feet landward in 3.5 years. Most of the resulting dune was actually shoreward of the front 

 edge of the original planting. Padre Island sea oats and bitter panicum dunes have not 

 responded in this manner. Growth has been vertical above the original planting, and only 

 slightly laterally. After 5 years, the 1,200-foot sea oats dune vegetation averaged only 10 

 feet east of and about 8 feet west of the original planting. The 4-year-old bitter panicum 

 dune has a comparable slow rhizomatic spread. 



After 5 years (March 1974), the 1,200-foot sea oats dune had several peaks 18.1 feet 

 above MSL or 14.1 feet above the planting surface, and an average on the south 800 feet of 

 about 15.5 feet MSL, or 11.5 feet above the original surface. Thus, the vertical growth 

 capacity of sea oats and bitter panicum exceeded their lateral growth potential (11.5 feet 

 versus 10 feet for sea oats). 



d. Dune Growth: Extending Dune Width. Due to the sand-trapping efficiency of both 

 grasses, and to the slow rate of lateral spread, it is possible within 5 years to build a dune 

 11 feet above the planting surface but no greater than about 75 feet wide. This height offers 

 excellent storm surge protection (Table 1), but the effective width may not be sufficient to 

 withstand severe surges with prolonged wave attack. Therefore, a method for broadening 

 dune width was tested in April 1973. A 50- by 400-foot strip of bitter panicum was planted 

 immediately shoreward of an established bitter panicum dune planted 4 years previously. In 

 another 4 years, or 8 years after the initial planting, the resultant dune should be over 

 100 feet wide and about 12 feet MSL across much of the width. The extension planting is 

 now only 15 months old, but the rapid sand accumulation (Figs. 49 and 50) indicates that it 

 is growing as predicted. It is too early to state conclusively the results of this experiment, 

 but based on present growth and the growth configuration of other experimental dunes, this 

 procedure is recommended for all plantings if a dune width in excess of 75 feet is desired. 

 The second extension planting should not be made until the original dune has reached at 

 least 12 feet MSL, since the extension will trap all available sand and the original dune will 

 stop growing. 



e. Dune Growth: Control (Unplanted) Beach. Reconstruction of foredunes by planting 

 on a denuded backshore simulates a process that occurs naturally, although more slowly, by 

 the interconnection of hummock dunes of seedling sea oats and other grasses. The artificial 

 process can create in just a few years what probably takes 10 to 20 years to occur naturally. 

 Before the 1,200-foot sea oats planting in March 1969, this area was devoid of vegetation 

 and the backshore elevation was about 4 feet MSL. About 750 feet west of the shoreline, a 

 barren dune field existed (Fig. 31), presumably comprised of mostly sand from the original 

 foredune present as late as 1951. For comparison, a one-half mile barren section of beach 

 immediately north of the sea oats dune has remained unplanted; all subsequent revegetation 

 has been natural. This comparison may be biased in favor of the control area, since it is 

 nearer undamaged dunes less than 1 mile to the north, and because the sea oats planting 



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