فصلنامه جغرافیای طبیعی
پیاپی 9 (پاییز 1389)

Soil properties can influence flood quality and have an important role on them success of flood spreading systems, because developing of flood spreading schemes in the unsuitable area form viewpoint of the soil and flood qualities may lead to desertification of such aria. Acceptance of the fact that flood spreading cause changes in soil characteristics. These changes can contain wide ranges of soil characteristics such as sand, silt, clay, gravel, and saturation percentage, TNV, Ca, Mg, Na, Infiltration, SAR and ESP. Therefore this investigation was conducted for detection of infiltration and influenced soil physical and chemical in flood spreading area of Mousian plain in southern Ilam. Sampling was based on systematic-randomized method from depths of 0-25cm; 25-50cm and 50-75cm in control, first, second and third bonds. Data analysis of variance was done. Mean comparison was based on Duncan’s Multiple Test. Results indicated that silt, clay, Ca, Na, saturation percentage and SAR in flood spreading area compared to control increased and infiltration, sand and gravel decreased. Soil texture in surface depth of control site was loamy sand and in flood spreading site was converted to sandy loam. Also, results indicated that bulk density in flood spreading site compared with control decreased. So, concluded that by entrance of flood, soil physical characteristics were changed.

In this study, data is used to identify trend of geo-spatial changes of dusty days from 16 Synoptic Stations in the West of Iran (19 Provinces). Selected weather stations have the most complete and longest periods of recorded data. First, to provide a preliminary view of the climatology of dust in the study area, yearly and monthly changes of average number of days with dust is analyzed by using charts and maps and determined that the west of Iran from the view of number of days with dust is not homogeneous region and these phenomena increases from north to south. Then, to review the trend of occurrence of these phenomenon two non-parametric statistical methods of Mann-Kendall and Sen, s Estimator was selected. The results showed that because of input data nature, the Mann-Kendall and Sen, s Estimator methods have very good performance for analyzing of dust phenomenon trend. The results of used statistical methods showed that all studied stations (except Khoy station) are a trend, but between them, only 8 cases have a significant trend (Three stations are decreased and in 5 stations are raising trend). Finally, trend type’s geographic distribution map of dusty days frequency in the study area were taken in the GIS environment and discussed about causes the formation of such trends.

Tehran is situated on and near active faults and has many urban run-downs, so it has become one of the most high risk cities in Iran. Because the markets and commercial zone located in the 12th area (the old zone of Tehran) and for ultra-zonal functions, it has become more vulnerable to earthquake risk. As the 12th area is situated near the Ray fault, if the fault activates, considering the area has 1/3 urban run-down, 80 percent of buildings and 15 to 20 percent people will be damaged. In this research the evaluative indexes of vulnerability to earthquake in the 12th area according to civil and planning is studied. Then the urban planning is done to reduce the earthquake risk by considering the texture, land use, network connections, installations and open spaces.

Larestan City is a memorial of ancient Iran the date of whose dwelling reaches over 3 thousand years ago. Its growth during this long period has encountered both ascending and descending trends. Its strategic situation has caused a considerable growth in settlement due to its adjacency to the establishments of great oil projects in Assaluyeh-Parsian and Dallan Ports on the one hand and proximity to goods input and output transportations on the other hand. Nevertheless, there seems an urgent need for the cession of lands and a change of utilization.
Of course, though such changes occur with special outcomes most of which have a negative aspect and nature, we can move towards a stable development with an understanding of the areas and analysis of dominant parameters as well as an optimal use of sciences and new technologies. It is completely clear that geography and its major branches such as geomorphology as a specialised and applied science play an important role in this process since cities are always under its influence and their formations mostly occur in an environment which is under the function of geomorphologic phenomena. Moreover, cities along with their increasing developments encompass different geomorphologic and topographic terrains. Thus, there is a possibility that cities take the influence of geomorphologic phenomena and other problems due to them more than before. In this confrontation, if we do not observe some necessary points and principles, a disturbance occurs in morph dynamic balance and great dangers threaten cities. It is even probable that sometimes the severity of such perils and disasters reach an extent that they cannot be compensated. Such phenomena as floods and river overflows, different types of mountain slope movements, earthquake consequences, etc which continually threaten cities are of those factors depending on geomorphology directly or indirectly. In this scope, we have tried to identify preventing geomorphologic factors for this city which is considered as an important commercial-cultural centre located in the southern part of Iran.

