Showing 13 results for Flood
Mohammad Darand,
Volume 15, Issue 37 (9-2015)
Abstract
The aim of this study is synoptic analysis of heavy precipitations in Kurdistan Province during 1/1/1961 to 31/12/2010(18263days). By using two thresholds of extensively and intensity of precipitation, 107 days have been recognized. In temporal view, the selected days occurrences in wet seasons of year that start from October to June. By applying the principle component analysis on the sea level pressure during the 107 days, the results showed that 12 components explain about 93 percent of sea level pressure variation. The results of the applying cluster analysis on the component score showed that two circulation patterns result in occurrence of extreme and heavy precipitations in Kurdistan province. In order to recognize heavy precipitation in dry season (June to October), the area mean precipitation for the province have been calculated. According to the 99 percentile threshold and extensively of precipitation the heavy phenomena recognized. By two thresholds 32 days selected and same as to the wet season precipitation the sea level pressure data from NOAA extracted. The data analyzed by Principle Component Analysis and 11 components extracted that explain the 93 percent of variation sea level pressure in the frame study. By doing cluster analysis on the 11 components, one pattern recognized for the sea level pressure. The results showed that in lower atmospheric levels (1000, 925 and 850 hpa) occurred highest convergence on the study region during wet season. The source of humidity in the lower levels is Arabian, Red, Oman, Persian Gulf and Mediterranean Seas. In the high level atmosphere, the value of convergence is low. The sources of humidity in high levels atmosphere are Red and Mediterranean Seas. In the mid level atmosphere (500 hpa) the presence of trough results in nutrition of the instability on the study region. Also during dry season, the highest moisture flux convergence occurred in the low levels but the resource of the moisture is Caspian Sea. In the upper levels (from 700 hpa to up) in addation to Caspian Sea, Mediterranean and Red sea are the resource of heavy precipitations.
Shamsollah Asgari, Amir Safari, ,
Volume 18, Issue 50 (6-2018)
Abstract
One of the important and effective factors in the destruction of natural resources is the flood phenomenon, identification of this phenomenon and effective parameters in flood occurrence in natural resources and catchment areas is necessary. The purpose of this study was to determine the flooding of sub-basins in Jafarabad basin in Ilam province. In this research, the Jafarabad basin in Ilam Province is divided in to 12 sub-basins. For each sub-basin, 28 geometric, climatic, permeable and physiographic parameters such as area, environment, length and slope of main stream, length and slope of the basin, time of concentration, The coefficients of shape and variability of precipitation, vegetation cover, CN, discharge and ... have been calculated using GIS software. Factor analysis was used to determine the flood potential of the sub basins. The data of 28 sub-basin variables were analyzed by SPSS software and summarized in 5 main factors (shape, flow, slope, drainage and runoff). The results indicate that the factor of the form with a specific value of 11/30 is the most important factor in the flooding of the studied basin. Channel, slope, drainage and runoff factors with a specific value of 7.21,4.34,3.22 and 3.10 respectively Priority is in the next rank. Then, based on the factor scores of the study area, three large, medium and low flooding categories were mapped and a zoning map of the flood potential of the sub-basins was drawn in the GIS environment. Sub-basins (9,8,5,3) in the shape of the sub-basins (1,6,11) in the gradient factor, sub-basins (2, 7) in the drainage factor and in the runoff factor of the sub-basins (4,10,12 ) Have a lot of flood potential. In sub-basins, the similarity of flooding, erosion, vegetation, and human performance impacts is divided into 3 groups with high, medium and low flood potential. Sub-basins play a major role in the flooding of the basin, which affects the vast agricultural fields of the lower reaches.
Mohammadreza Goodarzi, Atiyeh Fatehifar,
Volume 19, Issue 53 (7-2019)
Abstract
In the present time, with the increase of industrial activities and the neglected environmental issues, the effects of climate change have become more evident and poses this phenomenon as a global difficult. Increasing the probability of occurrence of extreme climatic events such as flood and increasing the frequency and intensity of the effects of climate change. The northwest of the country is one of the most vulnerable areas of the country due to its semi-arid and mountainous climates and high rainfall variability. Therefore, zoning due to climate change is essential. Therefore, in this study, in order to investigate the risk of flood in the Azarshahr basin, due to climate change, using the CanESM2 general circulation model under RCP8.5 scenarios negativity according to the assessment report fifth IPCC, rainfall and temperature variables were down scaling by Statistical down scaling model (SDSM). Then,with hydrological model SWAT the daily runoff, the basin map and the lines of the canals are achieved. The results of the evaluation of the SDSM model with a coefficient of determination and Nash-Sutcliff 0.95 on average represent the good performance of the model in the down scaling of large scale data. The results show an increase of 0.23 ° C and 4.53% rainfall and maximum discharge. The basin is zoned with the combination of the maximum mean discharge map, the coefficient and distance from the river with the AHP approach. Due to the zoning they are 41.55% of the area of the basin, at very low and low risk, 27.23% at average risk and 31.2% at high and very high risk. Also, with the final map, it became clear that the mid-basin had a high risk due to its prerequisite conditions and that it needed to carry out managerial actions.
