Composite Adaptability Index to Evaluate Climate Change Adaptation Policies for Urban Transport
Composite Adaptability Index to Evaluate Climate Change Adaptation Policies for Urban Transport
Harsha Vajjarapua, Ashish Vermab
a PhD. Scholar, Department of Civil Engineering, Indian Institute of Science, Bangalore. vajjarapu06@gmail.com
b Associate Professor, Department of Civil Engineering, Indian Institute of Science, Bangalore. ashishv@iisc.ac.in
Cities are a mix of people, vehicles, infrastructure and nature. They are vital to the country's economy due to which people migrate to them in search of opportunities to survive. Due to their high economic activity, cities are the major contributors to climate change. The transportation sector plays a crucial role in maintaining this economic activity, and that is how cities thrive. As beneficial are cities and transportation to the economy, they do as much wrong by following unsustainable ways. The land on which cities are built is usually vegetation and wetlands. Due to massive migrations and the need to accommodate various systems, the cities are rapidly expanding. How does the expansion happen? The answer is simple. They are spread across remaining vegetation and wetlands wherever necessary. This expansion allows for more vehicles and more travel, leading to increased emissions, fossil fuel consumption, congestion and climate change.
So, how does climate change greet us with all these unsustainable doings? It responds in the form of forest fires, glacier melting, sea-level rise, and extreme weather events such as droughts, intense rainfalls, and tsunamis. One of the prominent effects on cities is the intense rainfall event causing urban flooding. While sprawling, the cities consume a lot of natural vegetation and wetlands that naturally aid in rainwater infiltration. To overcome this issue, cities built drainage system to sideline the rainwater. Although drainage systems are consolidated in the city level planning, there are uncertainties associated with rainfall intensity, low maintenance, high imperviousness, and under-capacity drainage systems. These factors lead to flooding in urban areas, making them less resilient. Once the cities are flooded, the transportation system is directly affected, and so is the economy. Therefore the urban transportation should adapt to these changing climate, and adaptation measures are the way forward. Most developed economies have incorporated adaptation measures in their urban policymaking, planning, and projects. But the developing economies such as India still focusing on reactive measures like mitigation. Hence, the embodiment of risks associated with climate change in the city planning and execution, primarily in developing economies, is vital to heighten the urban transportation system's resiliency to urban flooding. Due to the persistent threat posed by urban flooding to the urban transportation system, it is critical to developing quickly understandable methods and be calculated with less difficulty. Also, the policymakers should be able to promptly evaluate the transportation sector's adaptability to urban flooding.
Composite Adaptability Index (CAI) is one such tool that allows policymakers to assess multiple adaptation strategies quickly. It is an indicator-based index that enables policymakers to compare numerous adaptation strategies and pick the best one for implementation. The index is on a scale from 0 to 1, while 0 being worst and 1 being best. Further, CAI can compare multiple cities' urban transportation systems' adaptability to urban flooding. Adaptability primarily relies on three main dimensions, social, economic and hydrogeological. Each dimension is influenced by 3 factors, exposure, susceptibility and resilience. The adaptability of the 3 dimensions is given by equation 1.
AImp=[Rsp+1-Esp+1-Ssp]3
Eq. 1
Where, mp – Main Pillar (Hydrogeological, Social & Economic)
R – Normalized Resilience
E – Normalized Exposure
S – Normalized Susceptibility
The CAI of the entire urban transportation system is estimated using equation 2.
CAIsystem= AImp3
Eq. 2
These equations are tested on Bangalore Metropolitan Region (BMR) urban transportation system using 3 adaptation policy bundles for 2030 and 2050. The adaptation policy bundles are shown in table 1.
Table 1: Climate change adaptation policy bundles for urban transportation
|
BUNDLE 1 |
|
Replacement of impermeable road surface with permeable material in vulnerable areas |
|
Slum relocation and rehabilitation |
|
Providing proper drainage facilities at vulnerable areas |
|
Construction of redundant infrastructure |
|
BUNDLE 2 |
|
Rerouting people during flooding |
|
Restricting development in low lying or vulnerable areas |
|
Slum relocation and rehabilitation |
|
BUNDLE 3 |
|
Replacement of impermeable surfaces with permeable material in vulnerable areas |
|
Providing proper drainage facilities at vulnerable areas |
|
Rerouting people during flooding |
The 3 adaptation policy bundles' composite adaptability indices are evaluated and compared, and shown in figure 1.
Figure 1: Comparison of Composite Adaptability Indices for Adaptation Policy Bundles and BAU
Figure 2 shows that the best CAI is achieved by the adaptation policy bundle 1, followed by bundle 3 and bundle 2 for 2030 and 2050. Bundles 1 and 3 have two similar policies; replacing the impermeable surface with the permeable surface and improving the drainage network. These two policies are the leading cause for their higher adaptability index. The other two policies: slum relocation and rehabilitation and redundant infrastructure, also played an essential role in achieving the higher CAI for bundle 1. The slum relocation and rehabilitation shift the people from low lying areas to another location resulting in changed trip patterns. However, these trips will not be affected by the flood signifying increased adaptability to flooding. Further, providing a redundant infrastructure will help the people make their trips, improving urban transportation adaptability to urban flooding. Therefore, it can be understood that slum relocation and rehabilitation and redundant infrastructure played a vital role in enhancing the urban transportation resiliency to urban flooding.
Additionally, urban transportation adaptability to urban flooding can be improved by increasing the mass transportation system, such as a metro network coverage area. Urban flooding primarily impacts the road transportation system and not the elevated metro system. Improving the metro network coverage will attract trips from personal transportation. This will reduce the vehicles plying on the road, the number of damaged vehicles due to flood, extra miles travelled, and extra time spent travelling, leading to increased resiliency and CAI.
Finally, the high CAI value of bundle 1 emphasizes that the proper combination of land use and infrastructure-related policies will increase the urban transport system's adaptability.
More information related to this topic is available at:
Vajjarapu, H., & Verma, A. (2021). Composite Adaptability Index to Evaluate Climate Change Adaptation Policies for Urban Transport. International Journal of Disaster Risk Reduction, 102205. https://doi.org/10.1016/j.ijdrr.2021.102205