Movement of a small slipfaceless dome dune in the Namib Sand Sea, Namibia

Abstract

The migration of a small slipfaceless dome dune close to the northern edge of the Namib Sand Sea has been measured by topographic survey. The dune dimensions are 45-m wide and 1-m high with a volume of 551 m 3 that has been calculated as the difference between the dune's surface elevation and an interdune surface extrapolated from measurements around the edge of the dune. The migration direction, 64°, and distance moved, 90 m, are measured against stakes set out in 1976. The dune has moved about 90 m between 1976 and 1999. This is an average linear migration rate of around 4 m year −1, and is equivalent to an annual sand transport rate of about 1.2 tonnes m −1 year −1. The calculated total potential sand flow in this part of the Namib Desert is 119 tonnes m −1 year −1, and the resultant potential sand flow is 63 tonnes m −1 year −1. The dune migration is therefore about 1% of the total potential sandflow and 2% of the resultant indicating that dune migration is only a small part of total potential sand transport. The results suggest that small slipfaceless dome dunes are very inefficient at trapping sand, and that winds blowing across the interdune in this area are undersaturated with sand.