individual monitoring project is a cooperative effort between the submit- 

 ting District/Division office and CHL. Development of monitoring plans 

 and the conduct of data collection and analyses are dependent upon the 

 combined resources of CHL and the District/Division. 



Inspections of the coastal structures for the study reported herein were 

 completed as part of the "Periodic Inspections" work unit of the MCNP 

 program. 



Objective of Periodic Inspections Work Unit 



The objective of the "Periodic Inspections" work unit in the MCNP pro- 

 gram is to monitor selected coastal navigation structures periodically to 

 gain an understanding of the long-term structural response of unique struc- 

 tures to their environment. These periodic data sets are used to improve 

 knowledge in design, construction, and maintenance of both existing and 

 proposed coastal navigation projects. These data also will help avoid re- 

 peating past design mistakes that have resulted in structure failure and/or 

 high maintenance costs. Past projects monitored under the MCNP pro- 

 gram and/or structures with unique design features that may have applica- 

 tion at other sites are considered for inclusion in the periodic inspections 

 monitoring program. Selected sites are presented as candidates for devel- 

 opment of a periodic monitoring plan. Those sites receiving favorable re- 

 sponse during MCNP program review are inspected and a monitoring plan 

 is developed and presented for approval. Once the monitoring plan for a 

 site is approved by the field review group and funds are provided, monitor- 

 ing of the site is initiated. Normally, base conditions are established and 

 documented in the initial effort. The site then is reinspected periodically 

 (frequency of surveys is based on a balance of need and funding for each 

 monitoring site) to obtain long-term structural performance data. 



Relatively low cost remote sensing methods and techniques, with 

 limited ground truthing surveys, are the primary inspection tools used in 

 the monitoring efforts. Most periodic inspections consist of capturing 

 above-water conditions of the structure at periodic intervals using high- 

 resolution aerial photography. Periodic aerial photographs are compared 

 visually to gauge the degree of in-depth analysis required to quantify 

 structural changes (primarily armor unit movement). Data analysis in- 

 volves using photogrammetric techniques developed for and successfully 

 applied at other coastal sites. At sites where local wave data are being 

 gathered by other projects and/or agencies, and these data can be acquired 

 at a relatively low cost, wave data are correlated with structural changes. 

 In areas where these data are not available, general observations and/or 

 documentation of major storms occurring in the locality are presented 

 along with the monitoring data. Ground surveys are limited to the level 

 needed to establish the accuracy of the photogrammetric techniques. 



Chapter 1 Introduction 



