ABSTRACT
A three component mixed Gumbel distribution is found to satisfactorily model the observed annual flood frequencies of rivers in coastal Peru which display highly variable annual peak flood characteristics corresponding to three sets of ocean-atmosphere conditions. Exceptionally warm waters (El Niño) cause extensive heavy rains particularly in the northern lowlands; unusually cold waters (anti-El Niño) restrict both the quantity and distribution of precipitation everywhere. Model parameters reveal marked spatial trends in the severity and extent of flooding during any set of offshore conditions and conspicuous alterations in the pattern of regional flood characteristics with elevation. The analysis suggests a strong negative correlation of rainfall-runoff relationships between northern and southern Peruvian rivers.
