On the west edge of the basin, canals in the Sabine 

 National Wildlife Refuge allow water flow across basin 

 boundaries and connect the Calcasieu and Sabine 

 basins. Because water follows the deeper, straighter 

 dredged canals the natural streams, such as North 

 Bayou, become filled with sediments. 



In addition to the ship channel, construction of 

 other canals has been extensive. Canals 1,271 km 

 (790 mi) in length now cover 2.6% of the land area of 

 the basin (table 3.71). Most of these canals were con- 

 structed either for navigation or for access to oU and 

 gas sites. 



These navigation projects have resulted in signifi- 

 cant modifications to the natural hydrologic patterns: 

 north-to-south circulation now largely bypasses the 

 Calcasieu Lake. The river presumably drops much of 

 its sediment load in the ship channel rather than in 

 the lake and adjacent wetlands. The channel permits 

 saltwater intrusion which increases the salinity. Higher 

 salinities have resulted in oyster beds becoming estab- 

 lished further upstream nearer to Lake Charles (Van 

 Sickle 1977). The many interconnecting channels of 

 the GIWW, Alkah Ditch, and oil well access canals al- 

 low the salt to penetrate far into wetlands. 



Further modifications have occurred because 

 levees and spoil bank construction has purposefully 

 or inadvertently impounded large wetland areas, re- 

 ducing flushing and overland flow. 



Habitat effects: These hydrologic modifications 

 have profoundly influenced wetland and aquatic hab- 

 itats. Since 1952, 19.029 ha (47,022 a) of natural 

 wetlands in Calcasieu Basin have been lost. Only 6,361 

 ha (15,718 a or 9%) can be accounted for by direct 

 cultural changes such as impounding, draining, etc. 

 (table 3.71). The remaining 12,668 ha (31,303 a or 

 17%) are lost to open water, a loss rate 0.75%/yr. By 

 contrast, although the rates of natural processes such 

 as sea level rise are similar in other basins, the unex- 

 plained residual wetland loss rate is only about 0.13%/ 

 yr (except Sabine Basin). The high wetland loss rate 

 in the Calcasieu Basin is almost certainly caused by 

 the changed hydrology coupled with saltwater intru- 

 sion, and the possible effects of discharges of toxic 

 materials and brine into the basin. 



Aside from the loss of wetlands to inland open 

 water habitat, agricultural area has increased by 1 ,162 

 ha (2,871 a) mostly by draining wetlands; urban ex- 

 pansion has claimed 1 ,428 ha (3,529 a) from wetland, 

 agriculture, and upland forest habitat (table 3.71). 

 Net shorehne erosion is very small, but erosion at 

 Holly Beach (a vacation town) is a critical problem. 

 There is some evidence of the development of off- 

 sliore mudflats also, but this is poorly documented. 



Effects on renewable resources: The loss of na- 

 tural habitats, particularly wetlands, signals a long- 

 term gradual decline in the living resources of the basin. 

 As discussed in part 3.5, these resources appear to be 

 exploited at their maximum potential. In the Calcasieu 

 Basin there appears to have been an increase in the 

 harvest of certain estuarine-dependent species such as 

 shrimp (fig. 3^6) since the widening and deepening 



of the ship channel. This may result from two factors. 

 First, the increase in salinity in the estuary and se- 

 cond, the temporary increase in the marsh to water 

 interface associated with the wetland degradation. 

 The potential fishery increase is balanced by other 

 factors; the probable inland migration of the marsh 

 zones with increasing salt and brackish marshes ac- 

 companied by loss of intermediate and fresh marshes 

 as degradation continues. The increase in brackish 

 marsh at the expense of fresh and inteiTnediate marsh 

 can be expected to be deterimental to the nutria har- 

 vest and to most waterfowl. Waterfowl hunters in the 

 basin already complain of the effects of salt encroach- 

 ment on habitat changes. 



3.6.6 SABINE BASIN 



General Features. The Sabine is the largest basin 

 on the Chenier Plain (plates lA, 3A, and 4A, and 

 fig. 347). Because it straddles the Louisiana-Texas 

 border, there may be political problems in managing 

 it as a single hydrologic unit. The land surface slope 

 is slight and about one-half of the inland area is wet- 

 land (table 3.72 and figs. 348 and 3-49). Sabine Lake 

 is approximately 32 km (20 mi) long and 13 km 

 (8 mi) wide and has an average depth of about 2 m 

 (6.6 ft). Sabine River empties into Sabine Lake from 

 the northeast; it has a drainage area of 24,152 km 

 (9,325 mi^). Most of the river is impounded by the 

 Toledo Bend Dam. The Neches River, emptying into 

 the Sabine Lake from the northwest, has a drainage 

 area of 20,584 km^ (7,948 mi^). Much of this river 

 is impounded by the Sam Raybum Reservoir. 



A deep draft ship channel enters the basin through 

 Sabine Pass from the Gulf and follows the western 

 edge of Sabine Lake to the mouth of the Neches River. 

 Here the dredged channel divides into two segments. 

 One segment goes up the Neches River to Beaumont 

 and the other goes up the Sabine River to Orange 

 (fig. 347). The channel is separated from the Sabine 

 Lake proper by a narrow strip of land, predominantly 

 a man-made spoil island. The Gulf Intracoastal Water- 

 way (GIWW) enters Texas from Louisiana about 

 4.8 km (3 mi) below Orange and continues south- 

 westward along the deep draft ship channel on the 

 west side of Sabine Lake. At the mouth of Taylor 

 Bayou near Port Arthur, the GIWW leaves the lake 

 and proceeds toward East Bay in a channel that is 

 almost completely man-made (fig. 3-47). An outcrop- 

 ping of high land along the ship channel on the 

 western side of Sabine Lake has provided a site for 

 the city of Port Arthur and intense industrial develop- 

 ment. Likewise, the cities of Beaumont and Orange 

 located on the Neches and Sabine rivers, respectively, 

 are industrial centers. This is the most industrialized 

 basin in the region and the only basin within which 

 high population densities occur. Even so only 5% of 

 the total basin area is urbanized (table 3.72), but 

 activities in this area have a strong influence on the 

 whole basin, and particularly on Sabine Lake. Thirteen 

 percent of the inland area of the basin is in agricul- 

 tural production, chiefly for rice and qattle. Most of 

 the farm land is located along the northern bound- 

 ary of the basin. On the Louisiana side of the basin 

 the large Sabine National Wildlife Refuge encompasses 



129 



