Abolghasem goorabi; Mojtaba Yamani; Seyyed Javad Hoseini
Volume 5, Issue 16 , December 2018, , Pages 81-100
Abstract
Abstract
Introduction
Rivers' pattern is seldom stable and is always subject to change. Rivers' banks have long been the most important areas of population settlement, especially in the semi-arid regions of Iran. This has made the recognition and assessment of the geometric deformation of rivers an ...
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Abstract
Introduction
Rivers' pattern is seldom stable and is always subject to change. Rivers' banks have long been the most important areas of population settlement, especially in the semi-arid regions of Iran. This has made the recognition and assessment of the geometric deformation of rivers an important applied topics. Alluvial beds of a river are divided into two groups of stable and unstable. While in a stable bed, the walls and the floor are stabilized, in the unstable bed, the walls and the floor are not constant and have a changing state. Zanjanrood is regarded as the natural bio-economical artery of Zanjan province. In the present study, by recognizing the temporal and the spatial hydro-geomorphological changes of Zanjanrood during the years 1955 and 2011, and in the western part of the river, which is more important for agriculture, the amount of morphological changes is calculated and presented in the form of a map.
Methodology
The method of the study was analytical by spatial-local comparison based on the direct and the indirect observations using satellite images, aerial photos, and maps.
In this method, the intervals were classified into distinct parts based on the morphology-hydrodynamic similarity. Then, by applying spatial analysis on the raster maps, the pattern and variation of the changes were estimated by plotting tangential transects on the extension and restriction areas in the right and left sides. By determining the extension and restriction areas in river sides, the type and amount of stream’s variation in various reaches was determined. Afterwards, the total areas of extension and restriction on both sides of the stream were computed. Transects are rectangles with constant angles whose area variations indicate the changes of the river banks in different time ranges. This technique was used to determine the area dominated every progression and regression area in order to analysis and assess of the main factor(s) affecting this change.
Result
The results of the study showed that the outcome of the action-reaction of the factors affecting Znjanrood changes in the studied area had been a stable trend over the past 56 years. The most important factors involved in this trend were the development of the agricultural activities, the increase of management actions to stabilizing the river for agriculture and infrastructure proposes, and dam construction. However, the effect of slope and geological conditions (neo-tectonic) should not be neglected as well.
Discussion and conclusion
The results indicated that the overall trend was to reduce the width of the channel to its axis. However, the process has increased from the first period (1955-1985) to the second (1985-2011) and the third periods (1985-2011), so that at the end of the given time intervals, there was an increase in the relative stability of the stream. The change in flow to the outlet reduced the erosion power of the river flow and increased the stability and relative stabilization of the bed. The development of the fairly stable gardening activities dispersed on the flood bed played an important role in the stability of the stream in the studied area, so that the gardens and fields on the stable river main bed sides exhibited great changes in the images and photographs.
The role of the human factors in the Zanjanrood Basin due to its relative geographical position (east to northwest transit), has been the basis for the development and launch of several road construction projects (railways, roads and freeways) during the period of 1955 to 2011 in Zanjanrood and caused the change of Hydro-geomorphological-Hydrodynamic systems. A quantitative assessment of the Zanjanrood river bed changes shows that the rate of change, overcoming the general trend of stability and stabilization, has increased from the first period to the last period. Indeed, while the stabilization rate in the first period was 0.16 km2, in the second and final periods, it was respectively 1.91 and 2.01 km2. Progressions are concentrated in the beginning and end of the research (Transects 1, 2, 6, and 9 to 13), which affects the lands of the villages of Nikpey, Darelik, Dolanab, Naji, Idalou, and Baghloja and Saifabad. The recessions are also focused on transects 3 to 8, excluding transect number 6. Based on the results, Zanjanroud shows the overall stability trend. The adjacent area of the upper and lower parts of the studied research (the areas around the villages of Nikpey and Baghloja) are among the most sensitive areas of the research.
Mojtaba Yamani; Abolghasem Goorabi; Shirin Mohammadkhan; Hamid Ganjaeian
Volume 4, Issue 12 , December 2017, , Pages 1-23
Abstract
Introduction Qorveh, one of the cities of Kordestan province, has high amount of precipitation and, consequently, a significant resource of water. Geological surveys, physiography and hydrology, and in particular field studies, have revealed rivers' significant role and influence on the formation ...
