Geomorphology
mohammad mahdi hosein zadeh; somaiyeh khaleghi; milad rostami
Volume 23, Issue 67 , April 2019, , Pages 129-149
Abstract
River channel change, bank erosion and bank sedimentation are natural process of alluvial rivers that cause destruction of agricultural lands and destroyed of structures around the river bank. The aim of this research is estimation of bank retrogression rate and bank erosion in Galali river (the reach ...
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River channel change, bank erosion and bank sedimentation are natural process of alluvial rivers that cause destruction of agricultural lands and destroyed of structures around the river bank. The aim of this research is estimation of bank retrogression rate and bank erosion in Galali river (the reach between Galali and Shirvaneh village) due to assessment of changes and estimation of potential changes in frequency of bank failures (Safety Factor) and sediment load from the river bank in two different scenario and 12 hours and three reaches by BSTEM model. The big floods can be caused bank erosion in this river and this issue is so important because there are some dams have been constructed in downstream of this river so estimation of erosion and sediment load is very important. Results show that total eroded areas in first scenario are 0.244, 0.372 and 0.054 m2 in reaches 1, 2 and 3 and the total eroded areas in second scenario are 0.272, 0.1 and 0.054 in reaches 1, 2 and 3 respectively. According to bank stability and safety factor, all of three cross-sections are unstable in first scenario and safety factor is less that 1 but safety factor increase in second scenario so that safety factor is around 1 in reaches 1 and 2 and in reach 3 is more than 1. Therefore, by protection works on the erodible banks can be reduced the total volume of the sediment load from eroded bank.
Geomorphology
Somayeh Khaleghi; Shahram Roostayee; Ali Mohammad Khorshiddoost; Mohammad Hossein Rezaee Moghaddam; Mhammad ali Ghorbani
Abstract
Catchments and river systems altered in response to changes of internal and external factors. Hence, several techniques have been proposed to simulate these changes and Evolution of the river systems. Cellular Automaton is one of the newest river cellular models that define the catchment landscape with ...
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Catchments and river systems altered in response to changes of internal and external factors. Hence, several techniques have been proposed to simulate these changes and Evolution of the river systems. Cellular Automaton is one of the newest river cellular models that define the catchment landscape with a grid of cells, and development of this landscape is determined by the interactions between cells (for example fluxes of water and sediment) using rules based on simplifications of the governing physics.This method is used for simulation of Lighvan catchment with 20 m cell size and 10 years precipitation data (1380 to 89). Simulation results evaluated in two qualitative and quantitative methods, So that the relative changes in the catchment and spatial distribution of erosion and aggradation value in the entire catchment and each cell was identified on Digital Elevation Model map and also, values of different particle size distribution in different discharges showed that with the increasing discharge, and amounts of sediment increased and among this coarse sand have the highest value and very fine sand, clay and silt particles have the lowest value. Also investigation of longitudinal and latitude profile show that Lighvan river is in mature stage and Lighvan channel has been underwent aggradation due to climate changes and increasing catchment precipitation in last decade that causes hillslope erosion and channel aggradation. Finally, Since certainty of Cellular Automata results is difficult and CAESAR is sensitive to input parameters but comparing the results with previous investigation and field observation shows that Cellular Automata has acceptable results.
