نشریه جغرافیا و مخاطرات محیطی
پیاپی 17 (بهار 1395)

Floods are among Earth's most common and most destructive natural hazards. Floods create geomorphic hazards via changes in sediment transport and channel configuration (e.g. channel width, lateral migration, planform changes, etc). In this context, floodplain zoning and its application in spatial planning is important in non- structural measures in order to reducing flood damages. One-dimensional models are the simplest option existing for modeling the flow conditions within a river channel. HEC-RAS, a commonly used one-dimensional hydrodynamic model, has the capability to perform both steady and unsteady state simulations. HEC-RAS is a hydraulic model developed by the Hydrologic Engineering Center (HEC) of the U.S. Army Corps of Engineers. The model results are typically applied in floodplain management and flood insurance.
The objectives of the current paper are flood hazard zoning and evaluating the geomorphological effects of flooding on Zarrineh-Roud River. This river is located in the northwestern Iran. It drains a watershed of 11788 km2. Zarrineh-Roud River, the most important river in the Urmia lake basin, supplies about 48 percent of the lake’s water.
Material and The West Azerbaijan Regional Water Authority topographic maps (1:2000 scale) are base data in the present study. Also, data from Sari-Qamish hydrometric station located in the main stream and Qureh-Chay and Janaqa stations on tributaries were used for calculation of return periods and discharge – stage relation. To determine the friction coefficient distribution of channel and floodplain, land cover maps was generated using Google Earth satellite imagery.
HEC-RAS uses a number of input parameters for hydraulic analysis of the stream channel geometry and water flow. For steady, gradually varied flow, the primary procedure for computing water surface profiles between cross-sections is called the direct step method. The basic computational procedure is based on the iterative solution of the energy equation. Given the flow and water surface elevation at one cross-section, the goal of the standard step method is to compute the water surface elevation at the adjacent cross-section. The flow data for HEC-RAS consists of flow regime, discharge information, initial conditions and boundary conditions (HEC, 2010). Hydraulic modeling of floodplains requires accurate geographic and geometric data for both river channel and floodplain. Geographic Information Systems (GIS) allow collection and manipulation of geographic or geometric data. Model geometry input and model output were done using the HEC-GeoRAS extension for ArcGIS. HEC-GeoRAS is a set of procedures, tools, and utilities for processing geospatial data in ArcGIS. Therefore, the GeoRAS software assists in the preparation of geometric data for import into HEC-RAS and processing simulation results exported from HEC-RAS (Cameron and Ackerman, 2012). Finally, we used the stream power index to evaluate the geomorphological effects of floods, which is a measure of the main driving forces acting in a channel and determines a river’s capacity to transport sediment and perform geomorphic work.
The studied reach of Zarrineh-Rud River was divided into two sub-reaches according to geomorphological characteristics: reach (1) from the beginning to Mahmudabad city and reach (2) from Mahmudabad city to Noruzlu dam. In the reach (1), due to the narrow floodplain, flood prone areas is limited. In this reach, a recurrence interval of 25 year flood, approximately covers the entire floodplain. In the reach (2), coincides with increasing of floodplain width, flood prone areas becomes wider. Floods with significant increases in stream power, play an important role in the morphological changes of river channel. In general, a decreasing trend could be seen in the studied river from upstream to downstream, due mostly to gradient reduce and therefore the decrease of flow velocity and shear stress of river channel.Although, potential perform geomorphic work of stream power in the reach (1), particularly in meander bends, is too much, but for the most part, river bed consisting of pebbles and cobbles; as a result, capability to perform geomorphic work is limited. Also, because of the armoring bed, ability for bed incision is very low. The same is true in the case of bank erosion, the channel banks in this reach, either formed from coarse sediment, which is often well-cemented, or as a result of the migration of the river channel bends, are directly connected to the mountains and hills. Mountain unit in the studied reach consists mainly of various types of conglomerate and limestone which are considered as a major obstacle in the channel changes. In this reach, sedimentary point bars are very limited. Therefore, it can be said that the limited sedimentary point bars are evidence of dominant the sediment transport process and limited deposition in many parts of studied reach. In the reach (2), although the stream power is lower than the upper reach, but, what is of utmost importance, is high erodibility of bed and banks of channel in the many parts of the reach. Thus, in this reach the flooding plays a major role in bank erosion and lateral changes of channel. So that, the erosional effects related to bankfull and overbank floods can be seen in abundance in the river margins. In this reach, the erosional and depositional features frequently can be seen adjacent to each other, which can be attributed to local changes in the stream power. Significant increase of stream power in meander bends associated with high erodibility of banks, leads to severe erosion during floods and large amounts of sediment entered in river channel. Conversely, in parts where the stream power is reduced, the deposition process occurs. Abundance of point bars, either in and side of convex banks of the meander bends evidence that during floods, large volumes of sediment entered into the river channel, which are not able to move all of them. So that, in some parts, river channels show threshold behavior (transition from meandering pattern to braiding pattern).
The results show that the river floods in the studied reach no threat to settlements, because, cities and villages are located at the piedmont and high terraces. However, the floods are a serious threat to agricultural activities existing on the floodplain. For example, nearly 1713 hectares of agricultural land in the floodplain was inundated with a recurrence interval of 25 years flood. In upper reach, although the power stream is high during floods, because of low erodibility of the bank materials and bed armoring, ability for forming is low and the dominant process in the reach is sediment transport. But in the reach (2), in addition to increasing inundated areas due to erodibility of banks materials, lateral dynamic of channel is high.

