Thailand’s tropical savanna climate leaves Thailand vulnerable to flooding during its monsoon season—this year in particular. The accumulated precipitation from January to October 2011 was 35% higher than average in consequence of La Niña—a phenomenon that, as a result of lower surface ocean temperatures, usually brings increased and, in this case, earlier than expected precipitation—, five key tropical storms, and monsoon troughs. Heavy rainfall raises the level of water in waterways, producing overflowing and flooding to adjoining areas. Another consequence of the heavy rainfall is the exceeding amount of water entering particularly Bhumibol and Sirikit dams that reached an overloading capacity. High tides and storm surge in the Gulf of Thailand during the months of October and November also raised the water level and hindered the draining system into the gulf. Lastly, obstacles like aquatic plants create a natural blockage in the sewer system.