مجله مخاطرات محیط طبیعی
پیاپی 18 (زمستان 1397)

Azores subtropical high pressure is accounted as the most striking and permanent features of tropospheric circulation in the Northern Hemisphere subtropical region and Iran. Assessing the published sources about the subtropical high-pressure variations showed that a comprehensive research of the high-pressure changes is needed in different seasons of the year. Increase or decrease in the severity index and eastern and northern extension index of the subtropical high pressure of 500 hPa level, is a major determinant index of the arid and wet periods in Iran. Therefore, the main goal of this research was to determine the tempo-spatial changes of subtropical high pressure or in the other words determining the northern and eastern borders spread and also the intensity of this system in different seasons over Iran. For this purpose, the data with NC format and geopotential height of 12GMT over a period of 68 years (1948_2015) were downloaded from the databases of National Center for Atmospheric Prediction (NCEP) and the National Center for Atmospheric Research (NCAR) NOAA and for seasonal classification and drawing the intended maps, they were converted to standard and intended formats Intended in the next stage. The maps and time series charts of mean STHP of Iran’s atmosphere indicate an increase in the severity and surface index during all the seasons of the year. The slope of the trend line has been increased for all the seasons and the average of geopotential height in Iran increased at a rate of 5.87 Geopotential meter per every 10 years and in 2015 reached to the maximum positive anomaly.

Forest fires have always been financial losses, physical and environmental, and the world has changed a lot in Iran. Identify and predict factors contributing to the occurrence of this event can the incidence of human and environmental catastrophes to prevent it. The research to identify effective synoptic patterns in forest fire took place in the city, Boyer Ahmad. Statistics on forest fires, including the location and time of the fire, The area burned by the Agency of Natural Resources Kohgiluyeh Boyer Ahmad, a 10-year period (2006-2015) As well as data needed to draw weather maps The US Climate Prediction Center of Weather America at 12 Zhu Lu The levels of 1000, 850 and 500 hp Pascal was received. The results showed that the fire on the earth's surface low-pressure prevailing pattern Gulf-Pakistan And the upper dominant pattern of Azores high pressure on Iran Underlying increase the temperature and reduce humidity in the area has been studied. Low levels of heat created by low pressure in the suction atmosphere and the scorching deserts of Saudi Arabia and Iraq warm Gulf The study was drawn to the area and consequently increasing the air temperature and the subsequent increase in soil temperature And the moisture content of the soil to a depth of 10 cm ground Anticyclone of the Azores in the middle levels of the high altitude and the atmosphere in the days studied causes subsidence and rising air temperatures in the region were affected by the cyclone. Factors cited an increase in air temperature, relative humidity decreases and the subsequent increase in soil temperature and soil surface was drying. Despite the conditions of fire in forest areas have been easier. The most important measure to reduce the effects of these fires on forest fires by forecasting and identify early trends affecting climate Meteorological Organization And give timely warnings to organizations forestry, natural resources, is fire.

The problem of soil waste and information is from the sediment load of the rivers. How to calculate landslide sedimentation in landslide basins. In this research, landslide lands of the ILAM dam basin were identified with the aim of quantitative estimation of landslide load using satellite imagery, Google Earth, and field analysis. The discharge data of the sediment was investigated. Using the method of daily discharge, the suspended sediment load and specific sediment were estimated during the existing statistical period and the sediment peaks were determined. The time of occurrence of landslides was adapted to the sediment yield of the statistical period. The average observed sediment in the non-slippery (sub-basin) sub-basin was 0.9 tons per hectare per year in the Chavez subzone of 10.4 tons and below The GOLGOL basin is estimated to be 18.8 tons per hectare. This trend follows a meaningful linear relationship. Using mathematical relations, an 85 percent increase in sediment yields in the sub-basin of Chavez land with an average of 36,510,800 tons during the statistical period is desirable, coincidence The occurrence of landslide with sedimentary peak shows the effect of a landslide on sediment load. Considering the significance of the linear relationship between elevation of landslide and increasing sediment in sub-basins, with a confidence coefficient of 76 percent. The results of the calculation of the average sediment recorded at CHAVIZ Station during the period, which is 146336 thousand tons, is about 130,000 tons due to landslide and 15,000 tons of outflow sediment in normal mode compared with the non-landslide control sub-basin. With these calculations, about 75 percent of the sediments in the ILAM province watersheds, which account for more than 1 percent of the landslide, is related to landslides.