Nowadays, population increase, progress in science and technology and development of industrial installations with the shortage of places in metropolitan areas have made considerable changes in the morphology of watersheds. Violation to territory of rivers, channels, and streams causes alterations in natural drainage pattern and overflowing due to the lower capacity of the changed channels and streams. This can increase the risk of flooding and inundation of the streets and also the costs of urban maintenance. Moreover, this will considerably increase the possible financial and life damages.
Study Area: Tehran is a city located in the southern slopes of Central Alborz downstream many watersheds. Furthermore, the excess expansion of urban areas to 2200 m foothills as well as uneven development and structural difference in physical texture caused the areas to be subject to serious risks of flooding. Among the Tehran municipality regions, the regions 2 and 5 have be developed to absorb the overflow of population and immigrants from central and southern areas of the region. These areas are in the vicinity of the rivers of Darakeh, Kan, and Farahzad, on one hand, and have high rate of constructions, instable residential areas, relatively high density of population and houses, landuse changes, violation to the territory of rivers, and improper use of the channels, on the other hand. As a result, they are subject to flooding. Thus, the areas are highly important due to the possibility of huge flood occurrences.
Material and The data of this study include elevation data extracted from topographic maps (1:25000), climate and hydrometric data (1995-2012), and landuse data from Tehran municipality. The effective or intensifying variables in vulnerability assessment of physical infrastructures in region 2 and 5 downstream the watersheds of Darakeh and Kan have been selected by field observations. As the variables of runoff, slope, aspect, landuse, elevation classes, curvature, old texture, surfaces perpendicular to slope and those parallel to the slope have different measuring units, they have been standardized by pairwise comparison method. For the lands upstream the study area, the runoff has been estimated by SCS (CN) model. Calculation of CN in urban areas has been based on landuse type and percentage of open spaces. The old texture is used in the method because of its influence in flood occurrence due to inadequate drainage, sound management, and permeability of urban structures. The integration of the data has been carried out by fuzzy functions using the weights obtained from the pairwise comparison. For vulnerability assessment, the gamma maps of 0.9, 0.85, and 0.7 have been prepared to compare their correlations with other variables. The gamma 8.5 had the highest correlation with the principal variables. To detect the role of effective factors, we have used water profile and hydrograph with the coefficients using the analysis of Multi-Layer Perceptron Network (ULP).
The vulnerability map resulting from comparison weights and fuzzy integration functions has indicated that the most vulnerable areas are near the channels; particularly those increase the risk of flooding in urban areas through higher discharge. The comparison of the vulnerability map with the transportation networks indicates that most of the vulnerable areas are coincident with the west-east networks crossing the natural slope of the streams. It also indicates that the most vulnerable areas are intersections of the transportation networks of north-south and west-east. These intersections impede the flow of water over the natural north to south slope of the area. Due to the importance of the volume of runoff upstream, the proportions of the runoff were determined based on the area of each region. The results have also represented that the proportion of runoff from Kan watershed on urban areas was more than others. To assess the entry of Kan watercourse into the city, the Soleghan precipitation station has been selected. Three time series of precipitation has been drawn from 27th to 30th October 2000, 2007, and 2012. Based on the data, flood discharge was calculated in three different states and its long profile and hydrograph was depicted. According to field observations, the Kan valley is 3 meters wide and 1.5 meters high. According to long profiles, water flows are increased with an increase in rainfall; this is along with peak discharges and likely flooding on the hydrograph of Kan watershed.
The results of vulnerability assessment in the study area indicated that a combination of upstream natural factors and urban agents make these areas vulnerable against the floods. Although outside the urban areas the lands near the channels and streams are more vulnerable, as also confirmed by field observations, there are some other factors affecting the vulnerability of urban areas. The old texture is greatly important in the vulnerability because it does not have a suitable drainage ability and the available drainage networks are also mainly in the ending part of the areas. Thus, the inundation can intensify the floods or even cause them. The vertical slope surfaces and the curvature in north and northwestern areas of Tehran also show conformity and non-conformity with the drainage and watercourses. The jumps of peak flow in the hydrograph of October 2012 make it necessary to pay more attention to the runoffs of Kan drainage basin as the city of Tehran is experiencing events related to the watershed.

If environmental hazards, including those with atmospheric origin and terrestrial origin cause economic and human life losses for human societies, they would be considered as disasters. Terrestrial hazards, which mostly occur as catastrophic, may have economic and human life damages when they occur in a small scale but with high intensity. Mass movements are among the most important terrestrial hazards in areas susceptible to environmental hazards. Land sliding is one of the most important mass movements. In fact, it causes thousands of deaths and financial losses to residential areas annually. It has been classified as terrestrial hazards which has a high frequency rate in Iran and its influences have been observed in susceptible half-dry and wet domains of the country.
Sliding is an integrated and often rapid motion of volumes of sediments along the domains. Land sliding is one of the natural disasters which causes extensive human life and property losses in mountainous, rainy, and seismic regions every year. Since predicting the time of land sliding occurrence is beyond the current knowledge and ability of mankind, the dangers of landslides could be partly prevented through identifying sensitive regions to landslides and ranking these regions. Most of the previous studies have been conducted on the zoning of slide danger and less attention has been paid to zoning the risk of slides. In the current study, the sensitivity map of the sub-basins under study to the occurrence of land sliding is created using one of the unranked methods called Viktor adaptive optimization method which is based on measuring maximum usefulness and minimum regret.
