Temporal and Spatial Variability in Rates of Eolian Transport Determined from Automated Sand Traps: Indiana Dunes National Lakeshore, U.S.A.
Keywords:Coastal dunes, wind storm, sediment transport, dune erosion
Automated Sand Traps (ASTs) were deployed in four subenvironments of the Indiana Dunes National Lakeshore (IDNL) and were monitored, along with near surface wind speed and direction, on a semi-continuous basis for two field seasons. An analysis of several individual wind storms indicated that sand transport rates at the field site are strongly affected by transient factors such as antecedent soil moisture, rainfall, snowcover, and ground freezing. Plots of measured (AST) sand-transport rates versus wind speed (at 1.5 m) consistently exhibited a histeresis loop wherein the same wind speeds were associated with different transport rates at the beginning and end of wind storms. The simultaneous measurements of sand transport by identical ASTs indicated that rates consistently differ by one-to two orders of magnitude in the primary subenvironments of the backshore-foredune area at IDNL. The data collected in this study testify to a large degree of variability in sand transport rates that is not adequately accounted for in conventional eolian transport models which assume that an equilibrium condition exists between wind flow and sand transport.