عنوان مقاله [English]
Relationships between alluvial fans and catchments are a basic concept in geomorphological studies and many empirical models have been used to study the variation between the properties of an alluvial fan and its drainage basin. TheTalesh Geomorphological Unit in northern Iran is one of the most important units in the country and so far, no morphological and morphometric study has been done on its coastal alluvial fan cones. Alluvial fans of the Talesh coastal plain are one of the most important geomorphological units in the region, with distinct differences in shape, size, and factors affecting their evolution The purpose of this study is to investigate the morphology of alluvial fans, and analyze the role of morphology and lithology of catchments in the alluvial fan geomorphology of this area using statistical relationships.
Basin and alluvial fan boundary extracted using Alos-Palsat elevation model, 1: 50000 map and Quickbird satellite images in Arcgis and Hec-GeoHMSsoftware.Ab catchment area ,Cb: highest basin elevation ,, Pb: basin perimeter,, Lc: river length ,, Rb: basin , (minimum difference and maximum basin height,), Db drainage network density as well as: M Melton coefficient in basins and Af: Alluvial fan area, Apf: apex, Lf: length of alluvial fan, Sf: Slope of alluvial fan, Cf alluvial fan,Ltf toe length of alluvial fan and alluvial fan volume (V) calculated and used In this study. In order to better analyze the factors affecting the formation of alluvial fans, using cluster analysis and n SPSS software, alluvial fans that are most similar together they were classified into 5 classes. Moreover, the role of the main factors in the formation and morphometric changes of alluvial fans was investigated.
Results and discussion
Based on the variance of factors among the variables measured in catchment related to variables: drainage basin area, catchment area, basin height difference, total length of channel network, basin elevation height, and melaton coefficient. Alluvial fan volume, Alluvial fan apex height, cone length, and cone slope. The results of the correlation matrix show the influence of the variables of melton coefficient, area, perimeters, roughness and erodibility of the basin on the geometric shaping of alluvial fans. Alluvial fan area has the highest correlation with catchment area of 0.629 and basin environment of 0.616 and erodibility of rock and sedimentary units with 0. 536.The effect of melton coefficient on other geometrical parameters of the basin is also quite clear. Among the catchment variables, cone slope with melton coefficient (-0.59) , length of cone (-0.569) , height of cone vertex (-0.525) , and difference of vertex height and cone height (-0.558) The highest correlation with the Melton coefficient of cone base length has the highest correlation with basin roughness (0.558) and later with erosivity 0.55 and basin environment (0.552). Among the statistical methods used to communicate and correlate between catchment geometric parameters and alluvial fans, allometric relationships show a very strong correlation between catchment area with alluvial area and melton coefficient with alluvial fan slope.Allometry results show a very strong positive correlation coefficient of about 0.78 between catchment area and alluvial fan area.The relationship between basin area and alluvial fan slope in the study area using this relationship was weak and positive.
The relationship between the melton coefficient of the basin slope is inverse. The results also showa strong positive correlation of 0.75 between these two parameters
The results show that the most important factor in decreasing or increasing the area of alluvial fan in this area is catchment area and with decreasing basin area, the area of alluvial fan also has a decreasing trend and shows a linear correlation coefficient of 0.41. The Melton coefficient, which takes into account the role of catchment area roughness and roughness, is the most correlated variable with volume, slope, cone length, apex height, and alluvial fan height difference in the study area. Correlation matrix, linear correlation and allometric matrix relationships were used to investigate the correlation between parameters. The results show that in addition to the relationship between catchment area and alluvial slope slope, relationships between basin area and alluvial slope area, as well as slope and melton coefficient, the coefficients obtained by allometric method are much better than other statistical methods in relation to the relationship between Morphometric variables have catchment and geometric shape of alluvial fans.The results show that in addition to the relationship between catchment area and alluvial slope, the relationships between basin area and alluvial area as well as melton coefficient and slope coefficients are much better than the other statistical methods in relation to the relationship between Morphometric variables have catchment and geometric shape of alluvial fans.
Keyword: Alluvial fan, Morphometry, Allometry, Talesh Unit