Master Thesis ______
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__________________________________________________________________________________ Master Thesis __________________________________________________________________________________ Urban Growth and Environmental Risks – A GIS-Based Analysis of Landslide Susceptibility in Bukavu (Democratic Republic of the Congo) By: Simon Sebastian Paul (Umu-ID: sipa0016) Supervisor: Magnus Strömgren Umeå University Department of Geography and Economic History Programme: Human Geography with Specialization in Geographical Information Systems (1-Year Master) Submitted: June 2019 Acknowledgements: I would like to express my gratitude to my supervisor Magnus Strömgren for the generous support and valuable suggestions during the process of writing this thesis and throughout the entire Master programme. I am equally grateful for teaching, assistance and advice provided by Cenk Demiroglu, Roger Marjavaara, Erika Sandow, and Kerstin Westin, who laid the foundations for this thesis with their respective contributions to the programme. Furthermore, I would like to extent my gratitude to my academic opponent Nils Wilhemsson, whose reflections, recommendations and constructive critique helped revising and finalizing my work. I also thank my classmates for the enriching times of learning, suffering and growing together. In addition, I owe a very special thanks to Ronia Anacoura for her unrelenting encouragements and generous emotional support. Without her, the burden of getting done all the work that went into this thesis within the short time period of just two months would have been twice as heavy. Thank you for being an infinite source of strength and motivation and for lending your ear in all our conversations about geography-related topics. I would also like to thank the people who granted me the great opportunity to visit Bukavu for the first time in March 2016. These are especially Prof. Dr. Martin Doevenspeck, Prof. Dr. Cyrus Samimi, and Dr. Claudia Gebauer from the University of Bayreuth, as well as Dr. Nene Morisho Mwanabiningo from Pole Institute in Goma. Likewise, I thank my dear friends in the D.R.C. who were involved in further visits by showing me around, sharing their knowledge about Bukavu or giving me travel advice. Therefore, the following people deserve my particular gratitude: Olivier Ngirabanzi, Gérard Saleh Bitendelo, Aspirine Emana Mwimuka, Emmanuela, Maurine, Maurice, and Shubu Ngesso. Cover page header picture: Nyamoma peninsula, northern part of Bukavu (Photo taken by the author on 17th February 2018) Table of Contents: I. List of Figures . p. I II. List of Tables . p. II III. List of Abbreviations . p. III Abstract . p. 1 1. Introduction . p. 2-5 2. Aim of the Thesis . p. 7-9 2.1 Purpose and Research Questions . p. 7-8 2.2 Limitations . p. 8-9 3. Different Landslide Types . p. 11-12 4. Literature Review . p. 13-19 4.1 General Overview . p. 13-14 4.2 Landslides and Anthropogenic Factors . p. 14-16 4.3 Environmental Risks in Bukavu . p. 16-19 5. Study Area . p. 21-24 6. Methods . p. 25-35 6.1 General Approach and Considerations . p. 25-27 6.2 Workflows Involving the Digital Elevation Model . p. 27-30 6.3 Workflows Involving Satellite Imagery and Satellite Data Properties . p. 30-35 7. Results . p. 36-53 7.1 Classification of Land Cover . p. 36-38 7.2 Aspect of Hillsides and Mountain Slopes . p. 39-40 7.3 Slope Inclination . p. 41-42 7.4 Urban Growth . p. 43-47 7.4.1 Urban Growth from 1990 to 2019 . p. 43-45 7.4.2 Current Urban Growth Tendencies . p. 46-47 7.5 Slope and Urban Growth Overlay . p. 48-53 8. Discussion . p. 54-56 9. Conclusion . p. 57 I. List of Figures: Figure 1: Overview map of the DRC and the study area’s location . p. 6 Figure 2: Overview map of the Kivu provinces in the eastern DRC . p. 10 Figure 3: Illustration of different landslide types according to Varnes 1978 . p. 12 Figure 4: Landslide susceptibility map of Africa . p. 14 Figure 5: Historical landslides in the urban area of Bukavu and the slopes to the west . p. 18 Figure 6: Map of communes and neighbourhoods in Bukavu . p. 20 Figure 7: 3D elevation map of the study area . p. 22 Figure 8: Aspect of central Bukavu facing eastwards, as seen from Nkafu . p. 23 Figure 9: Example of an aspect-slope raster of a larger study area than Bukavu . p. 29 Figure 10: Example of using panchromatic Band 8 to outline densely built-up areas . p. 33 Figure 11: View from western Ndendere neighbourhood towards the southwest . p. 36 Figure 12: Map showing a classified satellite image of the study area . p. 38 Figure 13: Aspect-slope map of the study area . p. 40 Figure 14: Slope map of Bukavu . p. 42 Figure 15: Graph showing the size of built-up areas . p. 44 Figure 16: Map showing the growth of densely built-up areas from 1990 to 2019 . p. 45 Figure 17: Map showing the growth of densely built-up areas from 2016 to 2019 . p. 47 Figure 18: Nkafu neighbourhood as seen from Lake Kivu (Bay of Bukavu) . p. 51 Figure 19: Overlay map of slope inclination and urban growth trends . p. 53 I