GEOGRAPHICAL RESEARCH
Year:2005 | Volume:20 | Issue:1(76)|Papers Count:12

Iran has a specific kind of climate due to its geographical location and some effective factors like topography and distance trom water bodies. Most of the country is covered by mountain ranges of Alborz and Zagros and some sparse mountains in the interior parts. Most of the roads pass through these mountainous areas. There are 237 dangerous and snow prone passes. Many of these passes are blocked during cold months by heavy snowfalls, avalanches, blizzards, black ice and dense fogs. This causes considerable damage to the economy of the country. Some of the main aspects of weather hazards which cause some unpleasant driving conditions are rainfall, snowfall, frost, fog and storm. Snowfall and frost usually are more dangerous than fog but their occurrence probability can be predicted and they can be controlled by some equipment such as snowplows and salt spreaders. Wind forecast is usually exact too. Road dangers may be decreased locally by appropriate road designing, bridge building, wind break, etc. but the prediction of fog is very difficult because of its spatial and temporal changes. Fog is one factor of weather hazards which may directly affect the transportation safety. Fog, specially dense fog, may affect the traffic and an increase in road accidents. In this paper, in order to study the impacts of weather conditions on transportation safety and determine critical thresholds, meteorological data in Iran have been analyzed. It is necessary to mention that in this research in order to simplify the application of data obtained in research centers outputs are on the basis of solar years.For the assessment of fogy situation, first we obtained for a period of 10 years daily data for 120 synoptic station to identify critical meteorological & climate for the roads according to some thresholds.Working on visibility data (less than 1000 m) of the above mentioned synoptic stations provided a background to determine spatial & temporal distribution of vulnerable spots.According to the results of visibility data; Khuzestan, Ardebil, and Sistan & Baluchestan provinces were the most vulnerable regions.Finally with the increasing trend of motor vehicles and traffic, there is a strong need to plan more and better roads, and we believe that study of road meteorology is very important in this regard.

One of the achievements of man in dry areas is obtaining water through subterranean water canals, locally called Qanat. As believed by some experts, it is an ancient Iranian innovation. According to Fisher, %80 of Iranian activities are based on underground water and one of the main ways for obtaining water, is through Qanat (subterranean water canal) in Baloochistan. It is a major factor in establishing human residences, and agriculture strongly depends on it. The present study, is based on a field research done in an area, called "Hichan" of the city of Nikshar in Baloochestan. It shows that the method of water utilization in this area is considerably different from other regions of Iran. They are as the following:1) The length of the subterranean canal (series of wells, connected together under the ground through which water is carried from one point toward the target area), does not exceed 3Km. .2) Because of being located in a mountainous region, some of the small, seasonal or local rivers feed the subterranean water resources.3) South-east of Iran, including the region under study, is affected by Indian Ocean's seasonal system, so the area enjoys summer rainfalls. As a result the system acts interruptedly with seasonal systems whenever the region experiences the summer rain. Because of a great deal of surface run off, the use of underground water, is not much needed. That is why, in the wet years, especially during rainy summers, the area under cultivation, will expand by 50% and the rate of crops (products), will increase by three times.Irrigation (Timetable)Irrigation cycle is a period of 5 days in the region of Hichan. During the first four days, irrigating water is divided into six shares and on the last day, it is divided into eight shares. The fifth day is locally called Meldari. The difference between one-sixth (hexadic) and one-eighth (octonary) shares is that in a one-eighth division, water irrigates eight smaller pieces of land than those of one-sixth division during each night-and-day.Distribution of water in Hichan is based on scale; called bowl (a bowl which has a small hole in the centre. The bowl is put on the water and it enters into the bowl through the hole). The time of filling is called a bowl or "tass" which is about 15 minutes.In each hexadic (one - sixth) and octonary (one - eighth) division, supply of water is based on "Zar" (=meter). Each zar in one-sixth division has 4 Tass and in one -eighth has 3 Tass. In other word, the total distribution period, in Hichan is equal to 450 zar which in a day - night is 90 zar. Since during the night, the rate of distribution is not accurate, each zar of water, in one- eighth pieces of land is divided into 3 equal parts in which each parts is one tass (bowl) or "Miri", but in one- sixth pieces of land, there are 4 tass (bowls). So in the latter case, water is divided in smaller amounts than those of one-eighth piece of land.The Scale of SunshineDuring day time, the sunshine indicator (index) is used for water distribution. The index height is 50 cm. At 7 o'clock in the morning, the shadow of the indicator reaches to 70 cm, this is the time when the sunshine indicator begins to be used. This is the first phase of distribution. The second phase begins at 10 o'clock when the height of the shadow is 30 cm westward. The third phase starts at 13 o'clock when the height decreased to 4cm. The forth phase begins at 15 o'clock when the shadow height of the indicator is 30 cm eastward. The fifth phase begins at 17 and sixth at 23 o'clock. During the night, this process is carried out by Mirab, waterman, based on Haghabe, the water share.