Viktor methodology is one of the multi-criteria problem solving methods for problems with disproportionate and incompatible criteria for which the decision-maker needs a solution near to the ideal solution and all the options are assessed based on the criteria. Also, in situations in which the decision-maker is not able to identify and express the advantages of a solution at the time of designing, this method can be an efficient tool for decision-making.
Study area: Taleghan drainage basin is one of the important sub-basins of Sefidrood drainage basin and it is located in the southern range of Alborz Mountain ranges and in the 100 km distance from the northeast of Qazvin and 120 km distance from Tehran in the northwest. The area of the studied region is 374.92 km2. The average altitude of the basin was 2307 m above the sea level. Taleghan River in the center of this basin emanates in the west of Kandivan and flows towards the west. After receiving high water level branches such as Alizan, Mehran, etc., it joins Alamoot River and after that, pours into the lake of Sefidrood dam. The average annual rainfall of Taleghan drainage basin is 660.41 mm and its average temperature is 10.5 C. Therefore, based on Domart-en’s climate classification, Taleghan basin falls into the sub-humid group.
Material and In order to create the land sliding sensitivity map in Taleghanrood’s drainage basins, first, the primary information such as topography (1:50000), geological information (1:100000), aerial photos and existing satellite images, the basic maps in the studied area including the slope map, geology map and geomorphology map were created. After providing the information and basic maps, the study was conducted in two stages. The first stage consisted of determining the main criteria affecting the susceptibility of different regions to land sliding and creating the selected criteria maps. The second stage of this research consisted of determining the importance ratio of criteria and implementing the Viktor algorithm for reaching the sensitivity to land sliding map and classifying the basins according to their degree of sensitivity.
At first, according to the condition of the region and the experts’ comments, nine main criteria related to the susceptibility of the basin to land sliding and affecting the occurrence of land sliding were considered in the studied area. After selecting the main criteria, the next stage was to draw the maps pertaining to each of the selected criteria for weighing and evaluating the sub-basins in the GIS environment.
Considering the effect of the above mentioned criteria on the occurrence of land sliding, the degree of plant coverage and distance from faults have a decreasing effect and the other seven criteria have an additive effect. After creating the map of the selected criteria, the importance ratio of the criteria from the viewpoint of importance in the occurrence of land sliding and the susceptibility of the basins to this phenomenon were determined with the help of AHP hierarchal algorithm.
The advantage of the Viktor model is that evaluating all the criteria does not necessitate expert investigation, rather, raw data may be used. For instance, regarding slope parameters, altitude classifications, drainage density, and rainfall, the mean of slopes, average altitude, drainage density and rainfall of the sub-basin were used and the exact values were inserted into the matrix. However, since the criteria of distance from fault, land use, plant coverage, type of soil and lithology did not have any raw data, they were evaluated on a scale from 1 to 10. In the current study, in order to weigh the options according to the role of each criterion in the specific option, the definite weighing period from 1 to 10 has been used, such that weight 1 shows the lowest impact and weight 10 indicates the highest impact on land sliding danger.
Among the nine factors which have an impact on the sensitivity of the basin to sliding, seven criteria (slope, altitudinal classes, drainage density, land use, rainfall, type of soil and lithology) have an increasing effect and two criteria (distance from fault and plant coverage) have a decreasing impact on the susceptibility of the basin to land sliding. After measuring the overall weights of the criteria having an increasing effect for each of the studied sub-basins, it was found that Zidasht 1, 2 and Danbalid sub-basins have the highest value and Shahrak, Navizak and Hasanjan sub-basins have the lowest values. In other words, Zidasht 1, 2 and Danbalid sub-basins have the highest sensitivity to the occurrence of land sliding. The sensitivity of Shahrak, Navizak and Hasanjan sub-basins is minimum.
Based on the sensitivity map of the sub-basins of Taleghanrood, less than 40% of the area of the studied basin consists of sub-basins with low sensitivity or low susceptibility to the occurrence of land sliding. This finding could be partly related to suitable topographic condition, plant coverage, and the hydrogeomorphic condition of this region in increasing the capability of these sub-basins against land sliding. In contrast, around 60% of the area of the basin are surrounded by highly sensitive basins regarding the occurrence of land sliding. Sub-basins such as Zidasht 1, 2 and Danbalid have a high susceptibility for land sliding. Since many residential and rural areas are embedded in these sub-basins, more attention and better crisis management is necessary for these areas. Unfortunately, intense changes in land use and destruction of plant coverage in recent years which has occurred due to the development of tourist areas and personal promenades has converted these areas into the critical center of land sliding in Taleghan basin. Retaining plant coverage, preventing intense changes in land use, reconstructing and increasing the moisture power of the soil and stabilizing the slopes in sensitive ranges of the studied area are recommended.
This research was one of the first to use Viktor adaptive optimization method to investigate and create the sensitivity map of a region to land sliding. After field investigations and selecting the effective criteria in the ranges sensitive to sliding, Viktor algorithm was performed for investigating the sensitivity degree of regions to land sliding and it was shown that Zidasht 2 sub-basin has the highest sensitivity to the occurrence of land sliding in the studied drainage basin. Also, Navizak basin has the lowest sensitivity or susceptibility to the occurrence of land sliding with the maximum optimization index (Q) and maximum distance from the ideal amount.
