15:30 〜 17:00
[HGM02-P10] Extraction and Quantification of concavity index for the channel steepness using river profile: Middle Alaknanda Catchment, Western Himalaya.
キーワード：steepness index, concavity, MATLAB, Chi analysis
The channel concavity Index (θ) which reflects how quickly the channel gradient index decreases with increasing drainage area, is one of the geomorphic indices that serve as a sensitive marker of the differential uplift-erosion rate in an erosional landscape of a drainage basin. The most widely used method to analyze the river profile geometry is the extraction of a concavity index (θ) over the channel steepness analysis. A reference concavity (θref) is frequently used to assess the steepness of a channel in different basins of various sizes, and then the data is utilized to obtain a normalised steepness of the channel (ksn). The selection of θref is crucial for calculating the relative ks values of various sections in the stream network and the θref value is chosen based on the regression analysis in the entire channel network. Therefore, we employed two methods to find the best-fit concavity indices using MATLAB-based TopoToolbox. The first is based on the Slope-Area plot (S-A) where the logarithmic of the equation S= ks A-θ is used and the second is based on the integral approach defined as Chi-Plot (χ). Despite its importance in calculating the steepness of a channel, the concavity index is difficult to constrain, hence we compare both these methods and determine which of the method is better. To determine the correct stream power incision ratio (m/n) we conducted a numerical analysis with varied m/n ratios as 0.45, 0.5 and 0.65. Furthermore, we plot steepness anomaly plot around the mean channel steepness value (ks) of the stream power model. The findings unravel the information about the variability of the concavity index across the different landscape and help in understanding geomorphic processes like tectonic activity, rock differential erosion, and hillslope formation.