exacerbated by urban development. We need to understand the processes that shape urbanisation and how they create or increase risk to hazards. Consider the city as an evolving biological system where there is no simple-one-way line of causality in the production of human or environmental conditions and so risk in the city is an outcome of many feedback loops and thresholds competing ideas, mechanisms and forms [Pelling, 2003]. Hence urban disasters are viewed as a result of inefficient urban management, inadequate planning, poorly regulated population density, inappropriate construction practices, ecological imbalance and infrastructure dependency [Pelling, 2003; Lewis & Mioch, 2005]. Good governance is a necessity in reducing urban vulnerability especially among the urban poor communities.
It is as a result of this vast background that various risk reduction measures have taken different methodological approaches in order to tackle the problem. Disaster risk reduction measures in South Africa focus on structural measures and non-structural measures are more orientated towards early warning systems that often do not assist the at-risk communities as warnings fail to reach them on time. So in order to achieve a balanced flood risk management strategy, both an assessment of the flood hazard and vulnerability conditions of an at-risk population is essential. A number of studies on flood disaster
management which have been undertaken in South Africa would be reviewed for methodological approaches applied.
Myburgh in 1991 used integrated hazards framework to explore the physical, behavioural and social aspects of flood and drought hazard in order to gain a more comprehensive understanding of the complex interrelationships at play in defining the hazardousness of the arid and semi-arid regions of the previously called Cape Province of South Africa. She adopted a human ecology approach through which a range of human adjustments and adaptations to the hazard were identified. Miller in 1997 adopted the technical-fix approach to develop a structural flood risk reduction strategy relying on the construction of physical structures to avoid flooding of the flood plains from rivers and storm water systems. Non-structural measures identified included proper development planning awareness or preparedness and social protection that gained increasing importance as time went on.
Mgquba [2002] investigated the physical and human dimensions of flood risk in Alexandra. The studies applied the Participatory Action Research (PAR) model [Blaike et al., 1994] to unpack the root causes, dynamic pressures and unsafe conditions of severe flooding of the Jukskei River in the township that increased vulnerability and associated risk of the urban poor living in the floodplain. It adopted a political ecology approach to flood risk because of the PAR model.
Pyle [2006] on his part looked at vulnerability analysis as being dependent heavily on census data at municipal scale. Through adopting a human ecology approach he ground- truthed the census data with field research which was qualitatively done through household interviews. This constrained the study’s explanation of the root causes of vulnerability. Through this temporal, spatial and impact characteristics of severe convective storm hazard, associated risk could be investigated. He then used this conceptual framework to emphasise the combined role played by hazard and vulnerability conditions in defining risk.
Durham [2007] adopted a disaster reduction framework to assess the effectiveness of existing flood risk reduction efforts along the Bath River in Western Cape. He conducted a risk assessment that considered physical hazard, the human, financial, technical or institutional capacity to manage the flood risk along the respective river. He used a
participatory approach of interview, focus groups and consultations with the community and key stakeholders. This public participation input was limited to the hazard analysis and damages.
Van Bladeren et al. [2007] criticised the use of deterministic flood hydrology looking at run-off and rainfall input since they have the same probability of exceedance. This method could only be applied to sites with no flow data for a range of storm durations, changing catchments conditions and provide an indication of the expected hydrograph shape for a storm event. They used an integrated systematic historic and palaeo-flood data to provide estimates of the flood peaks and their associated probabilities for all the regions of South Africa.
Reviewing the three perspectives about flood hazards, Nethengwe [2007] deduces a shortcoming to these conventional explanations as masking socio-economic and political dynamics as well as power relationships that enhance flood vulnerability. Some conventional methods used to combat floods have also been developed upon these perspectives. These have only succeeded partially as some techniques end up increasing flood vulnerability of the local populace. He then brought in the historical perspective into flood mitigation by using Participatory Geographic Information Systems (PGIS) to map vulnerabilities in the Limpopo province with two case studies.
This study shall then complement the storm management study commenced in 2009 for the City of Johannesburg, through which it was recommended that specific studies like this be done for effective management [Van Huyssteen et al., 2009]. The spatial dimension would be combined with a social survey to further identify areas vulnerable to flooding which would illustrate to what extent the people are at risk and eventually decision/policy makers within the City of Johannesburg to understand the flood vulnerability situation in Diepsloot township.
The perceptions of the people shall also be considered in policy developments since the survey shall find out what coping measures are in place for the community to adapt with floods. This study makes use of the floodline research done by SRK in Diepsloot to create a vulnerability map that can be used to assess households exposed to different flood events. The floodlines were calculated based on the physical hazard whereas the local knowledge shall be included to ascertain if other vulnerable areas do exist beyond these limits.
A major barrier that must be overcome if flood disaster management is to become more socially inclusive, concerns technological expectations the public have of the role and capacity of management institutions to deal with hazards like flooding [Wisner et al., 2004]. Expectations that floods can be eradicated completely, or that defences should be erected on all floodplains, regardless of the costs and benefits, are widely held among members of the public. In Diepsloot township in particular the populace feels the municipality and local councillors are to be blamed for every flood event that devastates their households. They fail to see their own contributions in the devastating nature of the floods. These unrealistic expectations generate disappointment when floods continue to occur (often aggravated by media coverage of the nature of events and who is to blame for them).
A successful management programme for disasters such as floods must therefore be integrative, with roles defined for every stakeholder. Since comprehensive hazard maps have the potential to define areas that are exposed to flooding (that are not revealed by floodline assessments) and might, therefore, benefit from attempts to reduce vulnerability [Brown & Damery, 2002; Maantay & Ziegler, 2006]. These maps provided the opportunity to change the way in which flood vulnerability information for this area is communicated to the public, as they delimit the geographical extent of flood inundation for events of a specified magnitude (1:50-year and 1:100-year).