فصلنامه پژوهش های جغرافیای طبیعی
پیاپی 82 (زمستان 1391)

Alluvial fans in Iran portray the extensive records of occupation by prehistoric human. In fact, alluvial fan had supplied good condition for the settlement of prehistoric human. Settlement pattern and human-environment interactions over this landform have been depended to the kind of sediments and distribution of braided rivers on the fans. Shifts in settlement patterns over these landforms are a subject that many archaeologist and geoarchaeologist have studied and researched it. Alluvial fan always becomes a landform that attracts human as a location for living. Fresh water and appropriate soil for drinking, cultivation, making pottery, making mud-brick and other activities are easily available for settlers without a need to high technology. In foot hill of Alborz and Zagros Mountains there are numerous alluvial fans and prehistoric settlements as well as many new towns and villages which are located over these landforms. The study area is located in Tehran and Qazvin plains, on the Jajroud and Hajiarab alluvial fans. Jajroud alluvial fan is located at the south west of Tehran. There are many prehistoric mound on this fan that belongs to Neolithic to Iron Age. Also in Hajiarab alluvial fan there are three sites that form a cluster that putative to Sagzabad Cluster including Tepe Zagheh, Tepe Ghabristan and Tepe Sagzabad located two kilometer for from each other. In this research SRTM images were used for producing the map of mounds position. For sediment analysis three trenches near to Sagzabad cluster were dug up to 10 meter deep. Over the Jajroud alluvial fan we considered artificial trench that was made for mud-brick inquiries as well as information of previous excavation and digging the new trench. In order to find new and old braided river in alluvial fan we used aerial photo of 1:55000 (1935) and 1:20000 (1967) as well as IRS satellite images (year 2008). For preparation of graphic logs and different maps and figures, ArcGIS and Freehand soft wares were used for drawing and manipulating the maps and figures. Results showed that in both alluvial fans, tells were located at the middle and distal of the fans, In fact fine sediment in lower part of fans is a good source for pottery and cultivation and making mud brick. In Kahrizak area, lots of Kilns for making the pottery showed vast industrial activities because of appropriate soil and water. Sedimentary records on graphic logs show a very thick of fine sediments that show a sheet flow with low energy in these sites. Also in both of two fans there was fluvial sediment with coarser sediment existed near the settlements tell. It’s obvious that in Qazvin plain these fluvial sediments are coarser with higher energy perhaps because of existing torrential rain and short distance between basin and alluvial fan. In Qazvin plain fluvial and coarse sediments in 5.5 meter deep showed a high energy fluvial system. If we accepted the sedimentation rate that mentioned by Schmidt (Schmidt et al, 2011) we reach to date of abandonment of settlement (Ghabristan). Therefore we concluded that the fluvial environmental condition forced people to leave the tell. Also fan head trenching by tectonic activities and climatic changes keeps the river 12 to 15 meter deep in Jajroud alluvial fan and 8 to 9 meter deep in Hajiarab alluvial fan. It finally led people to establish their tells in the lower part of alluvial fans. In fact prehistoric human couldn’t bring up water from such deep trench and they selected the lower part of fans for living. Interpretation of aerial photos also showed the changing and migration of braided river in both two fans especially Sagzabad cluster. In fact interdisciplinary approaches in archaeological research have a major role to determination of human-environmental interactions and social-economic activities of prehistoric people. In this research we tried to establish a framework for assessing the effect of alluvial fans on distribution pattern of settlements in Tehran and Qazvin plains. The study showed that in spite of this fact that these landforms create good condition for site formation but in some cases a different condition was shown due to active dynamism of themselves that led the settlement to shift over the fans. In fact High energy fluvial environment sometimes treated the settlement mound in alluvial fans. Future studies with precise sedimentology and chronological data could reveal more information about for mation of settlement and even subsistence practices as well as socio-economic and cultural situations in prehistoric era.

