, 1190 8 of 18

FigureFigure 5. Bands 5. Bands separated separated by 3.3 by km 3.3 starting km starting from from thethe core core of GSV, of GSV, and and extending extending to to the the upper upper end end of of the Guryongthe Guryong Area Area (GA) (GA) toward toward the the urban urban core core of of thethe GangnamGangnam District. District. There There were were six bandssix bands in total; in total; eacheach bandband was was 600 600 m m wide. wide.

2.4.2.2.4.2. Analysis Analysis of Relationships of Relationships between between LULC LULC Changes Changes and and Topographical Topographical Characteristics Characteristics The Theband band analysis analysis also also examined examined thethe associationassociation of topographicalof topographical characteristics characteristics with the with location the locationof spontaneous of spontaneous settlements. settlements. We overlaid We overlaid the spontaneous the spontaneous settlement settlement layers with layers the maps with of landformsthe maps of landformsand slopes and to slopes investigate to investigate their relationships their relationships within the specificwithin bands.the specific bands. 3. Results 3. Results 3.1. Changes in Land Cover Types over Time 3.1. Changes in Land Cover Types over Time 3.1.1. Changes in the Time Series across the Entire GA 3.1.1. Changes in the Time Series across the Entire GA The changes in LULC for the entire GA are presented in Figure6. The most significant change Thewas changes the transformation in LULC for of the other entire land-cover GA are presented types into in planned Figure 6. settlements The most andsignificant transportation. change was Approximatelythe transformation 405 haof ofother the GAland-cover were planned types settlementsinto planned areas settlements in 2015, compared and transportation. with 284 ha Approximatelyin 1985. Additionally, 405 ha of the the GA area we occupiedre planned by road settlements construction areas increased in 2015, 3.3-foldcompared between with 284 1975 ha and in 1985.2015. Additionally, The second the most area significant occupied change by road occurred construction in agriculture. increased The percentage 3.3-fold between of agricultural 1975 landand 2015.increased The second 1.63-fold most betweensignificant 1950 change and 1975, occurred but decreased in agriculture. by 90% betweenThe percentage 1975 and of 1985. agricultural The area land ofincreased agricultural 1.63-fold landwas between larger 1950 in 1975 and than 1975, in allbut other decreased sample by periods, 90% between occupying 1975 almost and 50%1985. of The the entire GA. However, by 2015, only a small amount of agricultural land remained in the outskirts of the area of agricultural land was larger in 1975 than in all other sample periods, occupying almost 50% district. The third most significant change occurred in woodland cover, which decreased year by year. of the entire GA. However, by 2015, only a small amount of agricultural land remained in the Most of the loss occurred in the periods 1950–1975 and 1975–1985, when the percentage of woodland outskirts of the district. The third most significant change occurred in woodland cover, which cover decreased by 17% and 25%, respectively, subsequently decreasing by a further 15% between decreased year by year. Most of the loss occurred in the periods 1950–1975 and 1975–1985, when the 1994 and 2015 (Figure6). percentage of woodland cover decreased by 17% and 25%, respectively, subsequently decreasing by a further 15% between 1994 and 2015 (Figure 6). SustainabilitySustainability2017 2017, 9, ,9 1190, 1190 99 of of 18 18

FigureFigure 6. 6.The The total total area area of of LULC LULC types types for for ﬁve five sampling sampling periods. periods. Annual Annual rates rates of of LULC LULC change change by by classclass from from 1950 1950 to to 2015 2015 in in percent percent (decimal (decimal fraction). fraction).

