MIGRATION AND BURIAL TENDENCIES OF VARIABLE DENSITY MUNITIONS: INITIAL RESULTS FROM A LARGE-SCALE STUDY Manoj Kumar Gangadharan, University of Delaware, manojkg@udel.edu Temitope E Idowu, University of Delaware, teidowu@udel.edu Emily Chapman, University of Delaware, echapman@udel.edu Jack A Puleo, University of Delaware, jpuleo@udel.edu Jacob Stolle, Institut national de la recherche scientifique, Jacob.Stolle@inrs.ca Damien Pham Van Bang, Institut national de la recherche scientifique, Damien.Pham_Van_Bang@inrs.ca INTRODUCTION Past military activity close to the coast has discarded numerous ordnances in the nearshore environment. These ordinances (some of them unexploded; also called UXOs or munitions) are transported by waves and currents and may become exposed on beaches. The increased intensity of storm events may lead to a subsequent increase in UXO exposure and migration. Prolonged exposure of UXOs to ocean conditions leads to surface growth that alters their bulk density. Hence, it is essential to understand the influence of bulk density on mobility characteristics. This study, funded by the Strategic Environment Research and Development Program (SERDP), aims to quantify the processes that affect the mobility and burial of variable density munitions in the surf and swash zones during scaled extreme forcing. EXPERIMENT The experiments were performed at the multifunctional large-scale wave flume managed by the Environmental Hydraulics Laboratory at the Institut National de la Recherche Scientifique (INRS), Quebec, Canada. The facility is one of the largest in North America, with dimensions of 120 m x 5 m x 5 m. The piston-type wave maker with active absorption has a maximum stroke length of 4 m and can generate regular and irregular waves reaching a maximum velocity of 4 m/s. The generated wave amplitude can reach the top of the flume walls with operational water depths ranging from 2.0 - 3.5 m and wave periods of 3 - 12 s. The beach profile used in the study was modeled from Mantoloking in Ocean County, New Jersey, USA. The wave conditions used in the study were scaled from the onset of hurricane Sandy off the coast of New Jersey between 27-29 October 2012. Water level data was obtained from the National Oceanic and Atmospheric Administration (NOAA) buoy 8534720 near Atlantic City, New Jersey. The Froude scaling methodology (Van Rijn et al., 2011) was used to scale the prototype conditions. Five test cases were formulated to address the following scientific objectives. 1. Evaluate the response of variable density munitions under the same forcing conditions. 2. Compare the response of munition and canonical shaped items under the same forcing conditions. 3. Identify the importance of storm onset, the temporal increase in forcing conditions, in variable density munitions mobility, burial, and exhumation. 4. Determine the net migration of munitions over the duration of a scaled storm event and identify conditions that lead to onshore migration of munitions. Traykovski and Austin (2017) identified mobility and burial characteristics of munitions as related to   /, the temporal variability in fluid velocity adjacent to the munitions. This parameter has a nearly 1:1 relationship to   /. Hence, we used   / to create five different rapid storm onset conditions (Figure 1) to provide the best opportunity for munitions migration. Figure 1 – Hydrodynamics and water level conditions used for the experiment. A Preliminary modeling study was carried out using XBeach (Deltares, 2018) in the surf beat mode to identify the regions of interest within the test domain. The simulations showed a net offshore migration of the berm and extensive erosion in the swash zone (Figure 2) when subjected to similar test conditions. Figure 2 – Results from X Beach simulation corresponding to the case 04 tests H s increasing from 0.21 m to 1.1 m, T p from 3.01 s to 7.1 s, and h from 2.23 m to 2.87 m over ten trials ((  )/=5).