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Geomatics-based assessment of the neotectonic landscape evolution along the tebessa-morsott-youkous collapsed basin, Algeria

Taib Hassan, Benabbas Chaouki, Khiari Abdelkader, Hadji Riheb, Haythem Dinar

Geomatics, Landmanagement and Landscape

2022

no. 3

131--146

The neo-tectonic research is interested in the study of the movements of Earth’s crust in recent geological times. It could explain the deformation mechanisms that lead to the structuring of drainage catchments. The Morsott-Tebessa-Youkous (Chabro) collapsed basin corresponds to a subsiding depression framed by brittle structures and filled with thick deposits. Our work aims to unveil the neo-tectonic activity and reconstruct the morphometric evolution of the landscape and the drainage network of the basin. For this task, our investigation applies a quantitative analysis of geomorphic indices extracted from the DEM of the study area. We used a GIS-based approach to compile seven morphometric factors namely Integral Hypsometry (HI), the Sinuosity of mountain fronts (Smf), the Valley Floor width to height ratio (VF), the Asymmetry Factor (AF), Basin Shape index (BS), and the topography (T). All these thematic parameters were processed in a Geo-database to calculate the study area’s Relative Tectonic Activity Index (IRAT) as a result. The IRAT map was categorized into three classes. The result highlighted the distribution of relative tectonic activity in the region and unveiled some unknown faults. It associated the sinuosity of rivers and the deformation of the substratum with active tectonic anomalies. This research work succeeded in drawing up a new scheme of the neo-tectonic activity and morphostructural evolution in the collapsed basin.

Meander migration and cut-off dynamics of Lower Disang River (Assam, India)

Begum Kashmiri, Sarkar Subhajit, De Sunil Kumar

Studia Geomorphologica Carpatho-Balcanica

2021

Vol. 55

45--69

Meander migration and cut-offs are important mechanisms causing changes in river channel morphology. The present work aims at investigating the dynamics of meander migration and cut-offs of the Lower Disang River (Assam, India) and its relation with planform parameters. Channel migration and cut-offs between 1916 and 2017 were studied on an approximately 203.89 km long meandering alluvial reach of the Lower Disang River. Topographical sheets, satellite imageries and Google Earth images (1916, 1969, 1990, 2005 and 2017) have been used to map, quantify, and analyse the development pattern of the meander bends. Only five natural cut-offs occurred during the 101-year time span in the study area. However, numerous cut-offs have occurred in the pre-1916 period, which is seen in the form of traces of oxbow lakes on its floodplain. No cut-off has been formed in the post-2005 period. For the period between 1916 and 2017, the average rate of lateral channel migration has been 1.35 m .y –1 due to the combined process of progressive migration and cut-off. An average of 2.98 % of the total channel length changed via cut-off while 97.02 % of the channel length changed by gradual migration. As a result, of low cut-off frequency and progressive increase in channel length through migration, there is a steady build-up of sinuosity and increasing complexity in meander forms. Thus, cut-off has been less dominant mode of channel change than progressive migration.