A new potentially devastating natural disaster with tragic human consequences could be brewing in Haiti. This event could make a disease outbreak there much worse as well. Tropical Storm Tomas will be moving over Haiti and the Dominican Republic tonight and Friday, and the National Hurricane Center has issued a hurricane warning for Haiti. The center also says rainfall in Haiti from Tomas may total 5 to 10 inches with isolated amounts up to 15 inches. Rainfall amounts this high could produce a catastrophic flooding calamity.
Haiti has endured decades of death and destruction for a variety of reasons. The latest natural disaster to strike this desperately poor county was the earthquake of January 12, 2010. The epicenter of the 7.0 quake was just 25 miles west of the capital of Port-au-Prince — an estimated 230,000 people were killed and 300,000 were injured. Additionally, 250,000 homes collapsed and 30,000 commercial buildings were either heavily damaged or destroyed. As a result, over one million people were made homeless. Surely that would be enough for one year — or a hundred years — yet on top of all that, a cholera outbreak is threatening to overrun the county. Now, with Tomas bearing down on Haiti, the potential for the outbreak to spread could increase dramatically.
What makes Haiti so vulnerable to tropical storms is near complete deforestation. In 1923, 60% of Haiti was covered with trees. Today, only 2% of the country has forest. There are several reasons for this, but the bottom line is that erosion is a terrible problem anytime it rains. Tropical rains can be very heavy and tropical storms have massive amounts of water stored in their clouds. You might think a hurricane would be the worst possible storm that could strike Haiti, but not necessarily. A weaker tropical storm, or even a tropical depression, if moving slowly enough can unleash torrents of rain. These less-developed storms can unload as much as 10 to 20 inches of rainfall in one day, even more if the storm stalls over an area. You don’t need a hurricane to get devastating floods.
Compounding the deforestation problem in Haiti is the topography. Three mountain ranges run across the country, covering two-thirds of the land — the peak elevation is 8,793 feet. When clouds are forced up over mountains, the amount of precipitation is increased due to a process called orographic uplift. As the clouds are lifted up over higher terrain they are pushed into cooler atmospheric temperatures. This increases the relative humidity of the clouds, and subsequently increases the amount of precipitation they produce.