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Showing 3 results for Flooding
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year 2, Issue 1 (6-2012)
year 2, Issue 1 (6-2012)
Abstract
The use of new methods of Remote Sensing (RS) and Geographical Information System (GIS) in zoning the flooding potential and its variations in a particular geographical area (Tang-e-Bostanak Catchment Area) constitutes the main subjects of this study. In this regard, the production, combination, and composition of effective information layers such as K index and run off in identifying these zones have been noted, highlighting the capacity of GIS. Theaim is the identification and percent of flood zoning and their variations within an 18-year period by RS and land use variation maps. In this study, we have observed excess rainfall under the curve number (CN). According to the results, the above mentioned area isexperiencing a 15% increase in flooding during the 18-year period.
Bahram Mir Derikvand, Alireza Sepahvand, Hossein Zeinivand,
year 13, Issue 2 (7-2023)
year 13, Issue 2 (7-2023)
Abstract
1- Introduction
Erosion is the main cause of wasting water and soil resources and causing natural damage. According to geological characteristics of erosion and sedimentation, it is very important to study the erodibility of the geological formations of the watershed to determine their constructive effects on sediment and runoff. Many factors affect soil erosion and one of the important factors is the erodibility of geological formations. Sediment that moves with water is called suspended sediment load, and the amount of suspended sediment material that passes through a river section in a certain period of time is called suspended load. The suspended sediment load (SSL) of a watershed, which passes through a certain section of the river, depends mainly on the climatic characteristics, the characteristics of the watershed and the capacity of carrying sedimentary materials. The input suspended load is one of the important and influencing factors on the amount of sediment input to reservoirs of dams and lakes. Determining the amount of sediment carried by rivers is important in many aspects. The calculation of suspended load is very important because of various reasons, one of the most important of which is the role of suspended sediment load in the quantitative and qualitative management of surface water resources. Therefore, the distribution and transportation of suspended sediment load (SSL) in rivers have a significant effect on the water resource management, design of hydraulic structures, river morphology, water quality, and aquatic ecosystems.
2- Methodology
The present study was carried out to evaluate sedimentation and runoff production of Asmari and Gachsaran Formations in Ghaleh Gol watershed around Khorramabad city, from Lorestan province, Iran, located between 48° 21 '2" and 48° 33 '1", and between 33° 15 '43" and 33° 21 '15" N with an area of 10.76 km2. The studied area has a semi-arid climate with a mean annual rainfall of less than 500 mm. This study aimed to measure suspended sediment load (SSL) and surface runoff during the November 30th, December 2th and 16th 2020 and also on the 12th of March 2021; for this purpose two square meter plots were used. A tank was installed at the plot outlet to collect sediment and surface runoff. After the rainfall finished, the volume of water and sediment collected in the tank installed at the end of the plot was measured.
3- Results
The results showed that during the mentioned rainfalls, the average volume of water output from Asmari and Gachsaran Formations were 1.802 and 1.345 liters, respectively; the average output sediment for these two formations were 1.133 and 1.048 g /l, respectively, ant the total output of suspended sediment load (SSL) was 3.083 and 2.227 gr, respectively from Asmari and Gachsaran Formations. Finally, the obtained results suggest that the Asmari formation has the highest erodibility. Also, according to the results, the Asmari formation has the highest flooding level in the study area.
4- Discussion & Conclusions
According to the results, considering erodibility and flooding features, Asmari Formation has higher sensitivity compared to Gachsaran Formation in the study area. In fact, the obtained results showed that Asmari formation based on the prioritization of erodibility and flooding has the first rank, which must be prioritized for conducting management operations in the Ghaleh Gol watershed.
Siavosh Shayan, Mojtaba Yamani, Amin Abdolalipour Adl, Nazfar Aghazadeh,
year 13, Issue 3 (10-2023)
year 13, Issue 3 (10-2023)
Abstract
1- Introduction
The natural hazards are impossible to avoid, and infrastructure elements and communities cannot be made totally invulnerable. The only viable solution is the complex risk analysis and subsequent development of combination of mitigation and adaptation strategies Floods are the most common natural disaster type worldwide. Between 1995 and 2015, 2.3 billion people were affected by floods, considerably more than any other type of natural disaster event. In general, the Givi Chai basin includes two cities, Khalkhal and Kausar. In recent years, floods have caused damage to gardens and facilities due to spring and summer rains to the extent that the villages that are located under the Sangur Chai basin because of being located at the source of the rivers and mainly in the course of the rivers are affected by floods; also in the whole basin due to droughts and the destruction of vegetation and the increase of man-made areas, the amount of impermeability has increased. Considering that Khalkhal is a mountainous area and is one of the areas sensitive to landslides in Azariaijan region, heavy rainfall and floods can wash away the slopes of this area.
2- Methodology
The Givi Chai basin in the south of Ardabil province with an area of 1554 square kilometers is one of the 3rd degree basins of Sefidroud, which is located in the geographical coordinates of 48°4' E longitude to 48°38' E longitude 37°27' N latitude 37°55' N latitude. In order to achieve the goals of this research, firstly, the theoretical foundations and the works done in connection with flood zoning of basins in Iran and outside Iran were examined. Many variables are effective in the flood of basins. In this research, from the 1.100000 geological map, the slope maps were obtained using the digital height model map; the land use map was obtained through the classification of the Maximum Likelihood in ENVI software. In addition, using the digital model of the height of resolution to extract, a drainage density map was prepared using the Line density tool. In this research, using the FAHP fuzzy hierarchical analysis model, Expert CHOISE software was used for weighting the layers, and finally, a map was prepared in the Arc GIS environment using gamma 0.5, 0.7 and 0.9The basin was flooded.