Access to agricultural information and statistics, is a prerequisite for many agricultural activities. Crop performance is measured and reported as a point data. While this parameter is a random and dynamic variable and due to the spatial variability of crop yields, it is obviously necessary to estimate of yield. Wheat is the oldest cultivated crops in different parts of the world, which is used to produce grain for bread, animal feed and industrial use. Prediction of wheat performance needs data in terms of location, amount and distribution in a given geographical area. Selected of predicting correct method of is essential and important in crop management. In recent years with the growth of science and computer technology and software development models have been used in the management. The model is effective and accurate method in overcoming the limitations and errors of point measurements. The main condition for the success of the model is to select the appropriate method based on factors. In this study, two methods were used for modeling: geostatistical method and artificial neural networks (ANN). Methods of geostatistical, due to the spatial correlation of data and artificial neural networks due to the use of input and output patterns are important as a powerful tool in forecasting. The study area is Razavi Khorasan Province that located in north-east country and at latitudes between 33O and 30' to 37O and 41' north and longitude 56O 19' to 61O and 18' east. This province area is 127 thousand kilometers with 65300 hectares agricultural land. Approximately 36500 hectares of agricultural land under cultivation is irrigated and dry wheat. In this study, we used wheat yield data from 17 cities with at least 26 years of statistics. Choice reason of these cities was according to the statistical period, the appropriate spatial distribution and no need to reconstruct the data. Wheat from terms of acreage and production rate is the most important agricultural products of the country from the economic point of view. The purpose of this study was to select the most appropriate method in estimating the spatial distribution of irrigated and dry wheat yield in Razavi Khorasan region. For this purpose geostatistics methods of ordinary kriging, simple kriging and universal kriging and ANN approach were applied. In this regard latitude and longitude information of 17 cities were used as input both methods (Geostatistic and artificial neural networks) and annual yield measurements as output. In section of neural network, learning rule of levenberge marqoate, momentum and conjugate gradient with back propagation algorithm and activation function of tangent and sigmoid for hidden layer and output layer were used. Finally, selection of the appropriate method was based on Wilmot index. Results showed that among the methods of geostatistics, simple kriging with circular model with NRMSE=0.120 and ordinary kriging with exponential model with NRMSE=0.348 was suitable to forecast wheat yield. In addition, results showed that the ANN approach with three layers consisting of two neurons in input layer, four neurons in the middle layer and one neuron in output layer had required accuracy in between various structures implemented for predicting wheat yield. Comparison of ANN and geostatistical showed that ANN capability is more than kriging method. The ANN results showed that artificial neural network model, as an independent estimate, can predict wheat yield variables in all 17 cities. Also, comparison of the results of both methods with Willmot index showed the accurately of ANN in prediction of dry wheat yield (81%) and irrigated wheat yield (65%). While in geostatistical method, Wilmot index for predicting dry wheat yield and irrigated wheat yield was 53% and 50%, respectively. In general it can be concluded that the ANN approach with combining latitude and longitude can forecast irrigated and dry wheat yield with sufficient accuracy. In this study, the statistical methods and artificial neural network were used to estimate the spatial distribution of irrigated and dry wheat yield. In both methods latitude and longitude information were used as input data. The results of this study showed the effects of latitude and longitude as independent variables in estimating the wheat yield of a regional. Also, it was found that the ANN is superior to kriging method and this method corroborate the nonlinear relationship between latitude and longitude value to wheat yield.

