نوع مقاله : مقاله پژوهشی

موضوعات

• ژئومورفولوژی- جغرافیای طبیعی

عنوان مقاله English

Studying the morphology and spatial changes of Azerbaijan Ergs using satellite images and analysis of erosive winds( case study: Qomtape and Maghsudlu Ergs)

نویسندگان English

کلیدواژه‌ها English

Extended Abstract

1. Introduction

Arid and semi-arid lands cover more than two-thirds of Iran's area. Due to the lack of humidity in these lands, the variety of vegetation is limited, so the wind easily attacks the land's surface and carries soil particles with it. The movement of sand dunes causes severe damage to Iran's infrastructure and rural settlements every year. Identifying active dunes and monitoring areas with dune migrating sands are important measures to reduce these damages. Most of Iran's sand dunes are located in the desert plain, Lut desert, and its surroundings. In addition to these cases, the presence of two sandy areas northwest of the country, including the two Ergs of Qomtepe and Maqhsoudlu, is interesting. The Erg of Qomtepe and Maghsoudlu resulted from thousands of years of wind and soil activity, which ultimately led to their formation. Erg Qomtepe and Maghsoudlu, with their unique nature around them, are some of the most attractive tourism phenomena in East Azerbaijan tourism. At the same time, the movement of sand and the destruction of the surrounding lands cause much damage to the people of the region every year, so monitoring the amount and direction of movement of these sand dunes for planning is one of the tasks of researchers. By analyzing the anemometer data of a station, it is possible to predict the type of malleable sand dunes and the amount and direction of sediment movement. One of the proposed methods in this field, which was used for the first time by Freiberger and Dean, is the statistical analysis of winds with speeds exceeding the threshold wind speed. This research aims to observe and monitor the amount and direction of movement of sand dunes and the amount of destruction of surrounding lands annually using Google Earth images and meteorological synoptic data.  

2. Materials and Methods

In order to investigate the changes and displacement of sand dunes and evaluate the changes in the range of sand dunes in the study area, Google Earth images with different time intervals were used. In the next step, the wind data of meteorological stations in the region was used to know the wind regime and also to know the potential of wind erosion, which includes statistical data from the establishment of 19 synoptic stations located in East Azarbaijan province until May 2022 as the most appropriate and available statistical data; A total of 164,869 data have been analyzed. Sand Rose software was also used to draw sand. The Sand Rose graph is a wind-powered sand chart that Freiburger and Dean first used. To draw this diagram, winds that are faster than the erosion speed threshold are converted into vector units as sand transport potentials, and by drawing them, the sand is drawn in different directions. A new method was used to draw a geomorphological map. The Alus Landform dataset presents the landform classes created by combining the ALOS CHILI Continuous Heat Load Index and Multiscale Topographic Position Index (ALOS MTPI). This index is coded based on the ALOS 30m Digital Elevation Model data in Google Earth Engine. 

3. Results and Discussion

Based on the drawn winds, the percentage of repetition of the wind direction is different in different stations. However, in general, in the studied stations, the wind frequency was highest in the north, northeast, and east directions. Tabriz Airport, Maragheh Airport, Mianeh, Marand, Warzghan, Shabestar, Ajabshir, Bonab, and Charaoimaqh had one-way prevailing winds. However, two-way prevailing winds were observed at Jolfa, Sarab, Kalibar, and Hari's stations. In other stations, the prevailing winds were multi-directional. The results of the calculation and preparation of the Sand Rose graph for the studied stations, the calculation of DPt showed that the maximum and minimum DPt are related to Khosrowshahr (V.U<20000) and Charaoimaqh (0.2 V.U) stations, respectively. Freiberger and Dean's classification showed that wind erosion potential was high except for the Sahand and Khosrowshahr stations. The resulting drift direction (RDD) in the studied area showed that the sand sediments in Khosrowshahr, Bostanabad, Ajabshir, Marand to the north, in Warzghan, Ahar and Haris to the northeast, in Tabriz airport to the east, in Maragheh and Bonab airports to the east. To the west, in Sarab, Malkan, and Sahand, east of Tabriz and Shabstar, they move to the northwest, in Kalibar to the southeast, and in Mianeh and Jolfa to the southwest. The analysis of the one-way index in the region showed that according to the classification of Freiburger and Din, Maqhsoudlu sand has unidirectional wind, and Qomtepe Erg has multi-directional wind. Google Earth images from 1985 and 2022 were used to estimate the displacement of the Maghsoudlu and Qomtepe sand dunes. The amount of displacement for Maghsoudlu Erg was estimated to be 7.31 meters per year, and for Qomtepe sand, the displacement cannot be measured. Due to encroachment in the sand area of ​​Qomtepe with the construction of an industrial town, excessive harvesting, and poor management in preserving and maintaining this natural heritage, it will be destroyed in the next few years.

4. Conclusions

This research shows that the amount of displacement related to Maghsoudlu Erg was estimated at 31.7 meters per year, and the amount of movement of sand dunes in Qomtepe Erg cannot be predicted due to poor management in preserving the sands of the region due to indiscriminate harvesting for sand factories.  Also, the rate of erosion and area change in Qomtepe sand has a higher trend compared to Maghsoudlu Erg, and it was estimated to be 72.41% for Qomtepe and 26.95% for Maghsoudlu Erg after 37 years since 1985. In the end, based on the results of this research, it can be said that by establishing a desert studies research center in this province, rather than studying, planning to deal with the development of sandy areas in East Azerbaijan province. Moreover, the research gap and the lack of research resources regarding the Ergs of the northwest of the country, especially the East Azerbaijan province, which caused many problems during the research, should be resolved.

5. Acknowledgment & Funding

• Authors are thankful to all interview participants for supporting this research.
• The manuscript did not receive a grant from any organization

6. Conflict of Interest

• The authors declare no conflict of interest.