Climate change and deforestation in Haiti: are historical hydro-meteorological observations relevant to describe present catchment hydrological characteristics?

Recent floods have highlighted the high vulnerability of Haitian territories to hydro-meteorological hazards. For example, the coastal city of Cayes (southern Haiti) has been heavily impacted by the torrential rainfall of October 5 to 6, 2018, with numerous damaged buildings. In Haiti, the only time period of continuous observations of both rainfall and streamflow lasts from 1920 to 1940. The concomitance of rainfall and streamflow observations at daily timestep enable the characterization of Haitian catchment hydrological response over that 20-year period. However, Haiti has experienced massive deforestation over the last century, and the Caribbean is a hotspot of climate change impacts such as warmer air and sea surface temperatures, leading to stronger hurricanes. Hence, the relevance of the characteristics estimated over the 1920-1940 period is questionable for present-time studies.

The objectives of this work are firstly to estimate flow characteristics of gauged Haitian catchments considering 1920-1940 temporal series, and secondly to use this historical information to estimate present-time hydrological characteristics. After digitalization and quality control tests of daily rainfall and streamflow temporal series, two types of hydrological characteristics were estimated on each gauged Haitian catchment. First, the catchment annual water balance was described by calculating the ratio between mean annual precipitation, evapotranspiration and runoff (using Turc-Budyko representation). Then, daily flood characteristics were estimated with a rainfall-runoff event-based study, focused on rainfall event duration and amount, peak streamflows and runoff ratio. Finally, present-time flow characteristics were estimated using a global rainfall-runoff model (GR4J) calibrated on the digitalized series, and then fed by the MSWEP dataset. This global database is available at the daily time step from 1979 to 2017, and merges gauge, satellite, and reanalysis data. The uncertainties related to the temporal stability of the rainfall-runoff model parameters and the potential impact of the deforestation on flow characteristics were then discussed.