The Landslide dams are the natural result of blocking of river channels by the mass movements. The effective factors of landslide dam formation include: the shape of valley in relation with the geometry, volume of debris, the characteristics of landslide debris, river discharge. The dam lakes are formed by landslide in the mountain valleys of Zagros and Alborz. Behind these dams, sediments were deposited simultaneous formation of the lake. After destruction of dams, several terraces are formed along the valleys. Investigation of the sequences, strata and streams are proxies to determine the tectonically and climatically changes of the past. The lake terraces can be formed by erosion of coastline, sediment accumulation, or a combination of these processes. These landforms are formed in various points of Iran. In the study area, blockage of Saymarreh River by Saymarreh landslide led to formation of a lake behind the landslide in the past. Primary field investigation revealed the several lakes and river terraces along the Saymarreh and Kahskan riverbanks and in the upstream Saymarreh landslide mass. The purpose of this study is the determination of the extent and sequence of these terraces and relation of their morphometric characteristics with the process of formation of large Saymarreh landslide. The used method in this research is the analysis of data that accrued based on fieldwork study. Therefore, we used the satellite images, topographic and geologic maps, SRTM10m and ArcGIS software. Accordingly, we measured height and distance of the terraces from active riverbed and their boundaries and area. Then, morphometry of these landforms was analyzed through drawing the cross sections, profiles and integrating sedimentary data. Saymarreh landslide has a large landslide mass in which length is more than 15×20 Kms; its volume is more than 40Gm3, which had occurred along the Saymarreh River in the southeast of Ilam province. The evidence of this survey showed that a strong earthquake can be occurred, joining Saymarreh and Kashkan rivers in front of this landslide and their undercutting and excavating the base of landslide are among the main causes of its instability. According to the evidence after the landslide, the following subsequences occurred: first, because of the flow of the landslide mass, the course of Kashkan River was changed; second, in the process of obstruction of Saymarreh and Kashkan rivers and formation of landslide dams, the little width of the valley (7.25 kms), the great volume of the landslide mass, the intensity of the landslide and the size of the landslide sediments and the little shear strength of Saymarreh river are the most important factors of formation a vast lake behind this landslide. The great volume of extant lake sediments and their sequences showed a large and stable lake environment for a long time. The first depletion canal had been excavated next to Helosh and Chenareh buried anticlines. This phenomenon is derived from the function of Helosh and Chenareh anticline's that had performed like a dam and caused compaction, a rise in height, and the stability of landslide sediments against the lake water. The research findings show that the depletion of the lake in the course of Saymarreh River had occurred during several stages. The comparison of the height of river and lake terraces shows a direct relation between them. The comparison of terrace height first (635m), second (595m), third (585m) and forth (575) with height of incision surface first (610-640m), second (590-610), third (570-590m) and forth (550-570m) respectively indicated that the formation of each terrace surface are related to cutting cycle of the landslide mass by Saymarreh river. By decreasing base level as a result of excavating landslide mass, the Saymarreh river had continued excavating lake bed until it had reached its old bed and formed a terrace surface. After this stage and cutting of lake sediments and approaching its old bottom, it started sedimenting alluvial at the lake terrace surface. This process had occurred many times and led in the formation of several terrace upstream this landslide mass. Of course, the thickness and volume of the terrace is not same. This difference is the result of the height and volume of the landslide dam and the stability of the lakes according to the chronological order. Therefore, reoverlaying new lake sediments on the old lake and river sediments (rhythmic sequence) are due to forming Lake Environment again. The findings of surveying sediments sequence of lake terraces indicate that the large Saymarreh landslide had been unstable during some stages (3-4 stages). Great extent and thickness of the older lake terraces indicate that the first landslide had a greater extent and the volume of sediments indicates its longer stability. The Less thickness of the new lake terrace and their overlaying on the old sediments indicate that the later landslides had less volume and extent, and a shorter stability.

