Journal of Spatial Analysis

Iran is among 10 top potential countries of occurrence of natural hazards in the world and from among 35 natural hazards, so far about 30 hazards have occurred in Iran(Negaresh and Latifi,2009). One of the different types of natural hazards which every year causes a lot of damage particularly in arid and arid regions of the world is the existence of sandy hills(Omidwar,2006); sandy hills are mostly created in coastal regions of most seas and oceans. These hills are the result of mutual effects of waves, marine currents, wind and sediments available in coastal regions. They are implemented with components of the coastal environment and construct the eco-systemic bases in which there are valuable collection flora and fauna(Kidd, 2001). The studied region is among the deserts near Gulf of Oman coasts. Sand on the coast are with marine origins and by getting far from the sea, sandy hills, in addition to having marine origins, have land origins. In some seasons of the year, particularly in summers and falls in which Monsoon winds start blowing up, the range of the movement of running sands is more towards rural regions in such a way that annually, a large part of sands covers residential areas, farmlands, road & building facilities, and infrastructural facilities in the rural areas of the west of Zarabad and left behind heavy damages and losses. The aim of this study is the detection of temporal-spatial changes in sand dunes in the Gulf of Oman coastal region. In addition, trend and severity of this hazard and the effects of climatic and environmental factors that intensified dimensions of risk were considered.

The present study, to achieve the mentioned objective is an applied study and in terms of research, a method is a descriptive-analytical one. To collected data, it uses library-documentary as well as survey studies in the rural areas of the west of Zarabad. After that, to investigate the changes of the degree of displacement in dunes of the studied region in the 23 year time period (1991-2014), GPS and the Enhance Thematic Mapper Plus (ETM⁺) images of the Landsat Satellite 7 and 8 with the spatial resolution of 15 and 30 m were used. The satellite images were used in this study with time intervals of 10 and 13 years were related to years of 1991, 2001, and 2014 in August respectively and they were extracted from USGS.The ENVI software and Geographic Information System were used for images processing and interpretation. The geometric and radiometric corrections were applied on images according to standard procedures. Finally, classification and related calculation were performed.

The conducted studies in the region based on the interpretation of satellite images and survey studies indicated that changes in the available users in the region, the top increases for dunes occurred in 1991 as 561.25 km², in 2001 as 568.10 km², and in 2014 as 575.45 km². In fact, it has experienced a growth as 17.198 km². The vegetation whose area covers 32 km² in 1991, in 2014 has reached an area with 45km² and increased as 1.6% compared to the previous period. In 1990 to 2014, the area of the user which has been changed in favor of dunes, includes 0.108 km² vegetation, 10.60 km² stream sediment, and 264.35 km² arid lands. Therefore, dunes move with high speed after each storm and during these displacements, a lot of damages are imposed on farmlands, facilities, and rural settlements. Investigating the degree of imposed damages indicates that annually, a large area of regions such as villages, roads, and facilities are influenced by running sands, which this trend can cover more regions in future years. The degree of displacement of dunes, according to the analyses conducted during the research period(1990-2014), has been so great that it has caused the burial of a large number of villages, infrastructure, farmland and roads and resulted in the unemployment of a large number of farmers in the region. Imposed damages to rural settlements have not been less than agricultural sectors and facilities. Therefore, due to the movement of running sands during recent years, 15 villages have been at the exposure of damages in such a way that compensation of these damages has imposed heavy costs, and consumed a lot of time on the shoulder of the society. As a result, the movement of dunes towards studied villages, i.e. Biahi, Mashkouhi, Abd, Rig Mostafa, Kalirak, Kerti, and Gati which are in the coastal regions, and Sohraki, Ganjak, Tanban, Zahrikar, and Kaidar which are located at far distances from the coast suffer from the highest amount of dunes and are considered as the most critical regions in terms of the movement of sand dunes. The results also showed that the important factors on severity and development of these critical regions are: a shortage of precipitation , loose and fine-grained sediments, low slope, no obstructions against the marine winds and high frequencies of winds and storms in this region.On the other hand, the lack of any varieties of vegetation on dunes, as well as the drought of recent years confirms spatial-temporal changes in the sand dunes towards the study area.

In this research, the hazards due to running sands in the West region of Zarabad (Baluchestan) were studied. The results from satellite image interpretation and field works were showed that the greatest change of land cover in recent years was related to sand hills. The total areas of sand dunes in 1990 are 561 km²,in 2001 these area increases to 568 km² and finally in 2014 reached to 578.5 km².The average growth rate is about 0.76 km² per year. The  landcover change from river sediments and barren land to sand dunes, during this period are estimated 10 and 264 km².

