EFFECTS OF COASTAL STRUCTURES ON SHORELINE STABILIZATION 

 AND LAND LOSS - THE TEXAS EXPERIENCE 



Robert A. Morton 



Bureau of Economic Geology 



The University of Texas 



Austin, TX 78712 



ABSTRACT 



Recent studies indicate that Texas is losing about 120 ha (300 acres) of wetlands 

 and 40 ha (100 acres) of gulf-front property annually. Although total land losses in Texas 

 are considerably less than those in Louisiana, they are still substantial and the reason 

 many shoreline protection structures have been erected. The structures have not always 

 produced the desired effects, however. Instead, some have accelerated erosion of nearby 

 beaches. Groins have generally been ineffective because sand supply is inadequate where 

 beaches are eroding. With one exception, seawalls built on Gulf of Mexico beaches have 

 failed or have been severely damaged during storms. Most bulkheads and seawalls have 

 protected the adjacent property, but at the expense of publicly-owned recreational 

 beaches that are eroded by the reflected wave energy. Because of similarities in 

 geologic setting and physical processes along the gulf coast, the effects of these 

 structures can be evaluated and the results applied to Louisiana where shoreline 

 stabilization is being considered to mitigate land loss. 



INTRODUCTION 



Public and private property worth millions of dollars is lost annually from coastal 

 environments around the world including areas of south Louisiana and Texas that border 

 the Gulf of Mexico (Figure I). Some of these land losses are natural products of 

 shoreline erosion and submergence of the land surface; other losses commonly result 

 from surface modifications such as dredging, river control, and building coastal defense 

 structures. 



The coastlands of Louisiana are dominated by extensive deltaic plain marshes and 

 bays bordered by minor barrier islands in the east and a broad chenier plain in the west, 

 all associated with construction and abandonment of the Mississippi River delta (Figure 

 I). In contrast, the Texas coast is characterized by much smaller oceanic deltas (Rio 

 Grande, Brazos-Colorado) and intervening barrier-strandplain features, bays, and minor 

 marshes (Figure I). Despite these proportional differences in coastal environments, the 

 similarities in physical processes, geologic setting, and human activities between the 

 areas make the shoreline responses to coastal structures in Texas applicable to similar 

 settings In Louisiana. In both states, coastal structures are being used to mitigate land 

 loss along migrating barriers that are remarkably similar In origin and geologic setting. 

 For example, the gulf beach and barriers (East Timbolier Island and Grand Isle), that 

 front the Lafourche subdelta are comparable in many respects to the gulf beach and 

 barriers (East Matagorda Peninsula, Follets Island, Galveston Island) that front the 

 Brazos-Colorado delta (Figure I). 



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