Every year we see natural disasters causing major financial and human losses to human societies, and unfortunately, our country also has a bitter taste of it every now and then. Floods, earthquakes, droughts, frostbites, storms, and so on ... There are a lot of financial and financial losses to the country, which will require measures to reduce the damage caused by these disasters. Definitely, the first step is to understand and understand these phenomena. The development of the process of urbanization and degradation of vegetation, soil erosion, and global climate change has already paid attention to the importance of addressing the issue of the urban flood. This research was carried out to determine the risk of flooding in Sari using multi-criteria decision-making techniques. Using nine criteria, the distance from the river, runoff coefficient, CN coefficient, population density, residential density, slope, land use, the age of the building and outdoor space were developed. By preparing the required layers, determining the weight of each layer based on their importance in the occurrence of a flood. After the final weighing, the layers were compared in two to two by Expert Choice software and the matrices derived from these comparisons were transferred to Idrisi software and the final coefficient was determined for each layer. Finally, by applying these coefficients, ArcGIS software provided a flood risk zoning map in the city of Sari. The results show that flood risk in the center and south of the city has been the highest. Flood risk zoning map shows that 12.24% of the map area is in a very high danger zone and 37.05% in very low-risk zoning. To reduce the risk of retrofitting buildings around the river to reduce flood damage.

Considering the significance of Zagros heights in precipitation distribution, the present study using the RegCM4 model and its simulations, the effect of Zagros heights on convective Cumulative precipitation and vertical velocity of different levels of the atmosphere was investigated. The required data was obtained from NCEP/NCAR with a 2.5 resolution from 22 to 38 latitude and from 38 to 58 longitudes on a grille with a horizontal resolution of 10 KMs and 30 SEC time steps for 2000 to 2005.Comprehensive cumulative convective systems were evaluated in two control run an experimental run and, effects of the Zagros heights in warm and cold seasons of the year was examined on these parameters. Results indicated that cores of rainfall during December-January after crossing system have been weakened, while April systems in East Zagros have continued to operate with the same power. Zagros heights in the months of December-January increased rainfall in West Iran and reduced in the Zagros East. In contrast, in April, there is no significant difference between the two runs in the Zagros East between convective precipitations. And maximum precipitation in both runs, is focused in West Iran and Zagros region and its minimum is focused Zagros East and Iran's central plains; But by eliminating the Zagros heights, the convective rainfall this month has increased on the shores of the Caspian Sea. The Zagros heights has to effect on vertical wind velocity profiles of Low levels and the speed and extent of the jet stream cores of high levels of the atmosphere; So that in April resulted movement atmospheric jet stream from level 200 to 400 hp and increases their speed and extent; So, the flows pattern of the mesoscale convective systems and the convective precipitation resulting from them were influenced by the elevation pattern; and kind and how the Zagros heights effects on convective precipitation and vertical profiles of wind speed in the warm and cold months of year is different; in a way that, the wind slowed down at low levels of the atmosphere in December and increased in January and April.

The focus of watershed management practices should be in the runoff control, flood prediction and determination of sub-watersheds contribution in producing flood with the aim of reduction its destructive losses. Proposing of practical management solutions of flood control needs the examining of rainfall-runoff models to simulate flow hydrograph, especially in ungauged watersheds. The aim of this study was to evaluate the effectiveness of HEC-HMS model in the rainfall-runoff simulation of Amoughin watershed and determination of sub-watersheds contribution in outlet flow hydrograph. Toward this attempt, the HEC-HMS model was run with SCS-CN method (loss module), SCS-Unit hydrograph method (rainfall-runoff transformation) and Muskingum method (flood routing) through 9 rainfall-runoff events. The input parameters of the model were optimized through applying 6 storm events considering Nash-Sutcliffe objective function and the mean values of the input parameters were used as input for three excluded storm events during the validation stage. In order to prioritize the potential flooding of sub-watersheds, the calibrated HEC-HMS model was employed by removing the sub-watersheds in each run with the 25-year design rainfall, then the flooding potential indices calculated. According to the results, the average value of Nash-Sutcliffe statistical criterion 0.63 in the validation stage demonstrates that the accuracy of HEC-HMS model in flood simulations of Amoughin watershed. The result of flooding potential indices showed that B1, B2, and B3 sub-watersheds have more effect on the flooding potential of Amoughin watershed. In conclusion, it can be said that flooding potential sub-watersheds are not affected only by sub-watersheds area. While, the physiographic characteristics, land use related factors, spatial location and flow routing through sub-watershed to outlet should be considered in determining the flooding potential of sub-watersheds in future studies.