3.1.2.3.1.2. Changes Changes within within the the Bands Bands across across the the Entire Entire GA GA TheThe percentages percentages of of various various land-cover land-cover types types within within eacheach bandband changedchanged overover timetime (Figure(Figure7 ).7). TheThe area area of of natural natural landscape landscape cover cover decreased decreased along along the the gradient gradient of of urbanization urbanization over over time. time. This This is is illustratedillustrated by by the the decrease decrease in in the the water water and and woodland woodland land-use land-use types types and and corresponding corresponding increases increases in in thethe planned planned settlements settlements area area and and transportation transportation categories. categories. The The water water landscape landscape type type disappeared disappeared inin bands bands 1 1 and and 2 2 by by 1985, 1985, but but reappeared reappeared in in band band 2 2 in in 2015. 2015. This This is is interpreted interpreted in in Figure Figure2, 2, where where mapsmaps from from 1950 1950 and and 1975 1975 show show a a tributary tributary stream stream originating originating from from the the Daemosan Daemosan and and Guryongsan Guryongsan Mountains,Mountains, and and flowing flowing through through the the GSV GSV to to the the Yangjacheon Yangjacheon River. River. In In the the 1985 1985 map, map, the the tributary tributary is is nono longer longer visible. visible. The The loss loss of of this this tributary tributary is is also also reflected reflected in in the the decrease decrease in in water water area area from from 17.07 17.07ha ha inin 1950 1950 to to 9.55 9.55 ha ha in in 1985 1985 (Figure (Figure6). 6). Furthermore, Furthermore, the the shape shape of of the the water water corridors corridors was was more more diverse diverse andand natural natural in in 1950 1950 than than in in 1975. 1975. The The reappearance reappearance of of the the water water landscape landscape type type in in band band 2 2 in in 2015 2015 is is duedue to to the the Korean Korean government government building building several several canals canals in in the the Guyongsan Guyongsan and and Deamansan Deamansan Mountains Mountains forfor hydrological hydrological projects. projects. MostMost of of the the woodland woodland area area was was located located in in bands bands 1, 1, 2, 2, 3, 3, and and 5. 5. The The percentage percentage of of woodland woodland covercover decreased, decreased, with with increasing increasing distance distance from from the corethe core of the of GSV. the ThisGSV. was This true was particularly true particularly in bands in 4bands and 5, 4 in and which 5, in it which decreased it decreased from more from than more 10% than (17.30 10% ha)(17.30 and ha) 60% and (73.02 60% ha)(73.02 in 1950ha) in to 1950 less to than less 4%than (5.96 4% ha) (5.96 and ha) 25% and (22.54 25% ha)(22.54 in 2015.ha) in The 2015. area The of area woodland of woodland in bands in 1bands and 21 decreasedand 2 decreased from more from thanmore 35% than (11.04 35% ha) (11.04 and 80%ha) and (174.17 80% ha) (174.17 to less ha) than to 30% less (7.78 than ha) 30% and (7.78 55% ha) (115.66 and ha),55% respectively. (115.66 ha), Betweenrespectively. 1985 andBetween 2015, 1985 the highest and 2015, percentage the highest of woodland percentage was of maintained woodland inwas the maintained bands where in the the GSVbands is located.where the While GSV the is percentagelocated. While of woodland the percenta decreased,ge of woodland the percentage decreased, of transportation the percentage and of plannedtransportation settlements and planned areas increased settlements correspondingly. areas increased Road correspondingly. construction began Road near construction the urban began core (bandnear 6)the in urban 1974, thencore spread(band 6) to in the 1974, marginal then areaspread (band to the 2) in marginal 1994, and area finally (band occupied 2) in 1994, approximately and finally 20%occupied of each approximately band in 2015. 20% The of planned each band settlements in 2015. The area planned gradually settlements increased area correspondingly gradually increased from bandscorrespondingly 6 to 1. from bands 6 to 1. TheThe agricultural agricultural area area almost almost completely completely disappeared disappeared with with urbanization. urbanization. It It peaked peaked in in 1975 1975 from from bandband 1 1 to to band band 4. 4. However, However, during during the the period period of of rapid rapid development development from from 1975 1975 to to 1985, 1985, large large areas areas of of agriculturalagricultural land land were were lost lost in bandsin bands 3, 4, 3, and 4, 5.and Currently, 5. Currently, agricultural agricultural activities activities remain remain only in only bands in 1bands and 2. 1 Agricultural and 2. Agricultural activities activities often developed often developed alongside alongside built-up villages. built-up We villages. examine We this examine feature this in thefeature following in the section, following where section, we analyze where we spontaneous analyze spontaneous settlements. settlements. Sustainability 2017, 9, 1190 10 of 18 Sustainability 2017, 9, 1190 10 of 18

