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Showing 3 results for Flood Risk

Farhad Azizpour, Mohammed Saeed Hamidi, Jamshid Chabok,
Volume 2, Issue 4 (1-2016)

Among the various environmental hazards, flood is the greatest and most important climate crisis which takes every year the lives of thousands people and impose severe damages on human society and environment. Today, it is clear that controlling all hazards, including floods is not possible. Suitable management can only minimize the damages. The literature on natural disasters management indicated that in the process of natural disaster management and their vulnerability mitigation, there are two dominant paradigm: technic-based approach and community-based approach.

Community-based approach welcome the local cooperation and participation in disaster management process and calls for strengthening local capacity through the participation of all individuals and groups at the local level. This approach is not only appropriate to provide solutions for disaster reduction, but build disaster preparedness. Because disaster preparedness planning requires special attention to local participation. In the geographic area of Bashar River Basin, due to the lack of suitable agricultural land and greater quantity of water for rice crop, villages have been built at rivers edge. So that, most of the houses and farms in the villages are located very close to the river. However, these locations are extremely vulnerable to flooding. This study reviews the status of local participation and its impact on reducing flood risks. Also, this research focuses on factors influencing local community trends and choices in the participation rate.

This study is applied research in terms of purpose and uses descriptive-analytical method. According to the nature of the study, data were collected through fieldwork and library research methods using observation, interview, questionnaire and evaluation card techniques. To understand different characteristics of community, Likert scale and one-sample t-test were used and measurement scale for data was ordinal. Also. The method of selective experimental approach based on profit was taken to evaluate the level of different trends in Community's financial participation for reducing detrimental effects of flood. To recognize the community awareness and perception toward flood risk and the probability of its occurrence in the future, the willingness level to participation and to explore the effective factors on villager’s decisions and to utilize modern management techniques the selective experimental approach based on evaluation card and logit model were employed.

The results of statistical analysis showed that in the study area, 86.5% of the community have experienced the damages caused by flooding and forecasted the likelihood of heightened chance of flooding in the future. Finding showed that although the people use traditional methods for managing flood, but they tend to employ modern methods such as dam building for reducing flood risk. This help them to increase the safety factor for their locations and farm lands. In spite of the fact that the villagers expressed the higher safety factor for new management methods such as (dam building, river broadening and preventing the destruction of forest and environment), but it seems that improper functioning, adverse consequences (environmental and socio-economic) of projects implementation (dam building) as well as the inability of villager's financial participation (high cost of this kind of methods), are barriers to using them for lowering the flood risks and damages.

The review of the possible role of some intervening variables to predict local communities' participation in decision-making processes showed that low-income, old age of the samples with high average (47.61) and education with lower average (3.16) are the most important factors influencing community decision making. The results of binominal logit model showed that the proposed variables is significant at the 5% level. If the offer price increase, the chance of residents' acceptance of participation will decrease and vice versa.

Dr Fariba Esfandiary Darabad, Sedigheh Layeghi, Dr Raoof Mostafazadeh, Khadijeh Haji,
Volume 8, Issue 2 (9-2021)

The zoning of flood risk potential in the Ghotorchay watershed with ANP and WLC multi-criteria decision making methods
Extended Abstract
Flood is one of the most complex and natural destructive phenomena that have many damage every year. The northwestern region of the country, due to its semi-arid and mountainous climate and thus of high rainfall variability, is one of the areas exposed to destructive floods. Flood risk zoning is an essential tool for flood risk management. Therefore, the purpose of this research was to determine the flood risk zones in the Ghotorchay watershed by using the analytical network process (ANP).
In this research,, with geographic information system (GIS), satellite images, synoptic station data, analytical network process and the combination of layers, the flood potential of has been modeled in the Ghotorchay watershed. The final map of flood risk based on a combination of factors and climatic and physical elements including land use, geology, vegetation, topography, slope and land capability was prepared. The weight of each criterion was determined by ANP method and used by weighted linear composition (WLC) method for spatial modeling and incorporation of layers.
The results of flood risk zoning showed that the Qal layers from geology, slopes of less than 3 precent, land capacity of units 5, 6 and 7, and as well as poor vegetation cover were identified as flood zones. The results obtained from the analytical network process model indicate the fact that part of the watershed is affected by the risk of flooding with the very high potential, which is mainly located in the downstream of watershed. For this reason, the streams of rank 3 and 4 are considered as flood zones and flood guide areas to the downstream areas. Also, river networks of 5 and higher ranks are in the range of floodplains or river coastal and usually have surface and extensive floods.
The flood prone areas and providing effective solutions for flood management is one of the main steps in reducing flood damage. Therefore more precise management and control of basins with multiple dams, embedding flood alert systems in flood plain areas and performing basic measures is one of the most urgent measures to prevent, improve and control this natural disaster.
Key words: Analytical network process, Biological protection, Floodplain, Flood risk assessment, Ghotorchay
Changiz Seravani, Gholamhossein Abdollahzadeh, Mohammad Sharif Sharifzadeh, Khalil Ghorbani,
Volume 8, Issue 2 (9-2021)

