The role of stereographic studies on the orientation of Suran`s barchans migration risk in Baluchestan

The sand dunes of the study area are located downstream of Routack watershed, 40 km west of Saravan city (Baluchestan province, Iran) and in the northern margin of the agricultural lands of the region. Wind velocity data (direction and speed) of Saravan, Khash and Iranshahr stations (2006-2012) were used to study the dynamics of the dunes. The geometry of barkhan dunes were analyzed using the stereographic approach and their spatial and temporal mobility by Freiberger and Dean (1979) method. The results showed that the direction of Barkhan`s migration was varied temporally and spatially; from W and NW to E and SE. While the prevailing winds in terms of frequency of occurrence were mainly blown from NE (wind-rose), but in most cases the sand dunes direction did not correspond to the prevailing wind direction. The RDD were 28.9% from the NW, 17.8% from the SW, NW and no-migration, 10.7% from the SE, and 3.5% from the W and S. The results of the stereographic approach showed the instantaneous dynamics of barchans were mainly consistent with the Fryberger and Dean (1979) methods; so that the rate of sand transport was between 17 to 20 m3/yr.m and the wind intensity classified as low energy. The sands are also transported when the velocity threshold is greater than 6.78 m/s or at least equal to it. This conclusion is important due to windbreak networks design. This means that to stabilize the dunes; windbreaks must be installed perpendicular to the wind`s direction (west to the northwest) and the wind velocity should not exceed 6.78 m/s, between the windbreak rows.