Geomorphology
Masomeh Rajabi; Shahram Roustaie; sara mataee
Abstract
Land subsidence as a geological and geomorphological disaster has serious negative effects in many countries and regions of the world. In this research, it was tried to use 5 images of Sentinel 1 satellite for the period of 27/02/2017 to 01/01/2021 in order to measure and calculate the land subsidence. ...
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Land subsidence as a geological and geomorphological disaster has serious negative effects in many countries and regions of the world. In this research, it was tried to use 5 images of Sentinel 1 satellite for the period of 27/02/2017 to 01/01/2021 in order to measure and calculate the land subsidence. For this purpose, the land subsidence was investigated in four time periods, and the results of these four periods show the maximum amount of subsidence in the first period of 17 cm, in the second period of 8 cm, in the third period of 5 cm, and in The last period was 12 cm. In terms of the spatial distribution of subsidence in all periods, the maximum subsidence corresponds to the western and northwestern parts of the plain. In order to measure the land subsidence potential in the Kermanshah plain, a possible subsidence map was prepared using a hierarchical analysis model. In order to do this, eight factors affecting land subsidence were used, including water level drop, land use, well density, land slope, well geological log, slope direction, soil geology, distance from the river. The final map of the risk of land subsidence shows that 50% of the area of the plain is in the area with a very high and high probability of subsidence, with the highest level of water level drop and the thickness of sediments , the high density of the number of wells and the type of agricultural use that in It is located in the western and northwestern part of the plain. Due to the fact that this part of the plain is also in the maximum range of land subsidence. Therefore, the comparison of the maximum subsidence in both mentioned methods shows the complete matching of the results.
Geomorphology
Masoumeh Rajabi; Shahram Roustaie; Seyed Mohammad Reza Javadi
Abstract
IntroductionLand subsidence is commonly referred to as vertical downward movements of the earth's surface that can be accompanied by a slight horizontal vector. Land subsidence is a global problem and a morphological phenomenon. This phenomenon is affected by human activities and natural factors that ...
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IntroductionLand subsidence is commonly referred to as vertical downward movements of the earth's surface that can be accompanied by a slight horizontal vector. Land subsidence is a global problem and a morphological phenomenon. This phenomenon is affected by human activities and natural factors that may become a threat to humans and human achievements. The phenomenon of subsidence, although imperceptible and gradual, but is associated with many risks, including the creation of potholes, failure and cracking of buildings, skewing of high facilities, damage to agricultural facilities, breakage and destruction of stairs Roads and network of urban thoroughfares. Therefore, this issue affects the urban areas more, which if not addressed can lead to many human and financial losses. Accordingly, monitoring the rate of land subsidence in order to reduce the negative effects as well as controlling its development process, will be very important and it is necessary to regularly estimate the area subsidence trend. Due to the importance of the issue, in recent years, various studies have been conducted in the field of subsidence and advances in the field of remote sensing have led to monitoring the phenomenon of subsidence, unlike in the past, with greater accuracy and speed. One of the methods that has received a lot of attention in recent years is the radar interference method, which has high accuracy and speed in processing information and monitoring land surface changes, so in this study, this method is used to monitor the situation. Subsidence of cities located in Hamedan-Bahar plain has been used.Materials and methodsIn this study, in accordance with the intended objectives of Sentinel 1 radar images (73 radar images during the period 16/01/2015 to 14/01/20120), the information of piezometric wells in the region (related to the Water and Regional Organization of Hamadan Province ) And the 30 m SRTM digital elevation model have been used as research data. Important research tools also include GMT (for radar interference measurement and SBAS time series) and ARCGIS (for mapping). This research has been done in 2 general stages. In the first stage, the amount of subsidence in the area is assessed using radar images. In order to perform this step, radar interferometry and SBAS time series method have been used. In the second stage, the annual drop in groundwater in the region is evaluated. At this stage, in order to assess the annual drop in groundwater in the region, information about 25 piezometric wells located in the study area in the period of 1375 to 1395 has been used.Discussion and resultsThe study of subsidence results in the study cities indicates that the average annual subsidence in the urban area of Hamedan was about 23 mm, the highest amount of which was related to the western regions of the city. The average annual subsidence in the urban area of Bahar was about 9 mm, the highest rate of subsidence was in the southern areas of the urban area. The average annual subsidence in the urban area of Salehabad with 6 mm was lower than other cities, but the average annual subsidence of Lalejin with 47 mm was the highest among cities. Also, in this research, information related to 25 piezometric wells (statistical periods of wells related to the years 1375 to 1695) located in the study area has been used. Examination of the level of water level drop in the studied wells indicates that these wells have faced a lot of water level drop, so the average annual drop of wells is calculated between 100 to 2070 mm. The study of the spatial status of