Placing the SSPs on the map: Spatio-statistical modelling of urban growth processes in the Upper Bhima Basin, India

R. Karutz, C. Klassert, S. Kabisch

2020 American Geophysical Union meeeting, San Francisco, CA

India’s population has almost doubled in the past four decades. Especially urban areas face unprecedented transformation dynamics, manifest in the spatial expansion of cities and the shift from rural to urban populations. In order to find sustainable and resilient development trajectories, reliable long-term, spatially explicit projections of both built-up area and population are critical.

We have developed a novel approach to simulate a region’s future urbanization in a spatially explicit way based on the Shared Socio-economic Pathways’ population estimations. The process comprises four steps: (1) determining the yearly total population change of the region based on downscaled SSPs, (2) deriving the corresponding total built-up area of the region through asymptotic regression, (3) allocating the built-up area on the map using cellular automata models building on the SLEUTH approach, (4) distributing the population among the built-up areas through dasymetric mapping.

We have applied and tested the approach for the Upper Bhima region in Maharashtra, India. The region comprises the two urban centres Pune and Solapur, several small towns, as well as rural areas.

We find three major patterns (here exemplary for SSP2):

1. Growth: The rapid growth in population and built-up area of the last decades will continue, but slow down: Until 2050, the built-up area of the region will increase by 20%, the population by 30%, respectively.
2. Urbanization: The trend towards the metropoles continues: While in 2015, 28% of the population lived in Pune and Solapur, until 2050 this share will increase to 35%.
3. Urban densification: While the urban areas (both core city and peri-urban belts) of Pune and Solapur will experience increases in population of 60%, this is not reflected equally in built-up growth, expanding by only 43%.

Overlaying our results with agricultural and hydrological maps, we can show where urbanization is likely to impact food and water system most severely. Such long-term challenges of the Food-Water Energy nexus will be explored further within a coupled human-geophysical simulation model.

Only through adopting a spatially explicit scenario approach of projecting the spatial and demographic development can the highly dynamic growth patterns of emerging megacities in the Global South be captured.