Extreme rainfall in Florida; local climatologies revisited
In general, partial duration data produced larger return values at shorter return periods and annual maxima produced larger return values at longer return periods. In order to focus on maximum rainfall, derived values were combined to produce distributions having the larger return value for each return period. Further, return values from these combined distributions were applied via the National Resource Conservation Service (NRCS) method to estimate local surface runoff. Such runoff estimates are considered to have the same return periods as the applied rainfall. Examples of rainfall and runoff curves derived from the combined distributions for both 24 and 48h periods are discussed.
Identification of added risk beyond 24 hours can be aided by considering both the 24h and 48h climatologies. An index to quantify any added risk in the 48h period was constructed from (1) the 100-year 24h rainfall and (2) the difference in return periods when that 24h amount is considered a 48h amount. Increased values of this index reflect continued risk in a 48h period and suggest added value in consideration of the local 48h climatology. Comparative results are discussed for various sites. In particular, the effect of hurricanes is evident.