Investigation of the sensitivity map of Taleghanrood basin to land sliding and also field visits confirmed the good performance of Viktor algorithm in ranking the susceptibility of basins to land sliding. The results of this study and the suggested method could be of use in future studies and it could be compared with other methods of estimating sensitivity to land sliding to better understand its strong and weak points.

Mountain regions are increasingly endangered by a variety of disaster, including avalanche, debris flows, and rock slide. Some characteristics such as elevation, angle of slope, vegetation and climatic elements could affect the avalanche event. Indeed, avalanche is the second factor in soil erosion that causes demolition; therefore, it threatens the food safety. Iran has two main large mountain ranges of Alborz and Zagros with risk of avalanches. In mountains and snow routes, avalanche is an inevitable event and due to special geomorphological condition, Meigoun- Shemshak road is significantly highlighted. Meigoun- Shemshak road has been situated in Shemshak drainage basin. The objectives of this study are to identify the role of effective factors in avalanche events and its zoning in Meigoun- Shemshak road and to find high risk regions.
Material and Meigoun- Shemshak road has been located in Shemshak drainage basin (51º26'49˝ to 51º31'39˝ E; and 35º57'28˝ to 36º3'15˝ N) with the area of 37.75 Km2 in Roodbar Ghasran District, Shemiranat County, Northeastern Tehran. The minimum and maximum elevations of the study area are 2200 and 4200 m, respectively.
Figure 1. Geographical location of Shemshak Basin
In order to prepare the effective factors in controlling the avalanche events, the primary data and maps including topographic maps in 1:25000 scale and geological maps with 1:100000 scale as well as Google Earth images were used. Independent variables including elevation, aspect, slope, curvature, outcrop rock and geological were prepared based on the basic maps. The snow accumulation area were found using Google Earth along with the researcher’s knowledge of the region, and then converted to polygon layer by GIS software. Since the area of avalanche zones is so smaller than the total area, the Rare Event Logistic Regression was used to find the effective factor in controlling the avalanche events. ROC index was used in order to evaluate the validity of the model, accordingly. Finally, the susceptibility map of avalanche events was prepared using the factors resulted from RELR.
Figure 2. Variables used in logistic modeling
The RELR was applied to find the relationship between the snow accumulation areas as dependent variable and independent variables, including slope, aspect, geology, elevation and other similar elements. The results showed that depth stratum, curvature, elevation, outcrop rock, slope, and aspect were selected as final factro in controlling the avalanch event. The susceptibility map of avalanche events resulted from controlling factors were classified into three classes, including low risk (67.35% of total area), medium risk (24.9% of total area), and high risk (8.06% of total area). Since the area of avalanche regions is less than total area; therefore, we considered 10 % of one and zero regions for the validity model and executed it in half of the basin. The area under the curve is 0.75, and it is reliable for being close to one.
Table 1. Rare event logistic regression Parameter Coefficient ᵦ
Fixed coefficient -6.247
Curvature -6.936
Elevation 4.436
Outcrop Rock 1.521
Slope 1.254
Aspect 1.079
Figure 3. Regional distribution map affected by avalanche
According to the results of the rare events logistic model, curvature, elevation, outcrop rock, slope and aspect layers were known as effective factors in the snow accumulation area, respectively. 61.49 % of the snow accumulation area is related to convex footslope and 38.51 of density in the concave area. The highest snow accumulation area ranges from 3200 to 3400 elevations and 13% of the basin total area is appropriate for snow accumulation. The slope map indicates that 58.22% of density is in the slope 30 -40º, which is the best slope for the occurance of avalanche. The most snow accumulation area is located in the southern part of the region (49.85% of the total area) and the western part with 29.14 %. 99.97 % of the region, which have no outcrop rocks prone to the snow accumulation area.

Glaciers and snow covers in the mountains play an important role in the water budget of many areas of the world (Ramage and Isacks, 2003). In high altitudes and mountainous regions, snowmelt is a great contributor to the yearly runoff. The snow melt supplies 1/6 of people's needed water but due to global warming these glaciers may be at risk (Barnett, et al. 2005). For the regions of the world that snowmelt provides the needed water, trend analysis of snow cover is of great importance. Therefore, using data and information that is limited to stations cannot be satisfactory as in many high lands no station exists and the density of them is not enough to make us able to monitor snow cover changes. But snow cover information based on remote sensing data is an alternative way to obtain necessary information in both regional and global scale (hall et al. 2005; Brown and Armstrong, 2010). For this purpose remote sensing products have been introduced to scientific community based on geosynchronous and pole orbiting satellites(Romanov, et al. 2003; de Ruyter, et al. 2006; Zhao and Fernandes , 2009; Hall et al. 2010). In this way a lot of research has been conducted to analyze snow cover changes that have been noticed as follow: Maskey et al. (2011) investigated snow cover trend in Nepal and nearby areas using MODIS terra data from the years 2000 to 2008. The analysis indicated that in elevations below 6000 m in January there is a downward trend (Maskey et al. 2011, 391). Ke and Liu (2014) applied MODIS Terra and MODIS Aqua data from 2000 to 2012 in order to analyze snow cover in Xingzan in china. The findings showed that in winter for the elevations below 2000 m and above 4000 m negative trend exists (Ke and Liu, 2014, 22). Akyurek et al. (2011) investigated snow cover area in Karasu basin as the headwater of Uphrate River from 2000 to 2009. Therefore MODIS data were applied for this purpose. The results indicated that in the study period no negative trend is detected (Akyurek, et al. 2011, 3647 and 3637). Sonmez et al. (2014) applied IMS data over Turkey from 2004 to 2012 to analyze snow cover trend. Using Mann-kendall trend test revealed that in general a decreasing trend can be seen in the country but in fall a positive trend and in spring and summer a negative trend was detected.
