"A flash flood is a flood in which the rapid rise in stream level and the resulting inundation follows the observable causative event by about four hours or less. For rain-caused flash floods meteorology is complex, and limited amounts of real-time data make timely forecasts of exact location very difficult. Lack of reports of flash-flood occurrences adds to the difficulty. Many occur that are never reported to the National Weather Service (NWS)"--Introduction.

Two commonly used methods of hydrologic analyses are parametric reconstruction and development of frequency distributions. Both techniques can be used to develop estimates of potential of damaging flash floods. However, under conditions of limited data, many areas may not have experienced enough flash floods to be recognized as prone to flash flooding. This paper gives a method to infer expected severity for flooding based on frequency analysis, which does not require a complete spectrum of data over a given basin. This method was used to estimate potential peak flows on Sabino Canyon, Arizona, and probability of occurrence of specified magnitudes was analyzed. These estimates indicate a strong possibility of damaging flash floods occurring in areas where none have occurred in several decades.