5 Prediction of Sediment 

 Transport Rates 



Calculations of Longshore Transport Rate 



Previously, numerous calculations have been made of the longshore transport 

 rate along the Texas coast. These calculations have varied in their methods and 

 reliability, and unfortunately, they have also varied considerably in their results. 

 Table 1 1 lists a representative sample of published estimates made between 

 Galveston and Corpus Christi. It is not meant to be inclusive, but rather to show 

 that the range of transport rate predictions in this area is rather large. In the 

 "Method" column in Table 1 1, Littoral Environmental Observations (LEO) 

 refers to data collected by standardized visual surf zone observations. For 

 further information on this procedure and the data see Schneider ( 1 98 1 ) or 

 Thomas (1994). "SPM" refers to obtaining longshore transport rates from wave 

 data using some form of the SPM (1984) formula discussed below. Gages refers 

 to data collected by this monitoring program, and "GENESIS" refers to the 

 numerical model discussed in Chapter 4. 



Methods 



One of the main thrusts of this research project was to determine the 

 average yearly sediment transport rate along this section of coastline. Attempts 

 were made to estimate this value by three methods. The first method was to 

 apply the standard SPM formula to the wave data. The second was to make 

 short-term measurements of the transport at points within the surf zone and 

 compare these rates with the measured offshore waves to produce an improved 

 transport model calibrated for this site. Then, this new model could be applied 

 to the entire wave record to obtam a yearly average transport rate. The third 

 method was to measure the infilling rate of the impoundment basin to obtain an 

 average yearly transport rate. Each of these methods is discussed in detail 

 below. 



Chapter 5 Prediction of Sediment Transport Rates 43 