Climate as a complex system is changing due to an increase in atmospheric concentration of greenhouse gases produced by human activities, according to IPCC reports, leading to global warming. Assessing the climatic characteristics and identifying the climatic elements and parameters of a region can have a major role in land use planning and the management of that region. Variations in the component of temperature, as one of the most important climatic elements in the North West region of Iran, with significant spatial and temporal fluctuations, have a major role in the environmental management, road transportations, agriculture farming. So dealing with climatic change requires strategies for future adaptation. One of the most common methods for assessing the future climate is using the general atmosphere circulation models. A group of these models provide useful information about the atmosphere's reaction to the increase in the concentration of greenhouse gases. Considering the low spatial clarity of the general atmosphere circulation models and the need for powerful software as well as the great amount of time that dynamic downscaling consumes, the statistical models were taken into consideration. These models change the general circulation data from large scales to smaller ones and use the output of GCM models and other special scenarios of the model that generate meteorological data.The most important advantages of these models include their inexpensive, high speed and capability of being used without the need of supercomputers. One of these statistical models is LARS-WG that we used in this paper to simulate tempreture for future in North West of Iran. The method of this research consists of two fundamental stages: first, downscaling the GCM data under the propagation scenario and the second step involves the clustering the daily temperature based on the past (1961-1990) and future periods (2011-2040) and comparison between these two periods. In the first stage of this research, for the statistical downscaling of the atmosphere general circulation model HadCM3 data based on the A1 scenario, the LARS-WG model, the 5.11 version was used, as one of the most famous models in generating random weather data. In this article, for evaluating the validation of the LARS-WG model in reproducing the meteorological data of temperature as the main component, data of the seven synoptic stations of Tabriz, Ardebil, Kermanshah, Hamedan, Sanandaj, Oroomieh, and Qazvin, in the North West of Iran for a 20-year period 1989-2008 were used. Note that by using statistics of the determination coefficient (R2), Root Mean Square Error (RMSE) and the Mean of Absolute Error (MAE), data evaluation produced by the model and the real data (observations) was done in the 1980-2008 period. In the second part of the research, the method of comparison of daily temperature components in different clusters, and based on the clustering approach within 6 conventional clusters for all the stations and the studied periods, was performed. Although the comparison of monthly data for the two studied periods, July and January as the hottest and coldest months of the year respectively, had no changes in ranking compared with other months: the total average temperature of Jan has been changed -1.27 °C for the observational period and -0.86 °C for the future, on the other hand, the average of time series of the observational data were 24.2°C in July which will reach 25.12°C with the occurrence of climate change. Evaluations show that as a result of global warming, the maximum increase in the average annual temperature is seen 2.30°C for Ardebil and the minimum 0.22°C for Oroomeih. The results show that based on the statistical period of the past decades, the maximum average annual temperature is observed 13.94°C for Qazvin and the minimum 9.05°C for Ardebil. Although these conditions will change in the future and the warmest station will be Kermanshah, with the average annual temperature 15.64°C, it will be Ardebil station that will be presented as the coldest station with the average of 11.35°C. Among the results of this research, the overall mean annual temperature increase for 7 studied stations was at the rate 0.94° C for the predicted years compared to the basic period 1961-1990. In evaluating the frequency of the thermal thresholds of the observational period which was done based on the scale of the six clusters, in most of studied stations, the highest frequency of days belongs to the sixth cluster. But the simulated data show the maximum concentration of the thermal data frequency for the first cluster in the case of Qazvin, Hamedan, Sanandaj, Oroomeih, and Tabriz stations.In general, comparison between different stations in this area shows that the thermal thresholds of two stations namely Ardebil (in the clusters two to six), Oroomeih (First to Six) and Kermanshah (the clusters two to four) will be increased, while in other cases the thermal threshold will be decreased in the next 30 years. Therefore, one of the practical results of this research is its application in the agriculture. Based on the results of this research, we can conclude that the length of the crop growth period will be increased due to an increase in threshold and extension of warm periods. But it is obvious that the outcomes of warming and the lengthening of the growth season will have more serious consequences like the increase in water demand due to longer warm season, evaporation and perspiration increase in the growth of some crops and sometimes vegetation water stress, changing the planting time, development and disorder in adjustment of North West region.