Parviz Ziaiian Firouz Abadi, Ayoub Badragh Nejad, Reza Sarli, Mahboub Babaie,
Volume 20, Issue 57 (6-2020)
Abstract
Rivers are the natural flow of surface waters that flow in a certain bed seasonal or permanently. Rivers include a vast range of narrow waterways and with mountainous high steep to low steep and wide beds flowing in plains. However, rivers have had an effective role in urban development and human civilization, therefore, identification of flood prone areas and flood part in the potent lower fields of Birjand watershed would lead to aid feeding the artificial environment of the water shed and would also lead to increase of quality in the environment fields. The purpose of this study is to identify the environment about the river and evaluating the danger in case of occurrence of flood crisis. All of the processes and analyses of data were performed in the GIS atmosphere utilizing the three methods of saw Fuzzy, AHP and Boleyn logic for weighting data such as (gradient, erosion, land application, watershed system, soil, geological fault distribution, quaternary unit, level of underground waters, and satellite imagery) and the potent areas in terms of confronting danger were located. The results of the study showed that the areas that the effort for exploiting floods was made have characteristics such as (existence of alluvium and colluvium sediments in the high steep feet of the slopes and watersheds with major stone occurrences, existence of fan-shaped sediments and alluvial fan in the external aperture of dry rivers and water ways with mountainous watersheds and hills leading to low steep fields, existence of low fields from the manner of altitude in proportionate to fields near). Finally, the best model that could present a better evaluation and conclusion about this matter was the Boleyn logic model in locating the flood part.
Amir Safari, Ali Ahmadabadi, Zahra Sedighifar,
Volume 20, Issue 57 (6-2020)
Abstract
Flood plains and adjacent rivers, which, due to their particular circumstances, are considered suitable places for carrying out economic and social activities, are always subject to the dangers of flood events. Hence, in these areas, determination of flood progression and its elevation relative to the surface of the earth, as well as determining the characteristics of the flood during the various return periods, which will be called flood zoning, will be of great importance. In this regard, this research aims at integrating the WMS hydrologic model with ARC GIS software to estimate flood zones in the Damand, Goladdareh, Saadabad and Maghsoud Baik watersheds on the main river of Darband. At first, the river Darband was divided into 19 main sections and in the HEC-RAS model, the river was zoned. In this research, using different digital maps, the flood extent in the riverside lands was calculated for a flood with a return period of 2 to 500 years. The SCS method was also used to increase the accuracy and reliability and also to identify areas susceptible to runoff production. The results of the study show that, due to land use changes, especially in the river basin and the abundant construction of the studied basin, there is no flood control power.
Mr Asadollah Mollazehi, Dr Mohammadreza Pudineh, Dr Mahmood Khosravi, Dr Mohsen Armesh, Mr Aliasghar Dehvari,
Volume 20, Issue 58 (10-2020)
Abstract
Today, due to climate change, natural hazards and how to deal with them are among the most important concerns of researchers in environmental planning and crisis management. The purpose of this study is the assessment of the potential flood risk in Sarbaz drainage basin. For this purpose, the databases including elevation, slope, geological characteristics, soil characteristics, precipitation, vegetation, land use, and vector layers of the main channel, streams and drainage densities of the basin were used. By using the questionnaire and experts' opinion as well as hierarchical analysis, the weight of influences of each layer was calculated in basin flooding. Each of these layers was classified based on the flood potential from low to high-risk scale and eventually merged with the weighted overlay model in Geographic Information System. The results showed that main streams, land use, and precipitation are the most important components in the flood risk of the Sarbaz river drainage basin. From the total area of the Sarbaz basin, only 0.5% has a high to extremely high flood potential, and the central areas of the basin have the highest potential for flood due to topography and special hydrographic conditions. In addition, the main river basin districts towards the outlet of the basin as well as parts of the margins of important sub-streams have the highest flood potential. Despite the limited area of the high-risk zone, due to population density and agricultural land, the importance of this area is very high in crisis management.
