MONITORING OF FOREDUNES ON PADRE ISLAND, TEXAS 



hy 

 B.E. Dahl and J. P. Goen 



I . INTRODUCTION 



Flood damage from hurricanes is a major concern to inhabitants 

 of the Texas gulf coast. Barrier islands, such as Padre Island, 

 provide significant protection against high water through the 

 damming effect of foredunes. which characteristically form parallel 

 to the beach. Where these foredunes have been lost, storm surge 

 erosion moves sand inland from the beach onto lowland vegetation 

 and into lagoons, and the sand accumulates on roads and in naviga- 

 tion channels adjacent to the islands. After severe flooding from 

 Hurricane Carla in 1961, mainland residents requested restoration 

 of these natural dams on Padre Island. 



From 1968 to 1974 the Coastal Engineering Research Center 

 (CERC) supported research to define propagation and transplanting 

 techniques with beachgrass to construct and rehabilitate these coastal 

 foredunes (Dahl, et al . , 1975). The data collected included infor- 

 mation on changes in dune dimension and beach topography, encroach- 

 ment of indigenous flora, and comparisons with naturally occurring 

 foredunes. During these studies, several foredunes were formed 

 from test plantings on the north and south ends of Padre Island 

 (Fig. 1]. Upon completion of the initial contracts, CERC continued 

 monitoring the foredunes formed from the grass planting on north 

 Padre Island beaches to evaluate the long-term performance and 

 effects of the foredunes. This report basically summarizes beach 

 and foredune cross-sectional profile surveys and vegetative transects 

 of four experimental foredune sections and one natural foredune 

 section conducted during 1975 and 1976. The foredunes are within 

 the boundaries of the Padre Island National Seashore. 



II. STUDY AREA 



Padre Island has a subtropical, semiarid climate, moderated 

 by maritime tropical air from the Gulf of Mexico. The summer 

 months are hot with little daily or weekly variation. Winter 

 (December to February) is mild with a wide fluctuation in temperature; 

 freezing temperatures are infrequent. Precipitation is irregular, 

 both monthly and annually, with no sharply defined seasons. Within 

 the last century, annual precipitation at Corpus Christi has ranged 

 from 48.16 inches (1,222 millimeters) in 1888 to 5.38 inches 

 (136 millimeters) in 1917. Excessive precipitation associated with 