Tectonic geomorphology is a relatively new and interdisciplinary field between structural geology/tectonics and Earth surface processes. The most common goal of tectonic geomorphology research is to use Quaternary landforms and stratigraphy to infer the nature, patterns, rates, and history of near-surface tectonic processes. Tectonic geomorphology provides a whole set of tools for deciphering the most recent activity on live structures (Keller and Pinter 2002; Pinter 1996). These tools kit is a quantitative measure of neotectonics landscapes giving useful information about neotectonic activities. In this work, Geomorphologic indices include: stream length-gradient index (SL), drainage basin asymmetry (Af), hypsometric integral (Hi), ratio of valley-floor width to valley height (Vf), index of drainage basin shape (Bs), and index of mountain front sinuosity (Smf). In this study fault density (Fd) index is investigated as one of the most important geomorphologic indices. The study area is located between the southern central Alborz and northern central Iran structural zone boundaries, two different tectonic active zones which are an ideal location to test new model (SAW). In this research, in order to increase the accuracy of calculating geomorphological indices in Habble Rud basin extract digital elevation model (DEM) by resolution and accuracy of 10 meters, from topographic maps at the scale of 1:25000 was used. Also, we used geologic maps of Tehran and Semnan (1:250000), Garmsar and Damavand (1:100000), satellite imagery include ASTER (2007), Landsat ETM (2002), TM (1988) and topographic maps (1:50000), 1:25000 shape files. The various indices were divided into three classes: form class one being high activity to class three being low activity. We set geomorphic indices in a matrix table and got values based on characteristics and field observations. The approach of this paper is a quantitative method based on local characteristics concentrating to distinguish the role of neotectonics on evaluation of quaternary landforms, so we used a simple additive weighting model (SAW) to accumulate variables and they are ranked. Some studies used a combination of two indexes (Smf and Vf) or Length gradient river to provide semi-quantitative information of relative degree of active tectonics. El Hamduni(2008) studied Izbor River basin using 6 indices including: stream length-gradient index (SL), drainage basin asymmetry (Af), hypsometric integral (Hi), ratio of valley-floor width to valley height (Vf), index of drainage basin shape (Bs) and index of mountain front sinuosity (Smf). He divides them into four classes from relatively low to highest tectonic activity. Due to the multitude variables, the technique in this study is a simple model (SAW) through GIS technique. In this method, Habble Rud basin was selected and divided into 22 sub basins, after calculating and classification of 7 tectonic geomorphology indices, in first place, all indexes were ranked and set in matrix table giving values to the index. Faults are one of the important tectonics phenomena; therefore we calculate the fault density as an index in the model. The classification used in this paper for each geomorphic index is calculated from El Hamdouni's method. Within the study area, about 1% (378 km2) belong to class 1 (very high relative tectonic activity) as measured by SAW; 48.3% (1683.6km2) shows high relative tectonic activity as measured by SAW (class 2); 37.4% (1300.9km2) moderate values of tectonic activity in terms of SAW (class 3); and 3.4% (119.6km2) belong to the lowest values of relative tectonic activity (class 4) based upon SAW. Thus, we can conclude that 1/3 of the study area is classified into classes 2 or 1 of high to very high tectonic activity in terms of the apparent geomorphic response. The study area is located between the southern Alborz and Central Iran structural zones, characterizing by active structural zone. Because of the lack of chronology of Quaternary units, Vertical rates of active tectonics in southern Alborz are unknown. N-S shortening across central Alborz has been evaluated to 5± 2mm/yr using GPS measurements (Vernant et al. 2004). The Mosha fault as one of the most active faults in this region causes several earthquakes greater than MS = 6.5 (Berberian and Yeats 2001). One of the greatest shocks (Ms~ 7.6) occurred in the Garmsar fault during the third century BC and in 743AD. Ashtari (2005) indicated a concentration of earthquake activities located north of the Garmsar and Mosha faults. Finally, the result of this method has been linked to seismic map showing concentration of seismic activity around of Garmsar fault. The descriptions of tectonic landforms corresponded to the classification of SAW of moderate to high tectonic activity very well. As an advantage of this method relative to the IAT, those indices is adapted to the characteristics of the studied area. Geomorphic indices of active tectonics are useful tools to analyze the influence of active tectonics. These indices have the advantage of being calculated using GIS and remote sensing packages over large areas as accurate tool to identify geomorphic anomalies related to active tectonics. The SAW result showed that the most active part of Habble Rud is Garmsar fault. Since the weighting in this model is based on natural characteristics, so it can be applied in different areas with different characteristics.