Determination and zoning of landslide hazard areas is a primary activity in environmental hazard management and reduce the landslide costs because this phenomenon is caused to financial and felon, soil and land degradation and increasing sedimentation in the watershed outlet. Therefore, identification of susceptible zones to landslide using experimental models is one of the basic steps in hazard management in basins. In this study, to effective factors in a landslide and also landslide hazard zonation in Ghomroud- Aligudarz basin was used LNRF model and GIS techniques. For this purpose, effective layers in landslide such as land use, lithology, rainfall, slope, aspect, distance to fault, distance from the river, Stream Transport Index and Topographic Wetness Index were prepared and digitized. The intersection of independent and dependent variables of mass movements and the weighting factor classes in each class have been executed based on LNRF model. The result of this investigation indicates that most of the landslide occurred in Gypsiferous and Sandy Marl, Shale with intercalations of limestone, Tuffaceous Shale and green Tuff units, slope class 5- 20 percent, and a north aspect. On the other hand, most of the instability occurred in rangeland and agricultural classes, a distance of 0-600 m from drainage network, and rain class 266-300 mm. Also, the class of 7.5- 10 for Topographic Wetness Index and class of more than 12 for stream transport index had shown the most susceptible to landslide. Also in the area, a landslide had a direct relationship to the distance of the fault and reflects the ineffectiveness of the faults in the landslide in the region. It is expected that based on these results, the best plan is done for the Ghomroud- Aligudarz basin, in particular, the construction of structures such as roads, building construction, and facilities to reduce the environmental and economic costs.

Earthquakes are presented as the most dangerous geological phenomenon which is causing many damages to cities, infrastructures, buildings, etc. Researchers have been extremely dynamic in assessing and predicting the earthquake events and have made noteworthy advances, but still, face many uncertainties. Along these lines, the best approach in this field studies the logical patterns and parameters involved and the interaction between earthquakes and urban construction or seismic retrofitting. In order to implement a seismic resistant structure, the first step is to have sufficient knowledge on seismicity and earthquake hazard analysis of the area in which for estimating and analyzing the sites seismic parameters, many empirical and computer-based approaches have been presented. In this regard, the computer-based methods (simulations) due to their high accuracy and computational power nowadays are getting more attention and application. One of the newest approaches for identification of different regions seismicity is using the next-generation ground motion analysis (NGA) models. This model by defining attenuation relations for the study area can estimate the seismicity parametrical coefficients with high accuracy. This advantage can help to describe the geological and seismotectonic structures of different regions to observe the impact of seismic parameters. In this study, the NGA model for the Assalouyeh area based on geological and tectonically conditions are prepared and engineering parameters for seismic design are estimated locally and the seismic zoning map of the region is provided. According to the NGA model results for Assalouyeh region within 100 km radius, the PGA, PGD, PGD and PSA parameters for the 100-year return period are estimated as 0.29g, 18.2cm/sec, 24.2 cm and 0.19g respectively. Based on the results of this research, the study area is divided into four zones in terms of risk potential degree and Assaluyeh is located in high earthquake risk potential one.

Due to the climate variation in different regions of the province of Kerman, and the importance of temperature in climatic hazards such as frostbite, late spring periods and heat stress, the extraction of temperature periods is necessary with a Scrutinyapproach to the natural seasons of the province. For this purpose, after providing daily databases, for the preparation of 73 rows and 12 columns per quadrant matrix, the average temperature data of the synoptic stations of Lalehzar, Baft, Shahrbabak, Kerman, Sirjan, Zarand, Anar, Rafsanjan, Bam, Jiroft, Kahnouj, and Shahdad were used. Then, using statistical analyzes and manual method, the beginning and the end of temperature periods in different regions of Kerman province were determined and the temperature seasons of these areas were extracted. The results of this study showed that with the exception of the Lalehzar area, which has three seasons of temperature corresponding to the natural seasons of winter, spring and autumn, the remaining regions of Kerman province have four separate seasons. However, it is different from time to time, the beginning and the end of the seasons in different regions of Kerman province. The longest natural summers are Shahdad and Kahnouj and the longest natural winters are Laleh Zar. In addition to the potential for temperature variation in different areas of the province, occurrence of climatic hazards, such as late pomegranate, can be detected.

In this research using the standard score of minimum temperature data, the statistical characteristics of the widespread cold west of Iran and synoptic conditions their occurrence was analyzed for period 1992-2015. first by study of coldness events and their classification and selection a certain threshold for determination of widespread cold, 176-days of intensive cold in the four months of December, January, February and March extraction then using the data of Geo-potential height at 850 hPa and use of correlation method, extracted 5 Circulating pattern in creating this widespread cold. Among these patterns, the fourth pattern with a 105-day occurrence as the main pattern and the third pattern was detected only with 3-days as a random pattern. In terms of monthly and annual frequency, some patterns as the pattern the third in 2006 and fifth pattern in 1996 have occurred only in the month of January. Some others as the second pattern in 2006 and fourth pattern in more years of the study period and occurred every four months. The first pattern also of 2001 onwards and in months of January and February have occurred. Synoptic analysis representatives' days of patterns showed that the main factor creating the widespread cold in the west of Iran according to locating pressure centers, influence coldness from the North East and North West of Iran. Such that in the two case of the patterns from the north-west, the other two case from the northeast and one case from the north, cold air advection has happened into Iran.