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Introduction Qorveh, one of the cities of Kordestan province, has high amount of precipitation and, consequently, a significant resource of water. Geological surveys, physiography and hydrology, and in particular field studies, have revealed rivers' significant role and influence on the formation of human activities and settlements. Unfortunately, much of the locally carried out planning has ignored hydro-geomorphological factors. In addition, population growth and the growth in residential and industrial areas have caused uneven progress of the residential areas towards the riverside which has, consequently, changed the natural shape of the river such as its width, length, slope, sediment, and the like. These problems shows the importance and necessity of thorough hydro-geomorphological studies. Therefore, the main objective of this study was to investigate the hydro-geomorphological status of the Shoor River's basin and evaluate the its lands' capabilities to develop urban areas, determine the optimum location based on hydro-geomorphological criteria, minimize the undesirable impacts of inhabitants of cities and villages on the highlands, especially the catchment areas, and minimize the harmful effects of the environmental hazards on agricultural products and inhabitants. Materials and methods The study is based on field, library, and software methods. Firstly, using the topographic maps, the study area of the basin was specified. In this study, 8 factors of lithology, faults, slope, aspect, elevation, distance from the river, vegetation, and land use were used in order to evaluate and zone suitable areas for urban development of Qorveh. After the preparation of the information layers, the coefficients and their values were estimated by the use of ANP model. In this model, like AHP, the measurement of the amount of the relative importance is done by pairwise comparisons with the help of the range of 1 to 9. Number 1 represents the equal importance of two factors and 9 represents the extreme importance of one factor over the other. To this end, for each model, a total of 15 questionnaires were distributed among specialists (5 Land use planning, 5 urban planning, and 5 geomorphology specialists) to rate each of the factors. After analyzing the questionnaires, to calculate the final weights of each criteria and subcriteria (according to the internal relations), Super Decisions software was used for the ANP model. Then, indicators and variables affecting urban development, using the Fuzzy function, were sub-Fuzzed and all layers of the study were standardized and compared. The coefficients were transmitted to the GIS polygonal descriptive databases to make them more quantitative and comparable. Finally, the final maps were made by overlaying the information layers maps. Discussion and results In the present study, to locate suitable areas for urban development, 8 factors were used and the classification was done. On this basis, the suitable areas for future development of the city have a slope of less than 11 %, the lithology persistent for building, low elevation, barren land use, and the changeable vegetation. In addition, they are distant from the fault lines and they are near the riverside. Additionally, the map of each criteria was prepared and the final map was obtained by combining the information layers, based on the weight obtained through ANP. Conclusion The ANP Model, because of having features such as simplicity, flexibility, simultaneous use of qualitative and quantitative criteria and final ranking of the options, can provide a suitable framework for analyzing the issue and determining the final ranking of the options. However, since allocating evaluation weights cannot provide enough reliability, the use of fuzzy logic, for more integration between layers and fixing possible errors, is needed. Finally, the study area was divided into five regions in terms of available potential and the ability for the purposes of the urban development. According to the criteria which was considered in this zoning, it can be said that, areas with the highest score, are located in ideal areas and away from danger. However, it should be noted that the significant presence of the geomorphologic phenomena, such as Bader and Parishan mounts in the southern parts of the study area, as well as the existence of faults in the southwest and southeast of the area have caused the basin to be in a very inappropriate class in relation to the development of the space. The results of this study indicate that the Shoor River's basin has a high potential for spatial development and urban planning in the future.
Mojtaba Yamani; Abolghasem Gourabi; Zahra Abedini
Volume 2, Issue 3 , January 2017, , Pages 137-157
Abstract
Rivers are dynamic systems and their space-time characteristics are constantly changing. This change and displacement creates problems in the human and ecological functions and the study of such changes are the main issues in the fluvial geomorphology. In this study, survey morphological changes in one ...
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Rivers are dynamic systems and their space-time characteristics are constantly changing. This change and displacement creates problems in the human and ecological functions and the study of such changes are the main issues in the fluvial geomorphology. In this study, survey morphological changes in one section of the Babolroud (Bobol River) will be examined during the time period of 1334-93 from Babol city to Kardgarkola village within 18/45 km. Using aerial photo from 1334 and 1383 and satellite images Landsat 8, 1393 the path of the river was digitalized in three time periods with Arc GIS software. To determine the type of changes in each of the beaches spatial and temporal interval were studied and the position of the coastline was compared to the previous coastline. Then, for each beach in each period shifts named layer was prepared and its surface was measured. Then for each time interval (period) studied, the spatial interval was specified. The statistical tables were considered for each time interval to provide possible comparisons between the spatial intervals. Finally, changes in the left and right of each interval in each period was compared to the period before. For a detailed analysis, changes in the stream in each of the study periods were considered after determining the thalweg, the fixed line and the taken transects within the interval of 1000 to 1000 meters. Then, in the Arc GIS, after the determining the transects and thalwegs, and creating a polygon, the area of polygon was compared to the previous periods. Finally, through the implementation of existing disputes, thalweg changes in the riverbed, which determined the cause of the change, was found in each transect. The results show that the interval in the regression process has three periods. The second interval depicted the greatest change. The main reason for this fact in the period of change is excessive land use and human intervention.
