GEOGRAPHICAL RESEARCH QUARTERLY
Year:2007 | Volume:39 | Issue:60|Papers Count:15

In this study, with the aim of evaluation of effect of geomorphological land forms on flood properties, the GIUH theory has been investigated in Kangir (Eyvan) catchment. The geomorpholgical instantaneous unit hydrograph model simulates and predicts the flood events for ungauged catchments by means of geomorphological characteristics. For testing the GIUH theory in Kangir watershed ,at first, quantitative geomorphological properties like bifurcation ratio (RB), area ratio (RA), length ratio(RL), length of highest order stream (LW) and then rainfall-runoff data and velocity- discharge equations were extracted and thereby QP (peak discharge) and TP (time to peak) were calculated for 5 storm events. The comparison of observed and estimated values represents that calculated QP values are, approximately, close to observed QP values. This study reveals that the performance of GIUH method in predicting QP values is relatively appropriate but its performance in predicting complete shape of hydrographs is inadequate. This study also reveals that geomorphological land forms such as karstic and tectonic holes and joints decrease the runoff velocity and coefficient and therefore affect the QP and TP values. Also, complex relationships between karstic landforms and surface runoff and groundwater as well as rainfall characteristics, have resulted in low performance and lack of distinct trend of GIUH model in predicting flood. Result of this study shows that QP and TP values, also, are affected by variations of rainfall intensity in each storm event.

Iran Plateau is located in a convergent zone, between Arabian and Eurasia plates, so that, tectonically it is an active area. Occurrence of permanent and damaging earthquakes prove this activity. Disastrous Barn earthquake of moment magnitude (Mw) 6.6 occurred on December 26.2003 and caused widespread damages. At first it was suggested that the rupturing of Barn active fault (striking north - northwest) caused this earthquake, but later studies showed that this earthquake is the result of a concealed fault activity that striking under the town of Barn and parallel to the Barn active fault. This fault is known as a branch of Barn fault. In this study in addition to reviewing the application of remote sensing, especially thermal remote sensing in seismic studies, the relationship between near surface geological formations and amplification of shaking during the earthquake, the geomorphologic evidences of tectonic activity in the barn area, and geomorphology and geometry of barn active fault is studied. This study shows that a 15 - 20 m high fault scarp, deflected steams, deep gullies and mass movements altogether are the result of tectonic processes in the area. Regarding these evidences, the active faults in the area may cause other earthquakes in the future.

The studies done by geomorphologists in the domain of environmental systems result in an understanding of theoretical frameworks which account for the structural and behavioral patterns of such systems, and whose codification and interpretation hold an irresistible fascination for researches; the analysis of the pattern in question, which sometimes enabled us to make contingent predications, calls for an unsophisticated style so that we can put across the concepts involved in the process. When designing a model, the point worth considering is that it is within a theoretical framework derived from our own impression of the external world that we evaluate a given phenomenon. Although efforts have been made to judge the accuracy and efficiency of a model by its correspondence to experimental reality, yet we must not ignore the fact that many existing models are purly conceptual in nature n that they are not realizable in the outside world; it is customary for the majority if researchers to base their proposed models on analogues borrowed from field not directly related to the area of their investigation. For instance, when hydrologists try to analogize the flow of a river to that of electricity, they have used an already - defined reality, thus interpreting the behavior of water - the phenomenon understudy in terms of a model of electric current. This, of course, is a common procedure and no one can find fault with it. Nonetheless, what the present paper has set out to address is rather the epistomologcal frameworks which are involved in condifying models, and which provide us with varied and conflicting principles. in other words this paper is meant to answer this question: if epistemological frameworks undergo a change, what impact will this have on the designing of a model? Put differently, what relationship can be said to hold between specific models and the geomorphological frameworks employed for the purpose?. The results obtained from this paper, which is founded on a research project conducted at Isfahan University, show that we can, on the basis of theoretical views prevailing in geomorphology (such as the Division, the catastophistic and the systemic paradigms), come up with specific models and interpret each in unequivocal terms. In other words, the current situation in geomorphology is that models are primarily a function of the particular epistemological and theoretical stance adopted by a researcher in evaluating phenomena, and only secondarily a means whereby facts are accounted for.

The term "nivation" is used to describe those geomorphologic processes that, because of the permanent presence or longer duration of snow, come into existence in some place and they may be appealed in order to justify the special manner of formation of some landforms. At the east slope of Sabalan, because of its geographical direction, the greatness of height, direction of the prevalent wind, and yearly and daily temperature fluctuation, snow has acted as a geomorphic factor and it plays a basic and primary role in creating and developing most forms and phenomenon of geomorphology. Considering the importance of such changes in the said area and in order to account to numerous questions about the causes and the special manner of formation of some shapes and occurrences of some phenomenon at the slope surfaces, in the present article it has been attempted to study about the nivation processes, forms related with nivation, and generally the role of nival processes in changing the appearance of Sabalan east slope.

