Analysis of Erosive Winds and investigating Wind Sediment Carrying Capacity in sabulous Sandy Regions of Khuzestan Province

Arid conditions limit human activities, so they destroy the sustainability between ecosystem components in more degraded areas.The concept of sustainability is related to an ecological principle according to which sustainability is maintained if the exploitations are commensurate with the capacity. Furthermore, the persistence of sustainability in arid regions requires the assessment of features such as human factors, natural factors, flora, fauna, and interactions between humans and the environment. Therefore, the evaluation and monitoring of climatic indicators such as wind, plays an effective role in maintaining sustainability as an influential factor in arid areas. Since the second half of the nineteenth century, wind erosion has been recognized as one of the most widespread environmental problems, especially in areas with different seasonal climates and high levels of human activities. Therefore, this research aims to study the state of annual winds through the analysis of Golbal and sand Golbal, and to investigate the role of wind regime in determining the amount of discharge and the final direction of wind sediment movement, as well as the activity of these sand dunes using the Lancaster model in Khuzestan province. Using the results, it is possible to fight against the harmful effects of sand dune sediments in the study area.

 In this study, in order to investigate the wind situation and study the erosive winds in Khuzestan sandy regions, anemometric data were used in five synoptic stations (in the statistical period of 20 years from 2000 to 2019) around these areas. In addition, Sand Rose Graph software was used to calculate the values of sand transport potential (DP) by Freiberger speed classes method. In fact, due to the complexity and high volume of statistical calculations related to drawing diamonds, Sand rose software was used to calculate and draw the maps. To calculate the values of sand transport potential (DP) in different geographical directions, the Freiberger-Dean relationship based on the basic equations of Begnold and Leto-Leto was used. From the sum of DP values in different directions, the total sand carrying capacity (DPt) is obtained and in fact it is an indicator that represents the total wind energy to carry sand to the desired station. RDP stands for the amount or size of the output vector (resulting vector) of sand carrying capacity, which is obtained by summing the DP values in 8 or 16 different directions and shows the final status of sand transport in the study area.

Analysis of anemometer data by Golbad showed that in all stations except Omidieh, wind from the west has the highest frequency and the most abundant/frequent winds for Omidieh station are observed from the northwest. Examination of the sand carrying capacity in different directions (DP) shows that the highest wind carrying capacity in sand was related to Omidieh station with 2226.13 units, and the lowest was related to Ramhormoz station with 11 vector units. The average monthly RDP at selected stations is estimated from 10.8 in November to 130 in June, and 80% of annual RDP occurs between May and September. During the summer, stability in the RDP between stations occurs only in June and July. Comparison of the direction of vector output of sand carrying capacity (RDD) in the studied stations shows that the direction of sand movement in Bostan and Ramhormoz stations is to the east, Omidieh to the southeast and Ahvaz to the northeast and Shush to the north. There is a high homogeneity between the total sand carrying potential (DPT) and the homogeneity index for sand transport (UDI) at Bostan station.  The total sand transported in different directions (TSF) is shown in Ramhormoz station with a rate of 8/15+10 kg/m per year; among other stations after Omidieh station with 8/17+10, Ahvaz station stands with 3/95+10 kg per meter. Among these, the lowest sediment discharge belongs to Shush station. The total displaced sand (DSF) is located in Bostan station with 2892.92 kg and then Ahvaz station with 1948.51 kg. Also, in order to determine the amount of rainfall (P) and annual evaporation (PE), the annual rainfall potential and transpiration potential maps of Iran were used, which were prepared by the Forests and Rangelands Organization of the country. The activity map of the sand dunes of Khuzestan is also presented.

The results of the present research in the field of sand carrying potential and the frequency of erosive winds showed that the majority of the winds blow from the west in all stations, but in the Omidiyeh station, the winds flow from the northwest.The analysis of the movement direction of the sand dunes shows the complete compliance of the movement of the sand dunes with the winds of the studied stations. The study of sand carrying power values ​​in different directions (DP) shows that the highest wind power in carrying sand was determined at Omidiye station with 226.13 units and the lowest one was determined at Ramhormoz station with 11 units. Examination of the homogeneity index shows that Omidiyeh, Shush and Ramhormoz stations have multidirectional winds and Bostan and Ahvaz stations have bidirectional winds between 0.3 and 0.8 with moderate variability between the total sand transport potential (DPT) and the homogeneity index of transport direction. There is high homogeneity of sand (UDI) in Bustan station.The total sand transported in different directions (TSF) shows that Omidiyeh station with 8/17+10 has the highest potential, and the lowest sediment discharge belongs to Shush station. And the total displaced sand (DSF) in Bostan station is 2892.92 kg, followed by Ahvaz station with 1948.51 kg. In this research, an attempt was made to determine the potential activity level of sand dunes and distinguish active from inactive areas by considering the weather conditions and sand wind regime of Khuzestan province.