Study area: Iran is located between 25° and 40°N and 44° and 64°E and is a mountainous country bordering the Gulf of Oman, the Persian Gulf, and the Caspian Sea. Overall, sixty percent of Iran is covered by mountains, with the central part of the country consisting of two dry deserts: the Dasht-e-Kavir and the Dasht-e-Lut. The Alborz range in the north, close to the Caspian Sea, extends in an east–west direction with a maximum elevation of approximately 5000 m. The Zagros Mountains are aligned in a northwest to southeast direction and reach a maximum elevation of approximately 3500 m. These two ranges play a significant role in determining the non-uniform spatial and temporal distribution of precipitation across the entire country (Javanmard et al., 2010).
Material and In the present paper MODIS Terra and MODIS Aqua data were used to identify the trend of snow-covered days across Iran. The selected study period covers the years from 1382 to 1393. As MODIS Aqua data are missing before the year 1382, we had to limit the study period only to the aforementioned years. The data of these products were downloaded in daily time scale. Before the analysis of the data, we applied two different algorithms to minimize cloud contamination that is a big hindrance against snow cover monitoring. One of the applied algorithms is based on three days filtering and the second is made on the combination of the two products. By exploiting these algorithms we managed to reduce cloud cover considerably. In the second step we started analyzing the data by creating different codes in Matlab. Application of cloud removal methods have been suggested by many researchers (Dietz et al. 2014, Ke and Liu 2014, Wang et al. 2009). In the numerical format of remote sensing data a especial code has been introduced for each feature, for instance the code 200 represent snow, the code 50 represent cloud and etc. As the spatial resolution of the data was in 500 meters, we needed a Digital Elevation Model to be consistent with snow data both in spatial resolution and projection system. Thus a DEM with the aforementioned attributes was provided from NASA. By using this DEM we also were able to calculate the mean altitude of regions that have had trend whether positive or negative. To examine the trend of snow-covered days the monthly frequency of snow-covered days were calculated for the period from 1382 to 1393 and in the next step the monthly matrices were converted to seasonal ones and then the slope of regression equations were calculated for each of the pixels and finally the slopes that had the same signs were considered as the regions with significant trend and these pixels were converted to maps.
The results of this study indicated the presence of trend in different seasons of Iran both positive and negative. The findings showed that in spring 1.1 and 0.32 percent of Iran’s overall territory has experienced negative and positive trends, respectively. In summer only 0.001 percent of Iran’s extent has had trend whether positive or negative in the number of snow-covered days. In the season of fall 3.8 and 3.2 percent of Iran’s was proved to have negative and positive trend respectively. In this season the areas having trend showed counterpart patterns of changes in the number of snow-covered days. For instance eastern regions of Iran indicates downward trend but conversely western counterparts have experienced upward trend in the number of snow-covered days. This similar pattern was noticed in some other parts of the country. In the season of winter the highest rate of trend was noticed. In this season some areas of mountainous regions especially those located in western Zagros have had the most downward trend in the number of snow-covered days. Some of these areas have significant trend of decrease equal 4 days or more. In this season the mean elevation of regions having decreasing trend was 1790 meters from sea level while the mean elevation of areas having upward trend was 2030 meters from sea level. In this season nearly 50 percent of the areas having trend have had the rate of trend equals -1 to 0 days annually. And the rate of decrease in over 30 percent of other areas was -2 to -1 days annually.
In this study MODIS Terra and MODIS Aqua data were applied to examine the trend of snow-covered days across the country. Before taking the daily data in to the analyses some pre-processing analyses were applied on the raw data to minimize cloud cover effects. The findings of the recent paper confirmed the existence of both downward and upward trend in all of the seasons in the country with the greatest rate of trend in winter. In this season nearly 22 percent of Iran’s territories were proved to have a significant decreasing trend in the number of snow-covered days. These areas are mainly located along Zagros and Alborz ranges that are considered to be Iran’s water supply. But only almost 2.6 percent of Iran has had an increasing trend in the number of snow-covered days and most are positioned in lower altitudes. It seems that the recent droughts in Iran stem from the noticeable decrease in the number of snow-covered days. And accordingly crucial steps should be taken and needed policies must be applied to mitigate the adverse effects of this phenomenon across the country.