This paper analyzes the spatial and synoptic patterns of the 20th October 2003 Flood in the 'Mazandaran and Gilan provinces using the air maps and hourly meteorological data. In this way we consider geographic conditions and physical characteristics of the southern coastal areas of the Caspian Sea and using daily and hourly (3 hours interval) data of each synoptic station. Duringa 8 daysperiod (14th- 21th October 2003) the Synoptic patterns arrangement and their displacements were investigated in the air maps include surface, 850, 700 and 500 Hectopascal levels. The result show that present of a deep trough in the northeast of Europe and it's axis orientation on the Caspian sea have been cause to polar air (C.P) advection from northern-latitudes on it. Also it has been amplified by present of a transition anti-cyclone with northwest-south orientation in the west of the trough and frontal cyclone in the east of the trough and because of to have a similar orientation between western anti-cyclone rotation and eastern part of the ahead trough cyclone. On the other hand vorticity has been amplified by considerable meridional motion of the middle level troposphere flows. Simultaneity with these factors and also intensification of maximum temperature difference between the polar cold air and Caspian sea water in this season are factors that causing the mentioned intense rainfall.

Evaporitic (diapiric) bodies of the Garmsar-Lasjerd area have been investigated. Halokinesis is the trigger of diapirism but, early Pliocene orogenic phase, has been distinguished as an external trigger to diapiric development. On the other hand, salt structures of investigation area that have been emergent by fault generally, classified to four types: Salt stocks, Salt welts, Salt walls, Salt tongues.

Landsat7 Scan Line Corrector (SLC) malfunctioning results in lack of data in some part of images. Different methods for replacement of these missing data are suggested. Depending on the application, these methods have different validities. Most of these methods are statistical and are not applicable to some application. Assessment of Evapo-Transpiration (ET), using SEBAL algorithm and satellite imageries in the regions not so vast is an example of this application. In the presented method, the NDVI data from LIS-III sensor will be used for replacement of the missing ETM+ data. In this method for correct comparison between data from these two sensors, use has been made from resampling pixels of 1 by 1 meter. This could be done once in a region of an image as a prototype. Then the resulting algorithm could be used for the replacement of missing data in the rest of image.

Drought is a creeping natural hazard, which is caused by short raining and humidity deficit. When a drought occurs dramatic social, economic and environmental effects are inevitable. Because of the vast impact of drought, it is essential to be monitored timely and spatially. Specifically, SPI was used as drought monitoring Index, and for zoning proposes four models (namely: Regression, Kriging, Splin and IDW) were employed. We studied drought periods in Khorasan using 33 years climatic data (1968- 2000). The study showed that during last years of the 33.years period recurring drought has been more frequent and also it lasted longer than the early years. However, the severity of drought has been reduced. It can be seen that the duration and severity of drought is more in the sought area than in the central and northern parts of the province. We used different methods to interpolate drought data for spatial analysis using Geographic Information Systems (GIS). We then concluded that Kriging method is suitable for this analysis this method was used for zoning drought over Khorasan province and produced zoning map of drought severity for different time scales. As a conclusion, Kriging was approved as the best zoning model among the four Models, due to its performance (Regression coefficient= 0.71, MDE=-1.1 and MAE= 0.95).

Tabriz is located on vast and gentle plain, in the east of Urmieh Lake. It limited by different units of topography, lithology and geomorphology. In recently decades, physical development of city, has require, extent and repair of old roads and build of highways on the around of city. Unfortunately, the hurried performance of the development programs (as extention of transportation networks) and the impacts of human activities intensify activities of the morphogenic systems and cause the geomorphic phenomena as mass movements. This paper, using a Satellite image (Landsat ETM) and geographic information system it emphasis with role of human activities, intensity of morphogenic factors and occurring different kinds of mass movement along roads and highways at the Tabriz city; The results, of this study, show that the landslides of Tabriz city are related with human factors (change of landuse, excavation of the base of slope).

An increase or decrease in the precipitation intensity compared to the normal conditions may lead to a higher risk of floods or a higher probability of incidence of drought. Knowledge of the probability distribution of precipitation is essential to the management of water resources. Such knowledge can be achieved using dynamical or statistical approaches. In the present article the probabilities of different drought states (very dry, dry, semidry, normal, semi wet, wet, and very wet) are calculated based on the annual and seasonal precipitation amounts in Ghazvin using the normal distribution and Markov chain methods. The results indicate that the probabilities of drought/wet states based on annual and seasonal precipitation data as calculated using the two methods are comparable. The statistical evaluation of the results using X2, however, reveals that the Markov chain method is superior to the normal distribution.

