جستجوی مقالات مرتبط با کلیدواژه "مدل l-thia" در نشریات گروه "جغرافیا"

Type of land use and changes in the type of land use are related to the amount of runoff and changes in it. The type of land use with direct effects on runoff velocity, permeability and flood concentration control is controlled; in this case, a change in type of farming or pasture Urban use has a large impact on reducing water quality and increasing runoff from rainfall. Increased runoff due to user change can be a good indicator of the probability of increasing the flood in a basin. Land use change and land cover, in turn, have hydrological results at local, regional and global scales. The hydrological effects of land use and vegetation management are evident in the form of changes in runoff depth, minimum discharge, maximum discharge, soil moisture and evapotranspiration.Due to the type of soil and topographical and climatic characteristics of the Ojan Tea (from the sub-basins located on the eastern slopes of the Sahand Mountains), changes due to man's loss to slopes and land use changes have been high. Considering the inducements caused by Erosion erosion and general ablation in the range of Ojan tea, it seems that variations in runoff rates are very significant due to changes in the range of the desired range.

In the drainage basins of arid and semi-arid areas where the ecosystem is not able to recover quickly, extreme care should be taken in land use. The hydrological effects of changes in land use are manifested in the form of changes in runoff depth, minimum flow, maximum flow, soil moisture, and evapotranspiration. Increasing runoff production in a particular area, in addition to increasing the potential for flooding, has other effects. Due to the type of soil and the topographic and climatic characteristics, the hydrogeomorphological changes caused by human encroachment on slopes and land use changes have been high in Ojan Chai area (from the sub-basins located on the eastern slopes of Sahand Mountain). Due to erosion in the slopes of Ojan Chay area, it seems that the changes in the amount of runoff are very large due to land use changes in the area. The study area is one of the rangelands of the country and unfortunately, cultivation is done in an unprincipled manner in the slopes that are not suitable for cultivation. In the coming days, the turbulence of the slopes will intensify and the amount of runoff will increase and the number of destructive floods will increase. Often, the soil of the slopes is severely eroded by runoff due to the extreme cultivation in the rangelands.

A flood is a very simple natural phenomenon that occurs when a body of water rises to overflow land that is not normally submerged (Ward, 1978). At the same time, a flood is a very complex phenomenon that connects the natural environment, people, and the social systems of their organization. Flood is the most expensive and devastating natural hazard (Wilby and Keenan 2012; Sanyal and Lu 2004), and it continues to be a concern in many parts of the world (Jha et al. 2012; Kundzewich et al. 2010; Chang and Franczyk 2008). Scenarios of future climate indicate a likelihood of increased intense precipitation and flood hazard in many areas (cf. Kundzewicz et al., 2010). Floods are currently one of the greatest threats to social security and sustainable development, and it is estimated that floods affect around 20–300 million people every year (Hirabayashi and Kanae 2009). In recent decades many studies have been carried out on floods that mainly approached to flood risk management. Flood inundation models are defined as the tools which could simulate the rivers hydraulic and also occurred floods in flood plains (Horrit, 2007, 61). Modern flood management should attempt to analyses the full scope of a flood event, using integrative concepts and taking into account multifaceted expertise from diverse fields. Reliable flood risk assessment and the development of effective flood protection measures require thorough knowledge about flood frequencies at different points in a catchment. In this research, quantitative approaches in order to flood zonation were used for the Ajirloo Chay Basin. Topographic maps with scale of 1: 50,000, digital elevation model (DEM) with 27 m resolution, and satellite imagery (Landsat 3 and 4 :2013) are most important materials in this research. In this study for flood hazard zonation were used the L-THIA method and fuzzy logic quantitative approaches. Fuzzy theory is inaccurate and ambiguous concepts and a variable makes the math. In this study, the operator sum, algebraic product and gamma are used. In order to run the model and research used from a series of climatology data, geomorphology and land surface coating. In flooding zonation an area can be considered many physiographic parameters that can influence. Among these parameters we select nine factors as the most important factors that influence in flooding. These nine factors are: drainage density, hydrologic soil groups, slope, climate, land use, run off, land units, altitude, and lithology.It is important for preventing and decreasing the effect of flood to avoiding expounding these risks. Zonation flooding that can be adopted. In this study we used LHTIA models and fuzzy logic in Ajirloo Chay basin. For this research we got help nine factors includes (altitude – climate – land units – slope – lithology – drainage density –hydrologic soil groups – run off and land use). In this area the results show that more than flood zonation are in very low, low and mediums risk classes (about 65/6 %) that these area are located in western and bathetic water shed and the most high risk area located in the eastern half and the northeast. The high class of land drainage density are in this area of land that is the factor of being prone to flooding The concentration of run off in the Ajirloo chay basin is in the eastern portion and in the upstream of the basin. Natural factors such as high slopes and high altitudes and poor vegetation can aggravated the flooding of the eastern portion of the basin and increase the flood hazard in this portion of the basin. Percent of high risks land is in much and too much potential that included (34/4%) of total area which is remarkable. According to the final map obtained from flooding zonation and for the sustainable development should be prevented from constructions in area with very high and high risk.The concentration of run off in the Ajirloo chay basin is in the eastern portion and in the upstream of the basin. Natural factors such as high slopes and high altitudes and poor vegetation can aggravated the flooding of the eastern portion of the basin and increase the flood hazard in this portion of the basin. Percent of high risks land is in much and too much potential that included (34/4%) of total area which is remarkable. According to the final map obtained from flooding zonation and for the sustainable development should be prevented from constructions in area with very high and high risk.The concentration of run off in the Ajirloo chay basin is in the eastern portion and in the upstream of the basin. Natural factors such as high slopes and high altitudes and poor vegetation can aggravated the flooding of the eastern portion of the basin and increase the flood hazard in this portion of the basin. Percent of high risks land is in much and too much potential that included (34/4%) of total area which is remarkable. According to the final map obtained from flooding zonation and for the sustainable development should be prevented from constructions in area with very high and high risk.