3- Results
After preparing the effective factors for zoning the flood potential of the basin, the gamma fuzzy operators of 0.5, 0.7 and 0.9 were used. 37 floods have occurred in the studied basin from 1365 to 1399 in different parts and villages, which caused the destruction of rural houses, gardens, agricultural lands and livestock. In order to determine the final flood map, points were randomly selected on the zoning map, then the correlation level was obtained based on the specified points with each of the criteria in the ARC GIS software. Based on the results obtained from the correlation, the highest correlation level is related to gamma 0.9. Vegetation has the highest correlation of 0.5 and lithology has the lowest correlation with gamma of 0.9 and 0.062. Also, the last flood occurred in the studied basin in the villages of Mustafa Lo, Bolokan, Morestan and Khoda Qeshlagi, which are located in the high-risk zone according to the final flood zoning map.
4- Discussion & Conclusions
In this research, using the FAHP model, flood potential zoning has been evaluated in Givi Chai basin. The data of height, slope, lithology, precipitation, vegetation, soil hydrology, distance from the river, drainage density and land use have been used for flood zoning. After preparing the zoning map, the studied basin was divided into five classes based on the severity of flooding: very low, low, medium, high, very high. The results obtained from the flood zoning of Givi Chai basin have shown that the largest area of the studied basin, which is 0.9 gamma scale, has the highest correlation. The strata with very low, low and medium potential, gamma 0.5 0.7, were showed. cover the area of Givi Chai basin. Also, the final flood map of the basin was validated with the villages that have been damaged by floods in recent years. The areas which are more exposed to floods are in the regions that have very low permeability in terms of lithology and hydrology of the soil and in the areas where the vegetation cover as less as.
The natural hazards are impossible to avoid, and infrastructure elements and communities cannot be made totally invulnerable. The only viable solution is the complex risk analysis and subsequent development of combination of mitigation and adaptation strategies Floods are the most common natural disaster type worldwide. Between 1995 and 2015, 2.3 billion people were affected by floods, considerably more than any other type of natural disaster event. In general, the Givi Chai basin includes two cities, Khalkhal and Kausar. In recent years, floods have caused damage to gardens and facilities due to spring and summer rains to the extent that the villages that are located under the Sangur Chai basin because of being located at the source of the rivers and mainly in the course of the rivers are affected by floods; also in the whole basin due to droughts and the destruction of vegetation and the increase of man-made areas, the amount of impermeability has increased. Considering that Khalkhal is a mountainous area and is one of the areas sensitive to landslides in Azariaijan region, heavy rainfall and floods can wash away the slopes of this area.
2- Methodology
The Givi Chai basin in the south of Ardabil province with an area of 1554 square kilometers is one of the 3rd degree basins of Sefidroud, which is located in the geographical coordinates of 48°4' E longitude to 48°38' E longitude 37°27' N latitude 37°55' N latitude. In order to achieve the goals of this research, firstly, the theoretical foundations and the works done in connection with flood zoning of basins in Iran and outside Iran were examined. Many variables are effective in the flood of basins. In this research, from the 1.100000 geological map, the slope maps were obtained using the digital height model map; the land use map was obtained through the classification of the Maximum Likelihood in ENVI software. In addition, using the digital model of the height of resolution to extract, a drainage density map was prepared using the Line density tool. In this research, using the FAHP fuzzy hierarchical analysis model, Expert CHOISE software was used for weighting the layers, and finally, a map was prepared in the Arc GIS environment using gamma 0.5, 0.7 and 0.9The basin was flooded.
3- Results
After preparing the effective factors for zoning the flood potential of the basin, the gamma fuzzy operators of 0.5, 0.7 and 0.9 were used. 37 floods have occurred in the studied basin from 1365 to 1399 in different parts and villages, which caused the destruction of rural houses, gardens, agricultural lands and livestock. In order to determine the final flood map, points were randomly selected on the zoning map, then the correlation level was obtained based on the specified points with each of the criteria in the ARC GIS software. Based on the results obtained from the correlation, the highest correlation level is related to gamma 0.9. Vegetation has the highest correlation of 0.5 and lithology has the lowest correlation with gamma of 0.9 and 0.062. Also, the last flood occurred in the studied basin in the villages of Mustafa Lo, Bolokan, Morestan and Khoda Qeshlagi, which are located in the high-risk zone according to the final flood zoning map.
4- Discussion & Conclusions
In this research, using the FAHP model, flood potential zoning has been evaluated in Givi Chai basin. The data of height, slope, lithology, precipitation, vegetation, soil hydrology, distance from the river, drainage density and land use have been used for flood zoning. After preparing the zoning map, the studied basin was divided into five classes based on the severity of flooding: very low, low, medium, high, very high. The results obtained from the flood zoning of Givi Chai basin have shown that the largest area of the studied basin, which is 0.9 gamma scale, has the highest correlation. The strata with very low, low and medium potential, gamma 0.5 0.7, were showed. cover the area of Givi Chai basin. Also, the final flood map of the basin was validated with the villages that have been damaged by floods in recent years. The areas which are more exposed to floods are in the regions that have very low permeability in terms of lithology and hydrology of the soil and in the areas where the vegetation cover as less as.
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