Enlargement of cities, population growth, lack of urban greeneries in big cities (especially Tehran), inappropriate distribution of greeneries relative to the urban area, high costs of preserving available greeneries in the city, all have made the environmental and landscape designers and planners analyze and review the aesthetic aspects again. These aspects have so far been the only intended element in designing, excluding environmental adjustment, geographical and domestic qualities; so the designers and planners are supposed to pay more attention toward biological, geographical, social, and economic qualities of each area, along with aesthetic dimensions (Considering the principles and parameters of sustainability).Restoring and regulating urban ravines and rivers because of their plenteous biological potentials is an effective step ahead toward developing sustainable natural greeneries. Recently, the Iranian government has paid attention to planning, preserving and restoring these beautiful divine gifts in the form of natural promenades. Tehran is one of the cities, which enjoy a rich treasure of these natural-urban elements. But overuse of these treasures has ruined these natural resources. So, it is very important and necessary to reassess the environmental capabilities and take measures to preserve and restore the natural eco -systems.This paper deals with analyzing strategies and geographical systems in the planning process of sustainable development of River-valley's by evaluating the environment and ecologic capabilities of the land.Thus, a brief introduction and analysis of Tehran's important River-vallies has been considered. Their strengths and weaknesses have also been evaluated.Kan River, one of Tehran's biggest River-vallies, has been introduced and studied. Its qualities have been mentioned as well.After that, an area seven kilometer north of Kan River-valley was chosen. For the sustainable development of this part of the River-valley through the process of preparation of the land, using SAD strategy, a part of this River-vally was chosen. Through this process Kan River-valley's attributes were artificially, naturally and visually analyzed. Map of the lands-proportion and environmental qualities of the specified part were made using sieving techniques. Finally, strategies including basic suggestions toward exploiting advantages and opportunities, and studying weaknesses and threats were provided through SWOT matrix.

To determine land typology on the basis of landslide variable and to prepare a map using Nilson method, a case study has been done. The area is located in the north of Semnan, in Chashm Khatir Koh. First the exact area for the study was determined and all land slides in the region were recorded. Point distribution and surface distribution maps were prepared. Then, on the basis of Nilson method, the slope of slide was drawn on a map at the levels of; 0-5, 5-15 and more than 15 percent and also the geological map was drawn. Then maps for three classes of minor slide or no slide units, slide units and units with slide potentials, were prepared. On the basis of Nilson method, comparing and combining two maps (slope and slide units), typology map of land slide with five units:stable, generally stable, fairly stable, fairly not stable and areas with mudflow potential were drawn. The land area for each classification are consequently 62, 18, 690 and 94 hectare. The result of the study showed that Nilson method cannot be recommended for the region because the stable land area, fairly not stable land area and fairly not stable are more frequent than the rest. Another deficiency with this method is the existence of stable area for lands with the slope of less than 5 percent. To overcome this deficiency,slope classification was grouped into five classes on the basis of land slide distribution:less than 5, 5-15, 15-25, 25-45 and more than 45. On the basis of conformation and comparison of new slope map and geology map, typological map land slide at five levels: stable, generally stable, fairly stable, fairly not stable and with mudflow potential was prepared. Land slide area for each of these levels are respectively 57,263,394,652 and 94 hectare which are fairly acceptable to be recommended to the administrative sectors in the region.

The maximum, minimum and mean temperature data for 4 stations from Kermanshah province namely Kermanshah, Sarepole Zahab, Eslamabade gharb and Kangavar in a period of 15 years from 1986- 2000 were obtained and used. After reviewing and comparing the results, finally agglomerative hierarchical clustering analysis techniques were selected for the determination of natural seasons in Kermanshah province on the basis of 7 days daily average temperature data.The results of the study show that in Kermanshah province, the hole year basically is divided into two main seasons. Summer and winter are more important than other two seasons namely spring and autumn in this region. The seasons of spring and autumn are very short. On the basis of combined temperature indices of absolute minimum, maximum and mean weekly temperatures in Kermanshah province, winter lasts 16 weeks, summer 19 weeks, spring 9 weeks and autumn only 8 weeks.Natural seasons in this province do not start at the beginning of calendar seasons. On the basis of the used indices, winter begins from the 48th week, spring from the 12th week, summer from the 21st week and autumn from 40th week of the year. These dates are true for other stations too. In the warm section of the province namely Sarepole Zahab station, spring begins when the temperature reaches 24.3 degrees centigrade, summer with 36.6 ,autumn with 34.5 and winter begins with 21.3 degrees centigrade. In the cold section of the province i.e. Kangavar station, spring begins when the temperature reaches 10.7 degrees centigrade, summer begins with 19.3, autumn with 15.8 and winter begins with 7.7 degrees centigrade.There is a general belief that says in cold regions of Kermanshah province the winter season is longer than the other 3 seasons and in warm section of this province the summer season is longer than the other 3 seasons too,but the results of this study did not confirm this belief.

