Urban form planning and tsunami risk vulnerability: Analysis of 12 Chilean coastal cities

Urban form has a significant impact on risk. Spatial planning instruments can optimize urban form in areas exposed to hazards. This work discusses how urban planning instruments, specifically Communal Regulatory Plans (CRPs), affect vulnerability to the risk of tsunami inundation in Chilean coastal cities. We analyze urban form and address exposure, susceptibility, and response capacity parameters. Exposure is evaluated by comparing existing and planned densities and to what extent planned risk areas coincide with inundation zones. We analyze existing critical facilities and land uses permitted by the CRP in inundation zones to evaluate susceptibility. We explore response capacity through the street network connectivity and green areas outside the inundation zone and how CRPs influence the structuring of new roads and new green spaces. We found that CRPs do not hold the sufficient capacity to incorporate and manage the tsunami inundation risk adequately. The planning scenario leads to a systematic increase in vulnerability as cities develop in exposed areas. We suggest to strengthen CRPs capacities to prevent the construction and reconstruction of areas affected by tsunamis, reinforcing the urban fabric's potential for evacuation, and to strengthen joint work between municipal urban planning and disaster risk management departments, among other recommendations.