Before 1881, the river mouth was natural, and ships visiting the ports of 

 Quintana and Velasco, on either side of the river, probably had to contend 

 with a shallow, frequently shifting channel through the ebb tidal delta. The 

 earliest available charts of the Freeport area show that in 1852 the Brazos 

 River mouth was flanked on the west side by a relatively small subaerial 

 delta, but the subaqueous part of the delta extended some distance into the 

 gulf and slightly eastward (Fig. 11, a). An initial attempt by the Federal 

 government to stabilize the entrance with jetties in 1881 resulted in rapid 

 accretion on the west side and lesser accretion adjacent to the east jetty 

 (Fig. ll,b). Accumulation on the west side of this significant sediment 

 source indicated net westward longshore sediment transport. The jetties were 

 completed in 1899, and by 1909 extensive accretion (particularly on the west 

 side) had occurred and a large ebb tidal delta existed (Fig. 11, c). The 

 diversion of the Brazos River to a new location 6 miles west of Freeport in 

 1929 eliminated the source of material to the surf zone, and the beaches both 

 downdrift (west) and updrift (east) of Freeport began eroding. At the new 

 Brazos outlet, a delta rapidly formed, reaching its maximum seaward extent by 

 1948. Again, the maximum accumulation was on the downdrift (west) side. Some 

 material in the new delta was probably derived from erosion of the large 

 accumulation west of the Freeport entrance; most of this bulge had been oblit- 

 erated by 1948. 



Dam construction on the Brazos River in the 1940' s greatly reduced the 

 peak flows, drastically reducing the sediment supply at the mouth (Mathewson 

 and Minter, 1976). This caused recession of the new Brazos River delta after 

 1948. Seelig and Sorensen (1973) estimated that only one-third of the pre- 

 1940 sediment supply was available after 1950. The major change in the 

 bathymetry offshore of Freeport entrance between 1946 and 1966 was a general 

 deepening of the entire area (Seelig and Sorensen, 1973). To determine recent 

 volumetric changes in the nearshore bathymetry adjacent to Freeport, SWG 

 surveys from 1966, 1970, and 1975 were used to construct Figures 12 and 13. A 

 planimeter was used to determine areas within selected contours, which were 

 multiplied by the average depth change within that area to yield volumetric 

 changes. Positions of the 12-, 20-, and 29-foot contours are plotted in 

 Figure 14. 



Within the survey limits on the east side of the entrance, a loss of 3.3 x 

 10° cubic yards occurred between 1966 and 1975, mostly in a zone centered 

 about 4,000 feet east of the jetties. Some material accumulated in a local- 

 ized area between this erosion zone and the jetties, and about 4,000 feet 

 offshore. These zones of deposition and erosion were formed primarily between 

 1970 and 1975. Within the scour zone, the 12- and 20-foot contours moved 

 inshore. This erosion may have contributed to the current increased shoreline 

 recession rates east of the jetties by allowing larger waves to reach the 

 foreshore, particularly at the apex of the zone where recent MSL retreat rates 

 have been about 33 feet per year. However, subsidence is also a possible 

 contributing factor. 



On the west side of the entrance, an accretion zone occurred between 1966 

 and 1975 in the same relative position with respect to the jetties as on the 

 east side: 4,000 feet offshore and 4,000 feet west of the jetties. However, a 

 net erosion of 2.1 x 10° cubic yards occurred between 1966 and 1975. Along 

 the offshore limits of the control area, extensive erosion occurred between 

 1966 and 1970, with some accretion immediately adjacent to the west jetty. 



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