Values of S for stations (the jetty heads) to -100 (the gulf ward limit 

 of dredging at the 40-foot contour 10,000 feet seaward of jetty ends) are 

 plotted in Figure 16. Note that the area of greatest deposition in the off- 

 shore section of channel is usually 3,000 to 4,000 feet gulf ward of the jetty 

 ends, while between the jetties a slight maximum occurs 1,000 feet inside the 

 ends. The offshore maximum may reflect material moved either from the offshore 

 bottom or from the adjacent (5,000 feet downcoast) disposal area by wind- 

 driven currents. Alternatively, it may be very fine material from the long- 

 shore transport regime which has been deflected gulfward by the jetties. 



Channel dredging rates have generally increased over the years (Fig. 17). 

 Between 1940 and 1957 the annual rate was about 940,000 cubic yards per year; 

 between 1957 and 1968 about 800,000 cubic yards per year; and between 1968 and 

 1975 about 1,450,000 cubic yards per year. This may be attributed to increas- 

 ing depths in the navigation channel (1932 to 1961, 32 feet; 1961 to present, 

 38 feet), but realinement of the offshore bottom adjacent to the channel may 

 also have increased maintenance requirements. 



e. Summary. Since Freeport entrance has no self -scouring capability. 



conventional stability analyses discussed later cannot be applied. However, 

 due to the lack of significant water exchange between Freeport Harbor and the 

 Gulf of Mexico, the dredged navigation channel serves as an excellent trap for 

 deposition of fine-grained sediment. Three possible sources of this material 

 are ( 1) dredged-spoil disposal too close to the channel with subsequent move- 

 ment into the channel; (2) seaward deflection of the longshore currents which, 

 when flowing over the channel; lose much of their transportive power and allow 

 fine sediment deposition; and (3) adjustment of the offshore bottom to the 

 artificially steep channel shape. 



Two approaches can be used to possibly reduce deposition in the entrance 

 and harbor. First, surveys indicate that hopper-dredged material, currently 

 disposed of within 5,000 feet of the channel, is not accumulating in the 

 disposal area. Therefore, the material may be returning to the navigation 

 channel. A tracer test could be used to determine whether moving the disposal 

 sites farther away from the entrance will reduce maintenance dredging require- 

 ments in both the offshore and jetty channels. Second, reducing the intake of 

 Dow Chemical Company's waterflow could produce beneficial results. However, 

 more data on inlet flow velocities and salinities should be collected before 

 such a procedure is considered. 



2. San Luis Pass. 



Historical Review. San Luis Pass, which connects the Gulf of Mexico 



with Christmas, Bastrop, and West Bays (Fig. 1), is located at the southwest 

 end of West Bay. Price (1951) characterized the southwest end as an equilib- 

 rium position for many Texas inlets. 



The first U.S. Coast and Geodetic Survey (USC&GS) chart survey of San Luis 

 Pass was made in 1853 (chart H389, Fig. 18), although the pass had been in 

 existence since at least 1834 (Lee, 1966). Additional USC&GS surveys were 

 made in 1867 (chart H931, Fig. 19) and 1933 (chart H5488, Fig. 20). There is 



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