sand volume data from Hurricane Anita should be used since measurements were 

 taken within a month of that hurricane. Except for the 366-meter bitter 

 panicum dune, the foredune segments all accumulated sand from August 1976 to 

 September 1977, despite Hurricane Anita. Thus, the erosion of sand following 

 Hurricane Anita was entirely from the beach — and not really a loss at 

 all — just a temporary displacement into the gulf. 



The net accumulation of sand in this 200-meter segment indicates that 

 some new sand, probably from longshore currents, was deposited on the beach, 

 and it was then windblown into the foredune and trapped in the vegetation. 

 From March 1975 to March 1981 the average net sand accumulation per linear 

 meter of beach for all profiles was 69.5 cubic meters. This was 61.0, 58.8, 

 105.8, 47.3, and 78.5 cubic meters for the unplanted, 366-meter sea oats, 

 dune-width extension, 335-meter bitter panicum, and 366-meter bitter panicum 

 area, respectively (Table 2). This is an annual accumulation of new sand of 

 11.5 cubic meters per meter of beach. Note that the dune-width extension with 

 its wider base accumulated considerably more sand than the other plantings. 



b . Sand Volumes Above Planting Elevation for 30-meter Segment of the 

 Foredunes . The only sand volumes measured from early in the initial study 

 were from those areas immediately affected by the 15-meter-wide test plantings 

 (Dahl, et al., 1975). About 8 meters on either side of the plantings were 

 measured beginning in 1970. The 1970 measurement is reported in Table 3, 

 along with the 1977 and 1981 surveys for comparison purposes. The dune-width 

 extension plantings were not included. It is apparent that the beach 

 plantings adequately trapped the migrating beach sand as intended. However, 

 Hurricane Allen did remove several cubic meters from the unplanted control 

 study area. Much of this sand was transported farther inland (Table 2). 



c. 88-meter Segment of the Foredune . Because the plantings influenced 

 sand accumulation for more than 30 meters in 1975, sand volumes were measured 

 for an 88-meter dune segment extending from 30 meters seaward of the grass 

 planting to 58 meters landward. 



The total sand accumulation in this 88-meter segment of the unplanted 

 control areas was well below that for the dunes resulting from the beach-grass 

 plantings (Table 4). The data in Table 2 show that this eroded sand was 

 transported farther inland. The major difference between this area and the 

 planted dune areas is that the planted dunes present a solid wall of 

 resistance to the sand being transported inland. Therefore, migrating sand 

 from the beach accumulates on the dune face. On the unplanted area, the front 

 "wall" is not solid, so migrating sand penetrates through and over a broader 

 base. The result is a relatively high "floor," around 2.6 to 3.0 meters MSL, 

 among the scattered hummock dunes. In contrast, the floor elevation behind 

 and among the dunes of the planted study areas is only from 1.7 to 2.1 meters 

 MSL. The planted areas have accumulated sand at higher elevations. 



2. Dune Base Width . 



According to the Dahl and Goen (1977) report, the planted grasses on the 

 experimental dunes spread laterally between 1.5 to 2.1 meters per year, based 

 on the 1975-1976 measurements. Because Padre Island has now had a major 

 hurricane, and it is difficult to assess the rate of grass spread, an 

 evaluation is made of the rate of dune widening from the cross-sectional 



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