IV. RESULTS 



1. Cross-Sectional and Longitudinal Profiles . 



a. Total Sand Volume from Mean Sea Level Inland 655 feet (200 

 meters) . From the past 2 years' surveys on Padre Island, sand 

 volumes have been computed several ways to understand dynamics of 

 sand acciimulation and redistribution. First, consider total sand 

 volume from mean sea level (MSL) inland through the part of the beach 

 normally occupied by the foredunes. In this study, a 655-foot 

 segment was used; the gulf side 355 feet (102 meters) was designated 

 the beach segment, and from 355 to 655 feet was designated the fore- 

 dune segment (Table 2; Figs. 5 to 10). 



Two things appear to be happening based on these data. One, 

 the north end of the study area, i.e., the unplanted natural 

 dune and the 1,200- foot sea oats dune accumulated little sand in 

 this 655-foot segment from August 1975 to August 1976. The middle 

 of the area, the dune-width extension dune, and the 1,100-foot 

 bitter panicum dune accumulated most. Sand accumulation for this 

 1-year period was 1.4, 0.2, 11.0, 8.9 and 7.0 cubic yards (1.1, 

 0.2, 8.4, 6.8, and 5.4 cubic meters) per linear foot of beach 

 for the unplanted area, 1,200-foot sea oats, dune-width extension, 

 1,100-foot bitter panicum, and 1,200- foot bitter panicum areas, 

 respectively. 



Secondly, during the March 1975 survey, unusually high tides 

 moved water all the way to the foot of the dunes several days in 

 succession. Apparently, this high water washed considerable sand 

 into the gulf from the 200 feet of beach nearest the gulf. This 

 is clearly shown in Figures 6 to 10. However, after 5 months 

 this sand was re-deposited on the beach, as shown in the figures, 

 so it was not lost, just re-distributed. 



For the beach segment (MSL to 335 feet) , the north two study 

 areas lost sand to the foredunes, but the south three had a 

 net sand gain on both the beach and the foredune segments. 

 Volume changes on the beach from August 1975 to August 1976 were 

 -1.2, -2.8, 3.6, 3.1, and 1.8 cubic yards (-0.9, -2.1, 2.8, 2.4, 

 and 1.4 cubic meters), respectively for the unplanted, 1,200-foot 

 sea oats, dune-width extension, 1,100-foot bitter panicum, and 

 1,200- foot bitter panicum study areas. For the foredune segments 

 of these areas, sand accumulations were 2.6, 3.0, 7.4, 5.9, 

 and 5.2 cubic yards (2.0, 2.3, 5.7, 4.5, and 4.0 cubic meters) 

 per linear foot of beach (Table 2). 



On the average, the beach and foredunes of this short section 

 of north Padre Island gained 5.7 cubic yards (4.4 cubic meters) 

 per linear foot of beach during this 12 -month period. Although 

 no segment lost sand, the stretch of beach from the south end 



