trophic state exists. The problem is probably confined 

 primarily to the Memientau Basin where runoff from 

 rice fields is heavy. The Chenier Basin is isolated from 

 population centers to the north by the extensive Mer- 

 mentau wetlands. The area is sparsely populated; 

 agriculture is not a major industry, and much of the 

 land is public or private refuges. For these reasons, 

 and because it is important to protect the unique na- 

 tural cheniers, the Chenier Basin seems most appro- 

 priate for the maintenance, futher development, and 

 protection of its considerable recreation potential. 



3.6.5 CALCASIEU BASIN 



General features. The Calcasieu Basin is a shallow 

 wetland/aquatic system with a single major freshwater 

 input at the north end and a generally north to south 

 circulation pattern through a large central lake (plates 

 IB and 3B and fig. 342). Some east-to-west water 

 movement through the GIWW also occurs. The chenier 

 ridges are well developed and effectively protect the 

 inland marshes from the marine environment. A single 

 major pass allows circulation with the Gulf of Mexico. 

 In addition, Creole Canal allows freshwater drainage 

 to the Gulf througli a one way flapgate control struc- 

 ture at Oak Grove. Brackish and intennediate marsh 

 habitats predominate in the basin (table 3.71; plate 

 33). Along the upper edge of the basin much of the 

 land is in agriculture, cliiefly rice. The Hackberry salt 

 dome protrudes to an elevation of about 10 m (33 ft) 

 midway up the basin. Hydrologically the basin is fed 

 by a fairly modest upstream water flow (table 3.71) 

 which, combined with an annual rain surplus of 49 

 cm (19 in), gives a maximum freshwater renewal time 

 of about 37 days. Therefore, the basin is well-flushed. 

 Salinities in the upper basin adjust with the discharge 

 of fresh water into the basin (fig. 3-43). Of all the 

 Chenier Plain coast, tides are the most well-developed 

 along this area. They are primarily semidiurnal and 

 are strong as far north as the Calcasieu Lock. Mean 

 water level shows typical seasonal peaks in April and 

 September (fig. 3-44). Water level is rising at an ap- 

 parent rate of 2 to 3 cni/yr (0.8 to 1 .2 in/yr), a rate 

 characteristic of the rest of the Chenier Plain. 



Major living resources of the basin are shrimp. 

 Gulf menhaden, nutria, muskrat. and waterfowl. There 

 are two major menhaden processing plants in Cameron. 



Socioeconomics. The basin itself is rural, with a 

 few small villages. However, the large industrial cen- 

 ters of Lake Charles, Westlake, and Sulphur lie just 

 outside the basin to the north. As with other basins, 

 the main industry is mineral extraction, but petro- 

 chemical manufacturing plants outside the basin are 

 the major employers. In temis of production of crude 

 products, minerals bring in about $52 million an- 

 nually. Commercial fishing and trapping are a distant 

 second with $3.6 million. Sport hunting and fishing 

 are conservatively estimated at $2.8 million and agri- 

 culture at $2.2 million. Thus, as elsewhere in the 

 Chenier Plain, the renewable resources are overshad- 

 owed by the mineral extraction industry. 



Waterborne commerce is also important econom- 

 ically and volume has been fairly stable for the past 



10 years. In recent years, imported crude oil and ex- 

 ported petrochemical products have been the primary 

 commodities. 



Effects of Human Activities on the Environment. 



Hydrologic effects'. In the mid-1800"s a natural chan- 

 nel with a maximum depth of 4 m (13 ft) ran through 

 the central part of Calcasieu Lake and exited via the 

 natural sinuous portion of the lower Calcasieu River. 

 The shallowest depth of the system was 1 m (3 ft) at 

 the bar at the mouth of Calcasieu Pass. This bar con- 

 trolled intrusion of salt water into the basin to the ex- 

 tent that every spring during the freshet, the lake and 

 pass were flushed with fresh water for periods pro- 

 longed enough to result in oyster mortality near St. 

 John's Island (Van Sickle 1977). From 1871, Calcasieu 

 Pass was dredged continuously to various depths to 

 allow ship traffic entry into the channel to Lake 

 Charles. During these dredgings the depth did not ex- 

 ceed 4m (13 ft) at the mouth, but increasing salinities 

 allowed the oyster population to move progressively 

 up the lower Calcasieu River (Van Sickle 1977). 



Navigation into Lake Charles from Sabine Lake 

 was first made possible by deepening and widening 

 the GIWW between Lake Charles and Sabine Lake. In 

 1937, a land-cut channel was dredged to a depth of 

 10 m (33 ft) along the western edge of Calcasieu Lake 

 and was separated from the lake by spoil banks. The 

 lower sinuous shallow pass to the Gulf was bypassed 

 by a 10 m (33 ft) bar channel that extended some 

 distance offshore. Although supportive data are lack- 

 ing, later studies (U.S. Army Corps of Engineers 1950, 

 Van Sickle 1977) suggest that saltwater intrusion up 

 the ship channel did occur at this time. 



In 1946 the existing ship channel was deepened 

 to 12 m (39 ft). In the mid-1960"s the ship channel 

 width was doubled and the channel was dredged to a 

 depth of 1 5 m (49 ft). Van Sickle (1977) demonstrated 

 a resultant increase of surface salinity at Lake Charles 

 from 5.5 to7.7%o for the 8-year period before (1955 

 to 1963) and after the channel dredging from 1963 to 

 1971 (fig. 3-45). 



The dredged material from the channel was used 

 to levee off the ship channel from the lake to the cast 

 so that Calcasieu River water that once circulated 

 througli Calcasieu Lake now was confined to the Cal- 

 casieu Ship Channel. At the same time (1968), the 

 U.S. Aniiy Corps of Engineers constructed a saltwater 

 barrier above Lake Charles to keep the saltwater wedge 

 from moving upstream. 



The levee system designed to isolate the ship 

 channel from Calcasieu Lake has subsequently been 

 breached at both the northern and southern ends. 

 Oyster populations have subsequently become estab- 

 lished in the washout fans and there is a hand-tong 

 fishery in the basin. There is some suggestion that the 

 Creole Canal can act as a saltwater pump. Salt water 

 coming in through Calcasieu Pass flows east into Lake 

 Calcasieu to Grand Bayou. It pushes fresher water 

 over the marsh along the southeastern shore of the 

 lake and into Creole Canal. This fresh water flows to 

 the Gulf and is replaced by saline water through Cal- 

 casieu Pass. 



120 



