1- sari agricultural and natural resources university
2- ostfalia university
2- ostfalia university
Abstract: (263 Views)
Introduction and Objective: Improving the hydromorphological conditions of the river is a very important issue in the sustainable management of rivers. In December 2000, the European :union: Framework Directive (WFD) was presented and published in the official journal (OJL327), and the most appropriate way to achieve this goal has been left to the discretion of the EU member states. A guideline published in Germany in 2000 by the Water Management Group for small to medium-sized rivers was developed as the River Structural Quality Classification Method (LAWA-OS) in the framework of the WFD. The review of previous studies indicates that the LAWA-OS method in domestic researches has been done in the form of evaluation of only one river, but in this research, two rivers of Pehnehkola and Hardau, were compared with each other. Also, the mentioned method has been investigated in Iran on large rivers with high width and flow. The purpose of this research is to investigate the "Structural Quality Classification of Rivers in Germany (LAWA-OS)" method and to compare the hydromorphological status of the rivers of Hardau in Germany and Pahnehkola in Iran.
Material and Methods: The River Structure Classification Method in Germany (LAWA-OS) examines the damage and negative changes caused by human factors over time. The evaluation of the mentioned method consists of four stages. The first stage is data collection and preparation of basic maps such as topography map, soil science map and land use map. The mentioned information for Pahnehkola River was obtained from Sari City Regional Water Company and General Directorate of Natural Resources and Watershed Management of Mazandaran Province. The topographic map of the Hardau River was prepared from the Topografic-Map.Com website. The second step is to determine the range and its type, which according to the location of the Pahnehkola river in the mountains and the Hardau river in the plains, the range type was determined and 1 km from both rivers was selected and divided into 100 meter intervals. The third stage is the field visit. Filling the forms related to the LAWA-OS method is by visiting the left and right banks and river elements. A set of 25 individual parameters is available in 6 groups from the main parameter in the mentioned form. The fourth step is to evaluate the results. Determining the river class is a process to evaluate it and it is classified into 5 classes, which is calculated according to the points assigned to each parameter, and finally, the structural quality class of the river is determined. The final evaluation includes two evaluation parts based on functional units (the performance of individual parameters with specialized evaluation of the water zone structure by an expert) and index-based evaluation (the performance of individual parameters based on index values). If the difference in the two evaluations is greater than one structural class, re-examination to determine the existing errors is on the agenda.
Results: The evaluations showed that in the Hardau River, the highest negative degradation score was related to individual parameters of flow curvature, special bank cover, special flow structures, depth changes, type of river profile and variety of bed materials. The parameters that are almost natural in the Hardau River are respectively: profile depth, width erosion, and land use. Except for the mentioned parameters, there are several parameters in the Hardau River in a completely natural state. In the studied area of Hardau River, there was no transverse structure either in the bed or in its body. In this regard, the Individual parameter of water return was not observed in any of the studied sections of the Hardau River. Individual parameters related to land use also have a low destruction score. Because the boundaries of the river are completely free and there are no factories, garbage, paved surfaces and even flood protection structures in the river floodplain. In Pahnehkola River, the highest negative degradation score was related to the individual parameters of special bank structure, profile depth and width erosion, respectively. The single parameters that received the minimum destruction score in the Pahnehkola River are the vegetation cover of the river bank, land use and the border around the river. Also, the individual parameters of transverse structure, water return, piping, changes in flow path, bed materials, bed cover and specific cases of land use in Pahnehkola River have not been affected by human interference.
Conclusion: The results of the present research indicate that the Hardau River with a score of 2.53 has been slightly changed in the structural classification, and the Pahnehkola River with a score of 1.71 is classified structurally without changes. According to the results evaluated in Hardau and Pahnehkola rivers, Pahnehkola River has a more natural hydromorphological condition than Hardau River. The reason for the placement of the Hardau River in a slightly changed structural layer can be the ease of access to the river and the use of nearby agricultural lands, which has caused human interference in disrupting the natural structure of the river.
Material and Methods: The River Structure Classification Method in Germany (LAWA-OS) examines the damage and negative changes caused by human factors over time. The evaluation of the mentioned method consists of four stages. The first stage is data collection and preparation of basic maps such as topography map, soil science map and land use map. The mentioned information for Pahnehkola River was obtained from Sari City Regional Water Company and General Directorate of Natural Resources and Watershed Management of Mazandaran Province. The topographic map of the Hardau River was prepared from the Topografic-Map.Com website. The second step is to determine the range and its type, which according to the location of the Pahnehkola river in the mountains and the Hardau river in the plains, the range type was determined and 1 km from both rivers was selected and divided into 100 meter intervals. The third stage is the field visit. Filling the forms related to the LAWA-OS method is by visiting the left and right banks and river elements. A set of 25 individual parameters is available in 6 groups from the main parameter in the mentioned form. The fourth step is to evaluate the results. Determining the river class is a process to evaluate it and it is classified into 5 classes, which is calculated according to the points assigned to each parameter, and finally, the structural quality class of the river is determined. The final evaluation includes two evaluation parts based on functional units (the performance of individual parameters with specialized evaluation of the water zone structure by an expert) and index-based evaluation (the performance of individual parameters based on index values). If the difference in the two evaluations is greater than one structural class, re-examination to determine the existing errors is on the agenda.
Results: The evaluations showed that in the Hardau River, the highest negative degradation score was related to individual parameters of flow curvature, special bank cover, special flow structures, depth changes, type of river profile and variety of bed materials. The parameters that are almost natural in the Hardau River are respectively: profile depth, width erosion, and land use. Except for the mentioned parameters, there are several parameters in the Hardau River in a completely natural state. In the studied area of Hardau River, there was no transverse structure either in the bed or in its body. In this regard, the Individual parameter of water return was not observed in any of the studied sections of the Hardau River. Individual parameters related to land use also have a low destruction score. Because the boundaries of the river are completely free and there are no factories, garbage, paved surfaces and even flood protection structures in the river floodplain. In Pahnehkola River, the highest negative degradation score was related to the individual parameters of special bank structure, profile depth and width erosion, respectively. The single parameters that received the minimum destruction score in the Pahnehkola River are the vegetation cover of the river bank, land use and the border around the river. Also, the individual parameters of transverse structure, water return, piping, changes in flow path, bed materials, bed cover and specific cases of land use in Pahnehkola River have not been affected by human interference.
Conclusion: The results of the present research indicate that the Hardau River with a score of 2.53 has been slightly changed in the structural classification, and the Pahnehkola River with a score of 1.71 is classified structurally without changes. According to the results evaluated in Hardau and Pahnehkola rivers, Pahnehkola River has a more natural hydromorphological condition than Hardau River. The reason for the placement of the Hardau River in a slightly changed structural layer can be the ease of access to the river and the use of nearby agricultural lands, which has caused human interference in disrupting the natural structure of the river.
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