physical and numerical model studies, and empirical relationships. Design 

 guidance used to predict beach response to detached breakwaters is presented 

 in Dally and Pope (1986), Pope and Dean (1986), Rosati (1990), and EM 

 1 1 10-2-1617. Dally and Pope (1986) discuss the application of detached 

 single and segmented breakwaters for shore protection and beach stabilization. 

 General guidance is presented for the design of detached breakwaters, proto- 

 type projects are discussed, and several design examples are provided. Pope 

 and Dean (1986) present a preliminary design relationship with zones of pre- 

 dicted shoreline response based on data from ten field sites; however, the 

 effects of breakwater transmissibility, wave climate, and sediment properties 

 are not included. Rosati (1990) presents a summary of empirical relationships 

 available in the literature, some of which are presently used for USACE brea- 

 kwater design. Rosati and Truitt (1990) present a summary of the Japanese 

 Ministry of Construction (JMC) method of breakwater design; however, this 

 method has not been frequently used in the United States. Guidance on Japa- 

 nese design methods is also provided in Toyoshima (1974). Engineer Manual 

 1 1 10-2-1617, Coastal Groins and Nearshore Breakwaters, contains the most 

 recent USACE design guidance for breakwaters. This manual provides guide- 

 lines and design concepts for beach stabilization structures, including detached 

 breakwaters, and provides appropriate references for available design proce- 

 dures. Although numerous references exist for functional design of U.S. 

 detached breakwater projects, the predictive ability for much of this guidance 

 is limited. Knowledge of coastal processes at a project site, experience from 

 other prototype projects, and a significant amount of engineering judgement 

 must be incorporated in the functional design of a breakwater project. 



Design guidance on the use of low-crested rubble-mound breakwaters for 

 wetland development purposes is limited and has been mostly based on 

 experience from a few prototype sites 1 . Further investigation and evaluation 

 of the use of breakwaters for these purposes is ongoing at WES under the 

 Wetlands Research Program. 



Numerical and physical models have also been used as tools to evaluate 

 beach response to detached breakwaters. The shoreline response model 

 GENESIS (GENEralized Model for Simulating Shoreline Change) (Hanson 

 and Kraus 1989b, 1990; Gravens, Kraus, and Hanson 1991) has been increas- 

 ingly used to examine beach response to detached breakwaters. A limited 

 number of detached breakwater projects have been physically modelled at 

 WES. Good agreement has been obtained in reproducing shoreline change 

 observed in moveable-bed models by means of numerical simulation models of 

 shoreline response to structures (Kraus 1983, Hanson and Kraus 1991). 



1 Personal Communication, 24 February 1993, Dr. Mary Landin, U.S. Army Engineer Water- 

 ways Experiment Station, Environmental Laboratory, Vicksburg, MS. 



10 



Chapter 1 Introduction 



