 Of particular note is the Katy Prairie to the west, the Big Thicket to the northeast, and the Galveston Bay ecosystem to the south.Additionally, the metropolitan region is crossed by a number of creeks and bayous, which provide essential drainage during rainfall events; some of the most notable waterways include Buffalo Bayou (upon which Houston was founded), White Oak Bayou, Brays Bayou, Spring Creek, and the San Jacinto River.The upper drainage basin of Buffalo Bayou is impounded by two large flood control reservoirs, Barker Reservoir and Addicks Reservoir, which provide a combined 400,000 acre-feet of storage during large rainfall events and cover a total land area of .