Application of River Longitudinal Profile Morphometrics to Reveal the Uplift of Lushan Mountain

The stream power model was applied to Lushan Mt. in South China in order to verify its capability of interpreting the uplift of a small block mountain. On a log-log plot, the longitudinal profiles of 9 rivers derived from a 30 m DEM exhibit primary characteristics similar to those derived from a 5 m DEM; however, the 5 m DEM clearly reveals more minor knickpoints, and the positions of knickpoints are pinpointed more accurately. All of the studied rivers on the block mountain are in a transient state due to geological perturbations. Some of them exhibit two segments in steady state separated by a slopebreak knickpoint. Such rivers generally develop in a longitudinal valley, which are less perturbed by substrate inhomogeneities. The similar heights of the slope-break knickpoints and the similar uplift rate indicated by the k_（sn） values demonstrate an almost simultaneous headward erosion induced by the fall in base level. This modelling result is consistent with the mode of formation of this particular block mountain. Our study demonstrates that the stream power model is applicable to a small tectonicallyactive massif only if the channel segments are in a steady state.

The methods and program implementation for river longitudinal profile analysis——RiverProAnalysis, a set of open-source functions based on the Matlab platform

River is one of the geomorphic units that are the most sensitive to tectonic activity, of which the longitudinal profile serves as a key archieve to record information on active tectonics. The stream-power incision model is an important means to analyze channel long profiles and to extract both temporal and spatial patterns of regional tectonic activity. Analytical solutions to the steady-state and linear transient-state equations of the model provides means to calibrate drainage basin concavity,calculate channel steepness index, determine drainage divide stability, project the paleo-channel profile, and to invert the tectonic uplift rate history. Yet, not all of these functions have been implemented in the published open-source tools. Here, we developed a set of open-source codes, RiverProAnalysis, which was based on the Matlab platform and integrated all of these functions. The products of the tool set are in the format of image, text and vector files, which not only can be used for visual analysis, but be read by softwares of geographic information system. Taking examples of two transient drainage catchments in the northern margin of the Taiyuan Basin, we analyzed the long profiles of the trunk streams, identified two generations of knickpoints, and estimated the minimum amount of river incision. We combined all the trunk and tributary channels together to model the catchment-wide uplift history and found moderate increases in the uplift rates since the Middle Pliocene and rapid accelation since the late Quaternary. The inverted results are consistent with the sedimentary records in the adjacent basin. By comparing the chi value,slope, and topographic relief of both sides of the catchment divide, we concluded the stability of the drainage divide. Our tool set integrates the main functions of the modern studies on fluvial landsape, thus providing a powerful tool for analyzing river long profiles and for understanding tectonic geomorphology.

Geomorphological responses of rivers to active tectonics along the Siwalik Hills,Midwestern Nepalese Himalaya

The Nepalese Himalaya is well known for ongoing collisional tectonics,witnessed by major historical and recent earthquakes.The Siwalik Hills in Midwestern Nepalese Himalaya are bounded by eastwest trending Main Frontal Thrust(MFT)to the south and the Main Boundary Thrust(MBT)to the north.The area is dissected by numerous southwest to south-flowing bedrock rivers.This study investigates geomorphic metrics of these rivers to unravel landscape evolution and active tectonics of the Siwalik Hills.Digital Elevation Model(DEM)analysis was conducted to extract structural lineaments and longitudinal river profile and their metrics(knickpoints,Normalized Steepness Index(ksn),concavity index,and chi integral)using steam powerlaw approaches.Most of the lineaments trend eastwest like MFT.River profiles exhibit convex to double-concave shapes with upstream-propagating tectonic knickpoints that separate upstream and downstream reaches,indicating different phases of river incision.The spatial distribution of ksn shows high values along with low concavity values at the eastern part of the study area,reflecting disequilibrium conditions that are likely responding to a high uplift rate.Chi integral distribution shows a variation in drainage divide migration between the eastern and western parts of the study area.This study suggests that the rivers in the Siwalik Hills are undergoing active incision likely related to the ongoing uplift and active deformation associated with the Himalayan tectonics.The above findings can bring fresh perspectives to comprehend the neotectonic deformation and lateral variability along the Siwalik Hills landscapes within the Himalaya.