The 2007 Tabasco flood occurred in late October and early November 2007 in the Mexican states of Tabasco and Chiapas, in which as much as 80% of the former was left under water. At least 20,000 people were forced to seek emergency shelter. Over 1,000,000 residents were affected. Geography The southern Mexican state of Tabasco is bordered by the states of Veracruz to the west, Chiapas to the south, and Campeche to the north-east. To the east Tabasco borders with the Petén department of Guatemala, and to the north with the Gulf of Mexico. Tabasco is in the northern half of the Isthmus of Tehuantepec. The state capital is Villahermosa. The hydrology of Tabasco is complex. Most of the state is a wide coastal plain crossed by rivers coming from the mountains further south in Chiapas and Guatemala. The two main rivers in the region are the Río Grijalva and the Río Usumacinta, which converge before draining into the Gulf of Mexico north of Villahermosa through the wildlife-rich wetlands known as the Pantanos de Centla. These rivers are considered mature, since they are in the lowest part of their course, and the plain they cross allows them broad, wide flows, meandering and dividing into separate branches. This is the case with the Grijalva, which separates into several branches in the central part of Tabasco (known locally as the Río Carrizal, Río Samaría and Río Mezcalapa). These three rivers converge at Villahermosa, where they recombine and again take the name Grijalva. The main branch of the Grijalva in Chiapas is dammed by the country's four largest hydroelectric plants. Causes of the floods The Tabasco floods caused largely by the sinking of the land over the last century. The constant extraction of petroleum and gas, the construction of dams in the zone, the erosion of land and deforestation have all contributed toward making this region more flood-prone. Deforestation has allowed silt to fill in rivers thereby reducing their capacity and making floods more likely. With the onset of constant rainfall due to a low pressure system located nearby, the combination of these influences contributed to making the flood event even worse than it might otherwise have been. Some have suggested that global warming has increased sea levels, making water regions at the low sandy zones of the Gulf of Mexico disappear. However, sea level rises due to global warming were probably still