152B—Western Gulf Coast Flatwoods

This MLRA (shown in red in the figure above) is in Texas (59 percent) and Louisiana (41 percent). It makes up about 5,880 square miles (15,240 square kilometers). It is just northeast of Houston, Texas, and north of Lake Charles, Louisiana. The towns of Kingwood, Texas, and Singer, Sulfur, and Oberlin, Louisiana, are in this MLRA. Interstate 10 is just south of this area. The Sam Houston National Forest and the Big Thicket National Preserve are in the part of this area in Texas. The Sam Houston Jones State Park is in the part in Louisiana.

Physiography

This area is in the West Gulf Coastal Plain Section of the Coastal Plain Province of the Atlantic Plain. The area is nearly level to gently sloping and has low local relief. Elevation ranges from 80 to 330 feet (25 to 100 meters).

The extent of the major Hydrologic Unit Areas (identified by four-digit numbers) that make up this MLRA is as follows: Louisiana Coastal (0808), 35 percent; Neches (1202), 25 percent; Sabine (1201), 19 percent; Galveston Bay-San Jacinto (1204), 11 percent; and Trinity (1203), 10 percent. This area is bisected by many small streams and rivers that run toward the Gulf of Mexico. From west to east, these include the San Jacinto, Trinity, Neches, Sabine, Beckwith, Calcasieu, and Mermentau Rivers. The Calcasieu River, in the eastern part of the area, has been designated as a National Wild and Scenic River.

Geology

The entire area is underlain by unconsolidated clay, silt, sand, and gravel deposited by ancient rivers in late Tertiary and Quaternary time. Recent silt, sand, and gravel deposits fill the valleys along most of the major rivers in the area.

Climate

The average annual precipitation in this area generally ranges from 46 to 60 inches (1,170 to 1,525 millimeters), increasing from west to east. It is as much as 64 inches (1,625 millimeters) in the extreme northeast corner of the area. The precipitation is evenly distributed throughout the year but is slightly higher in the eastern part during winter. Rainfall usually occurs as moderate-intensity, tropical storms that can produce large amounts of rain during fall and winter. The average annual temperature is 66 to 68 degrees F (19 to 20 degrees C). The freeze-free period averages 290 days and ranges from 265 to 320 days.

Water

Following are the estimated withdrawals of freshwater by use in this MLRA:

Public supply—surface water, 3.9%; ground water, 2.2%
Livestock—surface water, 2.6%; ground water, 1.6%
Irrigation—surface water, 1.3%; ground water, 7.2%
Other—surface water, 76.3%; ground water, 4.7%

The total withdrawals average 760 million gallons per day (2,875 million liters per day). About 16 percent is from ground water sources, and 84 percent is from surface water sources. Rainfall, perennial streams, and aquifers provide an abundance of water. Most of the soils must be drained for optimum growth of general farm crops. Reservoirs on the San Jacinto River provide industrial and public supply water to the eastern end of this area. Water diverted from the Sabine, Calcasieu, and Mermentau Rivers is used for irrigating rice, for cooling thermoelectric power plants, and for industrial purposes in the suburbs of Lake Charles, Louisiana. Because of high levels of fecal coliform bacteria, the Calcasieu River is one of Louisiana’s most polluted rivers.

The unconsolidated sediments in this area are the primary sources of ground water. The water is used as drinking water and for industry and irrigation. The Gulf Coast aquifer system in Texas has moderately hard water with 300 to 500 parts per million (milligrams per liter) total dissolved solids. Soft water can be found in this aquifer in wells deeper than 500 feet (150 meters). The Chicot aquifer in Louisiana is made up of numerous beds of unconsolidated sand and gravel separated by layers of clay. The water in this aquifer is hard and has a median level of 350 parts per million (milligrams per liter) total dissolved solids. High iron levels may require treatment before this water is used for public supply.

Soils

The dominant soil orders in this MLRA are Alfisols and Ultisols. The soils in the area dominantly have a thermic soil temperature regime, an aquic or udic soil moisture regime, and siliceous or smectitic mineralogy. They generally are very deep, moderately well drained to very poorly drained, and loamy or clayey. Glossaqualfs formed in loamy and clayey sediments on stream terraces (Caddo and Evadale series), in loamy marine sediments on uplands (Waller series), and in alluvium on flood plains and stream terraces (Guyton series). Glossudalfs (Messer series) formed in loamy marine sediments on mounds and ridges. Vermaqualfs (Sorter series) formed in old alluvium on uplands. Hapluderts (Kaman series) formed in alluvium on flood plains. Paleudults (Kirbyville and Malbis series) formed in loamy marine sediments on uplands.

Biological Resources

This area supports pine-hardwood forest vegetation characterized by longleaf pine. Sweetgum, blackgum, post oak, blackjack oak, and southern red oak are the principal hardwood species. Hawthorns, myrtle, and shining sumac make up the woody understory. Mid and tall grasses are dominant in open areas. Little bluestem, pinhole bluestem, big bluestem, switchgrass, and Indiangrass are the principal grasses. Longleaf uniola, Virginia wildrye, Florida paspalum, beaked panicum, and several low-growing panicums and paspalums are the principal grasses in shady areas. Lespedezas, tickclover, wildbeans, and several composites are the principal forbs in the area.

Some of the major wildlife species in this area are white-tailed deer, coyote, fox, nutria, raccoon, skunk, cottontail, gray squirrel, fox squirrel, mink, armadillo, wood rat, white-footed mouse, eastern harvest mouse, cotton mouse, golden mouse, hispid cotton rat, hispid pocket mouse, marsh rice rat, turkey, quail, and mourning dove. Other major species include cottonmouth moccasin, broad-banded water snake, coral snake, hognose snake, canebrake rattlesnake, pigmy rattlesnake, copperhead, Louisiana milk snake, speckled kingsnake, rough green snake, buttermilk snake, five-lined skink, broad-headed skink, green anole, smooth softshell turtle, three-toed box turtle, red-eared turtle, Mississippi mud turtle, marbled salamander, smallmouth salamander, Fowler’s toad, East Texas toad, spring peeper, eastern tree toad, northern cricket frog, northern leopard frog, and bullfrog. The species of fish in the area include spotted bass, largemouth bass, crappie, catfish, bullhead, carp, and bluegill.

Land Use

Following are the various kinds of land use in this MLRA:

Cropland—private, 1%
Grassland—private, 12%; Federal, 1%
Forest—private, 74%; Federal, 3%
Urban development—private, 7%
Water—private, 1%
Other—private, 1%

The forestland in this area consists principally of pine and pine-hardwood forests. Much of the forested acreage is owned by large corporations, and lumber and pulpwood are the chief forest products. Cleared areas are used mostly for pasture. The major pasture grasses are bahiagrass and coastal bermudagrass. Only a few small areas are used for crops. Many small subdivisions are being developed throughout the area, especially in the vicinity of Houston and Beaumont, Texas.

The major soil resource concerns are water erosion, maintenance of the content of organic matter and productivity of the soils, and soil moisture management. When areas are bare after a tree harvest, water erosion is a hazard on sloping land. Conservation practices on forestland generally include forest stand improvement, forest trails and landings, prescribed burning, riparian forest buffers, forest site preparation, bedding, establishment of trees and shrubs, and management of upland wildlife habitat. The soils in this area are low in content of organic matter and productivity. Measures that increase the content of organic matter are needed. Applications of lime in areas of low pH help to maintain or improve productivity. Many of the soils remain wet or have a high water table for some or most of the time during the year. Measures that improve drainage or adapt the land use to the wet conditions are needed.

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