Routing methods has an important role in flood forecasting, reservoir design, river training, etc. Flood-routing techniques are utilized to estimate the stages, or rates of flow, in order to predict flood wave propagation along river reaches. There is a multitude of flow routing models which can be broadly classified into hydrologic and hydraulic models. The hydraulic techniques are complex and often difficult to implement and in practical applications, the hydrological routing methods are relatively simple to implement and reasonably accurate. In this research some hydrologic approaches including Muskingum, Convex and modified Att-Kin methods were applied to flood routing. 26 flood events have been used to evaluation of the methods in the Harmaleh- Bamdezh reach that was situated in the Dez River. Some goodness of fit criteria such as RMSE, Coefficient of Correlation and Coefficient of efficiency used to estimation of methods accuracy. Visual comparisons show that RMSE is the best goodness of fit criterion. The results show that the graphical approach is most appropriate method for determining Convex and Muskingum parameters. It can be stated that Convex, Muskingum, Modified Att-Kin and Muskingum-Conge methods have the most accurate results, respectively. However, the average discharge or half of peak discharge shows better results, but in general, selection of different types of flow having no significant effect on model efficiency.

With regards to natural disasters that have occurred in the past decades which have affected human beings¡ the number and Frequency of drought phenomenon has proven to be the worst by far. In order to convert and consider the drought phenomenon in a quantitative manner, various indices are available. The following research uses and studies SIAP (Standard Index Annual precipitation), PN (Percent of Normal) and RAI (Rainfall Anomaly Index) in 2 synoptic stations in Abadan and Dezful with in a statistical period of 45 years (1961-2005).Results obtained reveals that drought frequency and duration with various degrees was shown greater in Abadan than Dezful. According to the SIAP and RAI indices intensive drought frequency in Dezful more than Abadan and only in PN index intensive drought frequency in Abadan station more than Dezful. also in three mentioned indices the most intensive drought in 1964 occurred at Dezful station and in 1964¡1973 and 2005 at Abadan station.

Instability of the slopes including the risk of landslides, are major hazards due to the nature of the mountainous regions with great abundance. Of course, if this risk be accompanied with other risks such as earthquakes and floods produce a wider range of severity. Binalood mountainous zone is due to expanded shale and Hyalite formation, sensitive and high intensity land use and other anthropogenic activities have a particular sensitivity of landslide hazards. The Frizzy basin with large area in the context of two different types of litho logy Hyalite and lime has a special situation. In this article we use AHP model and fuzzy logic to landslide risk assessment in the Frizzy basin. Total of 15 criteria associated with the occurrence of major landslide phenomenon was analyzed. Each of these measures as a factor map, separately classifieds and statistical methods were rate. Production of final map for landslide hazard zonation in the basin firstly showed that about 68 percent of the total area of the basin has critical and medium landslide hazard. Secondly, has been determined that the Hyalite variable have high significant (R2=0.835), compared to other formations in the basin and has a stronger correlation with the dependent variable of landslide. The GPS data have been determined a high level of compliance with the used technique based on fuzzy logic. Also the model application demonstrates a good suitability for slopes instability zoning in mountainous basins.

Various factors are involved in choosing the location, establishment and place of residence in rural change. Among environmental factors, human habitat and litter the ground as construction activity has an important role in every land .The Gilan province with focus to specific geographical location and natural environmental conditions such as weather conditions) rainfall, humidity (vegetation) pasture, jungle, (mountain, sea and ... Among the other provinces of the Iran has most affected in the process of rural transformation Settlements? Astara city as the most northwestern city of Gilan province due to this particular environmental feature is reason for researchers to changes settlements villages to study the city. This research is using descriptive -analyzed .Library studies and field observations according to topographic maps 1:50000 Geology, 1:10000 and 1:250000 and aerial photos and satellite images has been done .The results showed that the mechanism due to environmental factors and processes, natural beauty of landscapes such as city and beach) Sibly villages, Darband (green plains)Sheikh Mahale villages, Virmoni (A plain semi -mountain base) Syadlr village, Baharestan (and finally the last level but Theurgist elevation mountain area, forest pasture north of the country) Heyran villages, Agh masjed of course, along with all the power and natural potential mentioned above, research area is bordered with the Azerbaijan country .In all these cases are in addition to changes affecting Settlements rural lifestyle on the structure of economic, social and cultural effects of the residents .Building materials used in buildings and its architecture with other regions of Iran is different. Decades, changes in social, economic and cultural past are different Iran’s other regions; especially, after the collapse of the Soviet Union and a variety of natural environment. This has caused a good model and improved rural housing Astara city with different Iran’s other regions.