Geomorphology
Reza esmaili; Niusha Nourizadeh Nesheli
Abstract
Rivers are natural systems that have undergone significant changes in their morphology due to human pressures over the past decades. The factors influencing river morphological changes and their responses vary across different regions. Consequently, in the present study, morphological changes in a section ...
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Rivers are natural systems that have undergone significant changes in their morphology due to human pressures over the past decades. The factors influencing river morphological changes and their responses vary across different regions. Consequently, in the present study, morphological changes in a section of the Haraz River in of Amol city were investigated over a 53-year period (from 1968 to 2021).The changes in river width, planform, and riverbed landforms were examined using aerial photographs and satellite imagery. Subsequently, by calculating the specific stream power and conducting field observations, the hazards associated with the river channel were identified. In 1968, the average river width was measured at 141 meters, but by the years 2006 and 2021, it had decreased to 55 meters. The area of riverbed landforms, including the active riverbed and longitudinal bars, decreased by 50% and 95%, respectively, during this period. The river channel transitioned from a braided pattern to a single-channel pattern due to channel narrowing and significant reduction in longitudinal bars. These changes led to an increase in stream power and erosional processes, resulting in river incision and bank erosion. Key factors contributing to the morphological alterations in the study area included the reduction in base flow, irrigation channel diversion, and land use changes along the river margins. Considering the observed trends, the construction of a new dam (Haraz Dam), continued exploitation of floodplain areas, and channelization could exacerbate the risks associated with the river channel and lead to significant floods.
Hydrogeomorphology
eisa jokar sarhangi; ghasem lorestani; vahid falah
Abstract
The studied area on the Haraz Road from Poldakhter to Vana is prone to avalanches due to its cold mountain climate. The purpose of this research is to determine the most important factors affecting the occurrence of avalanches and its risk zoning using LNRF and Shannon Entropy models. For this purpose, ...
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The studied area on the Haraz Road from Poldakhter to Vana is prone to avalanches due to its cold mountain climate. The purpose of this research is to determine the most important factors affecting the occurrence of avalanches and its risk zoning using LNRF and Shannon Entropy models. For this purpose, the criteria of snow cover, elevation, slope, aspect, slope curvature, landuse and distance from the road have been used. The results of determining the most important factors affecting the occurrence of avalanches in the studied area using Shannon's Entropy model showed that the aspect, landuse, distance from the road and snow cover with weights of 0.541, 0.143, 0.129 and 0.083 respectively are more important. Avalanche risk zoning maps show that the highest avalanche risk is due to the location of these areas at an altitude of 2100-2700 meters and a slope of 30-60 degrees with the direction of the northeastern and northern slopes. Evaluation of avalanche risk zoning maps using the empirical probability index (P) indicates the appropriateness of Shannon entropy and LNRF models in the region, but the application of Shannon entropy has led to an increase in map accuracy up to 97%.
