Grand Lac Campground is in the Spring Bayou Wildlife Management Area, in the low-lying Red River backwater system. In general, the terrain is low, poorly drained land, with numerous lakes and narrow ridges. About 40 percent of the WMA is covered by water, with various open lakes, bayous, bays, and sloughs. The area is drained by Little River.
The forest cover consists of nuttall and overcup oak with bitter pecan on the higher elevations. The lower elevations contain overcup oak, bitter pecan, swamp privet, and buttonbush. Lake edges are fringed with cypress, willow, and buttonbush. The understory consists of deciduous holly, hawthorn, dogwood, and seedlings of the overstory. Other plants include rattan, greenbrier, peppervine, trumpet creeper, dewberry, smartweed, verbena, wild lettuce, vetch, sedges, and grasses. Aquatic species include water hyacinth, alligator weed, delta duck potato, water primrose, lotus, and duckweed.