1950 1974 100% 100% 90% 90% 80% 80% 70% 70% 60% 60% 50% 50% 40% 40% 30% 30% 20% 20% 10% 10% 0% 0% BAND1 BAND2 BAND3 BAND4 BAND5 BAND6 BAND1 BAND2 BAND3 BAND4 BAND5 BAND6

1985 1994

100% 100% 90% 90% 80% 80% 70% 70% 60% 60% 50% 50% 40% 40% 30% 30% 20% 20% 10% 10% 0% 0% BAND1 BAND2 BAND3 BAND4 BAND5 BAND6 BAND1 BAND2 BAND3 BAND4 BAND5 BAND6

2015 100% OPEN FIELD

80% WATER

TRANSPORTATION 60% AGRICULTURE 40% WOODLANDS

20% SPONTANEOUS SETTLEMENTS 0% PLANNED BAND1 BAND2 BAND3 BAND4 BAND5 BAND6 SETTLEMENTS

FigureFigure 7. 7. TheThe proportion proportion ofof LULCLULC types types within within the the 6 distance6 distance bands. bands.

3.2.3.2. Changes Changes in in Spontaneous Spontaneous Settlement Settlement Cover overover TimeTime 3.2.1. Transition Analysis of Spontaneous Settlements: The Entire GA 3.2.1. Transition Analysis of Spontaneous Settlements: The Entire GA The changes in spontaneous settlements in the bands between two successive sample periods The changes in spontaneous settlements in the bands between two successive sample periods were mapped to highlight differences. These maps illustrated not only where changes in spontaneous weresettlement mapped cover to occurred,highlight but differences. also whether These spontaneous maps illustrated settlement covernot only was lost,where which changes LULC in spontaneoustypes they were settlement converted cover to and, occurred, if spontaneous but also settlement whether coverspontaneous increased, settlement which LULC cover types was they lost, whichreplaced LULC [41 ].types Figure they8a showswere converted that the area to and, of spontaneous if spontaneous settlements settlement increased cover by increased, about 26 which ha LULCbetween types 1950 they and replaced 1985. However, [41]. Figure it decreased 8a shows markedly that the by area approximately of spontaneous 33 ha settlements between 1985 increased and by about 26 ha between 1950 and 1985. However, it decreased markedly by approximately 33 ha between 1985 and 1994, subsequently decreasing by a lesser amount between 1994 and 2015. Spontaneous settlement land cover developed alongside agricultural activities, yet the area is only Sustainability 2017, 9, 1190 11 of 18

1994, subsequently decreasing by a lesser amount between 1994 and 2015. Spontaneous settlement land cover developed alongside agricultural activities, yet the area is only shown to increase significantly in the 1975 map (Figure6). In the 1985 map, the area of spontaneous settlements increased by a lesser amount, but the area of agricultural land dramatically decreased at the same time. The size of a mean patch in 1985 was almost double that in 1975, indicating that settlements were more clustered in 1985 than in 1975 (Figure8a). Although the percentage of spontaneous settlements was largest in 1985, that was a transition period before the total urbanization of the GA. The settlements built in the present-day location of the GSV first appeared in 1985. In 2015, not only the GSV but also the remaining area of spontaneous settlements were informal settlements. Transition analysis indicated significant turnover in spontaneous settlement cover. The increase in spontaneous settlement land varied from 21% between 1985 and 1994 to 144% between 1950 and 1975, whereas the decrease varied from 36% between 1950 and 1975 to 89% between 1985 and 1994 (Table4). The largest decrease (89%) from 1985 to 1994 represented conversion to planned settlements land use (28.2 ha) during the period of rapid urbanization. Subsequently, only 4.26 ha was left unchanged from 1994 to 2015, compared with the 26.01 ha left unchanged from 1975 to 1985 (Table4). The GSV occupied the largest percentage of unchanged land from 1994 to 2015, after being converted from the land-cover types of agriculture and woodland since 1985 (Figure8b). The substantial area of spontaneous settlements that replaced woodland was due to rapid urbanization in earlier years. However, this phenomenon continued in the period from 1994 to 2015, indicating that the formation of spontaneous settlements occupying natural land continued after the period of rapid urban development.

