Aeolian sand transport at the Lanphere Dunes, Northern California

Abstract

Aeolian sand transport was studied at the Lanphere Dunes, a coastal dune complex in northern California, by comparing slipface advance rates with transport predicted based on local wind data. The slipfaces of a 2Á5 m high transverse ridge and 10 m high parabolic dune were monitored over a period of three months to estimate sand discharge. The study was performed during the dry season, which has the maximum sand-driving potential. Over the three month study period, average sand discharge was 12Á5 m 3 per m width per year at the transverse ridge and 8Á8 m 3 per m width per year at the parabolic dune. A method was developed for modelling slipfaces that are sinuous and where sediment transport rates are not constant across the width of the slipface. Field measurements were used to generate three-dimensional representations of dune slipfaces. Periodic measurements over the course of three months were used to compute the volume of displaced sediment.Theoretical sand transport was computed from local wind data using the Bagnold model and compared with the observed transport rates. Predicted rates were substantially lower than observed rates. Wind velocities rarely exceeded the threshold velocity. Discrepancies between the observed and predicted values appear to be caused by a combination of wind data recording procedures and differences between wind velocities at the anemometer location and the site where sand transport was measured.Wind data collected by weather bureaux have been utilized in numerous studies for modelling sediment transport. Such data typically have sample intervals of one hour or greater and are often averaged prior to reporting. The effect of averaging was investigated by comparing sand transport estimates based on daily average wind velocities with those based on the original hourly observations. The daily average data were depleted of high velocity winds and sand transport estimates were accordingly much lower than those based on the hourly data.

Patterns of wind flow and aeolian deposition on a parabolic dune on the southeastern shore of Lake Michigan

“…Robertson-Rintoul (1990) used anemometers, wind vanes and smoke candles to study the flow of air over a parabolic dune in Scotland and identified crestal jets, closed eddies on the lee and windward slopes, and spiral vortices along the arms. Craig (2000) used stakes placed near the base of the slipface to monitor the migration rate of a relatively small (10 meters high) coastal parabolic dune in northern California and used the results to calculate the amount of aeolian sand transport. Wolfe and Lemmen (1999) measured the migration of an inland parabolic dune in Saskatchewan over a three-year period and combined this with a study of elevation changes using pins placed on the dunes.…”

Spatial and temporal patterns of aeolian sediment transport on an inland parabolic dune, Bigstick Sand Hills, Saskatchewan, Canada

“…Following Craig (2000), the impact threshold normal velocity v t was calculated at the anemometer height (z = 3 m) and at the focal height z f , which is on the order of 0.01 m for normal dune sand (Bagnold, 1941). The velocities are 5.88 m s − 1 at the anemometer height (3 m) and 3.26 m s − 1 at the focal height.…”

“…The focal height z f provides a reference level for calculating shear velocity u ⁎ from (Bagnold, 1941;Craig, 2000): where v(z a ) is the observed wind velocity at the anemometer height, z a (3 m), and v t (z f ) is the threshold normal velocity at the focal height.…”

“…Research on the dynamics of parabolic dunes has focused on several key areas including: (i) dune distribution and morphology (Landsberg, 1956;Cooper, 1958;David, 1977David, , 1981Pye, 1982;Anton and Vincent, 1986;Pye, 1993;Wolfe and David, 1997); (ii) timing of past dune activity (Wolfe et al, 1995;David et al, 1999;Wolfe et al, 2000Wolfe et al, , 2001Arbogast et al, 2002;Forman and Pierson, 2003;Havholm and Running, 2005); (iii) rates of migration (Cooper, 1958;Pye, 1982;Anthonsen et al, 1996;David et al, 1999;Craig, 2000;Tsoar and Blumberg, 2002;Bailey and Bristow, 2004;Marín et al, 2005); (iv) internal structure (Bigarella, 1975;Halsey et al, 1990); and (v) contemporary processes (Robertson-Rintoul, 1990;Arens et al, 2004). Despite this progress, the current understanding of parabolic dune morphodynamics is based solely on investigations of form and process in two dimensions (i.e., plan view or profile form).…”

Statistical Modeling of Morphological Parameters of Barchan Dunes (Case Study: Chah Jam Erg in South of Haj Ali GHoli Playa, in Central Part of Semnan Province, IRAN)

“…Research on the dynamics of parabolic dunes has focused on several key topics including: (i) dune distribution and morphology (Landsberg, 1956;Cooper, 1958;David, 1977David, , 1981Pye, 1982;Anton and Vincent, 1986;Pye, 1993;Wolfe and David, 1997); (ii) timing of past dune activity (Wolfe et al, 1995;David et al, 1999;Wolfe et al, 2000Wolfe et al, , 2001Arbogast et al, 2002;Forman and Pierson, 2003;Havholm and Running, 2005); (iii) rates of migration (Cooper, 1958;Pye, 1982;Anthonsen et al, 1996;David et al, 1999;Craig, 2000;Tsoar and Blumberg, 2002;Bailey and Bristow, 2004;Marín et al, 2005); (iv) internal structure (Bigarella, 1975;Halsey et al, 1990); and (v) contemporary processes (Robertson-Rintoul, 1990;Arens et al, 2004). Despite this progress, they do represent the best-studied type of dunes, and both their morphological and dynamic parameters are well understood (e.g.…”