Rapid geomorphic assessments (RGAs) to investigating streambank stability in Qaleh Rudkhan Fooman river, Guilan

Document Type : original Article

Authors

Department of Physical Geography, Earth Sciences Faculty, Shahid Beheshti University, Tehran, Iran

Abstract

Background and purpose
Bank erosion is one of the geomorphic processes caused by natural and human factors. This phenomenon, as one of the types of water erosion, can create several geomorphic effects in the river. The increase in river erosion also causes the instability of the river and as a result changes the type of flow, changes the pattern of the river and changes the course of the river. So far, several methods of rapid geomorphic assessment have been used to investigate river bank erosion, and one of the most common and widely used in these assessments is the Channel Instability Index (CSI). The aim of our study was to know the applicability of the channel stability index to identify erosion-sensitive and unstable banks in the Qaleh Rudkhan Fooman river in Gilan.
Material and methodology
Qaleh Rudkhan river is located in the west of Gilan province in Fooman city. This river originates from the northeast heights of Sote village and flows into the Caspian Sea after traveling 40 kilometers from the Qaleh Rudkhan area. The area of the basin is 347.76 Km2. With the aim of studying the bank erosion and stability of the river bank of Qaleh Rudkhan, a part of the river path with a length of approximately 5 km was selected in near the city of Fooman. In this area, 8 reaches were determined based on river conditions (pattern and morphometric differences) and its sensitivity to bank erosion. Then, mapping of cross_sections, Channel morphometry, grain measurement of the bank sediments, state of compaction and stickiness of sediments, and examination of the vegetation characteristics of the bank and flood plain were carried out for each reaches. In eight reaches, using the channel stability index, the streambank erosion situation was investigated. In this model , the primary bed material ,bed/bank protection, degree of incision, degree of constriction, streambank erosion, streambank instability (percentage of mass movements), established riparian woody- vegetative cover, occurrence of bank accretion and stage of channel evolution model are scored.
Findings and discussion
Based on the findings of the channel stability index (CSI) on the left and right banks of Qaleh Rudkhan river, it showed that the index values ranged from 18.5 to 25.5. Based on these values, reaches one, two, three and four are in a very unstable state (high instability) in terms of channel stability, and reaches five, six, seven and eight are in a medium instability state. Based on the relative score method of bed sediments, bank protection and riparian vegetation are the most important factors affecting channel stability. Based on Pox-Whisker Plot diagram, the status of three variables of degree of incision, the available evidence of bank erosion, percentage of mass movements and occurrence of bank accretion are different in different reaches and as a result of these factors, the sensitivity of the river bank of Qaleh Rudkhan to instability is different.
Conclusion
The results of this research show that the three variables of the primary bed material, bank protection and established riparian woody- vegetative cover are the same in all reaches and are considered important factors affecting the stability and river channel stability. Based on the above findings streambank instability, occurrence of bank accretion, degree of incision and stage of channel evolution model are variable factors in each reaches, which cause differences and changes in the intensity of river bank erosion and river channel.

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References

Basher, L.R. and De Rose, R.C., 2011. Measurement of river bank and cliff erosion from sequential LIDAR and historical aerial photography. Geomorphology, 126, 132–147. doi.org/10.1016/j.geomorph.2010.10.037
Bernhardt, E.S., Palmer, M.A., Allan, J.D. and et al, 2005. Synthesizing U. S. River restoration efforts, Science, 308, 636-637. doi/10.1126/science.1109769
Chassiot, L., Lajeunesse, P. and Bernier, J.F., 2020. Riverbank erosion in cold environments: review and outlook. Earth-Sci Rev, 207, 103-123. doi.org/10.1016/j.earscirev.2020.103231
Collins, A.L., Janes, V.J.J., Nicholas, A.P. and Quine, T.A., 2017. Analysis of fundamental physical factors influencing channel bank erosion: results for contrasting catchments in England and Wales, Environ Earth Sci, 76(307). doi. 10.1007/s12665-017-6593-x.
Downs, P.W. and Simon, A., 1995. An interdisciplinary approach to evaluation of potential instability in alluvial channels, Geomorphology, 3, 215-232. doi.org/10.1016/0169-555X(95)00005-P
Freihardt, J. and Frey, O., 2022. Assessing riverbank erosion in Bangladesh using time series of Sentinel-1 radar imagery in the Google Earth Engine, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2022-319 Gasser, E., Perona, P., Dorren, L., Phillips, C., Hubl, J. and Schwarz, M., 2020. A New Framework to Model Hydraulic Bank Erosion Considering the Effects of Roots. Water: 12, https://doi.org/10.3390/w12030893
Heeren, D.M., Mittelstet, A.R., Fox, G.A., Storm, D.E. and et al, 2012. Using rapid geomorphic assessments to assess stream bank stabililty in Okkahmoma Ozarak streams, American Society of ty of Agricultural and Biological Engineers, 55(3), 9518-968. https://digitalcommons.unl.edu/biosysengfacpub
Krzeminska, D., Kerkhof, T., Skaalsveen, K. and Stolte, J., 2019. Effect of riparian vegetation on stream bank stability in small agricultural catchments, Catena, 172, 87-96.
https://doi.org/10.1016/j.catena.2018.08.014
Piegay, H., Arnaud, F., Belletti, B., Bertrand, M., Bizzi, S., Carbonneau, P., Dufour, S., Liebault, F., Ruiz-Villanueva, V. and Slater, L., 2020. Remotely sensed rivers in the Anthropocene: state of the art and prospects. Earth Surf Process Landforms, 45(1),157-188. doi.org/10.1002/esp.4787.
Sarma, J.N. and Goswam, U., 2007. Change of river channel and bank erosion of the Burhi Dihing river (ASSAM), assessed using remote sensing and GIS, Remote Sensing, 1, 93-100. https://doi.org/10.1007/BF02991837
Simon, A. and Klimetz, L., 2008. Magnitude, frequency and duration relations for suspended sediment in stable (reference) southeastern streams. Journal of the American Water Resources Association, 44 (5). 1270-1283. doi.org/10.1111/j.1752-1688.2008.00222.x
Vargas-Luna, A., Dur, G., Crosato, A. and Uijttewaal, W., 2019. Morphological adaptation of river channels to vegetation establishment: a laboratory study. J. Geophys. Res-Earth Surf. https://doi.org/10.1029/2018jf004878.
Wohl, E., 2020. Rivers in the Anthropocene: The U.S. perspective. Geomorphology, 366 p.
Yu, G., Li, Z., Yang, H., Lu, J., Huang, H. and Yi, Y., 2019. Effects of riparian plant roots on the unconsolidated bank stability of meandering channels in the Tarim River, China, Geomorphology, 351(21). https://doi.org/10.1016/j.geomorph.2019.106958.
Zaimes, G.Ν., Tamparopoulos, A.E., Tufekcioglu, M. and Schultz, R.C., 2021. Understanding stream bank erosion and deposition in Iowa, USA: A seven-year study along streams in different regions with different riparian land-uses. J Environ Manage. https://doi.org/10.1016/j.jenvman.2021.112352..
Sustainable Development of Geographical Environment
Volume 5, Issue 8
August 2023
Pages 139-153

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