Continuous Monitoring of Mobility, Burial and Re-Exposure of Underwater Munitions in Energetic Near-Shore Environments
MR-2319
Objective
The development of predictive models for the mobility, burial, and re-exposure of munitions is essential to planning remediation efforts. In sandy, energetic near-shore environments, migration, burial, and re-exposure processes all have potential to be active depending on the munition properties and forcing parameters. In particular, the parameter space in which objects migrate significant distances has not been thoroughly examined with quantitative field measurements. In order to obtain a data set to quantify these processes and test models, the researchers plan to conduct field measurements of mobility, burial, and re-exposure of munitions in energetic near-shore environments with high potential for mobility. The surrogate munitions type, size, and density will be varied to enhance potential for migration processes. The researchers will develop an autonomous four-transducer ultra-short baseline (USBL) transceiver system to continuously track objects during energetic conditions. The system will acoustically measure range and bearing to surrogate munitions equipped with acoustic transponders. The measurements will be examined to understand munition mobility and burial processes, and develop relations between these processes and bedform geometry, migration, and hydrodynamic forcing. Finally, the researchers will develop and test simple parameterized models in the parameter space consistent with observations.
Technical Approach
The measurements will include in-situ continuous monitoring of processes via seafloor frame mounted rotary sidescan sonar and an ultra-short baseline acoustic tracking system. Hydrodynamic forcing parameters will be measured using a combination of conventional acoustic Doppler velocimeters and more advanced pulse coherent profilers. The frames will be mounted securely to the seafloor so they do not move under energetic near-shore surf-zone forcing. The fieldwork will take place on the south shore of Martha’s Vineyard, Massachusetts, which is exposed to open ocean waves from the southerly direction and is the site of current unexploded ordinance (UXO) remediation efforts. One set of instruments will be located in the trough between the near-shore sand bar and the beach to examine potential for migration due to strong along-shore currents, and the second set of instruments will be located further offshore to examine potential for onshore wave skewness forced migration into the near-shore. Surrogate munitions with transponders and motion sensors will be deployed near the instruments. Rotary sidescan sonars will provide detailed views of the interaction between bedform migration processes and munition migration or burial. The USBL array will provide range and bearing of objects with high migration rates that leave the view of the sidescan sonars.
Analysis of the measurements will produce a data set of burial and migration rates along with hydrodynamic forcing and bed configuration throughout the course of energetic wave events. The data will be examined in the context of a simplified parameter space to classify the potential for migration and burial, and the data can be used to develop and refine predictive models for munitions mobility and burial.
Benefits
The measurements will provide a unique data set on burial, re-exposure, and migration of surrogate munitions in energetic near-shore conditions where the potential for significant migration is high. This part of parameter space has not been thoroughly explored by previous studies and is important for remediation efforts and public safety since objects may move into areas that have been previously cleared, or objects that have been located can bury before removal if energetic conditions occur. A thorough understanding of the parameters and processes defining munition mobility and burial will allow better decisions in remediation efforts. The measurements of hydrodynamic processes and bedform morphology, bedload, and suspended load transport will also further basic scientific knowledge of the relations between these processes, which are closely related to munition mobility and burial. (Anticipated Project Completion - 2016)
Points of Contact
Principal Investigator
Dr. Peter Traykovski
Woods Hole Oceanographic Institution
Phone: 508-289-2638
Fax: 508-457-2194
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