Table 4. Summary of results from the transition analysis of changes in spontaneous settlement areas for four periods.

1950–1975 1975–1985 1985–1994 1994–2015 Unchanged Land Cover (Ha) 14.35 26.01 4.05 4.26 Loss of Spontaneous Settlements Cover (Converted to) (Ha) Transportation 0.35 3.03 0.31 2.49 Open ﬁeld 0 2.52 12.58 0.12 Woodland 1.6 2.35 1.87 2.79 Agriculture 6.81 3.21 1.5 0.64 Water 0 0 0 0 Planned settlements 0 11.5 28.2 6.58 Total * 8.76 22.61 44.46 12.62 Percent ** 0.36 0.47 0.89 0.74 Gain of Spontaneous Settlements Cover (Regenerated from) (Ha) Transportation 0 0 0 0 Open ﬁeld 19.87 0 0.15 0.15 Woodland 12.8 6.1 4.69 6.46 Agriculture 2.68 17.93 5.83 5.12 Water 0.35 0 0 0 Planned settlements 0 0 0 0 Total * 35.7 24.03 10.67 11.73 Percent ** 1.44 0.5 0.21 0.68 * Total: the total area of spontaneous settlements gained or lost during the period between two successive sampling periods; ** Percent: the percentage total area of spontaneous settlements gained or lost compared to the previous sample year. SustainabilitySustainability2017, 9 2017, 1190, 9, 1190 12 12of 18 of 18 Sustainability 2017, 9, 1190 12 of 18

60 2.15 2.5 100% 48.48 50.06 60 2.15 2.5 100%90% 50 50.06 2 1.6448.48 90%80% 50 1.59 40 1.85 2 80%70% 1.64 1.59 1.5 70%60% 40 24.67 1.85 30 0.99 1.5 60%50% (ha) 40% 30 24.67 0.99 17.17 15.92 1 50%

