Storm surge damage to residential areas: a quantitative analysis for Hurricane Sandy in comparison with FEMA flood map

Abstract

A quantitative assessment of storm surge damage is used to analyze structural vulnerability and evaluate the performance of flood risk mapping by the Federal Emergency Management Agency (FEMA). Using a survey of about 380 structures in heavily impacted Ortley Beach, New Jersey, following Hurricane Sandy (2012), we first assess component-level damage to each side and story of a structure based on a percentage scale. For each structure, these physical damage percentages are then integrated into a single indicator of overall damage—the economic loss ratio. These performance assessments are combined with building information to develop an integrated Geographic Information System database. This detailed database allows for a quantitative analysis of damage features and causes. Damage at the overall, story, side, and component levels all decrease as the distance to the coast increases, with most severely damaged houses concentrated in a near-shore region. Despite being heavily damaged however, this region was assessed as a low-risk zone according to FEMA’s current flood risk map. In contrast, a neighboring inland region which experienced significantly less damage was assigned as a high-risk zone. The preliminary new FEMA flood map for the area is improved by increasing the risk category for the near-shore region, but the fundamental problem, likely induced by insufficient wave modeling, needs to be addressed further. This study demonstrates a method of quantitatively assessing and documenting storm surge damage and applying the damage information to evaluate flood risk maps.