groundwater depletion indicates that the middle areas of the study area have the highest average annual groundwater level depletion.ConclusionThe results obtained from the assessment of subsidence in the studied urban areas indicate that the highest amount of subsidence occurred in the urban area of Lalejin, so that this area during a period of 5 years (01/16/2015 to 01/14 /2020) had a subsidence between 26 and 234 mm (average annual 47 mm). In this study, the situation of groundwater resources decline has also been evaluated. The results show that the average annual drop of wells in the region is between 100 to 2070 mm, which is the highest rate of decline in the middle areas of the study area, and given that in this region, the highest rate of subsidence also occurred. Given that there is a significant relationship between land subsidence and groundwater level decline (correlation 0.7). In fact, a study of the subsidence of cities in relation to the decline of groundwater resources indicates that the city of Lalejin, due to its location in the middle of the area and the high annual rate of groundwater decline, had the highest rate of subsidence. Also, the results of evaluations have shown that in addition to the decrease of groundwater resources, constructions have also played a role in increasing the rate of subsidence, so that the city of Hamedan has faced less groundwater loss than the city of Bahar, but it had more subsidence. Considering that the highest rate of subsidence occurred in the western, southern and eastern regions of Hamedan urban area and these areas have faced a lot of physical development in recent years, so it can be said that in addition to water loss Underground, the development of construction has also played an important role in the rate of subsidence in this city.
Geomorphology
Shahram Roustaie; Davod Mokhtari; Zahar Ashrafi Fini
Abstract
Introduction Landslide is one of the most important and disastrous natural hazards which can bring many financial losses and heavy casualties worldwide every year. Entropy means a quantity of disorder between causes, results or decisions taken in different situations, it can be highly effective particularly ...
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Introduction Landslide is one of the most important and disastrous natural hazards which can bring many financial losses and heavy casualties worldwide every year. Entropy means a quantity of disorder between causes, results or decisions taken in different situations, it can be highly effective particularly in geomorphological studies such as landslide, where existing data are confused with uncertainties. Material and Methods Topographic maps 1: 25000 scaled, geological map of Makran and Marzanabad scale map 1: 100000 and ASAR images from ENVISAT since 2003 till 2009 in the region were used as the main data in this model. Active landslide also detected in the basin. Then, 17 zones were selected via field visiting and Google earth software images. Also location of landslides recorded using GPS. Analyzing the data and providing the required maps were done using Arc Gis10 and SAGA. A total number of 13 effective parameters were selected based on condition of studied areas for next step. Then slide layer, slide direction, elevation, geology, land use, distance to fault, distance from the river and distance from the road obtained by Arc Gis10 analysis, vegetation layer (NDVI) measured by ENVI4.2 software and the layers of surface area ratio (ASR), topography index (TPI), Topographic Wetness Index (TWI) and slide length index (SLS ) were analyzed by SAGA software. After providing the information layers and importing the landslide locations, the properties of each slip extracted due to the mentioned layers and scoring was regarding to the role of each factor in the occurrence of slide. And the primary matrix was formed according to the entropy method. The decision matrix contains information which can be evaluated by entropy as a criterion. Then by calculating the entropy matrix and weight of 13 factors (WJ), the (HI) index will be obtained as landslide risk hazard Results and discussions At first due to the characteristics of the occurred landslide, each class was scored from the information layers which were obtained by examining the region after two field visits, study of aerial photographs and satellite imagery and identification of the affecting factors and their roles to create slip. Then the information layers used in the research were categorized and scored as a raster data and utilized as the main data in the formation of an entropy matrix for further analysis. To convert qualitative values into quantitative a bipolar scale is used. The bipolar interval scale is a general method for ranking quantitative and qualitative indexes. Measurement in this technique is based on a 10-point scale so that zero specifies the lowest possible value which is practically comprehensible and ten represents the maximum possible value of the intended index. The middle point is also the point of dividing the scale into favorable and unfavorable data. Conclusion Prioritizing the effective factors using the Shannon entropy index indicates that data layers such as slides direction, land use, elevation, slope, normalized vegetation index and the distance from the river had the greatest effect on the landslide occurrence in the area. And the topography, moisture index, geology, distance from fault and road, and the rest of the information layers had the least effect. Based on landslide hazard map of Taleghan watershed, very low to low risks regions are some areas in the northeast, central and southwest regions, while most of the studied areas have a moderate to very high risks. In general, site locations which could be at risk in the event of a landslide are limited to residential areas, roads, rivers, lakes and power lines. There are various land use in the region and Residential and demographic areas are at the top of the priority list. One the other hand there is Taleghan dam which can create a much greater potential risk if landslide happens at its location.