(ha) 20 30% 1 40% 17.17 15.92 20% 20 10 0.5 30% 10% 20% 10 0.5 0% 0 0 10% BAND1 BAND2 BAND3 BAND4 BAND5 BAND6 1950 1975 1985 1994 2015 0% 0 Years 0 Spontaneous settlements area BAND1 BAND2 BAND3 BAND4 BAND5 BAND6 Years1950 1975 1985 1994 2015 1950 1975 1985 1994 2015 Mean patch size Spontaneous settlements area 1950 1975 1985 1994 2015 (a) (b) Mean patch size Figure 8. (a) Changes(a) in total spontaneous settlement area, and changes(b) in the mean size of Figure 8. (a) Changes in total spontaneous settlement area, and changes in the mean size of spontaneous spontaneous settlement patches from 1950 to 2015 in the GA; (b) percentages of spontaneous settlementFigure 8. patches (a) Changes from1950 in total to 2015 spontaneous in the GA; settlement (b) percentages area, ofand spontaneous changes in settlementthe mean patchessize of in settlement patches in different bands. differentspontaneous bands. settlement patches from 1950 to 2015 in the GA; (b) percentages of spontaneous 3.2.2.settlement Changes patches in Patches in different of Spontaneous bands. Settlements within Bands 3.2.2. Changes in Patches of Spontaneous Settlements within Bands 3.2.2. ChangesThe total in Patchespercentage of Spontaneous of spontaneous Settlements settlement within cover Bandsin the different bands showed not only Thedifferences total percentage in location ofduring spontaneous different settlementperiods but coveralso the in marginalization the different bands that accompanied showed not the only The total percentage of spontaneous settlement cover in the different bands showed not only differencesprocess in of location urbanization. during The different annual periods rate of but change also thein marginalizationspontaneous settlement that accompanied cover varied the differences in location during different periods but also the marginalization that accompanied the processsignificantly of urbanization. among The the annualbands. When rate of patches change began in spontaneous to appear in settlement band 1 in cover 1985, variedthe percentage signiﬁcantly of process of urbanization. The annual rate of change in spontaneous settlement cover varied amongspontaneous the bands. settlement When patches cover in began the other to appear bands in(2–6) band decreased 1 in 1985, gradually the percentage with increasing of spontaneous distance significantly among the bands. When patches began to appear in band 1 in 1985, the percentage of settlementfrom the cover GSV. in theIn 2015, other most bands spontaneous (2–6) decreased settlements gradually were in with bands increasing 1 and 3 (Figures distance 7from and 9). the The GSV. spontaneousGSV initially settlement consisted cover of small in the fragmented other bands areas (2–6) of decreasedinhabited land,gradually which with subsequently increasing expanded distance In 2015, most spontaneous settlements were in bands 1 and 3 (Figures7 and9). The GSV initially fromin thesize GSV. from In1985 2015, to 1994most and spontaneous finally shaped settlements into one were of the in biggest bands urban1 and informal3 (Figures settlement 7 and 9). areas The consisted of small fragmented areas of inhabited land, which subsequently expanded in size from 1985 GSVbetween initially 1994 consisted and 2015. of small In 2015, fragmented the GSV coveredareas of theinhabited largest land,percentage which of subsequently land in band expanded1, farthest to 1994 and ﬁnally shaped into one of the biggest urban informal settlement areas between 1994 and in sizeaway from from 1985 the tourban 1994 core and of finally the GA shaped (band into6) (Figures one of 7the and biggest 9). urban informal settlement areas 2015.between In 2015, 1994 the and GSV 2015. covered In 2015, the the largest GSV percentagecovered the of la landrgest inpercentage band 1, farthest of land awayin band from 1, farthest the urban coreaway of the from GA the (band urban 6) core (Figures of the7 GAand (band9). 6) (Figures 7 and 9).

Figure 9. Maps of spontaneous settlement cover lost to other land-cover types, and replacing other land-cover types during five successive sampling periods. Figure 9. Maps of spontaneous settlement cover lost to other land-cover types, and replacing other Figure 9. Maps of spontaneous settlement cover lost to other land-cover types, and replacing other land-cover types during five successive sampling periods. land-cover types during ﬁve successive sampling periods. Sustainability 2017, 9, 1190 13 of 18 Sustainability 2017, 9, 1190 13 of 18

3.3. Relationships between Topographical Characteristics and Spontaneous Settlements Cover among Bands 3.3. Relationships between Topographical Characteristics and Spontaneous Settlements Cover among Bands The locations of spontaneous settlements in Figure 10 show a clear pattern, generally occurring The locations of spontaneous settlements in Figure 10 show a clear pattern, generally occurring in in the landforms of rolling or hill, local alluvial, or slopes of 2–7% and 7–15%. Although the area the landforms of rolling or hill, local alluvial, or slopes of 2–7% and 7–15%. Although the area covered covered by spontaneous settlements in the mountain foothills was insignificant in all the historical by spontaneous settlements in the mountain foothills was insigniﬁcant in all the historical sample sample periods, it did increase approximately fourfold (2.71 ha) by 2015 compared with that in 1975 periods, it did increase approximately fourfold (2.71 ha) by 2015 compared with that in 1975 (0.7 ha) (0.7 ha) ( Figure 10a). Rolling hill soils occur along the ridgelines of both mountains, spreading north, (Figure 10a). Rolling hill soils occur along the ridgelines of both mountains, spreading north, in linear in linear patterns towards the Yangjaecheon River (Figure 4). Local alluvial soil fills the valleys patterns towards the Yangjaecheon River (Figure4). Local alluvial soil ﬁlls the valleys between these between these mountain ridges (Figure 4). Mountain foothills soil occur along the ridges of the mountain ridges (Figure4). Mountain foothills soil occur along the ridges of the Guryongsan and Guryongsan and Daemosan Mountains (Figure 4). Daemosan Mountains (Figure4).