II. List of Tables: Table 1: Temperature and precipitation by month in Bukavu . p. 24 Table 2: Origin of the satellite images used to map urban growth in Bukavu . p. 32 Table 3: Landsat 4 and Landsat 5 spectral bands . p. 34 Table 4: Landsat 8 spectral bands . p. 34 Table 5: Total size of built-up areas by year . p. 44 II III. List of Abbreviations: ASTER Advanced Spaceborne Thermal Emission and Reflection Radiometer EAR East African Rift DEM Digital Elevation Model DInSAR Differential Interferometry Synthetic-Aperture Radar DRC Democratic Republic of the Congo GCS Geographic Coordinate System GDEM Global Digital Elevation Model GIS Geographical Information System NASA National Aeronautics and Space Administration OLI Operational Land Imager QGIS Quantum Geographical Information System RGB Red, Green, Blue TIRS Thermal Infrared Sensor TM Thematic Mapper USGS United States Geological Survey UTM Universal Transverse Mercator WGS World Geodetic System WV WorldView (Satellite) III Abstract: The city of Bukavu, located at the eastern border of the Democratic Republic of Congo in the province of South Kivu, is a large and densely populated urban agglomeration that has experienced rapid growth during recent years. At the same time, Bukavu has been repeatedly struck by environmental hazards, especially by devastating landslides. The steepness of slopes in the city’s hilly and mountainous terrain is one of the most important factors contributing to landslide susceptibility, but the anthropogenic impact resulting from uncoordinated urban sprawl and land cover change additionally plays a crucial role in exacerbating the vulnerability of neighbourhoods. This thesis utilizes GIS software to provide cartographic material for landslide risk assessment in Bukavu and the city’s surroundings. It examines risk exposure related to slope inclination of densely built-up areas, the spatial development of the city and urban growth tenden- cies, and complements these aspects with information about land cover and the terrain. Keywords: Bukavu, Landslides, Environmental Risks, GIS, Urban Growth, Slope Inclination, Land Cover, D. R. Congo, South Kivu, Satellite Data, Digital Elevation Model 1 1. Introduction: In the past decades, the topic of urban settlements and their exposure to damage caused by environmental hazards has become a major research subject in both the social sciences and the natural sciences. Its transdisciplinary relevance originates from the fact that in many past sce- narios catastrophic events were linked to multiple interrelated factors (see Chang, Slaymaker 2002; Douglas et al. 2008; Satterthwaite, Sverdlik, Brown 2019). While in a worldwide context different types of hazards vary naturally in their origin, scope and impact, it has repeatedly been shown how exacerbated vulnerability of urban communities and higher prevalence of environ- mental disasters are influenced by anthropogenic activity (Petley 2012; Thomalla et al. 2006, 43-44). This can be observed in relation to human-made climatic change and cases of extreme weather events (Eckstein, Hutfils, Winges 2018, 9-11; Bele, Sonwa, Tiani 2014, 332-334) as well as on regional level where land cover alteration, population growth and settlement in risk- prone areas have resulted in intensification of damage suffered from environmental disasters in urban settings (Usamah 2017, 36-49; Jones 1992). A wide range of urban hazards pose a potential threat to the security of people living in cities and municipal areas that are located in vulnerable regions, depending on the respective geolog- ical and climatic conditions. For example, earthquakes and volcanic eruptions are reoccurring phenomena in zones of high tectonic activity, putting urban centres and smaller settlements alike at risk of being affected by destructive natural disasters (Thouret 1999). Many such inci- dents occur in hot-spot regions like the East African Rift (EAR) (D’Oreye et al. 2011), the subduction zone west of Indonesia (Marfai et al. 2008; Hadi 2008) or the fault systems in New Zealand (Dionisio, Pawson 2016). In coastal regions they can furthermore be exposed to tsuna- mis, as is the case along the Circum-Pacific Belt (see Liu et al. 2007; Dionisio, Pawson 2016), or suffer from increased damage by hurricanes, as for example recent incidents on the southern coast of the United States of America have shown (Curtis, Fussell, DeWaard 2015; Zhang, Peacock 2010; Olshansky 2006; Olshansky et al. 2008). Moreover, human settlements in many places of the world can experience flooding during times of high seasonal precipitation or ex- treme weather events (Ozkan, Tarhan 2016, 374; Chan 2011). The context of urban hazards is therefore a broad field that has to deal with multidimensional scenarios where humans may or may not play a significant role in causing a specific type of hazardous event. Yet, their exposure to such risks and the impact disasters have on urban spaces depend on the adaptive and preventive capabilities of societies as well as their ability and create hazard-resilient spaces of living.