The storm and marine winds moving  sand dunes and running sands from coastal regions to rural settlements,farmland,Roads and other Infrastructures of the region. This hazard was just too much damage like  buried villages, the destruction of roads and unemployment and migration of farmers. The number of evacuated villages are 15 cases that some of these villages is located in the coastal region(Biahi,Mashkohi,Abd,Kalirak……..) and others in inland(Soharaki,Ganjak,Tanbalan,…..).

This is the manifestation of crisis and instability in the rural communities that creating important obstacles to development and it is triggered vulnerable rural development was decreased.

Has been stated in various sources, soil as one of the most important natural resources has a major, role on the lives of humans. Today soil erosion and sediment production, a problem that is increasing day to day process and loss of surface soils and sediment accumulation in dam reservoirs, canals and also sedimentation damage to the country's economy. One of the most important types of water erosion, gully erosion or (Galli formation). This type of erosion and loss of soil due to sediment production and enormous damages to land, roads and infrastructures, is of great importance. Soil erosion is one of the most important factors that threatens large areas of Iran annually and decreases or eliminates the quality of agricultural lands and rangelands. Due to highlands of Iran in comparison with the grounds and surrounding plains (mean elevation of 1250 m), it has been affected by water erosion. So it is very important to study erosion and present management strategies to reduce the impacts of erosion in basins of Iran. This study to Target morphometry gullies and the influencing factors on gully erosion in the South West sub-basin of ILAM (Cham Fusel).

The average height in the area between 50 and 1,200 meters above sea level and has a dry climate with an average annual rainfall of less than 200 mm and the average annual temperature is above 25 degrees C°. In terms of the main geological formation of this area is affected by gully erosion, Aghajari formation (red mudstone, siltstone and sandstone) are related to Miocene period. Basin area of over 150 hectares affected by gully erosion and slope threshold for gully erosion in the area between 8-2 percent.

The research method in this study is field research, library study and morphometric measurements of gully erosion forms. Besides, on the basis of the geological maps of 1/100000 and topographic 1/50000 and DEM 30 meter area, the software of GIS Arc has been used to make the required maps. Furthermore, the GPS device and a camera has been used in the field to harvest. o

The average height in the area between 50 and 1,200 meters above sea level and has a dry climate with an average annual rainfall of less than 200 mm and the average annual temperature is above 25 degrees C°. In terms of the main geological formation of this area is affected by gully erosion, Aghajari formation (red mudstone, siltstone and sandstone) are related to Miocene period. Basin area of over 150 hectares affected by gully erosion and slope threshold for gully erosion in the area between 8-2 percent. The study, which the sub basin in Cham Fusel ILAM province is located in the South West, with the aim of gully morphometric including deep, height, length, height from sea level, and geographical location as well as classification criteria in three sample gully gully of area, In order to identify factors affecting the development of erosion in the basin plain Cham Fusel was evaluated. The results of morphometric and field visits to the region, factors such as climate factors, slope and aspect, geology (Land genus), tectonic activity and faulting, land use, overgrazing of amount plants, including the most important factors recognized were identified in the development of gully. Which layers to extract some of these factors in Arc GIS software designed and based on creation of maps and data to analyze each of these parameters and their impact on Gully Erosion percent has been paid.

According to the morphometric data, it can be concluded that the gullies basin largely toothed and clawed, permanent, of medium to large gullies, which have expanded continuously. Below you can see images of morphometric gullies sample was collected during the field visit of the area. The results show that due to the widespread earthquake in the region in recent years and local faults can be concluded that one of the most important factors in the formation Galli uplift of the Earth. Also overgrazing by cattle ranchers in the area Tuesday Abdanan city, murmury, Dahlgren and ranchers outside the province of Hamedan and Kermanshah provinces such as ranchers who use the area as Qishlaq, Another important factor in the development of gully erosion in the area. Due to the climatic amount of rain, sleet, snow, ice, temperature and wind could be the climate factors in the rise of water erosion. As the geographical location and local climatological data suggests, the study area is influenced by the Mediterranean winter rains. Which are imported to Country from the West in winter and more in the form of showers and hail rainstorm conditions caused severe erosion gully in the area easy. Lack of growth of vegetation and bare Land is another contributing factor is considered in the development of gully erosion in the area. That is because the rainy season in the winter when the soil in the area is almost devoid of vegetation. The lack of vegetation in the region as one of the important factors, has caused soil erosion, its most destructive erosion of the gullies show. Also according to the map slope and aspect of the region was marked within the range of between 2-8 percent and Create Gully and aspect with the West and the South West and North West are more affected by gully erosion. Finally, all factors except factors of land use, all other factors were named among the important factors affecting the development of gully erosion are the region. It was also found other factors in the evolution of land use contrary to gully erosion region. That is because of the lack of culture in this area and dropping land by farmers as wasteland, and also because of the recent drought in the region has caused more and more extend of gully erosion and land with the ability crop damage and destroy all. The results obtained showed that the study area in terms of of gully erosion in critical condition.