Characterization of Active Tectonics and their influence on Landscape evolution in the Lower Rhine Graben (LRG), Western Germany- a morphotectonic approach

Morphotectonic methods are commonly used to study landform evolution in regions with strong tectonic activity, like active plate boundaries. However, these methods are less often applied in low-strain but tectonically active intraplate areas such as the Lower Rhine Graben (LRG), even though the region has a history of recent and historical earthquakes. This study investigates how ongoing tectonic processes affect the landscape in the LRG. Using a 1-meter resolution LiDAR data, we applied GIS techniques, Topotoolbox (Schwanghart and Kuhn, 2010), and the SLiX model (Piacentini et al., 2020) to analyze lineaments, knickpoints, and key morphometric indices. These indices include the stream length-gradient index, hypsometric integral, basin asymmetry factor, valley floor width-to-height ratio, basin shape index, and transverse topographic symmetry factor. This study generated 53 knickpoints, and rose diagrams reveal identical trends between lineaments and existing faults. Further results show spatial correlation between anomalous indices' values, and knickpoints with existing fault structures and the generated lineaments. We interpreted the close location (< 600 m) of knickpoints to nearby fault structures, and their spreads at varied elevations to indicate 1) a passive or active tectonic control on landforms, 2) the influence of Variscan orogeny and glacial retreat on base-level changes in LRG, respectively.   Finally, we used the Index of Relative Active Tectonism (IRAT), which averages all indices, to classify the region’s tectonic activity as moderate. Consequently, it was concluded that although the LRG is not highly deformed, moderate tectonic processes continue to shape its landscape.