A GIS APPROACH FOR FLOOD VULNERABILITY AND ADAPTATION ANALYSIS IN DIEPSLOOT, JOHANNESBURG ADELINE NGIE (Student No. 201003585) Department of Geography, Environmental Management and Energy Studies Supervisors: Prof. H.J. Annegarn Maryna Storie Gauteng City-Region Observatory, (A collaboration between the University of Johannesburg, the University of the Witwatersrand, Johannesburg and the Gauteng Provincial Government) A minor dissertation submitted to the Faculty of Science, University of Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Environmental Management. 30 January 2012 Affidavit TO WHOM IT MAY CONCERN This serves to confirm that I, Adeline NGIE with student number 201003585 and bearer of Cameroonian Passport Number 01138195, enrolled for an MSc in Environmental Management with the Department of Geography, Environmental Management and Energy Studies in the Faculty of Science, herewith declare that my academic work titled: A GIS approach for flood vulnerability and adaptation analysis in Diepsloot, Johannesburg, is in line with the Plagiarism Policy of the University of Johannesburg, with which I am familiar. I further declare that this work is authentic and original unless clearly indicated otherwise and in such instances full reference to the source is acknowledged and I do not pretend to receive any credit for such acknowledged quotations, and that there is no copyright infringement in my work. I declare that no unethical research practices were used or material gained through dishonesty. I understand that plagiarism is a serious offence and that should I contravene the Plagiarism Policy notwithstanding signing this affidavit, I may be found guilty of a serious criminal offence (perjury) that would amongst other consequences compel the University to inform all other tertiary institutions of the offence and to issue a corresponding certificate of reprehensible academic conduct to whoever request such a certificate from the institution. Signed at Johannesburg Date: Signature____________________________________ A. Ngie STAMP COMMISSIONER OF OATHS Affidavit certified by a Commissioner of Oaths This affidavit conforms with the requirements of the JUSTICES OF THE PEASE AND COMMISSIONERS OF OATHS ACT 16 OF 1963 and the applicable Regulations published in the GG GNR 1258 of 21 July 1972; GN 903 of 10 July 1998; GN 109 of 2 February 2001 as amended. i Abstract The 2010/2011 floods saw the City of Johannesburg and many other municipalities in South Africa declared disaster ridden due to the number of deaths, homeless citizens and loss of property. Conventional Geographic Information System (GIS) approach is used to map flood vulnerable areas using floodlines while social surveys assess at-risk population through impacts of a hazard. This study then tests the hypothesis that combined approach to identify and map flood vulnerable areas is better than independent approaches, using Diepsloot township as a case study. Starting with aerial photographs as a base layer, ArcGIS 10™ was used to conduct spatial analysis of the flood-prone areas using the 1:50- and 1:100-year floodlines. The results mapped out dwellings vulnerable to flooding along the floodplains only. The survey probed the people’s perceptions, experiences and coping strategies with flooding. Findings from the field survey revealed some key observations, as follows: The perception of 95% of respondents is that flooding is a major environmental challenge in Diepsloot township as confirmed by their experiences; 61% attributed this to construction of dwellings within floodplains; and 71% agreed that how strong a dwelling is in terms of construction materials also determines its vulnerability to flooding. In addition to floodplains, other sections of the settlement were identified through local knowledge as being vulnerable to various types of flooding - fast-flowing water, ponding and slope run-off. Dwellings on hill-slopes and besides storm water drains were identified as vulnerable to flooding. Slope measurements over the area were done using contours which corroborated these further areas of flood vulnerability as both low-lying and high slopes. Due to poor layout of dwellings, vulnerable units could not be counted but the extent was visible in the mapping. Long-term coping strategies and adaptation measures do seem to be in place, without interventions from municipal authorities. The combined approach for flood vulnerability assessment proved successful in creating a practical and affordable means to create a more comprehensive assessment, called for local knowledge engagement in policy development to mitigate flood disaster risk in the Gauteng City- Region. Keywords: Diepsloot ·floods ·vulnerability ·adaptation ·informal settlements ii Dedication This work is dedicated to my son Muluh Dilane-Thierry who desires to see me on top. iii Acknowledgments For the realisation of this work, I am greatly indebted to a host of persons who supported me in one way or the order to make sure the best results were presented. I am extremely thankful to the Almighty for inspiration and strength throughout this programme. Great appreciations go to Professor Harold Annegarn and Maryna Storie my supervisor and co- supervisor respectively for the endless consultation meetings on academic and technical guidance. They took the pains of always reading through the draft write-ups and giving insightful comments. Friendly and technical support from the management and specifically Chris Wray at Gauteng City-Region Observatory (GCRO) through software and hardware used for this study is acknowledged, as are Dingaan Mahlangu of SRK for providing floodline data for Diepsloot and technical guidance; and Coleen de Villiers of the South African Weather Service for providing daily rainfall data over Diepsloot for a 50-year period. Residents of Diepsloot township especially the friendly respondents with whom we shared insights on their experiences and perceptions on reducing flood vulnerability not forgetting members of the field team, especially Richard Thaba, with whom over three weeks we took out our classroom friendship to experiencing the physical environment. You rock! Jaclyn Smith at Statkon is acknowledged for her assistance with statistical analysis. Management and staff at the Southern Mapping Company (SMC) (Pty) Ltd and Southern Mapping Geospatial (SMG) for the opportunity to be exposed into the geospatial world during which some experience and insight were gained for this study. They also provided spatial data with the authorisation of the Corporate GIS unit of the City of Johannesburg. Friends and staff of the department of Geography, Environmental management and Energy Studies for academic support are not left out for acknowledgement. My heartfelt gratitude go with my parents and siblings for continual support and encouragement which drove me to the end. My supportive friends who were there for me are also appreciated heartily. This work was supported in part through financial contributions from the University of Johannesburg grant to the Sustainable Energy Technology and Research (SeTAR) Centre. I acknowledge financial support from the Faculty of Science for a Merit Bursary and a Top- up Bursary. The generosity of GeoTerraImage (Pty) Ltd in providing a bursary, in support of studies in applications of GIS and remote sensing is appreciated. iv Table of Contents Affidavit ....................................................................................................................i Abstract ................................................................................................................... ii Dedication .............................................................................................................. iii Acknowledgments ...................................................................................................iv List of Figures........................................................................................................viii List of Tables............................................................................................................x 1. Introduction 1 1.1. Background .....................................................................................................1 1.2. Problem statement ...........................................................................................5 1.3. Hypothesis and objectives................................................................................7 1.4. Rationale for choosing the study area...............................................................8 2. Flood risk management in South africa 10 2.1. Legal framework............................................................................................11 2.2. Some definitions of floods .............................................................................12 2.3. Risk in the context of disasters.......................................................................13 2.4. Hazard...........................................................................................................15 2.5. Resilience or Capacity ...................................................................................16 2.6. Vulnerability in disaster management ............................................................16 2.6.1 Flood vulnerability.............................................................................19 2.6.2 Mapping flood vulnerability...............................................................21