Flooding effects combining storm surge and surface runoff during Hurricane Georges on the eastern coast of Puerto Rico

Abstract

Puerto Rico (PR) is located in a hurricane prone zone. The purpose of this study was to determine the flooding effects caused by the combination of the storm surge and surface runoff discharge during the passage of Hurricane Georges along the East coast of PR. The system was modeled using a combination of tools including: a two-dimensional hydrologic model and simulations of storm surge using a high-resolution oceanic circulation model. A coupling technique was developed to integrate the storm surge model results into the hydrologic model. The results show that the combined effect of storm surge penetration and inland runoff produced by heavy rainfall deposited by Hurricane Georges increased flood levels in the coastal zone. Without considering these effects, flood levels provided by tides and wind driven circulation models only, could underestimate the real hazard conditions. The net effect depends on the watershed conditions, the spatial and temporal distribution of rainfall and the local conditions of the river morphology near the coastline. Even though peak discharge is usually used as an indicator of hazard conditions and regulations promote zero increase in peak discharge, water volumes play a major role in water levels during flood conditions. This is more important during storm surge because ocean water penetrates inland, increasing water volumes and flood depths.

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