Iran is a dry and semidry country with precipitation less than one- fourth of the world because Iran is located in the vicinity of subtropical high pressure and is affected by such climate. Short time precipitation and falling as severe shower are climate patterns of this area. Because of topography condition and geography situation, the center of Iran has less precipitation than the other parts. Most of the systems that enter to Iran from south and south west lose more precipitation in the windward of Zagros. Sometimes these systems are invigorated after passing on mountain in some synoptic condition and cause heavy shower. Isfahan province with 10.6 million hectare area is located in the center of Iran between Zagros Mountain in the west and Central desert in the east. Climate condition and precipitation in Isfahan province is hardly affected by this situation. The mean annual precipitation about 120 mm is scattered over 85 percent of this area. Although the province vital artery that has named “Zayandeh Rood” is mainly dependent to water sources that placed in outside of this province, but supplying agricultural sector required water is dependent to precipitation and subsurface water (type of storage of precipitation). As well as Zayandeh Rood has have drought periodic. Therefore in this situation, precipitations have an important role and need management and schematization for water source to prevent wastage of water.

For determination of synoptic pattern of heavy precipitations in Isfahan province, statistics relating to precipitation in 44 synoptic stations, climatology and rain gauge of meteorology organization as well as Ministry of Energy rain gauge station were used. Through extraction of precipitation data in stations for statistical period of 20 years (1986-2005), heavy precipitations were extracted in each one of the station. With regard to expansion of Isfahan province and position difference between east and west of this province, criterion for heavy precipitation was the most repetitive precipitation which had occurred in each station during this statistical period. Data were sorted in SPSS software from maximum to minimum and we used the first quarter of data as heavy precipitation. Through data extraction, the heaviest and the most pervasive precipitation were identified in the province. Considering this criterion, 37 patterns were extracted. Through this patterns 4 patterns were selected. In order to determine synoptic pattern of these precipitations, data of pressure, specific humidity, orbit wind component (u), meridian wind component (v), vertical speed (omega), were prepared in different levels for 6 hours and two days before beginning precipitation till precipitation climax from national center environmental precaution of America (NCEP/NCAR).

Considering meteorological maps show four patterns for heavy precipitation in the Isfahan province. Most heavy precipitation has caused by Sudan and Mediterranean low pressure merger pattern. Two low pressures have been merged due to eastern motion Mediterranean low pressure and northeast motion Sudan low pressure on Iraq. This system has accompanied with pressure reduction in Iran center and positive vorticity advection and maximum negative vertical speed on half of western Iran. Sudan systems have entered to Iran from two ways: Khuzestan (track A) and Boshehr (track B). In these patterns, high pressure situated on Mediterranean Sea and high pressure tongues have expanded on southeast of Iran and east of Saudi Arabia. These systems were accompanied with convergence zone of atmosphere upper level and pressure increase as well as negative vorticity advection in sea level. These ingredients play important role in nutrition and determination of track in these patterns. The fourth pattern is Sudan and Mediterranean low pressure that have merged on the east of Mediterranean Sea. In this pattern, high pressure tongues have strengthened on center and southern half of Iran and have caused Sudan low pressure moved toward north. They are merged with Mediterranean low pressure in the east of Mediterranean Sea. In spite of high pressure has weakened on southern half of Iran but has still located there. This system has moved to east and entered to Iran. Positive vorticity advection and humidity maximum in front of cyclone have caused heavy precipitations in west of the province.

Patterns that cause heavy precipitations on Isfahan province include: 1- Sudan and Mediterranean low pressure merger pattern on Iraq cause the heaviest and pervasive precipitations over Isfahan. 2- Sudan and Mediterranean low pressure merger pattern on the east of Mediterranean Sea cause heavy precipitations over the west of Isfahan. 3- Heavy precipitation in center and east of the province are caused by Sudan systems which have entered to Iran from Khuzestan (track A) and Boshehr (track B) respectively.Finding indicates that the positive cyclone advection center situated on northeast of Saudi Arabia and over Persian Gulf both in sea level and level of 500 Hectopascal are considered as the main reasons for generation of heavy precipitations in all synoptic patterns. In addition, two high pressures on Mediterranean Sea and south of Iran and west of Saudi Arabia in the sea level and two high height on Saudi Arabia and Libya have important role in the system arrangement.

