Again, the only studies of East Pass current patterns identified in the 

 literature review are reported in the 1939 U.S. Engineer Office report and the 

 1992 USACE study (Morang 1992). These two field investigations bracket the 

 construction of the jetties. The 1939 study documents the results from drogue 

 studies performed during different times in the tidal cycle. Illustrations of drogue 

 paths show that before jetty construction, the current intensified on the east side 

 of the inlet throat during both flood and ebb tides. The report states that despite 

 their release location, all the drogues that passed through the inlet moved toward 

 the east side of the inlet where they experienced high velocities. 



The 1992 USACE report (Morang 1992) details experiments performed in 

 the years 1983, 1984, and 1987. Plots of the currents in East Pass Channel again 

 show an intensification of current velocity on the east side of the pass. Morang 

 (1992) suggests the ebb current impinging on the east bank is the main cause of 

 the rapid erosion of Norriego Point. In addition, Morang (1992) observes that the 

 300- to 120-deg orientation of the flood and ebb current directions in the northern 

 end of the inlet is almost identical to the 295- to 1 15-deg orientation of the 

 entrance to Old Pass Lagoon. 



This section outlined the tidal hydraulics of East Pass Inlet. Unfortunately, 

 except for the Wave Information Study (WIS) hindcast data, little is known about 

 the wave climate inside the inlet or in the Gulf. In the application of the DMS, 

 the information from this section will aid in the identification of the shoaling 

 mechanisms, as well as provide input into the model applied in the DMS- 

 Analytical Toolbox. 



East Pass - dredging history 



Reduction of dredging amounts and frequency is the objective of this 

 research. Thus, knowledge of the channel's dredging history is paramount to 

 understanding the behavior of shoaling. As with other pertinent channel 

 information, the channel's dredging history becomes key input data for the DMS- 

 Data Manager. This section documents the dredging activity at East Pass and 

 identifies the areas of shoaling that serve as the test case for the DMS. 



Between 193 1 and 1995, dredging removed approximately 4 million cubic 

 yards of sediment — about 64,000 cu yd/year — from the project channel. 

 Figure 2 illustrates the locations of the dredge sites and disposal placement areas 

 that encompass all dredging activity at East Pass. Figures 3 and 4 categorize the 

 dredged and placed volumes by site. Some of the designations required consider- 

 able estimation. As is usually the case, the dredging records (especially early 

 records) were incomplete. Figures 3 and 4 show that dredging frequency has 

 decreased, while the magnitude of volume dredged has increased. This trend is 

 explained by advances in economic dredging practice. Notably, before 1964, 

 Open Water/Surf Zone designation characterized much of the dredge-material 

 placement. Figure 2 does not denote this area because no reliable record exists of 

 the actual placements. Also, during its early history, side-cast dredges were used 

 to maintain the channel. Thus, the placement area depended on the maintenance 

 location. Table 1 summarizes the dredging activity at East Pass throughout its 

 history. 



Chapter 1 Background and Problem Statement 