Large E-W oriented, Neogene-Quatrnary structural depression, up to about 50 km long and 7.5 km wide, have developed between two mountainous chain (Mishow-Dagh on the south and Ghareh-Dagh on the north) on the northwest of Iran. The depression are now, deposited by Quaternary sediments as alluvial fans that lined along mountain fronts. Northern Misho fault is an E-W trending fault that is elongated on northern slope of Misho-Dagh chain and bound the southern boundary of basin. Investigation of the role of tectonic activities on basin formation and rate of this activity by analysis of sedimentary-Geomorphologic dates are the main goals of this paper. For this, geophysic and geoelectric sections and geomorphologic effects investigated on the base of field studies and topographic and geologic map analysis. The papers collect the information's about Quaternary tectonic activities in study area. Results showed that in spite of success of marand plain and their adjacent mountains from high tectonic dynamics, present landscape of those mainly resulted from the last and especially Quaternary tectonic activities. However, topographic and geomorphologic aspect of Marand plain severely affected from Quaternary tectonic activities and this factor plaied the main role in Marand extentional basin formation.

In this research the data relating to Sea Level Pressure (SLP) Oscillations index in North Atlantic and annual precipitation have been studied for East Azerbaijan Province in a time period of 43 years aiming at the calculation of coefficient of correlation and calculation of wet years and droughts. The main methodology being used in this research is the analytical statistics (Pearson and Spearman correlation coefficient methods, analysis of linear and polynomial trend components). The results of this study indicate that is being weak negative correlation (but meaningfully specially in intensive wet years and droughts) between annual precipitation and NAO index in Tabriz, Ahar and Jolfa stations.

The act of melting-freezing, temperatures difference at day and night on altitude, tectonical pressure and existence fissures and crevices in stones, to bring about a favorable base for weathering processes; At continually weathering processes ,in the course of time, deposited debris at footslopes, in valleys and in course of 2 and 3 orders of streams These debris, gradually by differences factors, for example, the occurrence of flood and Human activity in sensible parts of region, moving and transporting by streams and rivers to long distances. The debris flows in study area, have special characterizes, because existence topographical factors and morphogenes. The length of debris flows in the study area, longer than its width .This rate in difference of altitudes is 1:3 to 1:5. This ratio in old debris flows (near of Kutler and Yengeje village) is great and in present debris flows (everywhere of the study area), which often to be formed on Oligocene's granites, is little. The results of quantities investigation and statistical analysis, show that, the role of the depth of channels, on to be growth of the length of debris cones is remarkable. The study on paleoc1imaand deep channels on old debris flow, show that at Holocene age, increased the rate of debris. These debris and deep channels are results of spar vegetation covers, storm events, the occurrence of melts of snow on slope and the occurrence of large floods.

Quantitative measurements have allowed geomorphologists to objectively compare landforms and calculate geomorphic indices that for identifying a particular characteristic of the area; for example, its level of tectonic activity. The indices; the hypsometric curve (Hc) and hypsometric integral (Hi) are related to the degree of dissection of a landscape. Drainage-basin asymmetry is defined in terms of the Asymmetry Factor (AF) as well as the transverse Topography symmetry Factor (T). Both of these are valuable in rapid evaluation of drainage basin to determine if tectonic tilt may have been occurred. The stream length-gradient index (SL) is a useful tool for studying tectonic geomorphology; high values commonly are originated where stream cross resistant rock or where stream cross active structure. Mountain-front sinuosity (Smf) is an index that reflects the balance between erosion forces and tectonics forces at a mountain front. In general, active mountain fronts have relatively low values of sinuosity. The ratio of valley-floor with to valley height (VF) differentiates between broad floored canyons and V-shaped valleys. Low values of VF are associated with active tectonic. In this article seven indices of relative tectonic activity are used and evaluated for studying and analysis dynamic sequential process in earth shaping plus landscape and is used to classify darakeh basin for relative tectonic activity. Commonly, it is useful to classify area as being very active, moderately active, or in active. Such basic classification is useful in delineating area where more detailed field studies will identify active structure and calculate rate of active tectonic processes. Processing Geomorphic Indices of Active Tectonics in Darakeh Basin indicate that this basin is being a tectonic active region in Iran. Finally; darakeh basin is classified to the stream length-gradientindex (SL).