Aeolian dune migration along the Ceara coast, north-eastern Brazil

Aeolian dune dimensions and migration rates are analysed along the Ceara co ast, north-east Brazil. Dunes that are currently mobile along the Ceara coa st are composed of barchans and sand sheets. The results show that barchans maintain an equilibrium farm, which can be characterized by values of dime nsionless shape parameters H/W and W/L, where H is the dune height, W is th e wing-to-wing width and L is the dune length. Dunes are highly mobile, wit h average migration rates of 17.5 m year(-1) for barchans and 10 m year(-1) for sand sheets. The calculated migration rates were found to depend stron gly on dune dimensions for both barchans and sand sheets, i.e. the larger t he dune is, the lower the migration rate will be. This size dependence was associated with the existence of a representative common transport rate alo ng the dune fields, which induces a different dune migration rate dependent on dune size. Finally, from the observed dune evolution, am aggregated sca le aeolian sediment transport was inferred. This bulk transport rate, of th e order of 90-100 m(3) m(-1) year(-1), is only valid for a timescale of yea rs to decades, which is the timescale used in dune evolution analysis.