Figure 10. Quantification of five landforms (A) and six slope types (B) overlaying with spontaneous Figuresettlements 10. Quantification for five successive of five sampling landforms periods. (A) and six slope types (B) overlaying with spontaneous settlements for five successive sampling periods. The distribution of landforms and slope types overplayed by the spontaneous settlements in the The distribution of landforms and slope types overplayed by the spontaneous settlements in the bands reveals that before 1985 most spontaneous settlement areas were located on local alluvial land bands reveals that before 1985 most spontaneous settlement areas were located on local alluvial land (2–7% and 7–15%) in bands 3 and 6 (Figure 10). There was subsequent development in a few areas of (2–7% and 7–15%) in bands 3 and 6 (Figure 10). There was subsequent development in a few areas of band 3 that were rolling or hill (15–30%) and in band 1 with diverse landforms of local alluvial, rolling band 3 that were rolling or hill (15–30%) and in band 1 with diverse landforms of local alluvial, or hill, and mountain foothill (15–30%), followed by other mountain or hill (30–60%) areas by 2015 rolling or hill, and mountain foothill (15–30%), followed by other mountain or hill (30–60%) areas by (Figure 10). This indicates that the locations selected for spontaneous settlements moved from plain 2015 (Figure 10). This indicates that the locations selected for spontaneous settlements moved from areas to more steeply sloped and remote areas during the urbanization process. plain areas to more steeply sloped and remote areas during the urbanization process. 4. Discussion 4. Discussion 4.1. Historical LULC Changes from 1950 to 2015 4.1. Historical LULC Changes from 1950 to 2015 The mountain–river integrated landscape system was dominant in the GA prior to urbanization. BeforeThe 1950, mountain–river and up until the integrated period when landscape Gangnam sy rapidlystem developedwas dominant in the mid-1970s,in the GA the Gangnamprior to urbanization.District consisted Before of 1950, an integrated and up landscapeuntil the pe systemriod when with theGangnam Yangjaecheon rapidly River developed and Guryong in the mid-1970s,Mountain. the This Gangnam landscape District system consisted was comprised of an integrated of intact, landscape persistent system ecosystems, with the Yangjaecheon with scattered Riverareas ofand agricultural Guryong use.Mountain. Daemosan This Mountain landscape and Guryongsansystem was Mountaincomprised were of completelyintact, persistent covered ecosystems,with forests betweenwith scattered 1950 and areas 1975 (Figureof agricultural2). The historical use. Daemosan maps show Mountain an undisturbed, and Guryongsan continuous Mountainarea of vegetation were completely up to the covered boundary with of theforests valley between where the1950 present-day and 1975 (Figure GSV is located.2). The historical However, mapswith rapidshow urbanization,an undisturbed, much continuous of this forested area of vegetation landscape disappearedup to the boundary [41]. Large of the areas valley of naturalwhere theland present-day were lost when GSV is constructed located. However, areas dramatically with rapid increased. urbanization, For example,much of this between forested 1975 landscape and 2015, disappearedthe woodland [41]. cover Large decreased areas byof approximatelynatural land were 39%, lost while when the transportationconstructed areas cover dramatically increased by increased.3.3-fold (Figure For example,6). between 1975 and 2015, the woodland cover decreased by approximately 39%, while the transportation cover increased by 3.3-fold (Figure 6). Sustainability 2017, 9, 1190 14 of 18