Preserving the environment is one of the basic requirements of sustainable development, especially in rural areas. An issue which is a threat to the environment of rural areas is the lack of attention to collecting and burying wastes in the environment. In order to ensure that environmental regulations and the aims of sustainable development are observed and to prevent environmental pollution, the zoning of lands for hygienic burying of wastes and reaching the goals of sustainable development seemto be necessary. The current study aims to investigate the lands of Gonabad city for the burial of rural wastes. Hence, the main indices used for zoning in this study are: distance from water resources, plant coverage, soil texture, altitude, inclination, distance from road, distance from faults and distance from populated areas. The layers and data were weighted using ANP and the suitable locations for the burial of rural wastes were determined using Geographical Information System (GIS). The research methodology is descriptive-analytic in nature and functional-experimental regarding its purpose. In order to collect the data, documentary and field-survey data collection methods were used. The results of the study show that among the eight existing rurallocations for burial of wastes, only three locations match the environmental criteria and are located in exactly the right zone, one location is in an acceptable zone, three in a fairly acceptable zone and one location is in an unacceptable zone.
Lack of control of and inattention to the appropriate management of wastes regarding their collection and keeping, transportation and hygienic disposal causes disasters and results in the spread of different diseases and regional epidemics which in addition to threatening the health of the society and environment, impose heavy costs on the government (Costa, 2010). Currently, there is not a coherent management regarding rural wastes which over time, convert into irresolvable wastes with a long retention period, a fact which indicates the importance of waste management (Anabestani, 2013). Hence, protecting the rural environment is one of the necessities of rural development and one of the issues which threatens the rural environments in this regard is inattention to the management of wastes in rural environments (Farmohammadi et al., 2007). "There are different methods for the disposal of waste, but in today’s world, recycling and reusing non-recyclable waste materials is the only solution for sanitary disposal in intensive care" (Elimelech, 2011, p. 626). The aim of this study is to present optimal locations for burial of the wastes from rural settlements in Gonabad city.
Study area: Gonabad is located between the northern latitude of 34◦ and 2 minutes to 34◦and 46 minutes, and the eastern longitude of 58◦and 17 minutes to 58◦and 27 minutes in the south of Khorasan Razavi Province, Iran. This city is restricted from the north to Mahvelat, from northeast to Roshtkhar, from east to Khaf, from the south to Gha’en and from the west to Bajestan. The area of Gonabadregion is 5767.79 km2 and its center is Gonabad. Gonabad region has two sectors (Markazi and Kakhk), three urban points (Gonabad, Bidokht, and Kakhk), four rural districts (Pas Kalut, Zibad, Kakhk, and the Gonabad’s suburbs) and 430 villages. According to the census report in 2013, the total population of the region is estimated to be 80783 from which 34655 have settled in rural areas.
Material and Recognizing and determining the suitability or capability of the region for waste burial is one of the first actions in environmental planning. The aim of this study is to identify the suitable rural areas of Gonabad city for waste burial based on natural and human factors. This zoning was done through environmental, topographic and land coverage criteria and distance from dangerous phenomena. Each of the indices were classified by environmental regulations and experts’ opinions. Spatial analyses were done using the ANP model and the layers were overlapped and analyzed accordingly. The action of weighting was performed and the final weight of each index was applied to each of the layers in the GIS environment. In the next stage, the layers were assembled and the zoning map was created through overlapping.
In order to create the ANP network for the issue under study, first the more important and basic criteria and indices with regard to the issue were determined based on the available resources and experts’ opinions and then, these criteria and indices were weighted and their importance regarding the issue under study were compared to one another. The investigated criteria were placed in three dimensions and then, a questionnaire was designed based on the criteria and indices. The importance of each criterion was estimated on the basis of the mean of responses of experts and the relationship among purpose, criteria and indices were demonstrated by using Super Decision software. The sort of layout and connection of criteria and indices is such that the direction of the arrow not only determines the outer relationship, it also indicates the inner relationship. Weighting and comparing the importance of criteria and indices was done at this stage. In this prioritization, the highest numerical value accrued to the criterion of distance from underground water resources. According to the experts, underground water resources are very important and it is necessary to keep distance from them due to the contaminations resulting from wastes.
In case the location for burying rural wastes is selected without observing environmental regulations, the health of human beings and the environment would be endangered and this would have outcomes which hinder sustainable development. Since the purpose of this study was to reach sustainable development and prevent environmental pollutions, the basic information of Gonabad city were first analyzed and then,the Arc GIS software was used to perform the different stages of valuing at the level of indices, criteria and options by ANP. Finally, the importance of each of these items was determined at its own level. After performing these stages, the weighted maps of each criterion were created. The weighted maps were created based on the comments of experts and the given values pertaining to the aims of this study, such that in each map, the locations which were suitable for the purpose of the study received the highest value. Afterwards, the results of each map and its condition were analyzed. At the final stage, overlapping was done and the final map which demonstrates the optimal zoning for waste burial was created and presented. The existing locations were also identified and based on environmental issues and considering the criteria of this study, it was concluded that among the eight existing places for the burial of rural wastes, only three locations are in accordance with environmental criteria. Due to the size and population growth of rural areas, it is necessary to replace the existing burial places with more optimal ones.

Dust storm is an important atmospheric phenomenon. It has important environment, health, economic and social activities due to penetration of suspended particles of dust to the atmosphere. Measurements resulting from earth and satellite stations show the fact that particles of dust in storms, remain in the nature for a long time. They can get far away by wind, hundreds of kilometers from their origin and have destructive effects. This phenomenon is one of the most disastrous calamities in deserts and half dried regions of the world. It causes many environmental problems in these regions.
Iran is on the dried and half dried belt in the world. Therefore, it is exposed to local and synoptic dusts repeatedly.
