shore Gulf habitat, a remnant of an early delta lobe 

 built when the Mississippi River flowed in its most 

 westward course. Because of sediment discharge by 

 the Atchafalaya River, mudflats are again rapidly 

 forming off the Vermilion coast, and the coastline is 

 accreting at Chenier Au Tigre. 



Within Vermihon Basin most of the inland open 

 water is that part of Vennihon Bay within the basin 

 boundaries. The bay is protected from the Gulf by 

 Marsh Island, and exchanges water with the Gulf 

 through the narrow, deep Southwest Pass. The bay 

 is also open to the east, connecting with the West 

 Cote Blanche Bay. Westward-flowing freshwater from 

 the Atchafalaya River and the Wax Lake Outlet keeps 

 the whole basin rather fresh. Although the wetlands 

 of the basin exchange water freely with Vermilion 

 Bay, the area of salt marsh habitat is very small and 

 most of the marshes are brackish or intermediate 

 (table 3.68). 



Most freshwater flow from the north is through 

 the VermOion River (fig. 3-33). Bayou Teche water is 

 also diverted to the Vermihon River through Bayou 

 Fusilier and Ruth Canal. This fresh water is confined 

 by the high banks of the lower Vermilion River so 

 that overbank flooding does not occur normally ex- 

 cept near the mouth. Drainage is complicated by the 

 complex network of dredged canals that include the 

 Gulf Intracoastal Waterway (GIWW), that intersects 

 the Vermilion River about 5 km (3 mi) above its 

 mouth, the Vermilion River cutoff that bypasses Lit- 

 tle Vermilion Bay and Little White Lake, and the 

 Schooner Bayou cutoff that connects the GIWW with 

 Schooner Bayou (plate IB). 



On the west and northwest, drainage into the 

 Vermilion Basin is restricted by the embankment of 

 Louisiana Highway 82, by spoil banks along the 

 Schooner Bayou/Freshwater Bayou system, and by 

 control structures at Vermilion Lock, Freshwater 

 Bayou , and Schooner Bayou designed to preserve 

 fresh supphes in the Mermentau Basin (part 3.6.3). 

 Docks on Freshwater Bayou restrict direct exchange 

 of water with the Gulf and probably reduce the use 

 of wedands by estuarine-dependent organisms in the 

 area north of the locks. 



North of Vermihon Bay some high land exists with 

 a small forested area, agriculture, and a few villages. 

 The lower part of the basin has poor access, except 

 by boat, and no permanent settlements are found 

 there. 



Diurnal tides are pronounced as far north as 

 Abbeville . They average 3 7.5 cm ( 1 4.8 in) at Vermilion 

 Lock (fig. 3-33). Seasonal water levels peak in spring 

 and early fall (fig. 3-34), but do not show the distinct 

 low level during the summer found elsewhere on the 

 coast, perhaps because of Atchafalaya River water. 



Since 1945, mean armual water levels have shown 

 an annual increase of 0.94 cm (0.37 in) per year at 

 Vennilion Lock (fig. 3-34). This is comparable to, or 

 slightly lower than, rates elsewhere along the Chenier 

 Plain. At the Lock, water is nearly fresh (fig. 3-35). 

 The long-term trends at this location show a decrease 



in salinity since 1947 (fig. 3-36), due probably to a 

 combination of wet years and freshwater discharges 

 from the Mermentau Basin. 



Vermilion Bay and its adjacent wetlands support 

 large populations of shrimp, Gulf menhaden, blue 

 crab and other estuarine-dependent organisms. Nutria 

 and muskrat are harvested from the wetlands, and 

 waterfowl are abundant. The potential for fresh and 

 saltwater finfishing is also high (table 3.68). 



Socioeconomics. The Vermihon Basin has an ex- 

 tremely small human population— 804 individuals. 

 The work force is employed primarily in mining and 

 mineral fuel-related jobs (fig. 3-12). Only in Intra- 

 coastal City is there industrial development in the 

 basin. The annual values of commodities produced by 

 the basin are: oil and gas S53.2 million; agricultural 

 products, S2 million; fish and fur animals, $913,000; 

 and sport fish and game, 52. 5 million (table 3.68). As 

 in other basins, the mineral extraction industry dom- 

 inates the economy. 



Waterbome transport into and through the basin 

 was about 1 million tons (0.9 million tonnes) in 1976, 

 representing a decline from the peak of 1.9 million 

 tons (1.7 milUon tonnes) in 1967. Nonfuel mined 

 products are imported into the basin and oil and 

 petrochemicals are exported. 



Effects of Human Activities on the Environment. 



Hydrologic effects: The effects of modifications of 

 the normal hydrologic regime by canals, spoil banks, 

 and control structures in the Vermihon Basin may be 

 masked by the overpowering influence of the Atcha- 

 falaya River, which floods Vermilion Bay with fresh 

 water and high nutrient sediments. 



Habitat effects: Unexplained wetland losses in 

 the Vermilion Basin are occurring at a rate of about 

 0.09%/yr (844 ha or 2,086 a since 1952), the lowest 

 rate along the Chenier Plain coast, inspite of the ex- 

 tensive hydrologic alterations (table 3.68). The rela- 

 tive stability of the marshes may result from the heavy 

 sediment influx from the Atchafalaya River. Total 

 wetland losses have been 15.9% (6,800 ha or 16,803 

 a) since 1952. Over one-half of this loss (3,473 ha or 

 8,582 a) has resuhed from impoundment. Canal and 

 spoil area increases have amounted to 1 ,649 ha (4,075 

 a). Drainage for agriculture accounts for the majority 

 of the remaining area. Although there is shoreline ac- 

 cretion along the eastern coast of the basin, the re- 

 treating shoreline on the western coast has resulted in 

 a net loss of 200 ha (494 a) for the entire basin. 



Spoil area has tripled since 1952, indicating a 

 significant increase in the rate of canal construction. 

 In the entire Chenier Plain, about 85% of the present 

 canal system was dredged prior to 1952. 



The rate of conversion of wetlands to agricultural 

 land also has increased. As indicated in part 3.2.3, 

 agricuhural area in the Louisiana coastal parishes has 

 been declining slowly since the early 1930s. The Ver- 

 milion Basin is an exception; its agricultural area in- 

 creased 24% since 1952 and shows the highest dollar 

 return per hectare of farmland in the Chenier Plain. 



101 