Geomorphology
negin aali; Masoumeh Rajabi; Mir asadolah Hejazi; Shahram Roustaie
Abstract
Introduction Natural parameters are the main and determining factors in the physical development of mountainous cities. One of the mountainous cities of Iran, which has physically developed due to these parameters, is the city of Marivan. Marivan is located in the west of Kurdistan province, near the ...
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Introduction Natural parameters are the main and determining factors in the physical development of mountainous cities. One of the mountainous cities of Iran, which has physically developed due to these parameters, is the city of Marivan. Marivan is located in the west of Kurdistan province, near the western borders of the country, at a distance of 16 km from Iraq, between 25 degrees and 21 minutes to 35 degrees and 48 minutes north latitude and 45 degrees and 58 minutes to 46 degrees and 45 minutes east longitude. According to the last population and housing census conducted in 2016, it has a population of 151188. The city is located at the starting point of the Marivan-Esfandeghe geological region and is located in the geological-morphological structure of the young Zagros. Therefore, identifying and evaluating the factors influencing the physical development of this city is really important. To do this, the characteristics of elevation, slope and direction of slope, fault, focal points of earthquake occurrence, main and secondary waterways have been used.With regard to its location in northwestern Iran after the eight-year Iran-Iraq war, the study city has experienced significant physical growth and development due to its unique and pristine vital and natural location, which led to the development of this city. Regardless of geological constraints. At present, the city has the potential to benefit from high potentials in the fields of natural and cultural tourism, including (Zarivar Natural Lake, Bashmakh Regional Area, and Border Market, Bilo Plain, Garan Dam, Oramanat and Bazaar for supplying foreign supplies and products. It has become one of the dynamic and active economic-tourism hubs in the west of the country and there is a growing growth and development in the city; therefore, it is inevitable to pay attention to geomorphological factors and determine optimal directions for the development of this city. Methodology According to the National Physical Plan of Region 5, the city is in a relatively high risk of earthquakes, and with respect to available and cited maps, there are 7 sub-faults in the northern part of Marivan and 2 main faults in the western part of the city. For this reason, the physical development of the city is subject to certain restrictions. Marivan is also in a relatively high risk of earthquakes in terms of location in relation to natural hazards.It is an applied research and the method of work is descriptive-analytical and also the fuzzy logic model has been used to evaluate and model suitable areas for development so that each layer is fuzzy according to fuzzy membership functions in GIS environment. And then multiplication and addition operations and different values of fuzzy gamma have been performed on these layers. After overlapping and multiplying the fuzzy layers, a zoning map of the appropriate development route of the city was prepared and divided into 5 classes including completely suitable, relatively appropriate, appropriate, inappropriate and completely inappropriate for the physical development of the city.In the study, library methods, documentary and field studies have been used to collect the desired information and data. To evaluate the optimal development of urban lands, slope indicators, slope direction, fault zoning, main and secondary waterways, erosion, earthquake-prone points in and around the area have been used. The fuzzy and hierarchical analysis process (AHP) was used. Results and discussion In order to evaluate and weigh the information layers and to determine and score the impact factor of geomorphological indicators affecting urban development while extracting and reviewing the criteria examined in various valid researches and articles, scientific opinions and views of ten experts and specialists were counted and monitored. In order to determine the importance of each of the studied indicators on the location and physical development of Marivan city, the opinions and views of the experts were given based on the superiority of one factor over another and based on expert judgment, scores between 1 and 9 were given. The equivalence of expert scores based on fuzzy method was done by the authors of the article with the help of AHP & FUZZY software.Since 1996, due to the increasing growth and development of the city and the formation of informal settlements, the development of the city has taken place without considering geomorphological considerations, and this has caused the spatial-physical development of Marivan in the northern parts near the existing faults. The development of the city has taken place at relatively high risk. Conclusion Summarizing the research, it has been determined that the southern lands of this city have less proportion to the development of the city due to its proximity to Zarivar Lake and its location along the main and secondary waterways and its proximity to the earthquake centers. And to some extent, the East enjoys a higher level of development.