In studying erosion and sediment supply there are few researches done in Iran using remote sensing techniques. Given the importance of accurate estimation of erosion, lack of available measuring stations, and the existing problems with the traditional methods, it seems quite possible that remote sensing data can fill the gap. To overcome this condition in Sefid-Ab sub-basin in Haraz region, remote sensing and MPIAC model were used to estimate erosion and sediment supply. The findings were then compared with the previous data obtained from hydrometric stations. They included the data gathered from traditional methods of topography and lithology maps, and the land use map of Mazandaran. They provided the data to to be put into GIS techniques.Concerning remote sensing techniques, the author used landsat (TM) data along with geometric correction in band 7 for lithology, a combination of bands 4 and 3 to process NDVI, bands 2 and 5 for soil moisture, and bands 4,3, and 2 as false color composite (FCC) to study the land coverage. Analysis of the data indicated 4 t/ha/y sediment in the basin which was a little different from the data obtained from hydrometric station (3.95 t/ha/y). This showed 1.3 percent difference between the traditional methods and modem satellite techniques. It is concluded that using satellite data can improve the quality of data in inaccessible areas where there is no ground stations. Furthermore, it saves time and money.

Takhteh Soleiman region is located between 36° 30' 00" and 36° 42' 3D"N and 47° 21' 00"and 47°05' 00"E' east of Takab city on the southern part of west Azerbaijan in Iran. Geologic and climatic characteristics of Takhteh Soleiman region have provided good conditions for generating karstic features. The main carbonate rock of this region is travertine. Travertine has been generated from limestone and dolomite rocks of Cretaceous periods. Therefore, springs of different parts of this region have created travertine by solving carbonate rocks. Tectonic activities in different geologic times have made more then 85 faults in this region. These faults accompanying with cracks and joints have important potential for producing karestic features, especially, karrens in this region. Climatic conditions such as precipitation and relative moisture are important in karren generation. Among karstic features, karrens are found in different forms. The primary and superficial solution of travertine has produced karrens. Internal and external factors contributed to the production of various karrens. Precipitation is an external factor. Rock property is an internal one. From morphological point of view, karrens of this region can be classified into different types:I) Circular forms (such as: rainkarren or rainpits, pans and trittkarren).2) Linear form karrens (such as rillenkarren, solution flutes, grikes or kluftkarren).3) Polygenetic forms.Rainpits are produced by rain falling on uncovered rocks. In Takhteh Soleiman region, this type of microforms occurs on the gentle rather than steep slopes, and give them irregular, carious appearance. Such forms can be observed around Chal Tapeh doline. Pans are similar to rainpits but these are bigger than rainpits. We found this type of karren around Takhteh Soleiman Lake. Trittkarrens are mostly found around northward of Chal Tapeh Mountain and northward of Darya Tower. This type has curved headwall, flat floor, and is inclined toward downslope. Rillenkarrens developed due to channeled flow down steep slopes. Grikes were produced with concentration flow. In total, semi arid region of Takhteh Soleiman region preserved karrens from fast changing and erosion.Karrens have important role in environmental planning. Karrens have prepared the best conditions for reducing resistance of travertine against morphogenetic factors by creating pits and rills. Therefore, rocks begin to disintegration and erosion. Based on the results of this study, we found out that karrens with controlling water flow, and its concentration and infiltration caused to be effective in hydrologic cycle and feeding the under ground water table. These processes produce karestic water resources. Soil producing, displacement, and block debris creating are other results of karrens development in this region, which affect the morphology and human activities. In addition, karrens are attractive natural scenery. Thus they are interesting and attractive for tourists and groups of artists.

One of the climatological events is the occurrence of frosts. Depending on its intensity, duration and extension, it can extremely affect human activities, including agriculture, transportation, energy, bioenvironmental matters, and biological activities of animals and plants. Frosts have different elements such as beginning, end, frost season, duration, etc. Duration refers to the length of time in which the temperature falls down to zero or less than zero and continues for a while in a region. This duration is of great importance in agriculture. Since every type of plant has got a particular temperature threshold, the degrees below or above this threshold may lead to plant extinction. Therefore, the study of the duration of frosts is necessary. In addition, this type of study is indispensable and useful for construction works such as dam building, to increase safety coefficient. The purpose of this study is to calculate the duration of frosts by Delphi programming. To do this, the data related to the daily minimum temperature of four meteorology stations of Lorestan Province, i.e. Khoram-Abad, Boroujerd, Naseredin and Aligoudarz having a ten-year statistics (from 1989 to 1999) were obtained from the information bank of the National Meteorology Organization. After drawing out the frost days in desired threshold (zero and less than zero) during the statistical period, frost duration of each station was calculated and extracted, using algorithm of the aforementioned program. Then, duration periods were selectively divided into eight (three hour) classes. Their frequency percentile charts were drawn and all stations were compared to one another in three classes of 0 to 3 hours, 9 to 12 hours, and 21 to 24 hours. It was concluded that Boroujerd Station enjoys the most frost hours and, hence damages to crops were the highest in this station compared with other ones. It was further concluded that the land cover is the most influential factor in frost duration of the region, and that the height factor had no effect on the duration of frosts.