Wind with high speed in short time is called storm, storm with unstable air. If unstable air is humid, it is called storm and lightning. It is also called dust storm.
On the basis of the world Meteorological Organization agreement, in case in a station, the wind is beyond 15 meters per second and horizontal vision is less than one kilometer, dust storms occur. There are different methods and data for studying dust storm. One of them is synoptic-dynamic studying on this phenomenon.
According to the terms of the dust storms formation, bare lands of world desert regions (Africa, the deserts of the Middle East, China, Australia and the United States of America) are prone to such storms. Dust storm creative power can arise from the Ocean systems, such as Hurricane of North Atlantic Or due to high pressure gradient difference between two agent regions of this phenomenon, rare sand storms originating from the desert to reach the Arctic region.
In recent years, during which we have been faced with a lot of dust storms, the study of this phenomenon, especially for half western storms of the country and those derived from West surrounding borders confirms the importance of this phenomenon in all aspects of the inhabitant's life of this land. The current study seeks to investigate the pattern of atmospheric circulation and surface conditions that shape them in terms of spatial and temporal view, which has shaped after big dust storms identification in the period of 1985 to 2005.
Study area: Taking into consideration the accelerating trend of the emergence of dusts in the west of Iran, the mentioned region was selected to conduct the research. The mentioned region in the south covers the northern shores of the Persian Gulf from the 30 degree of the north latitude to the borders of north –north West of Iran.
Material and For doing such a research, the data of frequency of dust and standardized pressure of the sea level for the earth surface were collected from the state meteorology organization (dust data with code 6) and the ocean-atmospheric organization, respectively.
Also geo-potential-meter and wind orbit and longitude data were obtained from the National Organization of ocean-atmosphere. These data with local separation capability of 2/5 degree in longitude and latitude are in the form of daily average. The above data are NCEP-DOE Reanalysis 2, that is advanced version of data in model NCEP Reanalysis with no error in quantity.
To study the significant difference in the abundance average of dust stream in the west region of the state during 1989-2005, T test with the two independent samples was used. The prerequisite of doing this test is the study of normality of frequency data of dusts, because in the event of lack of normality of the frequency of dusts, it is necessary to use the equality of non-parameter of this test, i.e. Mann Whitney U Test. In order to study the normality of data, the Kolmogorov–Smirnov test was employed.
After testing comparative hypothesis, different time cycles, regarding to frequency of dust were specified. Then huge dust stream s occurred from 2000-2010. These data were obtained from the site of U.S.A National Organization of space aviation.
In order to study the presence of difference in the frequency of the data in the hot season (April to September) and cold season (October to March), the t test with two independent samples were used.
The test is used to calculate confidence interval or difference hypotheses test of two independent samples. In other words, in this test obtained averages from random samples are judged. This means we choose random samples from two different communities (here warm season and cool season) (recorded stations of dust frequency) and also compare average of two communities with each other.
This method is based on the t normal distribution and it is best used for small samples that the data are near normal or normally distributed. So at the beginning of the notion normality of the data must be calculated. In the current study the Kolmogorov - Smirnov test was used.
Results showed that the dust frequency mean has normal distribution in studied stations during 1989 to 2008. Thus, t test with two independent samples can be used for investigation of dust frequency differences in the two warm and cool seasons.
To interpret the t test results with two independent samples first equality or inequality of dust frequency variance should be investigated in the two warm and cold seasons. The test which is used to this purpose is Levene's test. In this test, first conversion is performed on dust frequency in both warm and cold seasons and thus new data is calculated for each of these two groups. Then, t-test is done on the new data.
Comparative analysis of 40 dust stream occurrence during the last 11 years and considering different periods (calculated in testing difference hypothesis) led to presenting the patterns of occurrence of dust stream During hot periods (April to September) and cold periods (October to March).
The monthly average of dust in the west of Iran indicates the maximum of frequency for the occurrence of dust in April to September and contrary to that, in other months, the frequency of this phenomenon reduces.
The synoptic analysis of dusts in hot seasons: Studying the maps of pressure of ground surface and geo-potential height, the speed and direction of wind at the level of 850 hPa during the hot season, it was specified and that in most cases, a low pressure has taken shape at ground surface located in the west of Iran , i.e. in agreement with the centers of dust (so called Oman-Persian gulf low pressure which are observed in form of a flare of seasonal low pressure of India) and at the level of 850 hPa, a low height in the north, west and north west of Iran is observed which transfer dust into the western regions of Iran.
The synoptic analysis of dusts in the cold season: Studying the maps of the land level and geo-potential height, the speed and direction of wind at 850 hPa during the cold season, it was specified that an asymmetric model leading to the dust (opposite to the hot season which was fixed for all samples) results from different conditions. In line with this, with the study and cultivation of samples collected, it was specified that the emergence of dust in the cold season is mostly a function of the 850 hPa rather than surface.
Research results show that the frequency of dust in hot seasons is more than that of the cold season and this difference is meaningful with confidence level of 95%.
This meaningful difference derives from their creator systems and specifications of the earth during hot and cold systems. Although instability in the cold season is more than the hot season, the humidity on the earth surface, prevents the formation of dust. The comparative patterns show that those factors that create dust in cold seasons are more variable due to the variety of pressure systems that affect Iran.

