Gulf 



of 



Mexico 



Figure 2. Plan view of the Colorado River project site 



crown elevation of +2.4 m and extends seaward to about the 1.5-m depth 

 contour. Cover stone on die southwest jetty ranges from 3.6 to 5.5 mt at the 

 landward end to 9 to 1 1 mt on the outer section. 



The impoundment basin is a rectangular area situated between the weir 

 section of the northeast jetty and the entrance channel. It is positioned to trap 

 the littoral material carried across the weir by the longshore currents. Prior to 

 jetty construction, littoral drift estimates at the mouth of the Colorado River 

 were obtained from two sources. A 7-year (1964-1971) sediment accumulation 

 on the updrift jetties at the Matagorda Ship Channel ( ~ 40 km southwest of the 

 Colorado River mouth) indicated that there was a southwesterly littoral drift in 

 excess of 153,000 cubic meters/year. Also, a 14-month accumulation 

 (1953-1954) in the mouth of the Colorado River between two dredging events 

 was found to be 200,000 cubic meters. Based upon these data, the littoral drift 

 was estimated to be 230,000 cubic meters/year, and the impoundment basin 

 was designed to hold a 2-year supply of sediment, 460,000 cubic meters 



Chapter 2 History 



