Abstract. Coastal regions become unprecedentedly vulnerable to coastal hazards that are associated with sea level rise. The purpose of this paper is therefore to simulate prospective urban exposure to changing sea levels. This article first applied the cellular-automaton-based SLEUTH model (Project Gigalopolis, 2016) to calibrate historical urban dynamics in Bay County, Florida (USA) -a region that is greatly threatened by rising sea levels. This paper estimated five urban growth parameters by multiple-calibration procedures that used different Monte Carlo iterations to account for modeling uncertainties. It then employed the calibrated model to predict three scenarios of urban growth up to 2080 -historical trend, urban sprawl, and compact development. We also assessed land use impacts of four policies: no regulations; flood mitigation plans based on the whole study region and on those areas that are prone to experience growth; and the protection of conservational lands. This study lastly overlaid projected urban areas in 2030 and 2080 with 500-year flooding maps that were developed under 0, 0.2, and 0.9 m sea level rise. The calibration results that a substantial number of built-up regions extend from established coastal settlements. The predictions suggest that total flooded area of new urbanized regions in 2080 would be more than 25 times that under the flood mitigation policy, if the urbanization progresses with few policy interventions. The joint model generates new knowledge in the domain between land use modeling and sea level rise. It contributes to coastal spatial planning by helping develop hazard mitigation schemes and can be employed in other international communities that face combined pressure of urban growth and climate change.

Abstract. Coastal regions are under intense development because of their biodiversity and economic attractiveness. Meanwhile, these places are highly vulnerable to coastal hazards that are associated with sea level rise. Continuing urban development in these coastal areas that are prone to be flooded increasingly poses unnecessarily risk to their residents. While overwhelming efforts have been made to investigate coastal land use changes, few studies have simultaneously explored urban growth dynamics and its interaction with the coastal hazards. This paper applied the cellular automaton-based SLEUTH model to calibrate historical urban growth pattern from 1974 to 2013 in Bay County coastal areas, Florida. Three scenarios of urban growth – historical trend, compact development, and urban sprawl – up to 2080 were predicted by applying the calibrated SLEUTH model. To assess the effects of different policies, we developed three excluded layers – no regulations, flooding-risk mitigation, and conservational/agricultural land protection – and evaluated how different urban growth scenarios were oriented under these policies. Eventually, flooding maps were overlaid with future urban areas, and the exposure of different urban growth patterns to sea level rise induced flooding was examined. The findings suggest that if coastal cities expand in a compact manner, areas vulnerable to flooding will increase compared with historical trend and urban sprawl scenarios. With respect to policies, if no regulations are implemented, on average the flooded area in 2080 would be more than 25 times under flooding-risk mitigation. The joint model can serve as a decision support tool to assist city officials, urban planners, and hazard mitigation planners in making informed decisions. The visualization results can be also useful in public outreach regarding coastal communities' increasing risk to flooding enhanced by sea level rise.