4.2. The Spatial Characteristics of Informal Settlement Formation in the GA as Indicated by Topographical Characteristics The spatial characteristics of spontaneous settlements were shown through the degree of aggregation and locational shifts. While the total area occupied by spontaneous settlements in 1975 was almost equivalent to that in 1985, the mean size of the patches was markedly smaller (Figure8a). This indicates that the informal settlements were distributed at a smaller scale with decentralized agricultural activities in 1975, but in 1985, they began to form larger clusters (Figures8a and9). The band analysis indicated that the rates of change in spontaneous settlements varied significantly depending on the distance from the urban core to the GSV. The trend of marginalization was reflected in the increasing spontaneous settlements in bands 1 and 2 since 1985 (Figure8b). When patches began to appear in band 1, the percentage of spontaneous settlements in the other bands (2–6) decreased gradually with increasing distance from the GSV. Since 1994, the location of spontaneous settlements has moved away from most planned urban areas and into natural areas such as the mountains. In addition, the transition analysis revealed a similar trend, which found that most of the new areas of spontaneous settlements in 1994 and 2015 had once been woodland cover in the outskirts of the district (Figures7 and9). From 1945 to 1961, many refugees from the Second World War and the Korean War settled in the hillside green spaces around Seoul. This was the beginning of the hillside informal neighborhoods that appear in the 1950 map of the GA (Figure2). Han et al. (2004) have concluded that most of the citizens of new informal settlements and squatter settlements in the urban fringe of Seoul in the 1980s came from the 1970’s inner-city government’s slum clearance projects. This accounts for the trend of marginalization in the GA. In general, city governments have often turned to abolishment as a solution to the informal settlements, subsequently transferring and displacing residents [42]. Yet, without a clear understanding of the potential needs of the affected residents, the results have often led to a vicious cycle of forced relocation and informal settlement development [10]. Firey (1946) has argued that the isolation from other highly developed areas plays a key role in the process of informal settlement formation. The city of Seoul is spread across an intricate landscape defined by watersheds, mountains, and rivers [29], and the topographically isolated areas, particularly the mountains, have often been chosen by low-income citizens. Our analysis of the relationships between spontaneous settlements and topographical characteristics showed that the early sites of spontaneous settlements were in flat, plain areas (0–2%, 2–7%) (Figure 10b). However, as urbanization spread from the north side of the city to the south, informal settlements were established on steeper slopes (15–30%), in areas such as the mountain foothills (Figure 10). These areas had little construction and were relatively undeveloped. Therefore, they were easily ignored by the government, which motivated informal city inhabitants to choose these sites for their living areas. As an example of this trend, the GSV is surrounded by forest vegetation to the east, west, and south. There is only one entrance to the village, which is located at the north end, the side closest to the urban Gangnam District.

4.3. Implications for Urban Planning and the Redevelopment of Informal Settlements La Rosa et al. (2014) have indicated that urban fringes were comprised of the complex LULC types including some highly sensitive habitats such as forests, wetlands, and rivers. The GA supported a complex pattern of LULC types with different ecological characteristics that were related to persistent features [41]. The transition analysis, as well as the historical preference for settlement construction in mountain areas, showed that the spontaneous settlements of the GA took place primarily in the forests and on agricultural lands (Figure9). This trend suggests that advantageous soil fertility was offered by forests, paddies, and croplands. Figure4 shows the natural areas of rolling hill and local alluvial soil extending from the mountain toward the Yeongjaecheon stream. The linear pattern of this soil type represents a continuous vegetation system that extends from the Daemosan and Guryongsan Mountains all the way to the Yeongjaecheon stream, offering a natural landscape corridor (Table3). Furthermore, the southern area of the Yangjaecheon offers an excellent habitat for wild birds since it Sustainability 2017, 9, 1190 15 of 18 contains forest linking the Daemosan and Guryongsan Mountains [43]. This implies that the urban fringe landscape of the GA has retained high biodiversity potential [44]. Thus, development planning approaches should be unique to metropolitan fringe areas and should consider the biodiversity of the area [45]. The existence of the natural resources represents an asset to urban fringes, which should, in turn, be considered in the redevelopment of informal neighborhoods. Despite this notion, much of Seoul’s rapid population growth was accommodated via informal settlements, with little attempt being made to limit the risk of environmental impairments [46]. Previous strategies for the preservation or restrained upgrading of informal settlements commonly focused on ﬂuctuating elements of the settlements or communities, such as citizen demands, facilities, and economic development regarding social issues and regional economies [4,11,47–50]. These strategies placed little value on the areas’ natural and permanent features. The GSV and other remnant informal settlements in the GA have neighbored with persistent forest landscapes for decades. In addition, the soil system directly beneath the GSV is unique in that the rolling hill and local alluvial soil types appear further up the mountains, and the soil types are more diverse in the GSV area than in any other area in the Gangnam District (Table3). This suggests the potential for a wide range of vegetation types to exist within the small area of the GSV. For example, the mountain foothill soil is suitable for sustaining a healthy forest with diverse tree communities including Quercus acutissima and Betula schmidtii [43]. Therefore, it is important for future policy-making to consider the ecological potential both in urban fringe developments and in the redevelopment of informal settlements.

