Rainfall-runoff simulations using the CARIWIG Simple Model for Advection of Storms and Hurricanes and HEC-HMS: Implications of Hurricane Ivan over the Jamaica Hope River watershed

Abstract

Jamaica is the third largest island in the Caribbean. It has a history of being significantly impacted by flooding associated with tropical storms and hurricanes. In this study, model-generated rainfall data are used to investigate implications for peak discharge in the Hope River watershed in eastern Jamaica, for different scenarios of a hurricane passing over the island. While predictions of storm and hurricane hazards are available on a climate scale, sub-daily rainfall and wind data for scenarios of their passage (i.e. variations in path, speed and/or intensity) over a given Caribbean island do not exist. The rainfall data are obtained at 25 km spatial resolution using a new tool known as the Simple Model for Advection of Storms and Hurricane (SMASH). SMASH provides rainfall and wind speed data over Caribbean islands under varying tracks, speeds and/or categories for a select group of historical hurricanes. Hurricane Ivan is explored using three user-defined tracks and two user-defined forward speeds. The rainfall data are then conditioned over a hydrological model for the watershed to derive peak discharges at significant sections affected by flooding from such extreme events. The results show that SMASH reasonably represents the two peaks in rainfall but underestimates their magnitudes for a scenario configuration that approximates the historical passage of Hurricane Ivan over Jamaica. SMASH also approximates well the first 6 h of cumulative total rainfall intensity, but thereafter underestimates cumulative totals. Flow scenarios from HEC-HMS indicate higher intensity of discharge for a track south of the island (as opposed to a direct hit) and a shorter lag time to peak discharge with increase in speed of the hurricane. The results also suggest that, even for a direct hit, the orientation of storm path is seemingly significant when assessing vulnerability. The potential to use both SMASH and a hydrological model to create awareness to flooding from different types of tracks and speeds of hurricanes is demonstrated in this study. The benefit for planning to avoid loss of life and property is also discussed.