Mohammad Reza Rahdari

Desert regions face unique challenges under climate change, including the emerging phenomenon of sand dune expansion. This research investigates aeolian sand transport in the Seqale watershed (eastern Iran) using geostatistical and machine learning methods to model and forecast dune spread, aiming to reduce the loss of sustainability in these valuable landscapes. Predictor variables (altitude, slope, climate, land use, etc.) and wind erosion occurrence were analyzed using classification algorithms (decision tree, random forest, etc.) and bivariate methods (information value, area density) in R software 4.5.0. Risk zoning maps were created and evaluated by combining these approaches. Results indicate a higher sand dune presence in regions with specific altitude (1200–1400 m), gentle northeast-facing slopes (2–5 degrees), moderate rainfall (250–500 mm), high evaporation (2500–3000 mm), outside flood plains, and far from roads (>3000 m) and water channels (>500 m). Dune expansion maps based on density area and information value methods showed substantial areas classified as high to very high movement risk. Machine learning analysis identified the Support Vector Machine (SVM) algorithm (AUC = 0.94) as the most effective for classifying sand dune zones. The study concludes that spatial forecasts, combined with tailored physical and biological measures, are essential for effective sand dune management in the region.

In recent years, northeastern Iran, particularly Khorasan Razavi province, has experienced wind erosion and dust storms, although large-scale studies are limited. To assess wind patterns, sand drift, and dust events, hourly wind data were analyzed using Fryberger’s method, along with trend analysis through the Mann–Kendall and Sen’s slope tests. Additionally, MODIS satellite data and Google Earth Engine helped identify event frequency and spatial patterns. The results show that east (12%) and southeast winds (9.6%) are the most frequent, with an average annual wind speed of 4.39 knots. Sand drift potential (DP = 96, RDP = 21.6) indicates sand movement from southeast to northwest, with a multi-directional wind system (unidirectional index of 0.22). The results of the AOD index show that the amount of dust in the north and northwest part is more than other locations, and more than 500 events with dust has been registered over the last two decades. These findings suggest that policymakers should monitor these trends to mitigate the environmental and infrastructural damage caused by blowing sand.

The Sistan region in Southeastern Iran is one of the world’s most sensitive areas when it comes to sandstorms and wind erosion. One of the most influential factors in interpreting sandstorms is sand drift potential (DP), which is directly related to wind speed. Accurately, monitoring this phenomenon is still being determined, considering various temporal scales. Therefore, the main aim of this research is to analyze the trend of DP on monthly and annual scales. Our results showed that monthly variations of DP reached the highest and lowest values in July (609 VU) and January (47 VU), respectively. Blowing sand predominantly moved southeast, and the directional index fluctuated from 0.88 to 0.94. The annual DP was measured equal to 2700 VU, signifying a relatively high value when compared to other arid regions worldwide. The trend analysis results obtained from the Mann–Kendall test revealed both positive trends during the period 1987–2001 and negative ones from 2002 to 2016). However, the positive trend was found statistically insignificant. Furthermore, Sen’s slope test results demonstrated that a negative trend could be observed with a steeper slope during July, September, and August, while a positive trend could be observed with a steeper pitch during November, December, and June. We recommend that land managers and stakeholders involved in controlling blowing sand using biological and physical methods should consider these trends in the Sistan region. Implementing nature-based solutions or control strategies should focus on these temporal sequences.

The Sistan region located in Southeastern Iran is one of the most sensitive areas related to sandstorms and wind erosion in the world. It is well-known that one of the most influential factors in sandstorm interpretation is sand drift potential (SDP), which is directly related to wind speed. However, accurate monitoring of this phenomenon are scarce considering different temporal scales. Therefore, the main aim of this research is to analyze the trend of SDP on monthly and annual scales. Our results showed that monthly variations of SDP obtained the highest and lowest values in July (609 VU) and January (47 VU), respectively. Quicksand moved to the southeast, as well as the directional index fluctuated from 0.88 to 0.94. The annually SDP was equal to 2700 VU, which represents a relatively high value compared to other arid regions of the world. The results of trend analysis applying the Mann–Kendall test showed that there is a positive (1987–2001) and negative (2002–2016) trend, but the positive trend is not significant. Furthermore, the results of Sen’s slope test demonstrated that the negative trend could be obtained with a higher slope during July, September, and Au-gust; as well a positive trend could be obtained with a higher slope during November, December, and June. We concluded that land managers and stakeholders that are in charge to control quicksand using biological and physical methods should pay attention to these trends in arid environment to apply nature-based solutions or control strategies focusing on these temporal sequences.

Aeolian sediments cover about 6% of the earth’s surface, of which 97% occur in arid regions, and these sediments cover about 20% of the world’s lands. Sand drifts can harm sensitive ecosystems; therefore, this research has aimed to study wind regimes and the monitoring of sand drift potential and dune mobility in the Khartouran Erg (NE Iran). The study investigated 30 years of wind speed and direction to better understand sand dune mobility processes using the Fryberger and Tsoar methods. The results of the wind regime study showed that the eastern (33.4%) and northeastern (14.3%) directions were more frequent, but the study of winds greater than the threshold (6 m/s) in winter, spring, and autumn indicated the dominance of eastern and northern wind directions. Findings of calm winds showed that winters (40.4%) had the highest frequency, and summers (15%) had the lowest frequency; the annual frequency was 30%. The average wind speed in summers was the highest (4.38 m/s), and, in the winters, it was the lowest (2.28 m/s); the annual average wind speed was 3.3 m/s. The annual drift potential (DP = 173 VU) showed that it was categorized as low class, and the winds carried sand to the southwest. The monitoring of drift potential showed that there was a sharp increase between 2003 and 2008, which could have been attributed to a change in wind speeds in the region. Unite directional index, the index of directional variability, has been alternating from 0.3 to 0.6 for 30 years. Furthermore, monitoring of sand mobility recorded a value from 0.1 to 0.4, and the lowest and highest values were registered from 0.08 to 0.9, with an average of 0.27. Finally, it can be concluded that sand dunes have been fixed for a long time, and the intensity of the mobility index is affected by climate changes.

Gully erosion is considered one of the major issues of land sustainability because it can remove considerable volumes of sediment and productive soils. Once started, gullies can continue to move by headcut retreat, or slumping of the side walls. Studies of gully development require constant monitoring activities which are not possible in not-well-explored areas, such as the arduous region of Iran, due to costs and a lack of geoinformation. Thus, the present research attempts to assess gully evolution using only two digital aerial photographs of different periods (1968 and 1994) and field assessment (2009) to estimate the gully head advancement based on frames geometry and rigorous procedure in southwestern Iran. Also, the gully head advancement was estimated and compared among them by different empirical equations. The results indicated that the mean of gully head advancement was 1.4 m year⁻¹ and 1.2 m year⁻¹ during 1968–1994 and 1994–2009, respectively, and the annual average of sediment mobilization was 26.8 m³ ha⁻¹ in 2009. The model assessment indexes indicated that SCS (Soil Conservation Service) II was the best model for gully head advancement estimations in this study area. The main reasons for this can be associated with the R_p factor (previous gully head advancement) and the local environmental conditions. We conclude that the sustainability of the territory has been greatly affected due to this advancement. We also hypothesize that gully head changes could be related to the susceptibility of geological formations, climate, soil properties, and the coincidence of other gullies’ formation with common drainage networks in the study area. Based on the obtained results, land managers can use the results to distinguish the gullies in this region with a higher environmental risk, and to decide an effective implementation of soil conservation measures in order to include them in the land management plans.