SETTING
As is typical for the Caribbean region, the climate is marine tropical with a hot and humid summer and a cooler and drier winter season. There are two distinct rainy seasons; one April to June the other October to November. Leogane has no long term records of its climate but we have installed a hydroclimate station that has been producing data since 2012. Haiti is hit, on average, by one cyclone (defined as a climatic event with windspeed over 250 km/h) with devastating effects every five years.
The ~180 km2 coastal plain is underlain by a productive shallow unconfined aquifer that typically can be accessed at depths of 5-10 meters below the surface. At greater depths (25-30 meters) a confining layer separates the unconfined aquifer from a deeper confined one. Two rivers bisect the commune and are accompanied by a multitude of smaller tributaries, irrigation canals, and drainage ditches.
Léogâne’s plain is stroke southward by the prolongation of the Massif de La Selle which is itself the northwestward prolongation (100 km) of the Sierra de Bahoruco of the Dominican Republic. The plain consists mainly of alluvium deposited by the Momance, Rouyonne, and Cormier Rivers while the mountains are composed mainly of limestone.
The coastal plain of Leogane is drained by 3 major watersheds, i.e. the Rouyonne, Cormier, and Beloc rivers, in addition to about a dozen smaller streams in the plain. Note that the large river to the NE, the Momance, does not contribute much to the overall drainage because its watershed lies much further to the SE inside the southern mountain range. The highest point is about 900m MSL and the plain starts at about 60m from where it gradually slopes down to small digits at the shore.
The 3 watersheds have a combined drainage area of about 131 square kilometers, thus comprising approximately 70% of the entire plain and its associated watersheds. All 3 streams are ephemeral in nature, i.e. there is no baseflow and they will only carry water when it rained in the mountains. Note that they will not carry any water when it only rained in the plain. The soil, made up of alluvial deposits, is quite permeable and rain typically percolates downward rather rapidly.
This image shows a detailed street map of the Town of Leogane and its surroundings in the coastal plain. It has been offered up by OpenStreetmap.org and proved a to be a valuable tool for our work in the area. Note that the only paved road is the Rte National 2 and since 2017 the connection to Darbonne in the eastern sector of the plain.
The coastal plain of Leogane is drained by 3 major watersheds, i.e. the Rouyonne, Cormier, and Beloc rivers, in addition to about a dozen smaller streams in the plain. Note that the large river to the NE, the Momance, does not contribute much to the overall drainage because its watershed lies much further to the SE inside the southern mountain range. The highest point is about 900m MSL and the plain starts at about 60m from where it gradually slopes down to small digits at the shore.