Table 1 



Summary of Dredging Activity at East Pass (1931-1995) 



Location 



Volume, cu yd 



First Year Reported 



Last Year Reported 



Dredging Site 



East Pass Channel/ 

 Deposition Basin 



2,083,779 



1937 



1995 



Entrance Channel 



356,939 



1966 



1980 



Old Pass Channel 



1,142,459 



1931 



1995 



Outer Bar 



417,206 



1986 



1995 



West Cut 



89,029 



1972 



1972 



Dredge-Material Placement Site 



East Jetty 



407,526 



1970 



1995 



Nearshore Site 



353,747 



1986 



1993 



Norriego Point 



1 ,408,809 



1964 



1995 



Open Water/Surf Zone 



1,355,213 



1931 



1962 



Scour Hole 



190,084 



1988 



1993 



West Side 



374,033 



1966 



1972 



Table 2 summarizes channel-dredging operations since jetty construction. Notably, most of 

 the material dredged came from the main channel and Old Pass Channel. The overwhelming 

 majority of material-placement activity occurred on Norriego Point. As a comparison, Norriego 

 Point received more than three times as much material as the material bypassed (Nearshore Site). 



Examining the dredge plans from recent years in more detail identifies the location of 

 several shoaling "hot-spots," areas where dredging activity has been concentrated as evidenced 

 by recurrence in the dredging plans. Figure 5 illustrates these locations (crosshatched areas). 

 The three areas have been given names to facilitate discussion. These shoaling hot spots will be 

 analyzed using the DMS in order to test the validity of the methodology. 



Problem Statement 



The US ACE maintains thousands of miles of navigation channels throughout the coastal 

 waters of the United States and its territories. These Federally maintained channels comprise the 

 maritime heart of the Nation's waterborne commerce and national defense. As such, their 

 maintenance commands a major share of the US ACE O&M budget every year. With the 

 continued ebb and flood of the tide, sediments enter and deposit in these channels, often in areas 

 neither welcomed nor anticipated. Excessive deposition causes shoaling that reduces channel 

 depths, leading to navigational hazards that require frequent and expensive dredging. 



Traditionally, once designed and constructed, channels and their ancillary structures have 

 rarely benefited from evaluation against expected performance standards or efforts to reduce 

 their maintenance cost by improving their performance. Consequently, frequent dredging of 

 channel shoals is routinely prosecuted as part of the US ACE annual O&M budget at ever 

 increasing cost. 



Experience indicates a majority of the most frequently maintained channel reaches and 

 structures share key characteristics that define localized hydraulic conditions and attendant 

 sediment deposition. This tendency for commonality suggests that a reasoned diagnostic 



Chapter 1 Background and Problem Statement 



13 



