Flash floods are among the deadliest weather phenomena in the world. Because of the short lead times associated with these events, it is important that those in danger understand their risk in order to respond appropriately to watches and warnings. There are, however, many factors involved in one's likelihood to respond. To assess these factors, a mail survey was conducted for a random sample of the general public in flash flood-prone Boulder, Colorado. The survey results were coded into indices representing flash flood knowledge, risk perception, previous experience, and trust in watches and warnings. A combination of statistical and geographical analyses were used to evaluate the variables that influence the indices and thus response.