نوع مقاله : مقاله پژوهشی
1 دانشیار گروه مهندسی طبیعت، دانشکده منابع طبیعی و محیط زیست، دانشگاه ملایر.
2 دانش آموخته کارشناسی ارشد آبخیزداری، دانشکده منابع طبیعی و محیط زیست، دانشگاه ملایر.
عنوان مقاله [English]
One of the quantitative and experimental methods that has been used by researchers in recent decades to study the relationship between drainage network and hydrograph forms is the use of fractal dimension. Some hydrogeological and morphometric parameters of watersheds that have a special geometric shape can be studied more accurately with fractal geometry and by calculating the fractal dimension of each of the characteristics of the river basin, new parameters can be prepared for watersheds that can Explain more features of watersheds in terms of flooding, erosion, runoff estimation, and sediment. (Ildoromi et al. 2019).
Mohammadi Khoshoei et al. (2020) Comparing fractal dimension and geomorphological features in Aqda watershed management showed that there are significant relationships between fractal dimensions of basin shape and drainage network with geomorphological features, and the highest correlation coefficient belongs to regression relationships. Drainage network can be seen between the total length of the drainage network and the fractal dimension Dutta et al. (2014) in the study of glacial landforms in Himalia using multi-fractal analysis showed that with fractal analysis, landforms created by different processes can be separated. Hui et al. (2017) in examining the relationship between the fractal dimension of the drainage network and the evolutionary stages of erosion of the China Yellow Basin showed that the fractal values of the drainage network have a positive and linear relationship with the sediment delivery and runoff values of the basin. The purpose of this study is to find relationships for concentration of time based on the fractal dimension by producing a fractal triangular unit hydrograph under the basins of the River basin kalan Malayer in Hamadan province.
The Kalan Basin is located in the branches of Karkheh watershed.In this study, to extract the geomorphological parameters of the watershed from the GIS, DEM map, elevation difference, basin slope, flow direction layers, cumulative flow direction, flow length layers and streams categories and river chanal map, River Networks length the original was extracted and prepared for each sub-basin. In this research, the results of fractal dimension by box counting method, the results of drawing NRCS triangular unit hydrograph, the results of drawing fractal unit hydrograph, the results of comparing NRCS unit hydrograph and fractal unit hydrograph in all sub-basins kalan has been validated and the relationship between river basin concentration of time and its fractal properties has been evaluated based on computational error including peak flow error rate (CFS), peak time error percentage (Hr), and base time error percentage (Hr). The sub-basin hydrograph has been modified.
Results and Discussion
The results show that the greater the difference in basin height, the less the agreement between the NRCS unit hydrograph and the triangular unit hydrograph and shows that fractal hydrographs in all sub-basins have improved the concentration time relative to the hydrographic network .Below basin C, there is an acceptable agreement between the fractal dimension and the NRCS hydrograph, which indicates the accuracy of the results of the fractal dimension analysis of the drainage network. It can be concluded that the NRCS unit hydrograph and the fractal unit hydrograph are well matched .However, in the river basins B and E, the hydrograph of the NRCS unit of the fractal unit does not match well, which is due to the low level of the River Networks, (drainage network). The results showed that the greater the height difference, the less the agreement between the NRCS unit hydrograph and the triangular unit hydrograph. This study confirms the error percentage of fractal hydrograph and NRCS parameters related to each sub-basin.
Production of artificial unit hydrograph based on concentration time, main river networks, length, height difference and geomorphological characteristics is one of the important and accurate tools in this regard that can be used to produce artificial unit hydrograph based on fractal timec enter and corrected. The results of artificial unit hydrograph production based on fractal characteristics of the kalan basin river basin showed that the NRCS triangular unit hydrograph can be plotted and estimated only by having a morphological image of the chanals and without the need for complex calculations. Examination and comparison of fractal unit hydrograph and NRCS unit hydrograph showed that the fractal dimension hydrograph provided a relatively good agreement with NRCS.This raises the accuracy and efficiency of the fractal dimension hydrograph using geomorphological indicators in particular, the drainage network, especially in river basins without a measuring station shows. Examination and comparison of fractal unit hydrograph and NRCS unit hydrograph showed that the fractal dimension hydrograph provided a relatively good agreement with NRCS and this issue of accuracy and efficiency of fractal dimension hydrograph using geomorphological indicators, especially drainage network, in river basins without indicates the measuring station. It is suggested fractal unit hydrograph with other hydrogeomorphological parameters such as basin shape coefficient should be performed and checked with HEC-HMS hydrograph.
Keywords: Fractal, Geomorphology, Triangular Unit Hydrograph, Time Center, Kalan