Evolution of river terraces along the Lan-Yang River, northeastern Taiwan: A river response to base level change

During the last 2000 years, several alluvial fans were formed along the upper reach of the Lan-Yang River, northeastern Taiwan. They were subsequently undercut into different levels of river terraces. Slope profiles of the river terraces were measured in the field to study the evolution of the terrace scarps. River terraces can be chronologically correlated by morphological dating according to the proposed diffusion equation model and scarp retreat model. Evolution of the longitudinal profiles of the Lan-Yang River and its tributaries was reconstructed based on the correlation scheme of the river terraces. The model of evolution suggests that changes in the local base level of erosion play an important role in the formation of the river terraces. The local base level elevation changed as a result of alluvial fan deposition, rather than tectonic uplift or climatic changes.