The Humboldt Bay jetties at Eureka, CA, have experienced a long history of damage and subsequent repairs since original construction was completed in 1899. Since dolos rehabilitation of the heads of the jetties in 1971, damages have been primarily along the trunk (stone) reaches of the jetties. No extensive work has been required along the dolos fields since their constmction. Prior to the study documented in this report, no sound, quantifiable data relative to the movement or positions of the dolos concrete armor units had been obtained for the jetties. Data were obtained under the Monitoring Completed Navigation Projects Program from limited ground-based surveys, aerial photography, and photogrammetric analysis to establish very precise base level conditions for the seaward dolos covered portions of the Humboldt Bay jetties. A method using high resolution, aerial stereo photographs, a stereoplotter, and Intergraph based software has been developed to analyze the entire above water concrete armor unit fields and quantify armor positions and subsequent movement A detailed broken armor unit survey conducted during the current effort has resulted in a well documented data set that can be compared to subsequent survey data. This study has defined base conditions and has developed a methodology that can be used to compare subsequent years of high resolution data for the Humboldt Bay jetties and use these data to assess the long term response of the structure to its environment. These efforts will allow engineers to decide whether or not closer surveillance and/or repair of the structures might be required to reduce their chances of failing catastrophically.

The Humboldt Bay jetties at Eureka, CA, have experienced a long history of damage and subsequent repairs since original construction was completed in 1899. Since dolos rehabilitation of the heads of the jetties in 1971, damages have been primarily along the trunk (stone) reaches of the jetties. No extensive work has been required along the dolos fields since their constmction. Prior to the study documented in this report, no sound, quantifiable data relative to the movement or positions of the dolos concrete armor units had been obtained for the jetties. Data were obtained under the Monitoring Completed Navigation Projects Program from limited ground-based surveys, aerial photography, and photogrammetric analysis to establish very precise base level conditions for the seaward dolos covered portions of the Humboldt Bay jetties. A method using high resolution, aerial stereo photographs, a stereoplotter, and Intergraph based software has been developed to analyze the entire above water concrete armor unit fields and quantify armor positions and subsequent movement A detailed broken armor unit survey conducted during the current effort has resulted in a well documented data set that can be compared to subsequent survey data. This study has defined base conditions and has developed a methodology that can be used to compare subsequent years of high resolution data for the Humboldt Bay jetties and use these data to assess the long term response of the structure to its environment. These efforts will allow engineers to decide whether or not closer surveillance and/or repair of the structures might be required to reduce their chances of failing catastrophically.