TEMPORAL RAINFALL DISTRIBUTIONS IN PUERTO RICO

Abstract: 
Spatial and temporal variabilities of rainfall in Puerto Rico are significant. A predominant storm distribution considered to be representative of a critical storm for design purposes in Puerto Rico is the Soil Conservation Service [SCS] Type II distribution. The main objective of this project was to determine the temporal rainfall distributions of extreme storms in the historical records in Puerto Rico and their similarities with well known design storms published in the literature. The impact of rainstorm sequences on the response of a typical small watershed was evaluated. The sensitivity of the watershed runoff response to rainfall record sampling time interval, curve number and lag time was determined. Extreme rainfall sequence events were identified from the historical records by comparing the historic rainfall sequences with the SCS Type II distribution. 24-hour rainfall periods with a sequence of rainfall similar to the SCS Type II distribution were found. These were not necessarily periods of continuous rainfall. These critical rainfall sequences were mainly the result of low pressure troughs. The historical impacts of the rainfall events with distribution similar to Type II were significant and site specific effects such as flooding and landslides were documented. The time interval of the sample had an effect on the response of the watershed used in this study. This difference in the watershed response is reduced as the lag time is increased.