This project funded three sets of field experiments (2011, 2013, and 2014) in the active, aeolian sand-transport environment at Jericoacoara, Ceará, Brazil. The site was selected for the project because it is an extremely active aeolian environment where the constancy of sand transport allows more efficient time in the field and more replicates of measurement. Total time in the field is reduced and the reliable wind allows different instrument configurations and sampling schemes. The site also comprises several distinct aeolian sub-environments (e.g., nebkha, barchans, and parabolic dunes, inland sand flats and coastal environments) so that comparative measurements can be made conveniently.

The 2011 experiments focused on linking the unsteady behavior of wind and saltation systems caused (mainly) by coherent turbulent structures, the relationships between vegetation cover and small-scale dunes, the initiation of sand transport, and developing new methods. The 2013 experiments measured wind flow and sand transport across the crest of barchans dunes and the characteristics of resulting grain flows (avalanches) down the dune slip faces. In 2014, the research examined the development of aeolian ripples and their adjustment to changing wind regimes.

The outcomes of the research program included five technological/methodological innovations that have the potential to impact this field of study. First, associated with the dissertation research of Swann, is the development of a new sand trap designed to segregate bedload from saltation load. Second, and related to the first, we developed a new low-cost, high-efficiency sand trap. Third, we developed protocols for the use of videography to record Lagrangian aspects of aeolian streamers that are also innovative. Fourth, we collaborated with a research team from the Netherlands to use some of the data derived from this experiment to test new, more efficient means to analyze acoustic saltation sensor data. Fifth, we have developed a new protocol for the measurement and reporting of saltation intermittency data.

There are also several conceptual/theoretical outcomes. First, our results characterized the behavior of aeolian streamers, especially as related to coherent turbulent structures (and we continue to work with these data). Second, we studied the effects of vegetation density on a nebkha sand mound and quantified the relationship between increased sand transport and decreased vegetation cover. Third, we developed a new model for the dynamics of grain flow processes down the lee slopes of barchans (a key element in dune migration). Fourth, we established estimates of relaxation times between wind conditions and ripple development. And fifth, we have demonstrated through simulation that the quantification of the so-called Activity Parameter is an unstable function of experimental design and methodology, and offered a protocol for standardization.

In addition to the results listed above, major outcomes include the training of students and early career academics and the development of extensive professional networks of collaborators. This project has contributed to the training and professional development of seven undergraduate students, three M.S. students, two Ph.D. students, and a post-doctoral scholar (detailed in next section), all of whom benefited from their participation in different phases of this project with a large number of US and international collaborators. Scientists from six countries participated in one or more of the field experiments. Findings from this program have resulted in the publication of six research papers and eight oral or poster presentations at conferences. It is expected that three more papers will result from this research program. 

Last Modified: 06/11/2015
Modified by: Douglas Sherman