The development of a flash flood severity index

Severity indices exist for droughts, hurricanes, and tornadoes, but a widely used scale for flood severity has not been established. Return periods are utilized, but the general public cannot easily relate to that system. Additionally, the National Weather Service utilizes a 3-tier, impact-based flood severity scale, established for many United States Geological Survey streamgage sites, but the scale is vague and is only applicable for locations in which a streamgage is available and the scale has been established. The purpose of this project was to develop a flash flood severity index using a more detailed, impact-based approach. Damage assessments for numerous flash flood events caused by excessive rainfall across the United States were conducted, retrospectively, and these case studies aided in the establishment of the tiered index. Additionally, National Weather Service employees and local emergency managers were queried during the establishment of the index to get a sense of its usefulness and practicality. The overarching goal of the project is to establish a universally applicable flash flood severity index to help professionals better communicate the risks associated with past, present, and future flash flood events.