SALTATION SAND TRAPS FOR THE MEASUREMENT OF AEOLIAN TRANSPORT INTO THE FOREDUNES

An omnidirectional vertical sand trap is described for use in the meas urement of sand transported by wind in the dune environment. In the fi eld these traps yielded good results. The traps were calibrated by com paring them with a Bagnold trap of known efficiency and by wind tunnel experiments. Efficiency of the trap was not constant, being dependent on the wind speed, the grain-size distribution of the sediment and th e moisture content. The calibration resulted an efficiency of between 15 and 20%. The highest efficiencies were observed for wind speeds of 8 m/s. For lower wind speeds the efficiency decreased because of the i ncreasing importance of creep. With higher wind speeds the efficiency was reduced because of an increasing loss by blowout.