The dunes now migrating across northern Padre originated almost entirely by 

 devegetation of once-stabilized dunes (Hunter, et al., 1972). However, studies by Hayes 

 (1967) in the central part south of Big Shell beach indicate that hurricane washovers supply 

 sand to the back-island sand fields. In the northern part, washover fans and other effects of 

 hurricanes are small because the foredune ridge is high and broken by only a few narrow 

 gaps (Hunter and Dickinson, 1970). At Big Shell beach, a continuous, unbroken, well 

 vegetated dune ridge and vegetated flats exist with very little change since 1937 (Hunter, 

 et al., 1972). This 12-mile-long section at the westernmost bend of tbe shoreline has not 

 been breached by recent hurricanes. 

 3. Hurricanes and Storm Surges. 



During the first 63 years of this century, 42 tropical cyclones have struck the Texas 

 coast. Of these, 28 were classed as hurricanes, an average of one every 2.3 years (Hayes, 

 1967). However, associated storm surges varied. Hurricane Celia (1970), with extremely 

 higli and damaging winds, caused a maximum surge of about 5.5 feet on the gulf beaches. 

 Old washover channels were briefly reopened, and small coppice dunes of the backshore 

 were removed, but the surge caused no erosion to the foredunes (McGowen, et al., 1970). 

 Hurricane Carla (1961), with lesser winds but a more erratic track, had an open gulf surge of 

 over 12 feet (Bodine, 1969). Foredunes in central Padre Island were cut back an average of 

 100 feet, and were completely leveled along some stretches of beach. Associated flooding 

 from the surge was the most severe on record in Texas., On Mustang Island, 50 to 100 yards 

 of dunes were eroded, and some steep-faced dune cliffs were 10 to 15 feet high (Hayes, 

 1967). The ability of a well vegetated primary dune line to minimize hurricane surge effects 

 in this area has been noted by several authors (Price, 1956; Hayes, 1967; Behrens, 1969; 

 McGowen, et al., 1970; Hunter and Dickinson, 1970). 



Without a dune barrier, even minor surges of weak storms may cause damage to 

 manmade structures. In February 1969, a high-pressure system surge washed out several 

 sections of road on south Padre, and bridge approaches on Mustang Island. The surges of 

 Hurricanes Camille and Laura (1969) and Hurricanes Celia and Ella (1970) left drift lines on 

 the experimental plantings, but caused no serious dune erosion. 



Observations by the U.S. Army Engineer District, Galveston (1962, 1968, 1971) for 

 Hurricanes Carla, Beulah (1967), and Celia, revealed that barrier islands of the Texas coast 

 were breached in about 100 places, averaging a storm surge breacli every 3 to 4 miles along 

 the island chain. In each storm, sizable volumes of sand were transported from the beach 

 and foredune across the island. Hayes (1967) described three types of breaches in the 

 foredunes caused by Hurricane Carla in central Padre Island: (a) major hurricane channels 

 which erode below mean sea level and maintain an open connection with the gulf for several 

 weeks after the storm. These channels usually leave a persistent cut through the foredunes 

 that is opened during every major storm; (b) minor hurricane channels or high-level channels 

 which cut through the foredune ridge during high water stage of the storm, but does not 



23 



