When a coastal structure is photographed at low tide, an accurate per- 

 manent record of all visible armor units is obtained. Through the use of 

 stereoscopic, photogrammetric instruments in conjunction with photo- 

 graphs, details of structure geometry can be defined at a point in time. By 

 direct comparison of photographs taken at different times, as well as the 

 photogrammetric data resolved from each set of photographs, geometric 

 changes (i.e., armor unit movement and/or breakage) of the structure can 

 be defined as a function of time. Thus, periodic inspections of the struc- 

 tures will capture permanent data that can be compared and analyzed to 

 determine if structure changes are occurring that indicate possible failure 

 modes and the need to monitor the structure(s) more closely. 



Study Scope 



It was requested in the 1996 Program Review that structures monitored 

 during past MCNP efforts be revisited to determine how they are perform- 

 ing in their environments. These were to be expedient, low-cost inspec- 

 tions, and would be performed under the "Periodic Inspections" work unit 

 of the MCNP program. 



The coastal structures visited during the conduct of this study included 

 those monitored under the MCNP program since its inception through 

 1995. Fourteen coastal structures were visited with their approximate lo- 

 cations shown in Figure 1. Numbers in the figure correspond to the sites 

 shown in the following tabulation. 



Number 



Coastal Site 



1 



Nawiliwili Harbor breakwater, Hawaii 



2 



Kahului Harbor breakwaters, Hawaii 



3 



Laupahoehoe Boat-Launching Facility breakwater, Hawaii 



4 



Yaquina Bay north jetty, Oregon 



5 



Siuslaw River jetties, Oregon 



6 



Umpqua River training jetty, Oregon 



7 



Crescent City Harbor breakwater, California 



8 



Spud Point Marina breakwater, California 



9 



Fisherman's Wharf Harbor breakwater, California 



10 



Burns Harbor breakwater, Indiana 



11 



Cleveland Harbor east breakwater, Ohio 



12 



Cattaraugus Creek Harbor breakwater, New York 



13 



Manasquan Inlet jetties, New Jersey 



14 



Ocean City Inlet south jetty, Maryland 



Chapter 1 Introduction 



