BASTROP BAYOU. The channel of Bastrop Bayou begins near the Missouri Pacific Railroad two miles southwest of Angleton in central Brazoria County (at 29°09' N, 95°27' W) and runs thirty-two miles south and then northeast, through Cox Lake, Lost Lake, the Gulf Intracoastal Canal, and Bastrop Bayqqv to its mouth on Christmas Bay, in east central Brazoria County (at 29°06' N, 95°12' W). Austin Bayou, a major tributary, enters Bastrop Bayou eight miles southeast of Angleton near Demi-John Island (at 29°06' N, 95°18' W). Bastrop Bayou is intermittent in its upper reaches. Upstream, it crosses rolling terrain surfaced by sandy loam that supports post oaks and grasses; downstream, it traverses brackish saltwater marshland surfaced by mud and sand that support rushes and grasses.