1 Background and Problem 

 Statement 



The report herein documents a joint demonstration project conducted by the U.S. 

 Army Engineer Research and Development Center (ERDC), Coastal and HydrauUcs 

 Laboratory (CHL), and the U.S. Army Engineer District, Galveston, to assess the 

 functioning of the Diagnostic Modeling System (DMS). In this demonstration project, 

 the DMS is applied to understand the causes of erosion at a Federal inland coastal 

 waterway in Matagorda Bay, TX. 



Background 



The DMS is being developed under the Coastal Sedimentation and Dredging 

 Program administered by the Headquarters, U.S. Army Corps of Engineer (US ACE). 

 The DMS is intended to provide the USACE with a reUable capability that can be rapidly 

 applied to identify, formulate, and evaluate alternatives for operation and management 

 (O&M) of Federal navigation channels. It is assumed that DMS methodology and tools 

 win be appUed with limited information on the hydrodynamic and sediment-transport 

 conditions at a site. The core of the DMS is a compilation of experiences with high- 

 frequency dredging sites, translating into a "lessons learned" guide called the DMS 

 Manual (Kraus et al., in preparation). 



The DMS wiU allow rapid and inexpensive evaluation or diagnosis of a problem 

 shoaling area and provide guidance for determining possible solutions. The economic 

 lever underlying the DMS concept is that a low-level analysis, possibly supplemented by 

 a modest numerical modeUng effort, can yield substantial cost savings while not 

 interrupting ongoing O&M activities and schedules. That is, the DMS is intended to 

 provide feasible alternatives for reducing O&M costs within the dredging cycle of the 

 subject project. The application time and effort in applying the DMS are, therefore, 

 relative to the maintenance time of the project. 



The Galveston District agreed to serve as a partner in identifying a weU-defined 

 problem as the first exercise and evaluation of the DMS concept. The District 

 recommended a specific high-shoaling area in Matagorda Bay, TX. At this site, dredging 

 frequency is increasing and navigation is becoming more difficult. This report describes 

 appUcation of a DMS approach to Matagorda Bay. For the application, the District 

 provided data and evaluated performance of the DMS approach. 



Chapter 1 Background and Problem Statement 



