| Laboratory experiments were conducted to investigate the relationship between dune erodibility and sand grain size and dune density. For each test, a single bore was generated using a head tank. Bore strength was varied by changing the depth in the head tank. Dunes were constructed of two different sands: North Carolina (NC) and Oregon (OSU) in which from each of those materials, dunes were built in two different ranges of the relative density.; Data were collected for each experiment to determine the bore force acting on the dune, the dune erodibility, and the dune characteristics. Four capacitance probes were placed on the sloping beach to capture the depth of the bore during the experiment. From these data, bore depth in front of the dune and the velocity of the approach of the bore were determined. These data were used to calculate a specific bore force at the dune face. Dune erodibility was measured as the erosion per unit width of the dune after the bore retreated from the dune face. A photograph was taken after each experiment to document the volume removed from the dune. Finally, a sample of dune material was taken from the dune after each experiment to determine dune density.; These data were analyzed using Maximum Likelihood Estimation (MLE) and Likelihood Ratio (LR) Test methods. The following conclusions were reached. One, in each of the four sets of experiments it was found that specific force and specific erosion are related linearly. Two, the head tank performed reliably during the experimentation, reproducing bores with statistically consistent characteristics. Three, dune face erosion, in these experiments was uniform. Finally, sand grain size and dune density are significant parameters which determine the erodibility of the dune face. The OSU sand dunes were less erodible than those built from the NC sand. In addition, for each category, NC and OSU dunes, the high density dunes were less erodible than the low density dunes. |
