Regional Rainfall Frequency and Ungauged Basin Analysis for Flood Risk Assessment in Haiti

Flood risk assessment in many locations, especially in low-income countries, is severely hindered by a lack of hydrologic data. This study illustrates the application of regional rainfall frequency analysis, combined with ungauged basin analysis, to estimate flood discharges in the Gonaives basin in Haiti. Using limited daily rainfall data from seven gauges within and near the watershed, a regional extreme value distribution is selected and design storms are developed. These design storms are then input to a rainfall-runoff model, the parameters of which are estimated from spatial analysis of physical watershed characteristics. As a case study, the flood discharge and associated return period are estimated for the 2004 event that claimed 1,650 lives, and model outputs for other synthetic design storms are compared with large observed floods in other Caribbean basins similar in size to the Gonaives basin. Results of the comparative analysis indicate that the simulated peak flood flows of the Gonaives watershed are within the range of the maximum floods observed in other Caribbean basins with similar drainage areas, topography, and vegetation cover.