to the Corps correspondence; the pernnit is 

 still pending. 



Model tests of Galveston Bay hurricane 

 protection plans . --Our last annual report men- 

 tioned that the model study (Waterways Experi- 

 ment Station, Vicksburg, Miss.) by the U.S. 

 Army Corps of Engineers demonstrated that 

 essentially no change in tidal ranges resulted 

 from either the "Alpha"or "Gamma" barriers. 

 The data indicated that the Gamma barrier 

 would concentrate contaminants in upper Gal- 

 veston and Trinity Bays, particularly during 

 low fresh-water inflow. The Corps indi- 

 cated that this condition could be corrected 

 and has since returned to model testing this 

 fiscal year. Its aims are to correct the re- 

 stricted water circulation by relocating open- 

 ings in the hurricane protection structure. 

 Results of these tests have not been released 

 to date. 



Evaluation of estuarine data. - -The com- 

 plexity of the large developments and the num- 

 ber of smaller projects made it difficult to 

 treat easily each proposal in sufficient detail. 

 Our goals, however, were made simpler by 

 our organizing and distributing new and exist- 

 ing inforn-iation. We performed these services 

 by means of an inventory of the Texas estu- 

 aries. 



This past year we continued to prepare the 

 area-description portion of the inventory for 

 the Texas Gulf coast. We obtained data from 

 sources such as topographic maps and naviga- 

 tion charts, stream discharge records, oyster 



lease statistics, meteorological data 



While compiling these data, we learned many 

 facts about Texas estuaries that were not 

 widely known. Three examples illustrate this 

 point. 



1. Although the extent of shoreline develop- 

 ments in the Texas estuaries has aroused 

 anxiety over the possible effects on fish and 

 wildlife resources, the total area involved has 

 not been fully determined. It now is known, 

 however, that about 47 percent of the shore of 

 Sabine Lake has been altered primarily by 

 channelization, spoil placement, bulkheading, 

 and filling for industrial and residential de- 

 velopments. Conversely, about 3 percent of the 

 Lag una Madre, which is relatively inacces sible, 

 has been disturbed by human encroachment. 



Z. One of the most serious forms of man- 

 made changes in the estuary results fronn 

 domestic, industrial, and agricultural 

 effluents. For a long time local interests have 

 known about polluted waters (i.e., waters 

 closed to shellfishing) in Texas estuaries, but 

 these data were never widely published. The 

 percentage of polluted (or unapproved) waters 

 in the various estuarine systems of Texas 

 ranges from 100 percent in Sabine Lake to 

 about 10 percent in the Laguna Madre system. 



3. Over 250 significant reservoirs are situ- 

 ated on rivers which flow through Texas before 

 emptying into estuaries of the Gulf of Mexico. 

 These reservoirs are in Colorado, New Mexico, 

 Texas and Louisiana and the Mexican States of 

 Chihuahua, Coahuila, Nuevo Leon, and 

 Tamaulipas. The construction of a reservoir 

 usually brings a change of volume, a reduc- 

 tion of seasonal fresh-water inflow into the 

 estuaries, and ultin-iately a general deteriora- 

 tion of estuarine habitat. 



Richard J. Hoogland, Project Leader 

 Richard A. Diener 



Ecology of Western Gulf Estuaries 



Studies were planned and initiated to de- 

 termine how landfill housing developments af- 

 fect the ecology of natural marsh areas. We 

 selected this type of modification for study 

 because it is one of the greatest threats to the 

 continued existence of natural marshes. Little 

 is known about the effects of housing develop- 

 ments on the ecology of an area, how the 

 alterations might be made so that destruction 

 of an estuary will be minimal, or how, once an 

 area has been altered, it n-iight be rehabilitated. 



After we reached an agreement with the 

 developers and landowners, we selected for 

 study the resort housing development (fig. l6) 

 of Jamaica Beach on the west end of Galveston 

 Island, Tex. The housing project is the largest 

 and has the most complex canal system of any 

 in the area. The project was developed by 

 dredging, filling, and bulkheading a natural 

 marsh area, and it is bordered on each side by 

 extensive natural marshlands. 



Specific aims of our research were to 

 compare the abundance and size of the domi- 

 nant organisms, environnnental features, and 

 the setting and growth of oysters in the natural 

 and altered areas. 



Abundance and size of organisms .-- We began 

 biological and environmental sampling in 

 March 25, 1969, and took samples every 2. 

 weeks. We analyzed only the information from 

 four collections through May 6; therefore, the 

 results are preliminary. Samples were col- 

 lected during the day (between 9:00 a.m. and 

 2:00 p.m.) and night (between 9:00 p.m. and 

 2:00 a.m.) within the same 24-hour period. 

 About 3 hours were required to sample at all 

 stations. The order of the stations at which 

 samples were taken was random. 



Figure 16 shows sampling stations, and 

 table 7 gives information describing each 

 station. 



Biological san^ples were taken in a trawl 

 that had an opening of 0.6 by 3 m. (2 by 10 ft.) 

 and a stretched mesh of 28 mm. (1.1 inches) 

 in the body and 1 6 mm. (0.6 inch) in the codend. 

 The trawl was towed at each station for 200 m. 

 (660 ft.) at a speed of about 2 knots. We 



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