Zoning map Vulnerability of Flood Spreading areas
(Case study: Musian Flood spreading station in Ilam province)
One of the flood plain hazards is a change in the pattern of surface flows due to natural factors or human activities. Changes in the stream pattern are the changes that occur due to the surface stream patterns in terms of the shape of the drains, drainage form and quantitative morphological indices of the basin. These changes ,by formation of flood, submersibility, erosion, longitudinal and transverse displacements of rivers and streams, environmental degradation, etc., have a great deal of risk and harm to residents of the land adjacent to the watersheds, including the demolition of residential buildings,  valuable agriculture lands, facilities, river structures, buildings and relation routes, etc. There are several watersheds in the Musian Plain Basin that regularly change the direction of surface streams and, while displacing large volumes of sediments of erosion-sensitive structures, degrades crops, rural dwellings, connection paths, facilities, Irrigation canals obstruction, water supply and a lot of financial and physical damage to the residents of the region. Therefore, in order to solve these problems, in 1997, the Dehloran flood spreading plan was carried out at a level of 5000 hectares from the Basin of Musian Plain. Although some of the changes in the dynamics of the region, such as stream pattern, flood control, supllying groundwater aquifers, etc., have been caused by the implementation of this plan, but the problem of the concentration of watersheds behind the embankments composed of sensitive formations ,and the release of these areas will have many financial and even physical losses. Therefore, with the implementation of this research, it is attempted to identify the domain and risks that threaten the lowlands and to identify the appropriate measures to prevent them from happening with the zoning and inspection of the vulnerable areas of the Musain Plain.
This study was conducted in five stages to prepare a vulnerability map of the flood spreading area of ​​Mosian plain. First, the implementation phases of the flood distribution plan were separated. In the second stage, information layers of effective factors in changing the flow pattern and concentration of surface currents behind the flood spreading structures were prepared. These layers included elevation, slope, and direction classes, which were prepared based on the Digital Elevation Model (DEM) extracted from the 1: 50,000 topographic maps of the Armed Forces Geographical Organization, as well as the layers of geological formations and land use changes. The lands were prepared based on the maps of the Geological Survey of Iran and the processing of Landsat satellite images of eight OLI sensors in 2013, respectively, by the method of determining educational samples. In the third stage, each class of effective factors in changing the flow pattern (mentioned layers) was given a score based on the range of zero to 10. The basis of the scores of the classes of each factor was according to the number of classes and the average of the total classes of that factor. The fourth stage in the GIS environment was created by combining the weight layers created, the vulnerability layer of the study area (quantitative map of vulnerability areas) of the basin. Then, by analyzing the vulnerability layer (filtering), the pixels and small units were removed or merged into larger units. The last (fifth) step was to classify the quantitative layer and then extract the qualitative map of the vulnerability zoning according to the range of scores based on the five very low, low, medium, severe and very severe classes. A summary of the research steps is shown in the form of a diagram.
Results and Discussion
The results showed that the most important threat and danger factor is the concentration of waterways behind erosion-sensitive embankments. Also, the study area in terms of vulnerability includes three classes with medium risk, high and very high and covers 16, 62 and 22% of the area, respectively. Flood and upland Spreading areas, risk areas and lowland lands are the most vulnerable parts of the basin in terms of floods and sedimentary deposits.
Based on the results obtained by combining the information layersof the factors influencing the stream pattern change, the zoning map of vulnerable areas of the region was created in 5 classes. Except for very few and very small classes that are not present in the region, there are other cases at the basin level:
Medium class:Includes about 16% of the basin. The existing watersheds in this part are ranked 1th class, and some of them are entering the rivers of Dojraj and Chiqab in the eastern and western parts. The formations of this part are often Bakhtyari and limitedly Aghajari. The floors have a height of 100 to 400 meters and the gradient is from 0-2 percent to 20 percent.
Medium class: About 62% of the basin level. The watersheds that flow in this section are in 1to 5 class. The formations of this part are often alluvial and bakhtiari of lahbori sections. It has a height of less than 100 meters to 300 meters and a gradient of 2-0 percent to 20 percent.
very intense: it covers about 22% of the basin's surface. The existing watersheds are of of class 2 and 3. The formations of this part are often alluvial and bakhtiari of lahbori sections. They have height classes of 100 to 300 meters and the gradient is 5-2 percent and is limited to 5 to 10 percent in the slopes.
Keywords: Vulnerability, Aquifer, zoning, Satellite imagery, Environmental hazards, Musian

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