Dynamic Catchment Topography in Active Mountain Regions

A simple geometric model is proposed to reconstruct the topography of entire catchments in Taiwan, a region characterized by highly active mountain systems. This model will be tested in the Laonong River Valley, a highly dynamic river catchment in southern Taiwan, using high-resolution topographic data. The model assumes a landscape in sustained uplift, incorporates dynamic steady-state parameters, and uses the stream power law to describe bedrock incision. Additionally, it accounts for valley slopes constrained by critical thresholds where landslides occur.

Building on previous models, the elevation profiles of main channels and tributaries are integrated from the catchment outlet, based on a power-law relationship between slope and drainage area. For non-steady-state conditions, elevation changes are calculated using topographic data from different years. Lateral incision is included to simulate river meandering. Beyond the stream network, valley topography is reconstructed by assuming constant slope patches equal to the maximum channel slope. A simple algorithm connects points within the basin to the river network by tracing steepest descent paths.

This model is supported by three years of topographic data, extracted from digital terrain models using elevation-distance plots. Distances are measured either along river channels or along the steepest descent paths. The model’s accuracy is evaluated by comparing the reconstructed elevations and slopes to actual topographic data. Any discrepancies can highlight anomalies such as variations in uplift rates, lithological differences, or remnants of past valley features, including landslide deposits.