A set of four investigative studies has been formulated to address knowledge gaps based on the stakeholder input that were synthesised in Chapter 6. Conducting these case studies will constitute the next phase of the GCRO’s GAI project. Their ultimate aim is to develop a case for incorporating GI into municipal planning and investment processes. Furthermore, they are designed to extend the current understanding of how to apply a GI approach in the GCR and to explore existing challenges. The four selected investigative studies are outlined below.
7.2.1. Green infrastructure and municipal
asset registries
This study is based on the extensive debate on the need for green assets to be valued and maintained in a similar way to grey infrastructure. Based on the suggestion that this could be facilitated through incorporating green assets into municipal asset registries, the aim of this project is to identify the requirements for this process and to investigate the possible methodologies to achieve this. It is anticipated that workable pilot methods will be identified that could be scaled up in the future. This investigative study will also explore how best to map green assets and determine which valuation exercises can be used to quantify the provision of ES by GI.
This study will include the following components:
• An investigation into how to capture and represent green assets in municipal asset registries (e.g. through a Geographic Information System (GIS) and Lidar data);
• Explore how the ES provided by green assets can be included in an asset registry; and
• Suggest approaches for financial measurement of green assets and their associated ES.
7.2.2. Exploring surface water
management options in Diepsloot
Stakeholder insights on some of the challenges and breakthrough actions for GI revealed that there is a need for projects and design solution alternatives that demonstrate how GI can be used to achieve developmental objectives for stormwater management and flood control. It was further highlighted that there is a need for the impact of GI projects to be understood at a system scale, not only at the scale of individual green assets. The aim of this project is to develop alternative stormwater management interventions for Diepsloot using GI.Diepsloot is a low-income settlement without a formal drainage network and limited infrastructure, located on the northern outskirts of Johannesburg. The project aims to explore whether GI can provide cost-effective infrastructure that reduces disaster risk, provides job opportunities and improves the liveability of the settlement. This project responds to a study undertaken by the City of Johannesburg (CoJ) that estimated the cost of building a traditional stormwater system in the area would be roughly R140 million (in 2010). This figure is beyond the budget available for such a project.
This investigation will explore how a range of GI alternatives can be used to address surface water problems. The investigation will be done through participatory planning approaches and will explore opportunities for mobilising capacity in local
communities. This project will entail engagements with international experts, city officials, local community leaders, and local specialists in the fields of engineering.
7.2.3. Monitoring and evaluating a green
infrastructure stormwater scheme in
Atlasville
Stakeholder insights highlighted the importance of cost-benefit analysis and included the need for a better understanding of the maintenance requirements for various GI solutions. This study seeks to build the GI evidence base in the GCR, and to explore how a recent project that used GI to deal with flood issues compares with a grey infrastructure alternative. Particular emphasis will be placed on conducting a comparative cost-benefit analysis between the GI solution that was used and a traditional concrete alternative, including the respective maintenance requirements for each of these options.
The aim of this project is to conduct cost- benefit and lifecycle costing exercises, and present a post-project analysis of the flood relief scheme that has been implemented along the Atlas Spruit in Atlasville, a suburb in the Ekurhuleni Metropolitan Municipality (EMM). This project utilised a combined grey-green infrastructure approach to solve the area’s flooding problems. Initial evaluations suggest that an alternative grey infrastructure approach (a simple concrete channel providing equivalent flood capacity) would have cost roughly R2 million more than the adopted grey-green infrastructure scheme. However, the GI option that was used has had a number of additional benefits that have not yet been accounted for. This investigation will reflect on the
potential for this project to inform the development of other GI projects and plans in the GCR. It is anticipated that it will further demonstrate the cost saving opportunities associated with this type of GI alternative.
7.2.4. Retrofitting green infrastructure to
reduce flood risk in Mogale City
This project addresses the need to demonstrate how GI can serve as a retrofitting solution for existing infrastructure to address key challenges and risks in municipalities. The aim of this project is to explore the potential for retrofitting an established residential area in Mogale City with GI solutions to help address downstream stormwater flooding issues. The site identified for this project is the upper catchment area of the Muldersdrif se Loop, above the Walter Sisulu National Botanical Gardens. This project was proposed by a municipal official from the Mogale City Local Municipality in light of significant damage downstream of the botanical gardens, which is caused by flood peaks. The extent of the flood peak (in terms of volume and velocity) has undermined infrastructure belonging to CoJ and Mogale City (electrical and sewage lines), and poses high risk to houses on the banks of the river. This project further responds to the need to establish how GI projects that extend across municipal boundaries can be co-ordinated and planned.
This project will explore how a catchment scale GI design solution could be developed to reduce the storm peak and associated downstream flood risks. Work will entail engagements with international experts, city officials, local community leaders, and local specialists in the fields of engineering, to determine how a catchment-wide GI plan could be developed.