Shamsi Sadat Mir Asadollahi, Sadraldin Motavali, Gholam Reza Janbaz Ghobadi,
Volume 20, Issue 59 (1-2021)
Abstract
Natural disasters are a set of harmful events that are natural origin that sometimes human factors are also effective in exacerbating. In the same vein strengthening the social and economic component and after that resiliency can play an important and effective role in reducing flood damage. This research is applied in terms of purpose and descriptive –analytical and field nature. Survey method and data gathering tool were closed questionnaires, the analysis method is based on correlation and regression test. The statistical population includes citizens living around the river and flood areas that 383 people selected as sample and the questionnaire was distributed by cluster sampling among respondents, according to research finding , the average social resilience 1/60 , average economic aberration ( the amount of damage ) 4/53 ,average capacity with ability to compensate 8/69 , eventually average return to appropriate condition 4/67 .in the test section, hypotheses are determined according to the result of the regression test and correlation which has a significant relationship between urban and urban spatial and social dimensions. Strengthen local organs and organizations in a decentralized state , one of the important ways to increase the social participation of citizens of Gorgan during the crisis.by providing people's participation and strengthening the people's economic ability when natural hazards occur including flood, the initiative of the people is strengthened and the scope for reducing the damage caused by the flood is reduced . people are faced with real and tangible issues with the executive and so on their gap crisis management and conflicts of interest will diminish.
Khadijeh Heydarian, Siavash Shayan, Hossein Jahantigh,
Volume 21, Issue 63 (2-2022)
Abstract
Summer catchment basins surrounding the city of Tehran, due to their remoteness from atmospheric pollution and urban manifestations, is considered as a place for exploring and recreating for many people, and as a place for money making out of restaurants attracting many tourists for others. Sangan is taken into consideration as one of the most beautiful valleys in Northwest of Tehran. The summer catchment basins due to the phenomenon of counter urbanization and also escape from city pollution, easy access, and short distance, has taken too much attention, so much that the inhabitants mostly spend winter in Tehran and summer there. Since some buildings have been built along the main river, the study of the effectiveness of riparian zone and also the specification of areas susceptible to flood is of great importance. In this research, using the HEC-RAS RAS model, flood- prone areas with different return periods (2 to 100 years old) were calculated, and then for the floodplain zoning the morphological characteristics of the flood zones gathered during the fieldwork have been used. The careful study of these flood fringe zones indicates that a small percentage of the lands are included in flood hazard zone with the 25-year return period. Also, the comparison of the pictures taken from the Sangan River in the past and present shows that the use of lands in the river bank has been changed and due to unauthorized constructions and gardening along the river, the width of the bed has dramatically been decreased. This factor increases the size of the floodplain area and consequently the damages.
Fariba Sfandyary Darabad, Mansour Kheirizade, Masoud Rahimi,
Volume 22, Issue 66 (10-2022)
Abstract
Floods are one of the most abundant and destructive natural disasters that every year are caused heavy losses of life and property. Due to human activity in river systems and construction in rivers, flood damage has an upward trend. One of the most important actions to reduce flood damage is the provision of flood hazard zoning maps and their use in spatial planning. In this study, the risk of flood in the Nirchay River Basin that located Ardebil province was investigated. For this purpose, the HEC-HMS model was used to simulate rainfall-runoff and to identify flood zones and fuzzy logic in order to overlay the layers and prepare a flood hazard zoning map.The simulation results show the high performance of the HEC-HMS model in simulating rainfall-runoff of the Nirchay River Basin and estimating peak flood discharges. Rainfall conversion to runoff at the Nirchay River Basin controlled by slope and land-use.The most runoff height and peak flow in Nirchay River Basin are located in the upstream sub-basins. This is due to the steep, low permeability soil, frequency impervious surfaces and high CN. The combination of layers using fuzzy logic has shown that about 8.6% of the surface of the basin are located with a high risk of flooding. These zones are located mainly on the floodplain of the Nirchay Basin. Due to the Low valley width and low slope, these lands are always at flood risk. Most settlements in the study area are located at downstream of the basin. This has increased the risk of flooding.
Dr Esmaiel Najafi, Dr Amir Safari, Dr Ezatoalah Ghavavati, Dr Amir Karam,
Volume 24, Issue 73 (8-2024)
Abstract
Geomorphology is related to the processes and forms of the earth's surface, and any human activity, including the construction of bridges, leads to quantitative and qualitative changes in the movement and displacement of materials and kinetic energy and affects the geomorphic system, is the concern and involvement of geomorphologists. Geomorphology, as a systematic science can also study and explain the environmental realities that have been objectified in the form of processes and forms in nature, and introduce their results and output spatially in the form of maps and models. The type of research is applied and the research method is descriptive-analytical and based on the results of the Ph.D. Thesis entitled "Geomorphological modeling of the construction of bridges in urban floodways (Case study: Tehran metropolis)". The results indicate the capability and application of geomorphology in modeling and optimal location and construction of bridges, in order to create more security and welfare of citizens, reduce costs and prevent financial and human losses due to the destruction and improper location of such structures in an urban floodway- river valleys and other natural environments. Also, this study, while enriching the literature of the field in question, has studied, explained, and conceptually modeled the role and application of geomorphology in the optimal location and construction of bridges in urban issues.
