Measuring crowding levels using circle packing method: Application at Hawaii's beaches

Measurements of human crowding (occupancy) levels at various locations are crucial for transport planning research. Since information about visitor crowding might change over time and space, keeping track of data would be helpful in analyzing significant changes. In this study, we employ a circle packing approach to measure occupancy levels and variations seen over time on beach extents. As a representative case study, Waikiki Beach in Hawaii was studied. We then analyze beach loss scenarios (due to a sea level rise) using the classification of visitors by groups of one, two, and three or more individuals. For example, a reduction of 49.2% of beachgoers is seen in a 50% beach loss scenario compared to the existing situation. This means that a loss in beach area has a likewise loss in beach visitors, with a caveat that this loss in visitors is not dependent on the beach area but on beach topology. We provide an accurate surveying of the beach profile to extend the research to various sea level loss scenarios, since beach extents are unknown relative to expected sea level rise. The findings show that by including occupancy assessment in beach nourishment planning, stakeholders can be informed of the long-term effects of beach nourishment and the economic implications of losing beach space and visitors.