%0 Journal Article %T Quantitative and Morphological Analysis of Longitudinal Profile of Northern Alborz Rivers in Mazandaran Province %J Physical Geography Research %I University of Tehran %Z 2008-630X %A Esmaeili, Reza %A Salehi, Maryam %D 2019 %\ 12/22/2019 %V 51 %N 4 %P 597-611 %! Quantitative and Morphological Analysis of Longitudinal Profile of Northern Alborz Rivers in Mazandaran Province %K river lonitudinal profile %K Cancavity Index %K Northen Alborz %K Mazandaran %R 10.22059/jphgr.2019.281486.1007383 %X Introduction The longitudinal profile of river is one of the main components of the fluvial system. It is result from the interaction between lithology, tectonics, fluvial incision and base level change. The longitudinal profile of the rivers that are in a Equilibrium state have concave form, but several factors cause changes to the longitudinal profile of the river, including lowering base level, rock resistance, structural control, sediment input, non-fluvial processes, bed load effects, and human changes. Alborz Mountains are considered as one of the geomorphological zone of Iran, which geological, climatological and vegetation characteristics have created a special geographic landscape. In this study, longitudinal profiles of the northern Alborz rivers (Mazandaran province), as part of the Caspian Sea basin, have been investigated in this research. The aim of this research is to make a quantitative analysis of the longitudinal profile of the rivers in the region. Methods and material   The longitudinal profiles of 15 rivers in the northern Alborz were investigated by quantitative measures. The drainage network was extracted by the 12.5-m DEM and longitudinal profiles of the fifteen trunk channels were extracted using the ArcGIS 10.3. Geological maps were used to interpret lithology and fault distribution. The form of longitudinal profiles was measured by the concavity index (CI) and SLK index. The longitudinal gradient index (SL) was also calculated for each segment of the profiles. The concavity index was computed based on deviations from a straight line profile (Philips and Lutz, 2008). The SL Index analysis was performed with Hack's (1973) method. The SLK index for the longitudinal profile of the river was calculated by normalizing the distances in the horizontal axis and the elevation in the vertical axis. To normalize the values ​​(SLK), in the horizontal axis of the graph, the normalized distances are represented as (d / D), where d is the distance between the specific points along the longitudinal profile and D is the total length of the profile. In the vertical axis of normalized height (e / E) the e is the elevation of specific points along the longitudinal profile and E is the elevation difference between the beginning and the end of the longitudinal profile (Vojtco et al., 2012). The maximum amount of concavity along the SLK profile was determined as Zmax. Results and discussion The northern Alborz Rivers do not have smooth concave profiles and there are numerous knickpoints in their longitudinal profiles. In all cases, the best fit (R2) of regression has been matched with polynomial equations of degrees 2, 3 and 4.  The coefficient of determination of these regression equations was very high (>0.96). Some of the rivers such as Kheyrood, Kojur and Noor have a convex profile with concavity index of -4, -4, and -11, respectively. A number of other rivers such as Tajen, Babol, Sardabrood and Chalakrood with CI 8, 7.5, 9 and 8, respectively, have more concavity than other rivers. Based on the relative concavity index (CIrel), 20% of the longitudinal profile of the North Alborz in the convex form (CIrel <0), 53% had a relatively straight or very low concavity (0