Abstract

Gully erosion was the primary driver of land degradation in Southern Piedmont, site of the Calhoun Critical Zone Observatory (CCZO), during the cotton farming era. Understanding of underlying erosion processes is essential to develop a model useful in assessing the effectiveness of gully stabilization and soil erosion control.

Development of process-based gully erosion models is difficult because observations of the formation and progression of gullies are limited. In this study, analytic formulations of the two dominant gullying processes, namely, plunge pool erosion and slab failure, are utilized to simulate the gullying processes in the 4 km² Holcombe’s Branch watershed. Gully features (e.g., depth and area) automatically extracted from high-resolution LiDAR DEM are used to calibrate parameters of the gully model. The statistics of the spatial extent of simulated gullies are in close agreement with the gullies obtained from the LiDAR map. Simulations initialized with contemporary topography suggest that few gully complexes have the potential to progress further. Several simulations are used to evaluate the effectiveness of various gully treatment measures, such as backfilling of gullies and revegetation, by initializing the model with the historical topographical surface. Simulation results show that in the short-term, the reshaping of the topographical surface by backfilling and compacting gullies is effective in slowing down the growth of gullies (e.g., backfilling decreased the spatial extent of gullies by 20-38% and decreased the average depth by 0.005-8%). Revegetation, however, is a more effective approach to stabilizing gullies which would, otherwise, expand if left barren. Moreover simulations suggest that the gully stabilization effect of revegetation can lead to a 23-70% reduction of gully area and 1.3-45% reduction in the depth of gullies, depending on forest type and management practices.

Citation

Bastola, S., Y.G. Dialynas, R.L. Bras, L.V. Noto, and E. Istanbulluoglu (2016): The role of vegetation on gully stabilization at a severely degraded landscape: a case study from Calhoun experimental critical zone observatory. American Geophysical Union 2016 Fall Meeting, San Francisco, CA.

This Paper/Book acknowledges NSF CZO grant support.