Table 3.74. Texas landings of blue crab for Sabine 

 Lake, and Galveston and Trinity bays, 

 showing amount and value of landing, 

 1962 to 1975. 



Sabine Lake 



Galveston and 

 Trinity Bays 



by Bolivar Roads, an improved natural pass between 

 the Gulf and Galveston Bay which is flanked by jetties 

 several miles in length projecting into the Gulf. Water 

 depths in East Bay range from about 1.5 to 2 m (0.9 

 to 1.2 ft) at its western end to about 1 m (0.62 ft) at 

 the eastern end. The eastern arm of the bay, called 

 Rollover Bay, contains about 255 ha (556a) and is 

 about 0.5 m (1.6 ft) deep. It opens to the Gulf through 

 an old natural pass. Rollover Pass, which was reopened 

 by dredging in 1955. 



East Bay Bayou, Oyster Bayou, and Onion Bayou 

 constitute the natural drainage system (approximately 

 660 km^ or 255 mi") of East Bay. The Gulflntra- 

 coastal Waterway extending from Sabine Lake enters 

 the East Bay Basin through East Bay Bayou, crosses 

 the northern end of Rollover Bay and extends along 

 the bay side of Bolivar Peninsula to deep water in 

 Bolivar Roads. 



Geologically the East Bay Basin has attributes of 

 the Barrier Strand Plain of Texas as well as the Chenier 

 Plain. Most of East Bay Basin consists of Recent de- 

 posits of sand which fomi dune ridges on Bolivar 

 Peninsula. Behind the beach ridge is coastal marsh. 

 Farther inland appears the Beaumont clay surface, a 

 coastal Pleistocene terrace that dips seaward under 

 the Recent marsh and beach deposits (Houston 

 Geological Society 1959). Most of the area is nearly 

 level coastal plain comprised of the Harris-Vest on Soil 

 Association with poor internal and surface drainage 

 (U.S. Department Agriculture 1976). The average 

 ground surface slope is about 0.2 m/km (1.06 ft/mi). 

 Marsh elevations are somewhat higher than those fur- 

 ther east toward Sabine Lake. The bay shoreline 

 generally lacks sand beaches and in many places is 

 associated with low-lying marshes, particularly on the 

 back side of Bolivar Peninsula (plates 3A and 4A). 

 On the north shore of East Bay low bluffs exist 

 where wave-action has eroded the Pleistocene terrace 

 deposits. 



Mean rainfall surplus is 20.6 cm/yr or 8.1 in/yr 



(table 3.75 and fig. 3-52). Most of the small bayous 

 are weired, have low flow rates, and drain southward 

 and southeastward into East Bay. The average annual 

 flow of freshwater from Oyster, Onion, and East Bay 

 bayous into East Bay is only about 2.1 x lO^m 

 (7.4x 10''ft^) (Rice Center 1974). The primary 

 drainage into the whole Galveston Bay system, how- 

 ever, is via the San Jacinto and Trinity rivers, and 

 these discharges indirectly modify salinities in East 

 Bay through mixing with Galveston Bay waters. The 

 Trinity River Basin is outside of the study area and its 

 influence on East Bay will only be briefly described. 



Based on local freshwater drainage the maximum 

 freshwater renewal time for East Bay is calculated to 

 be about 577 days. This estimate is undoubtedly high 

 because of three factors; freshwater input via die 

 GIWW from the Sabine Basin, indirect input of fresh- 

 water from the San Jacinto and Trinity rivers, and 

 tidal mixing. Fresliwater from the Sabine Basin 

 draining into the GIWW is considerable. Maximum 

 flow rates of 113m^/sec 3,991 ft'^/sec) have been 

 measured in the GIWW with maximum current 

 velocities of 0.396 m/sec or 1.3 ft/sec (Jarnes et al. 

 1977). This results from a difference in water eleva- 

 tion between ends of the GIWW, brought about by 

 tlie difference in tidal ranges and lag times between 

 Sabine Lake and East Bay, the small tidal range in 

 the GIWW, wind set-up and/or excess freshwater 

 inflow into Sabine Lake (James et al. 1977). 



Water renewal times in East Bay are also strongly 

 influenced by tides, which are well-developed at both 

 ends of the bay (fig. 3-53). The tides in the Gulf near 

 Rollover Pass lag behind those at Bolivar Roads by 

 3.2 hr at high tide and 4.3 hr at low tide. However, 

 since the tide gage trace at Hanna's Reef does not con- 

 sistently lead or lag the one at Marsh Point, the tidal 

 waters apparently enter and exit the adjacent passes 

 without much interaction. This conclusion is sup- 

 ported by Prather and Sorenscn (1972) who predicted 

 that only 1% of the flow througli Bolivar Roads will be 

 exchanged at Rollover Pass, and that the area in East 

 Bay affected by water exchange through Rollover Pass 

 is only about 205 ha (507a). Tides from both passes 

 are probably attenuated somewhere in mid-bay. Wind- 

 driven circulation is also apparently poor, probably 

 because the bay is oriented east-to-west, whereas pre- 

 dominant winds are north to south. Figure 3-54 shows 

 patterns of mean, extreme higli, and extreme low 

 salinities that document the poor circulation in mid 

 East Bay because salinity changes occur most slowly 

 there. The presence of live oysters in the bay is some- 

 what contradictory to those conclusions, and further 

 studies of East Bay circulation are needed. Seasonal 

 peaks in mean water level occur in spring and late 

 summer, as elsewhere in the Chenier Plain (fig. 3-53). 

 Since 1964 the mean annual water level has risen at 

 tlie rate of about 1.5 cm/yr(0.6 in/yr), approximating 

 changes elsewhere on the Chenier Plain. 



The rather saline estuary provides excellent habi- 

 tat for estuarinc-dependent fishes and shellfishes. 

 Coupled with West Bay and Galveston Bay, this is the 

 most productive estuary on the Texas Coast, particu- 

 larly for shrimp, trout, redfish. Gulf menhaden, and 

 oysters. Texas catch data for these species, as tabulated 



142 



