Extreme Floods and their Relationship with Tropical Cyclones in Puerto Rico

The island of Puerto Rico is known for its large flood peaks when compared to other locations in the US. Many of those flood peaks are associated with the passage of tropical cyclones (TCs). This study examines the role that TCs play in the flood distribution of Puerto Rico. Mean daily discharge from 12 stations with complete data from 1970-2010 and the tracks of 86 TCs that passed within a 500 km radius of Puerto Rico are used to study the TC-flood relationship over the island. An extreme value analysis (EVA) point process (PP) approach is implemented to examine the flood characteristics of the island when TCs are present in the discharge data series and when they are remove from it. Mean daily discharge values that exceeded the 99th percentile thresholds of each station were used in both the TC and Non-TC data series. In nine of the twelve stations the maximum mean discharge value was associated with a TC, with hurricanes Hortense (1996), Georges (1998) and Eloise (1975) responsible for most of the maximum peak flows at each site. Percent changes between the EVA parameters that include location (mean), scale (variance) and shape (skewness) between the TC and Non-TC data exhibited a decrease at the majority of stations, which suggests that TCs play a major role in the flood peak distribution of Puerto Rico. Stations in the eastern interior and the northcentral region showed the highest decrease in all parameters when TCs were removed from the series.