year 13, Issue 1 (Spring 2023 2023)
E.E.R. 2023, 13(1): 114-134 |
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ghodrati A, habibi A. Investigation of Vegetation in River Bank Stabilization, Soil Erosion and Sediment Production in Pesikhan Watershed (Guilan). E.E.R. 2023; 13 (1) :114-134
URL: http://magazine.hormozgan.ac.ir/article-1-691-en.html
URL: http://magazine.hormozgan.ac.ir/article-1-691-en.html
Forests, Rangelands and Watershed Management Research Department, Agricultural and Natural Resources Research Center of Guilan Province, Agricultural Research, Training and Extension Organization, Rasht, Iran. , ghodrati_2000@yahoo.com
Abstract: (1361 Views)
1-Introduction
The main problem in river engineering is to investigate the mutual effects of water, soil and plants in the river and to identify and introduce compatible tree species and the appropriate patterns of its stabilization for different climatic conditions of the river in terms of water quality and quantity, the type of river bank and its hydraulic characteristics. River erosion reduces sedimentation and increases the efficiency of surface water reservoirs, and the stabilization of riverside lands creates social and work security in relation to the displacement of the river. Vegetation on the margins and wide plates of rivers slows down the flow. From the hydraulic point of view, the slowness of the flow caused by vegetation in natural channels is an important factor in the flood design of the plain and the management of the river and natural channels. The role of vegetation in the protection and stabilization of river walls and banks has been widely studied by researchers in all parts of the world and they have all recognized it as an economic and environmental option. This method has the power and capability for regeneration in a natural way (Agha Razi, 2002). The results of a study that investigated the effect of vegetation on the protection of the banks of the Qara Chai River in the central provinces showed that the amount of erosion and destruction of the river bank, in the direct route and in the winding route, is far more in places without vegetation cover than in places with vegetation (Morgan, 1999). For a better understanding of erosion, effective factors in its occurrence have been identified and the practical natural and biological methods for controlling erosion along waterways have. In the book on river management techniques, while studying the effect of vegetation cover on manning flow roughness and flow speed distribution, the author has provided recommendations about the type and location of planting various tree species (Schiechtl, 1997).
2- Methodology
The purpose of the present study was to identify and record the geographical locations of suitable points and the required numbers for each of the design treatments, including tree stands, shrub stands, bush stands and parts without vegetation along the river. Tree vegetation (alder), shrub cover (willow), and grass cover (three drip washes and swamps) have covered most of the rivers of Guilan. At each selected point in the field operation, 6 metal pins are hammered at distances of 2 meters from each other and perpendicular to the direction of flow. These pins must be fixed during the execution of the design and no movements must be made in them. The numerical analyses conducted based on vegetation conditions (tree, shrub, and herbaceous) indicated the amount and extent of erosion resulting from changes in soil surface at the location of pins in each layer at different temperatures. Based on the design of the study, the collected data, which are both numerical (i.e., number of species) and in the form of percentage (i.e., percentage of canopy cover of plant species) are compared by t-test, and the relationship of vegetation (trees, shrubs, and grasses) with erosion had been examined by using bivariate regression equations.
3- Results
The executive works of river engineering, especially in Gilan province, should be carefully considered in the current weather conditions. The conditions of Gilan province in terms of the stability of river walls are different from the provinces of arid and semi-arid regions; Because the water regime is very high in spring and autumn, and its frequency is also associated with a large volume of water. Therefore, the cultivated seedlings will not have much resistance against a huge amount of water and most of the seedlings will die in the first year. Also, the right opportunity in the first year is not enough for the root to strengthen the walls and stabilize at least 50%; Therefore, it is recommended to stabilize the walls with natural structures and unnatural mechanical structures such as rip-rap at the base of the wall and gabions and other structures after planting the desired species. The research showed that the grass cover in the surface part has little erosion. This does not mean that the presence of grass cover has been able to provide good protection against erosion; Because there was no flood. Therefore, the erosion is also less, but in the tree and shrub cover, the roots of the plants are exposed to the washing of the lower floor, therefore, the recorded statistics show a high number of erosion. But during severe flooding - during the removed statistical period, it was observed that the grassy cover is destroyed in a blocky way, but in the tree and shrub cover, the walls maintain their stability, and in general, the protection of the river walls that It flows in the whole region, subject to changes in land use, upstream destruction, changes in the morphology of the river bed, and the cutting of tree cover along the river's walls, all played a role in lateral erosion. Therefore, the authorities should pay attention to the important points of watershed management and river engineering in order to create stability of the river walls in order to prevent erosion.
4- Discussion & Conclusions
First of all, it should be noted that in order to maintain the river bank and its On both sides of the river stability, the pressure on the wall should be reduced as much as possible. Having tall and heavy trees can increase the force in the form of a lever and thereby can increase the pressure on the wall bed. Therefore, it is possible to use short stature with very low weight in these places (Davoodi, 2013) grass cover and alder roots are shallow and deep and are suitable for preventing soil erosion along the river (Ghobadian,1989). It is suggested that in this area or in areas with similar ecological conditions, in order to control surface erosion along the rivers, plants such as watercress, grass should be used. The important issue in this project is that the method of breeding branches will be suitable for the establishment of tree species in the walls and along rivers. And in some areas, the walls must be accompanied by mechanical operations in the first 5 years of wall protection. The use of non-woody (herbaceous) native plants such as watercress, grass cover to protect topsoil from water erosion can be very effective.
Keywords: River wall stabilization, Biomechanical method, Biological method, Mechanical method, Flood and erosion
Type of Study: Research |
Received: 2021/11/8 | Published: 2023/04/28
Received: 2021/11/8 | Published: 2023/04/28
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