Louisiana, which ranks 31st in size among the states, covers 134,265 sq km (51,840 sq mi), including 10,759 sq km (4,154 sq mi) of inland water and 5,012 sq km (1,935 sq mi) of coastal water over which it has jurisdiction. It has a maximum length, from north to south, of 440 km (275 mi) and a maximum width of 480 km (300 mi). Elevations range from 2 m (8 ft) below sea level, at New Orleans, to 163 m (535 ft) above sea level, at Driskill Mountain, in northwestern Louisiana. It has an average elevation of only 30 m (100 ft) and, along with Florida and Delaware, is one of the three lowest states. Louisiana lies wholly within the gulf portion of the Coastal Plain, which is one of the principal natural regions, or physiographic provinces, of the United States.
The Gulf Coastal Plain can be divided into three subregions, or sections, all of which lie partly within Louisiana. They are, from east to west, the East Gulf Coastal Plain, the Mississippi Alluvial Plain, and the West Gulf Coastal Plain.
The Mississippi Alluvial Plain in Louisiana extends from the Louisiana-Arkansas border in the north to the Gulf of Mexico in the south and parallels the main channel of the Mississippi River. In Louisiana the region is commonly referred to as “the Delta,” a term that, in local usage, is not confined to the delta at the mouth of the Mississippi River. Largely a low-lying and swampy area, the Mississippi Alluvial Plain has an average width of about 80 km (about 50 mi) and slopes gently southward from 35 m (115 ft) on the Louisiana-Arkansas border to sea level at South Pass, one of the delta’s chief channels at the mouth of the Mississippi River. Near New Orleans, parts of the plain lie below sea level.
Along the banks of the Mississippi and other rivers are natural levees, which have been built up from river silts deposited by floods. The levees rise as much as 4.5 m (15 ft) above the general level of the surrounding plain, although most are about 2 to 3 m (about 6 to 10 ft) high. The levees, some of which are very wide, include some of the state’s best farmland.
Because of the protection from flooding afforded by their greater elevation, the levees are also used for transportation purposes. Many levees have been further heightened for flood control purposes. In the Mississippi Alluvial Plain away from the levees are vast poorly-drained areas, generally called backswamps. However, when drained and cultivated, as in the northeast, the backswamps are productive farmlands. The West Gulf Coastal Plain, west of the Mississippi Alluvial Plain, occupies the western half of Louisiana. Hilly regions, often with steep bluffs 90 m (300 ft) high, mark the transitional zone between this region and the Mississippi Alluvial Plain.
The northern and north central areas of this region are primarily areas of rolling hill country, much of it still heavily forested. The most prominent features of the hill country include Driskill Mountain and the Kisatchie Hills. Farther south are extensive areas of prairie, or grassland, which lie mainly along the southeastern bank of the middle course of the Calcasieu River. In the southern part of the West Gulf Coastal Plain, marshlands rim the coast and extend inland as much as 30 km (20 mi). They are generally separated from the Gulf by low sandy ridges called cheniers.
The East Gulf Coastal Plain, a small area east of the Mississippi, is similar to its counterpart in western Louisiana. Steep bluffs as much as 90 m (300 ft) above sea level occur in the Tunica Hills of West Feliciana Parish. The rest of the region is lower in elevation with numerous steep bluffs, clear springs, pine forests, and deep ravines. "Louisiana" © Emmanuel BUCHOT, Encarta, Wikipedia
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