Isohyetal map is the prerequisite of hydrology, meteorology and climatology studies. Precipitation distribution in a region is related to regionalization method of precipitation data. Khuzestan elevation fluctuates from sea level up to 3712 meter while the elevations of meteorological stations fluctuate from 3 meter up to 875 meter. Due to the complex topography of Khuzestan province and the lack of high elevation meteorological stations with long-term data, it is necessary to determine the appropriate interpolation method for monthly and annual precipitation data in this region. In this study, in order to determine the best method for regionalization of precipitation data, seven interpolation methods were compared together. These methods are ordinary kriging, Cokriging, kriging with external drift, regression kriging, inverse distance weighting, spline and three-dimensional linear gradient. The monthly average and annual long-term data were used from 37 meteorological stations (synoptic, climatology and rain gage) over the 22-year period (1984-2005). In variography analysis, five variogram models (spherical, exponential, Gaussian, linear and linear to sill) were fitted to precipitation data and the best one was selected based on higher correlation coefficient and higher structured component to unstructured ratio. Cross validation technique was used to compare the interpolation methods and the best one was chosen based on regression analysis, and calculation of some error indices like as root mean square error and mean bias error. The probability distribution of precipitation data were tested for normality with Anderson Darling (AD) method. The results showed that precipitation data had normal distribution throughout the year except January and December. Non-normal data in other months were normalized with logarithmic transformation. Variography analysis results showed that structured component in more than 85% of the months was more effective than unstructured component. Our results confirmed that precipitation data had strong spatial structure. Effective ranges of precipitation data vary from 81.1 Km (in warm months) to 250.3 Km (in cold months). Also spatial structure of warm months was weaker than cold months. The goodness of fit results for different variogram models showed that the optimal model was the spherical model. These results were obtained based on evaluation of different interpolation • The optimum power in Inverse Distance Weighting method among the five powers (1-5) was the power 3. It was also found that in this method the variation of adjacent point’s number does not have significant differences in results. • The Cokriging method was removed from calculations, because spatial correlation was not strong enough in cross variogram models for different months,. • Altitude variable and altitude, longitude, latitude variables were selected as covariate variables in kriging with external drift and regression kriging methods, respectively. • The results of three-dimensional linear gradient method showed that meridional, zonal and altitudinal gradients are positive in all months. In other words, precipitation increase from west to east and south to north of region and also increase with increase in altitude. • Selection of regression kriging and kriging with external drift methods as the best methods based on the regression analysis showed that there is a consistency between results of these methods with real data. So that it can be considered as a result of using elevation as covariate variable. • Regression kriging was selected as the best interpolation method in monthly precipitation data based on error indices and regression analysis results in Khuzestan province. • In annual precipitation data, Regression kriging and ordinary kriging methods were selected as the best interpolation methods based on regression analysis and calculation of error indices. But precipitation of highland area was underestimated by using ordinary kriging method. Considering the importance of precipitation in the highland area and slight difference of root mean square error between these two methods, regression kriging was selected as the best interpolation method for annual precipitation data. In this study, long-term weighted average of annual precipitation data in Khuzestan province was calculated by using regression kriging. It was 391 mm, which is 41 mm more than the amount reported by the Iran meteorological organization. Among the interpolation methods which were investigated in this study, regression kriging method is introduced as the most suitable interpolation method in Khuzestan province for monthly average and annual precipitation data. The average annual precipitation obtained from regression kriging map was 41 millimeter more than the average reported by the Iran Meteorological Organization. This difference is due to accurate estimation of precipitation over highland area of this region.