Thunderstorms are one of the climatic phenomena that cause numerous damages in different parts of the world, due to the accompaniment with thunder, high winds, hail and heavy precipitation. In this study, the probability of thunderstorm days in Tabriz in the spring is analyzed using probabilistic rules and Markov chain model. For this purpose, the daily data related to thunderstorms (codes 95 to 99) was used for 65 years (1951-2015). At first, the daily data is classified into the normal days (code 0) and thunderstorm days (code 1). Then the frequency matrix is formed and the probability matrix is created accordingly based on maximum likelihood method. The Markov chain properties such as empirical probability and equilibrium probability, Frequency of occurrence, mean time periods and weather cycle were investigated. Finally, Occurrence Probability and return period of these spells were determined. The results show that the shortest weather cycle is in May, which has the highest frequency of thunderstorms. Conversely, the longest weather cycle is in April, which has the lowest frequency of thunderstorms. Also, in 65 years period, the one-day and two-day stormy sequences have the highest frequency. And For longer sequences, the frequency of thunderstorm days is reduced. The return period of one-day and two-day stormy spells is 1.5 and 5 days. Regression relation between the observed and estimated values of n-step periods of thunderstorm days shows that the considered accuracy and reliability for all months is more than 99%.

Earthquake is a natural hazard that can cause irreparable damages. Its damages are often more severe in rural areas. One way to reduce the earthquake damage is promotion the knowledge of people, especially rural managers. Based on this, the purpose of this study is evaluating the knowledge and skills about earthquake crisis management in the rural local managers of the central division of Bastak County that located in Hormozgan province. This research is an applied type, and its method is descriptive-analytic. Data were collected in two ways including document-library and field survey based on a questionnaire. Questionnaire reliability based on Cronbach's alpha coefficient was measured at the primary test. Statistical society is 130 rural manager of a central division of Bastak County. The sample size was determined 97 persons by Cochran formula. Data analysis included quantifying answers; calculate averages, and Student t test using SPSS software. The results indicate that more than 94% of answers are lower than average of the test. According to triple phases of earthquake crisis, an average of readiness before an earthquake is 1.95, an average of crisis phase is 1.47, and post-earthquake phase is 1.73. So, appropriate training courses to increase readiness for earthquake crisis management have to be considered.

The water crisis is one of the most important global issues in the South West Asia region. Iran as a dry country in this region has many challenges in this area. Isfahan province is one of the driest provinces in Iran, which needs high water for industrial and agriculture centers. Due to excessive consumption of water from the Zayandeh River, the water bill has been negated. The aim of this study was to control and balance the amount of water in the river through the establishment of a comprehensive water pricing system as an instrument of demand management in the Gavkhooni basin. Accordingly, first the actual rate price per cubic meter of water was calculated as the cost price per cubic meter of extracted water in two newly operational facilities, one for supplying the river water of Koohrang storage dam and the other for third tunnel of Koohrang In the form of the price paid per cubic meter of extracted water. Then the original cost estimate of water was compared with the prices set by the Ministry of Energy. The research methodology is according to using a cost "net present value" and Based on Based on the relationships existing in the economics of engineering science and the ratio of benefits to costs equals one. After final calculations in dam and tunnel sector, the calculated cost price of water was 10298 Rials. As a result, a large gap between the actual cost and tariffs issued by the Ministry of Energy is observed. Also, the calculations showed that there is no correlation between price paid by consumers for water supply and water price, as well as the economic break-even point in terms of water consumption tracks to zero.

The emergence of environmental crises has always been a global concern. This concern becomes more acute when such crises affect large metropolitan areas. The purpose of this research is to evaluate and prioritize the consequences of the crisis of soil pollution, water pollution, air pollution including chemical and particulate matter pollution, as well as noise, optical and visual pollution of Isfahan city.
Therefore, using environmental data (e.g. particulate matters, air pollution, visual contamination, non-drinking water contamination, soil contamination, noise pollution and light pollution) related to the years 2016-2017 and employing the hierarchical process models as well as the William-Fine method, the impacts of environmental crises on the metropolitan area of Isfahan have been reviewed. The results of the research indicate that environmental crises of air pollution, visual contamination, non-polluting water pollution, soil contamination, noise pollution, and optical pollution with the alternative weights of 0.228, 0.258, 0.135, and 0.105, 0.084, 0.073 and 0.063 have the greatest impact on the metropolitan environment of Isfahan, respectively. Comparison of these results with the results of the simple hierarchical process method showed different ranking in the environmental crises. Simple hierarchical process method showed that optical pollution, visual contamination, and soil contamination have a priority of 1 to 3 which was unreliable due to the expertise