Aeolian saltation at Esposende Beach, Portugal

This paper reports results from a field experiment at Esposende Beach, Portugal, conducted in May/June, 2006. The purpose of the experiment was to measure characteristics of the aeolian saltation system, including sand transport rates, vertical distribution of mass-flux, and the associated wind speeds. The measurements were made on a sand flat, near the top of a parabolic dune flat. The mean grain size of the surface sediments was 0.32 mm. There was an unobstructed fetch exceeding 60 m in length and sloping at approximately 10°. Sand transport was measured with vertical stacks of hose-type traps and wind profiles were measured with a vertical array of three or four, Gill-type, cup anemometers. The transport rate data are compared to predictions made with the BAGNOLD (1936), KAWAMURA (1951) and ZINGG (1953) models. Vertical flux profiles were analyzed using a geometrically-weighted, trap centering method; using 1 mm as an estimated apparent roughness length, and by fitting a non-linear least-squares curve to find the empirical constants to describe the exponential decay of saltation intensity away from the sand surface. For the 13 data runs that we examined, α averaged 18.663 and fi averaged -0.016. These constants yielded an r² of 0.992 and an error sum of squares of 1.897 for our data.