Decoding landscape evolution: A geomorphometric approach to the Lebanese terrain

Theories of landscape evolution by Davis, Penck, and King describe the development of terrain through successive stages, but the choice of the most suitable model for a particular region needs to be supported by quantitative geomorphometric evidence. This study addresses two questions: which descriptive model best explains the topographic evolution of Lebanon, and at what stage of its development the present terrain is. Strahler stream orders 3 to 11 were used to construct nine isobase surfaces using GIS-based hydrological analysis with ALOS digital elevation models at 12.5 m resolution. The hypsometric integral, hypsometric curves, fractal dimensions, profile curvature, relative relief, and a modified surface index were used to characterize each surface. Results show a proportional decrease in slope and elevation with increasing number of isobases. Isobases 5-7 are indicative of equilibrium landscape development, while isobases 8-9 represent an older, disequilibrium stage. Of the three competing theories, Penck's model of simultaneous uplift and erosion best explains Lebanon's terrain, given its tectonic history along the Dead Sea Transform Fault System. The results are used to create a predictive landscape evolution map of Lebanon, defining five spatial zones of progressive terrain dissection. Besides the Lebanese context, the proposed isobase-based geomorphometric framework provides a reproducible methodology for other tectonically active regions and a physiographic baseline for future geological mapping, tectonic analysis, and natural hazard assessment.