5. Conclusions This study aims to improve understandings of informal settlement formation in a metropolitan fringe, through a comprehensive spatiotemporal analysis of topographical characteristics, using the case study of the Guryong Area (GA) in the Gangnam District of Seoul, South Korea. The LULC changes indicated that (1) large areas of natural land were lost due to the dramatic increase in constructed areas (Figure6); and (2) spontaneous settlements occupying natural lands continued to emerge after the period of rapid urban development (Table4). The transition analysis showed that while the total area occupied in 1975 by spontaneous settlements was almost equivalent to that in 1985, the mean size of the development patches was markedly smaller (Figure7a). The band analysis indicated that the trend of marginalization was reflected in increasing spontaneous settlements in bands 1 and 2 since 1985 (Figure7), while the percentage of spontaneous settlements in the other bands (2–6) decreased gradually with increasing distance from the GSV (Figures8b and9). The analysis of the relationship between spontaneous settlements and topographical characteristics showed that early spontaneous settlements developed in flat areas, while later settlements were established at the district’s border in steeper areas with slopes of 15–30%, such as the mountain foothills (Figure 10). These results suggest that the spatial characteristics of informal settlements are shown in the degree of aggregation and marginalized trend indicated from the analysis of spontaneous settlements. The results also support the idea that isolation from other highly developed areas plays a key role in the process of informal settlement formation during the urbanization process. However, the informal settlements at the urban fringe are location-specific, and the urban fringe landscape often retains high ecological potential. For example, the soil system directly beneath the GSV is unique in that the rolling hill and local alluvial soil types are ideal for a wide range of plant communities. Therefore, we suggest that the development of the urban fringe should consider ecological potential as an ecotone bridging the natural and urban systems. This idea can be applied to urban planning and policy-making for informal settlements in the metropolitan fringe. Understanding the strategies of informal settlement redevelopment in rapidly expanding cities requires not only the assessment of the site’s current living environments or social structures, but also land-use history and landscape systems. Although the comprehensive spatiotemporal analysis is a useful tool for understanding informal settlement development, there are still limitations to this study. The less accurate nature of historical data required us to use the term “spontaneous Sustainability 2017, 9, 1190 16 of 18 settlements” (Figure3A) to research and speculate the characteristics of informal settlements (Figure3b). Also, we chose not to focus on the sociopolitical issues concerning informal settlements in hopes of homing in on specific spatial and ecological factors. However, we believe the political and social implications of informal settlement development are integral to the field and this study should be considered alongside socioeconomic studies of informal settlements. We hope to pave the way for future studies that can further elucidate the relationship between informal settlement development and complex social factors. Finally, we hope the spatial analysis can be used as a basis and starting point for the evaluation process of informal settlement redevelopments in other areas of Seoul, as well as in other Asian cities.

Acknowledgments: We would like to express our deep gratitude to Wybe Kuitert from the Graduate School of Environmental Studies and Youngryel Ryu from the College of Agriculture and Life Sciences at Seoul National University for their helpful advice in the course of writing this paper. This work was supported by the BK21 plus Project in 2017 (Seoul National University Interdisciplinary Program in Landscape Architecture, Global Leadership Program towards Innovative Green Infrastructure). Author Contributions: Yiwen Han designed the study, analyzed the data and prepared the manuscript with Youngkeun Song; Lindsay Burnette and David Lammers conceived the original research idea with Yiwen Han. Lindsay Burnette conducted the final English language and style check. Conflicts of Interest: The authors declare no conflict of interest.

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