Historically, the shoreline along the Matagorda Peninsula of the Texas coast 

 has been erosional in nature (Morton, Peiper, and McGowen 1976; Paine and 

 Morton 1989; Heilman 1995). Comparing topographic charts (dated 

 1855-1857) and aerial photographs (taken in 1937, 1956, 1965, and 1974), 

 Morton, Peiper and McGowen (1976) found that a 30-lcm length of shoreline 

 around the mouth of the Colorado River (their stations 12-31) has retreated an 

 average of 91 m over the time period 1856-1982 (0.72 m/year). Heilman 

 (1995) found that over half of this amount (49 m or 0.39 m/year) could be 

 attributed to sea level rise. The largest erosion rates in this section are just 

 southwest of the river mouth, and the smallest rates are just northeast of it. By 

 comparing changes in the shoreline before the river mouth was opened in 1935 

 to shoreline changes afterward (1856-1937 changes versus 1937-1982 changes) 

 Heilman (1995) concluded that the Colorado River historically affected the 

 shoreline for a distance 5.4 km northeast and 18.4 km southwest of the mouth. 

 Effects may have extended further to the southwest, but were masked by 

 overlapping effects of the Matagorda Ship Channel. 



Federal Project Description 



History 



In 1937, Federal authorization was granted to build the GIWW 

 approximately 10.5 km above the mouth of the Colorado River. Authorization 

 was also provided for maintenance of a flood discharge channel (the 10.5-km 

 reach of the Colorado River located between the GIWW and the channel 

 mouth). Maintenance dredging of the channel was conducted in 1941 and 

 1953. The Tiger Island Channel, which serves as an outflow from the 

 Colorado River to west Matagorda Bay, was dredged in the early 1950's (see 

 Figure 1). 



The Mouth of the Colorado River (MOCR) project was authorized by 

 Section 101 of the River and Harbor Act of 1968, and included improvement to 

 navigation features, construction of related recreational areas, and diversion of 

 Colorado River flows into Matagorda Bay. Initiation of the MOCR project was 

 delayed for several years as a result of interagency conflicts involving 

 HQUSACE, natural resource agencies, local interests, and members of 

 Congress. Eventually, the project was allowed to proceed and funding was 

 appropriated in 1979. 



Construction of the jetty strucmres at the MOCR was completed in 1985. 

 Dredging the impoundment basin located between the jetties, the final step in 

 this portion of the MOCR project, was completed in 1990. Material removed 

 from the impoundment basin was discharged by pipeline dredge in the surf 

 zone approximately 600 m southwest of the southwest jetty. 



Chapter 2 History 



