2.400 ft 



1966 

 1970 

 1975 



Figure 14. Positions of 12-, 20-, and 29-foot contours in 

 1966, 1970, and 1975, Freeport entrance, Texas. 



The 29-foot contour moved landward near the dredged channel; away from the 

 channel the contour moved offshore. The 20-foot contour, located in the off- 

 shore erosion zone, migrated landward in two locations between 1966 and 1970. 

 However, the 12-foot contour, which moved inshore between 1966 and 1970, 

 showed extensive offshore movement in later years, corresponding to the depo- 

 sition zone shown in Figure 13. 



This concurrent erosion in the area of the 20-foot water depth and the 

 deposition near the 12-foot contour led to an examination of beach profiles 

 taken between 1966 and 1975 within 6,000 feet west of the jetties. The pro- 

 files showed a zone of anomalously steep offshore slope between the 18- and 

 30-foot water depths which eroded rapidly during that period. It is spec- 

 ulated that this is the slipface of the old Brazos River delta which is erod- 

 ing and supplying sediment to the shallower areas near the 12-foot contour. 

 If this is the case, then rapid beach recession west of the jetty may occur in 

 the future as the offshore zone reaches equilibrium. Morton (1977) documented 

 erosion of the delta between 1937 and 1974 (Fig. 15). Over the long term 

 (1855 to 1974), Morton showed net nearshore deposition with offshore and 

 downdrift erosion. 



b. Tide Characteristics . Two tide gages have been in continuous opera- 

 tion at Freeport (see Fig. 10): an NOS control station near the Dow barge 

 canal since May 1954, and an SWG gage between the jetties since June 1965. The 

 tide characteristics at these locations were determined by calculating the 

 mean monthly diurnal tidal ranges and levels, and the annual means, for the 

 representative year (1974). Unfortunately, some days in April and May were 

 missing from the SWG gage, so these months were not included. The 1974 mean 



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