Promoting green urban development in Africa enhancing the relationship between urbanization, environmental assets and ecosystem service

Urbanization is taking place at an unprecedented rate throughout the world, often outpacing plans and the capacity of city managers. As a result, natural open space areas in cities are being degraded and diminished, and problems such as flooding, air and water pollution are getting worse. The environmental problems associated with increased hardened surfaces and the loss of natural areas and ecosystem services are particularly acute in developing country cities, where a lack of regulation and resources has led to poor planning, the expansion of informal settlements in high risk, marginal areas, and the inability to adequately manage the quantity and quality of surface water flows.
While conventional storm water conveyance measures contribute to reducing flooding impacts, they have not been able to keep ahead of the problem and have also contributed to pollution and degradation of downstream aquatic systems. However, great strides have been made in the design of more sustainable engineering mechanisms to deal with urban flooding and water quality problems, and the management and planning of cities is increasingly focusing on a more holistic approach that includes the conservation of natural areas as part of a green urban development (GUD) strategy. A GUD strategy does not only focus on surface water issues but also involves the maintenance of natural open space areas for recreation which is essential for human health and wellbeing. One of the challenges of green urban development will be to find the right balance between natural, semi natural, innovative and conventional built infrastructure. Understanding the costs and benefits associated with the different types of measures is important and requires careful consideration of their potential benefits and cost effectiveness in managing urban environmental problems. Durban, located within the eThekwini Municipality on the east coast of South Africa, is rich in biodiversity, but faces a number of environmental and developmental challenges. While green open space areas make up some 33% of the total area within the municipality, less than one third of this falls within the urban edge and only about 10% is formally protected and just under 7% is actively managed. Rapid urbanization and the continued expansion of informal settlements contributes to the degradation and loss of natural systems and biodiversity.
Key environmental issues include more frequent and intense flooding events, solid waste pollution, elevated flows and nutrients as a result of increases in wastewater outflows, erosion, poor air and water quality, overexploitation of natural resources, and the spread of alien invasive species. All of these issues contribute to rising infrastructure and human health costs as well as livelihood and property value losses which in turn affect municipal finances and GDP outputs.
Green urban development is an approach that aims to minimize the impacts of urbanization on the environment, and tackles the core problems of pollution and waste, the consumption of natural resources, the loss of urban open space and the degradation and loss of biodiversity, as well as mitigation of the urban contribution to climate change. In addition to a range of policy interventions, this involves investing in natural capital as well as use of green structural engineering and conventional grey infrastructure. Green urban development includes (1) sanitation services and regulations to mines pollution, (2) applying “green engineering” approaches to urban problems such as stormwater management, (3) controlling consumption and carbon emissions, (4) protecting natural assets and (5) maintaining parks, street trees and gardens.
The aim of this study was to explore, using a case study and scenario-based approach, the potential costs and benefits of undertaking a green urban development approach to address some of the main environmental issues described above, and to explore the potential tradeoffs between different types of interventions, with an emphasis on assessing the desirable balance between engineered interventions and the conservation of natural open space areas. The study focuses on three elements of green urban development, all of which impact on ecosystems and biodiversity: sewage and solid
waste management, active stormwater management and the conservation of natural systems and riparian corridors.
The study involved modelling current flooding and water quality in the Umhlatuzana – Umbilo catchment, and determining the change in water quality and flood hydrographs under a series of hypothetical scenarios in which the past development of the area had involved different combinations and extents of green urban development measures including better sanitation, stormwater management and conservation measures. The economic implications of these changes were assessed in terms of implications for aquatic ecosystem health as well as the infrastructure costs, and losses in
property, tourism and fishery benefits that would have been avoided under these alternative scenarios. The relative costs and benefits of different scenarios were then evaluated using a cost benefit approach.
source :
https://openknowledge.worldbank.org/entities/publication/1cf72e7b-b19e-558a-aa91-410db5012f02
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