Assessing coupled human-flood interactions using LiDAR geostatistics and neighbourhood analyses

The paper integrates well-established methods from other spheres of flood risk assessment in a novel way to explore the currently poorly understood Safe Development Paradox (SDP) phenomenon in coastal settings. The study contributes to addressing this knowledge gap based on insights from contrasting UK case studies: Portsmouth, Weston-super-Mare, and Southport. Differential analysis of historic LiDAR Digital Surface Models (DSMs) was used to identify temporal changes in the urban landscape to create a DSM of Difference (DoD), representing elevation change between two locations over time. Geostatistical testing, specifically t-tests, were then used to infer statistical significance of changes in urban development. The findings reveal a consistent pattern: following completion or improvement of large-scale structural coastal flood defences, there is subsequent, and statistically significant, increases in urban development within/near flood-exposed areas across all three case studies, contrary to the limited flood-exposed development in neighbouring settlements, with no comparable defences constructed during the same period. On average, new urban development occurs approximately 2 years after the completion of coastal flood defence projects. The study emphasises the importance of context-specific and neighbourhood analyses, considering settlement size, economy, and extraneous factors influencing the nature of development to better understand the SDP’s long-term implications.