year 13, Issue 1 (Spring 2023 2023)
E.E.R. 2023, 13(1): 53-69 |
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Hosseinzadeh M M, sartipzadeh namin M. Investigation of Lateral Erosion of Qaleh Rudkhan River in Guilan Using Streambank Erosion Potential Index. E.E.R. 2023; 13 (1) :53-69
URL: http://magazine.hormozgan.ac.ir/article-1-741-en.html
URL: http://magazine.hormozgan.ac.ir/article-1-741-en.html
Earth Sciences Faculty, Shahid Beheshti University, Tehran , m_hoseinzadeh@sbu.ac.ir
Abstract: (2264 Views)
1- Introduction
River canal changes are natural river processes and part of the systematic functioning of rivers that cause the destruction of agricultural land around the river and damage to human facilities and roads. Due to the frequent occurrence of lateral erosion risk in Qaleh Rudkhan Fooman river in Guilan province, identification and determination of stable and unstable shores and the degree of this stability can play an effective role in controlling erodible river environments, and preventing environmental hazards. The purpose of this study is to investigate riverbank erosion using Oklahoma Ozark streambank erosion potential index (OSEP).
2- Methodology
Qaleh Rudkhan watershed is located in the west of Guilan province in Fooman city. This river originates from the northern slopes of the Talesh Mountains and after leaving the mountains in the Fooman region, enters the Guilan Plain and finally flows into the Caspian Sea. The study area is approximately 5 km long, upstream of the river and near the city of Fooman.
In order to investigate the erosion of the river bank, a part of the river with an approximate length of 5 km near Fooman was identified and in 8 reaches, the parameters in the Oklahoma Ozark streambank erosion potential index (OSEP) were examined. In this method, eight factors of bank height, bank angle, percentage of bank height with a bank angle greater than 80 degrees, evidence of recent mass wasting (percentage of bank), unconsolidated material (percentage of bank), streambank protection (percentage of streambank covered by plant roots, vegetation, downed logs and branches, rocks, etc.), established beneficial riparian woody-vegetation cover, and stream curvature are scored. In this method, based on the scores calculated for each reach, the stability situation is as follows: 0-25: highly stable, 26-35: moderately stable, 36-45: stable, 46-55: unstable, 56-65: moderately unstable, 66-85: highly unstable. The relative average of the scores has been used to determine the factor affecting lateral erosion and river bank stability. For statistical analysis of the studied intervals, two statistical methods of Box Whisker plot diagram and correlation coefficient with regression have been used.
3- Results
Based on the available findings, in the reaches 1 to 5, the river canal is an irregular one in shape and the river pattern is straight. Bed sediments in this reaches are gravel; the predominant vegetation along the river is grassland along with single trees across the river, and land uses are also agriculture and grazing pastures. One of the geomorphic forms connected to the river bank is intermittent lateral barriers. Along these reaches, massive movements of the transition slip type have been observed. The human evidence influencing the shape of the river includes the destroyed bridge and the sand and gravel resulted from mining operations from the riverbed. In reach 6, the river channel is an asymmetrical channel in shape and the river pattern is sinusoidal. The properties of bed sediments, vegetation and geomorphic forms are similar to previous periods.
In the seventh and eighth reaches, the river channel is asymmetric in terms of shape and the river pattern is of the meandering form. The condition of bed sediments and vegetation is similar to previous reaches. Among the geomorphic forms connected to the river bank in the reach of seven and eight are alternating lateral barriers, point barriers and paleochannel. Along these reaches, mass movements of transfer slip and debris type have been observed.Based on the results obtained from the eight reaches, in general, the right bank of the river, except for the second reach, has been recorded and classified in an unstable state, while the left bank has had different classifications in different reaches. Therefore, the results of one, five and eight reaches are unstable, the results of two, three, four and six are stable and the results of seven show moderate instabilities. Based on the calculation of the relative scores of effective factors in the erosion of Qaleh Rudkhan river bank, in both left and right banks, streambank protection and established beneficial riparian woody-vegetation cover are the most important influential factors and have the most important role in the occurrence of lateral erosion risk. The Box plot diagram of effective factors in shore instability shows that the values of some parameters such as two parameters of riparian vegetation and riparian protection on the left and right banks did not change at different intervals and the same values were recorded.
The correlation coefficient obtained between the right and left sides of the Oklahoma Ozark streambank erosion potential index (OSEP) is 0.259, which indicates a weak correlation, which means the change in parameter values at one edge is not the same as the values measured at the opposite edge. Therefore, if there is instability on one shore, it is not associated with instability on the other shore. Examination of the values in the 8 studied reaches showed that the values obtained and the sensitivity to erosion varied along the study area on the opposite shores.
4- Discussion & Conclusions
The results obtained from the scores of the studied parameters in the Oklahoma Ozark streambank erosion potential index (OSEP) showed that in the left bank, the reaches 1, 5 and 8 were unstable, the reaches 2, 3, 4 and 6 were stable and the reach 7 was moderately unstable, while on the right bank, all the reaches except reach 2 were unstable.
According to the results of relative scores, the streambank protection and established beneficial riparian woody-vegetation cover have been the most effective factors in the instability of the left and right shores of Qaleh Rudkhan river. In general, it can be said that instability has prevailed in the banks of Qaleh Rudkhan River, which is due to human intrusion and occupation in this part of the river.
Keywords: Qaleh Rudkhan river, streambank erosion potential index (OSEP), streambank erosion, Fooman city, Guilan province.
Received: 2022/06/29 | Published: 2023/04/28
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