One of man's wishes is to gain access to the unceasing energy resources. Energy from fossil fuels (oil, gas, coal) will finally come to an end. It is generally accepted that the existing energy resources are not sustainable. Phenomena such as global warming cause climate change. Renewable energy technologies can make significant contribution to reducing greenhouse gases emission, acid rain and so on. Because of the massive pollution in the global environment non-polluting forms of energy such as wind are recommended. The burning of fossil fuels is the predominant anthropogenic source of air pollutants worldwide. Carbon dioxide, sulfur and nitrogen oxides threaten not only those in the immediate vicinity, but also the health of the global ecosystem. Renewable energy forms such as solar, wind, wave, geothermal, biomass etc. are used in some places particularly in developed countries. In these countries in general, environmental concerns are the driving force behind the development of renewable energy sources such as wind. While people have been using wind power for thousands of years, it has only been used to produce electricity in the last century. There is a good potential for generating wind powered electricity. There are many windy regions in our country. In this paper, wind power density is calculated by both direct methods and Weibull wind frequency distribution in some meteorological stations in 10 years time (1986-1995). We used hourly wind speed data from some synoptic stations. Researches recently show that Weibull and Rayleigh distributions are the best for calculation of cubic wind speed and have particularly more usage worldwide. So we can determine the best regions in our country for wind energy to produce electrical power. Results show that except Manjil valley, there are some regions which have high potential wind energy in Iran such as Sardasht and Mahshahr. It is very important to determine wind regime and topographical features in every station.

Due to rapid urbanization and industrial developments in recent years there have been significant changes in meteorological fields and surface characteristics of large cities. The extents of these changes depend on many parameters such as the amount of released energy, population, geographical latitude and air ventilation. One well-known example of these is that the paved roads have changed the absorbed solar energy by the surface. In order to study the effects of urbanization and land-use change in large cities on some important weather parameters the trends of temperature and wind in the large city of Tehran has been compared with that of Varamin for the last forty years. Results showed an increasing trend of minimum temperatures in Tehran compared to Varamin. The rate of change in the annual mean of minimum temperature in Tehran is four times larger than that of Varamin (0.065 versus 0.016°Cyr-I).Examining the changes of the monthly trends of temperature showed that the rate of increase is not the same for all months and decades. Maximum increase of monthly mean of minimum temperature for Tehran and Varamin is 0.116 and 0.053°Cyr-Irespectively occurred in November and minimum increase of monthly mean of minimum temperature for these two cities is 0.03 and -0.008°Cyr-1 occurred in February. The difference between the annual mean of minimum and maximum temperature for the first and last ten years was calculated and it was seen that the minimum temperature in Tehran has significantly changed during the last ten years especially in the month of November. Fifty years time series of temperature for the period of study (1951-2000) for Tehran also shows that the minimum temperature has a significant increase compared to the maximum temperature. In general the mean temperature of Tehran has increased but the rate of increase is not the same for the whole period of study. Moreover, the rate of increase in the temperature has accelerated in the second 25 years and is concurrent with urbanization and industrial development in Tehran. This increase in the temperature and especially the minimum temperature in Tehran may have destructive effects on the environment and can cause local climate change.Aerosols and pollutants existing in the air are taken away from over the city and thus green-house effects are reduced and minimum temperature is not shifted to higher values i.e. the wind plays an important role in decreasing the temperature difference between the city and the surrounding areas. Most of the times, Tehran is affected by catabatic and anabatic winds that have an important role for taking the pollutant from over the city away. Thus any decrease in the local wind speeds can increase the pollution of the city. Studying the fifty years (1951-2000) records of winds over Tehran shows a weakening of the night time winds. Considering the topographical features of Tehran, ventilation is being done only from north and east of the city. When the northerly local winds are weakened the ventilation is also lesser and there is a favorable conditions for the aerosols and pollutants to become stagnant over the city which means an increase in the minimum temperature. Moreover, the relationship between urbanization and weakening of the local night time winds over the city seems to be logical. Thus, further weakening of the local winds at night time, more increase in the minimum temperature and more polluted air are the results of further urbanization.