Keywords: Geomorphology, Conceptual Model, urban floodway- river valleys, Bridge Construction.
Ms Akram Hedayati Dezfuli, Ms Zahra Ghassabi,
Volume 24, Issue 73 (8-2024)
Abstract
Flood is one of the most destructive natural phenomena. Every year it brings extensive losses to the country’s financial and human resources. In our country, major parts of Iran’s provinces are always at risk of flooding. The Gorgan and Atrak catchments have also become more important, as several floods have occurred in Golestan province in recent years, causing many deaths and economic losses. The purpose of this study was to investigate the synoptic and thermodynamic conditions of the March 2019 flood event in Golestan province in order to atmospheric system that lead to such floods. This study includes statistical analysis of provincial stations (Gorgan, Gonbadkavus, Aliabadkatol, Hashemabad, Kalale, Maravetape and Bandaretokman), calculating of the return period of precipitation during the available statistical period of each station, analysis of synoptic maps on the day of the flood event, the analysis of satellite images of the days involved in the flood, and calculation of instability indices of the Gorgans’s station. Statistical results showed that Gorgan and Gonbadkavus stations, with the highest amount of rainfall in March 2019, had a return period with 800 and 400 years respectively. Also the highest amount index of Gorgan with values of K=26°c, PW= 0.27 cm and TT= 48 was obtained with high relative humidity (about 80%). The analysis of the synoptic maps showed the severe sea level pressure and mid- level height drop with a deep trough in the study area, which led to extreme rainfall.
Key words: Flood, return period, Synoptic maps, instability indices, Golestan province.
Dana Rahimi, Javad Khoshhal Dastjerdi, Dariush Rahimi,
Volume 24, Issue 74 (12-2024)
Abstract
Among natural disasters, floods have the highest human toll. The economic impacts of floods are greater in developing countries, including Iran, and are particularly severe in the colder months of the year in the west of the country. The purpose of the present study is to analyze the most severe historical synoptic floods that occurred in Karkheh Basin (1 April, 2019). Descriptive - analytical research method and its environmental approach into circulation. Analysis of synoptic systems of large floods such as the April 12, 2019 floods show that Western Europe's high-pressure systems, Black sea, East of the Caspian and low pressure north of the Red Sea, Eastern Mediterranean in harmony with the high-rise systems of Western Europe, Low Mediterranean East with a temperature drop of about 50 degrees Celsius(The temperature at sea level In the eastern Mediterranean and Red Sea about 25 degrees Celsius and in the middle of the atmosphere -25 degrees Celsius) also the climb Humidity from the Arabian Sea, North Indian Ocean, Red Sea, Oman Sea and Persian Gulf and Along with Mid-width cold air loss On the area and the establishment of the Polar jet stream) Core up to 70 m(And the establishment of the front jet stream And positive rotation area On the area shows the structure of the synoptic systems causing the flood in the area.
Dr Mohammad Ebrahim Afifi,
Volume 24, Issue 75 (2-2025)
Abstract
Among the natural hazards, without a doubt, the flood is known as a natural disaster. In this research, Shannon entropy model was used to prepare a flood sensitivity map. First, 34 flood watersheds were selected from Firoozabad basin, and then these 34 points were classified into two groups. With 22 points, 65 percent of the points for training and modeling, and 12 points, 35 percent of the locations that were not used in modeling were used for validation. First, a map of the status of the floods was developed and Then, 10 factors, slope, tilt, lithology, land use, NDVI, SPI, TWI, altitudes, rainfall and distances from the river were selected as flood factors in Firoozabad basin. Prioritizing the effective factors in the occurrence of flood by Shannon entropy index showed that the NDVI layers (2.03), rainfall (0.00), distance from the river (1.89), SPI (385.1), elevation classes (999 (0/19), gradient with weight (0,932), lithology (478/0), TWI (379/0), and land use (280/0), respectively (0/184) have the highest and the least impact Flood events. Based on the results of the ROC curve, the predicted surface area under the curve with 35% of the validation data is equal (91.42%) and for the success rate with 65% of the equal education data (92.53%).