The effect of climate of the Earth's surface is the result of interaction of different levels of atmosphere and lithosphere. One of the factors which influences that interaction is the way the system pressure transcends it. In this way, the system pressure changes and can be changed and eventually may become an environmental hazard and geomorphodynamic phenomenon. Hazards are an integral part of human societies. Landslide hazards are considered as important Iranian geomorphclimatic hazards that every year brings a lot of damage to different areas. In the area study, the northern Alborz and Zagros Northwest, precipitation system paths have effective roles due to surface characteristics to create the landslides in the period from 14 to 31 March, 1998. The purpose of this study is tracking synoptic patterns conducive to landslides in the area study from 14 to 31 March 1998, to provide guidance for applied anticipations. The important low-pressure systems have entered in the study area from the routes: -North Europe-Black Sea- East Mediterranean
- North Africa (Libya) - South Mediterranean -East Mediterranean
- East Mediterranean -North Iraq-Caspian Sea
- West Mediterranean- East Mediterranean -the Caspian Sea
- North Africa (Sudan) - Saudi Arabia - Persian Gulf.
Study Area: Due to the occurrence of landslides in the northern and western of Iran, the study area selected is the northern Alborz and Zagros northwest. Northern Alborz and Zagros northwest coordinate 30 to 40 degrees north latitude and 42 to 55 degrees east longitude (Figure 1).
Material and The study is based on analysis of terrestrial and atmospheric data. The general research approach is synoptic analysis based on the outputs of the Grads software and matching with the data recorded in the land stations Analytical and quantitative methods were performed by using statistical and geo-statistical software GIS and Excel. The database was created base on landslide database Iran Watershed Management Department under the Ministry of Agriculture, data of Iran meteorology organization and data from National Center Environmental Prediction (NCEP). The geographic coordinate of landslides, kind of landslides, occurrence date is extracted from the landslide database of Iran. The daily precipitation data are extracted from Iran meteorology organization. The rain, surface level pressure, geopotential height, specific humidity, zonal and meridian winds are extracted from the National Center Environmental Prediction. (Figure 2).
Figure 2. Diagram of research
74 landslides have occurred during 14-31 March 1998. The landslides occurred on Zagros and Alborz mountain ranges (Landslide Investigation Group, 2005). This area contains Ardabil, Charmahal va Bakhtiary, Khorasan Shomali, Kordastan, Kerman, Golestan, Gilan, Lorestan, Mazandaran and Hamedan provinces. Several factors contributed to the occurrence of landslides. In the north range of Alborz, most rain systems have received the moisture from the Caspian Sea. Winds while passing from the sea when they reach the shore are unstable and moist. Current water erosion is the dominant cause of the Alborz range. Northwest Zagros has heavy precipitation due to being in the flow path of the west winds. Landslide phenomena are abundant in Zagros and Alborz. Asmari, and Pabdeh, Gurpi, Shemshak formation with inter bedding, marl, shale and limestone and quaternary deposits are prone to landslides (Nikandish, (2001). Evaluation of precipitation data of 38 synoptic stations shows that slope's instability is the result of the two periods of precipitation which are separated by a pause of several days (Nikandish.2015). The spatial distribution of cumulative rainfall will reveal that the Zagros highlands role is strongly positive in receiving rainfall. Rain distribution on the North Alborz is more regular throughout the year. Significant proportion of the annual precipitation in the northwestern Zagros falls in short time which could cause flooding or landslides. The first rain has continued from March 14 to 18, 1998.The paths of causing precipitation systems during the first rainfall include: path 1 is Northern Europe - Black Sea - East Mediterranean, path 2 is North Africa (Libya) - Southeast Mediterranean - East Mediterranean, path 3 is East Mediterranean - North Iraq - Caspian Sea, path 4 is Northeastern of Iran – Uzbekistan. High pressures paths are located on the Kara Sea Route - Siberia and the Arabian Sea. Surface low pressure systems are controlled by a trough in 500 hpa. Apart from the southern east, Iran was located in the area of positive vorticity on March 18. The base on moisture and wind maps, Mediterranean Sea, Red Sea, Persian Gulf and Arabian Sea are water sources in the surface and 500 Hpa especially on 16- 18 March. Period of several days without rainfall continued in most stations from March 19 to 23. The loss of climbing mechanism and stopping the rain, intensified and accelerated the penetration of rainwater and snowmelt water, prepare the background for slope instability. Second precipitation has continued from 24 to 31 March 1998. General paths of precipitation systems include path 1 West Mediterranean - East Mediterranean – Caspian Sea, path 2 North Africa (Sudan) - Saudi Arabia - Persian Gulf, the path 3 Azerbaijan - Caspian Sea - Armenia and paths of high pressure are located on the Baltic Sea - Poland - Russia and the Arabian sea.
Through the process of locating emergency accommodation in the area, we came to the following conclusions. According to the environment criteria, earthquake (weight: 569/0) and landslide (weight: 228/0) have higher priority coefficient in locating. This means that villages that are suitable for locating temporary housing are away from environmental hazards. In general, only the village of Mayvan takes the highest scores for the physical location of temporary housing. In addition, the villages of Se Gonbad, Bash Mahale, Kharagh, and Yenge Ghale are placed at the next level benefiting from good conditions, whereas 26 villages under the study are not appropriate in terms of physical facilities and are thus not suitable to locate as temporary housing base.