Building urban development scenarios into assessments of future flood risk

The devastating impact of flood events around the globe demonstrates the need for more comprehensive assessments of future flood risk in urban policy. In Aotearoa-New Zealand, flooding is one of the most costly natural hazards, in part due to the relatively high clean-up costs, but mostly due to the frequency of flood events. With a warming climate, changing precipitation trends, and rising sea levels, flooding is expected to become more frequent and more severe in the future. 

Flood risk assessments based on future flood projections paired with current urban plans are missing a key element of the hazard exposure – where will people be living by the end of this century? How might flood risk change over the next 100 years due to changes in urban landscapes? With a continually growing and urbanising population we are facing a housing affordability crisis, we must build houses. The result is a fundamental policy challenge of how to facilitate future urban development while also managing the risks of future flood events.

Mā te haumaru ō nga puna wai ō Rākaihautū ka ora mo ake tonu: Increasing flood resilience across Aotearoa-New Zealand, is a five-year multi-stakeholder Endeavour research programme supported by the New Zealand Government via the Ministry for Business, Innovation and Employment (MBIE) and led by Earth Sciences New Zealand. The programme aims to improve New Zealand’s understanding of, and resilience to, flooding risk. The programme seeks to create a better evidence base for public policy relating to planning, mitigation, and response, including the challenge of enabling future development with a changing climate. 

Research Aim

My PhD research will contribute to the flood resilience programme by exploring, testing and developing methods to generate a range of alternative long-term urban development scenarios. My goal is the successful integration of urban futures with flood futures to provide more comprehensive assessments of the uncertainties and inequalities of future flood risk.

Research Questions

1. What is the current state of research in urban growth modelling over the longer-term horizons required for assessments of future flood risk?

2. How do methods for modelling urban growth vary across urban practitioners in NZ and what are the key issues to be addressed?

3. What is the sensitivity of urban growth predictions to diverse modelling methods and how does between-model variability compare to within-model variability?

4. How can a range of future urban scenarios be generated and integrated with flood risk models to deliver a more comprehensive picture of the uncertainties and inequalities of future flood risk?

Research Methods and Objectives

Review of urban growth modelling literature

Develop a decision pathway that identifies appropriate methodological choices at critical junctures in the urban growth modelling process when predicting future urban form over the longer-term horizons required for planning under future climate uncertainty. (Booker et al. 2025)

Survey and interviews with NZ urban planning and research community

Investigate the extent to which urban growth modelling is currently used for long-term planning in NZ, identifying potential barriers and exploring requirements needed to advance its practical utility and collaborative application to planning under future climate uncertainty. (In review)  

Model benchmarking and selection

Report on urban growth model sensitivities and calibration requirements by comparing within-model variability to between-model variability for a case study NZ urban area that has experienced strong growth but is also susceptible to climate hazards. Identify the method and calibrated model that appears most fit-for-purpose.

Model simulation and integration

Develop a methodology for building urban development scenarios into assessments of future flood risk by 1) simulating a range of plausible future urban forms for the case study area, including incorporating global climate change scenarios 2) generating model output maps, consistent with other flood programme mapping, demonstrating distributions for uncertainty, and 3) investigating mechanisms for linking the model with the RiskScape software and/or ESNZ flood modelling workflow.

Research Team