Flood, as one of natural disasters, causes considerable damages in almost all parts of the world including Iran. Therefore, watershed prioritization is a practical useful tool which provides relevant information in the flood prevention planning. Floods cause severe damages in terms of both natural environments and human lives, making the hydrologists and water resources managers to be concerned with estimating the potential risk associated with these events. Recent trends in storm-water best management practices are aimed at finding and focusing on high potential flood generation in parts of a watershed. In order to prevent flood occurrence, it is essential to find out the areas of the watershed where the potential of runoff generation is high and how to use and incorporate available information to improve prioritization process. Such a process is vital to support the decision making and watershed monitoring, modeling, and management. It also helps in reducing the set up and running cost and improves efficiency. For example, it is usually time consuming and costly to set up a monitoring station in each sub-basin when a watershed consists of a large number of sub-basins. For this purpose, Akhtar Abad Watershed was chosen as a case study for flood potential zoning based on the Fuzzy Analytical Hierarchy Process (FAHP). The watershed has an area of 30785.28 ha which is located in the southwestern part of Alborz province and northern part of Markazi province. Over the last years, floods have resulted severe damage to the infrastructure and human life losses in this region. The analytic hierarchy process (AHP) is one of the most commonly used methods of assessment which works on a premise that decision making of complex problems can be handled by structuring the complex problem into a simple and comprehensible hierarchical structure. Despite of its wide range of applications, the conventional AHP approach may not fully reflect a style of human thinking, in which human’s judgments are represented as exact numbers. However, in many practical situations, decision makers usually feel more confident to give interval judgments rather than expressing their judgments in the form of exact numeric values. Therefore, AHP technique involves subjectivity in pair-wise comparisons and vagueness and uncertainty dominate in this process. Combining AHP into the fuzzy system brings the triangular fuzzy number of the fuzzy set theory directly into the pair-wise comparison matrix of the AHP. The purpose is to solve vague problems, which occur during the analysis of criteria and the judgment process. FAHP should be able to tolerate vagueness or ambiguity, and should thus be more appropriate and effective than conventional AHP in real practice. In order to find out the most relevant factor in flood occurrence potential, a literature review was conducted and the suggested criteria was adjusted based on the expert's ideas and geographical facts of the region. Then, each criterion was weighted based on a paired questionnaire and Fuzzy AHP approach. A fuzzy set is a class of objects with continuous grades of membership which represents the degree of truth as an extension of valuation. Fuzzy sets generalize classical sets while the indicator functions of these sets are special cases of the membership functions of fuzzy sets for the latter only take values 0 or 1.This classification approach is able to categorize the sub- basins and identify the ones which can sufficiently represent the watershed characteristics in a reduced number in terms of their runoff generation potential. A fuzzy set operation is an operation on fuzzy sets, which are a generalization of crisp set operations. The most widely used operations are called standard fuzzy set operations, which include unions, complements, and intersections. Fuzzy set theory has been introduced into classification to help reflect uncertain information. Then Fuzzy functions were considered for spatial modeling and zoning based on the membership function of each factor. Finally, the most prone areas of the watershed to flooding were mapped. In order to find out the potential areas, weights of each factor and sub factors were determined based on questionnaire and membership function of each responsible factor. Then fuzzy map of the each factor was incorporated to have the flood zoning map based on the most susceptible fuzzy operator. In this way, the final map was classified into seven classes based on standard deviation. The developed FAHP system in this research is able to meet the needs of more efficient and reliable approaches for watershed classification to deal with complex and uncertain features. The results showed that the most prone areas are located in the north and south of the region while the most part of the region is in the class 4 of moderate flooding potential. The overlaid maps showed that the most susceptible areas are mostly located in areas of more than 60 percent of slope and annual precipitation range of 300-400 mm. Watershed prioritization is the ranking of different sub-watersheds according to the order in which they have to be taken for treatment and flood control measures. According to the resulted map of flooding potential, the most prone areas are located in the north and south of the region where land slope is relatively high which increases runoff travel time and decrease time of concentration. Meanwhile, increased precipitation means higher potential of flooding in terms of higher runoff potential. Application of Analytical Hierarchy Process with Fuzzy logic shows better adjustment with human explanation of the environment and could provide better and flexible results compared to other overlaying approaches.