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Geomorphic responses to post-grazing recovery and stream restoration in semiarid grassland streams

Richardson, Owen1; Wohl, Ellen1

Research facility: Colorado State University
Published Feb 26, 2026 on Dryad. https://doi.org/10.5061/dryad.4b8gthtsp

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Abstract

Semiarid grassland streams are sensitive to land use, climate, extreme discharges, and internal geomorphic thresholds that drive episodic erosion. Rooted in a process-based philosophy and commonly applied to historically wood-rich, beaver-modified systems, low-tech process-based restoration using structures is increasingly being extended to other geomorphic settings, including grasslands. In these wood-poor systems with fine-grained substrate, channel adjustment depends primarily on subsurface soil piping and asynchronous responses to changing boundary conditions. We evaluate post-grazing recovery and structural restoration outcomes at transect-to-landscape scales in southeastern Colorado. Following grazing cessation, soil compaction decreased after roughly a decade of rest, as indicated by a multivariate linear regression analysis of 238 bulk density samples. In contrast, visible above-ground upland vegetation recovers on timescales longer than the observation window (>10 years), based on analyses of growing-season composite Landsat imagery from 2013–2024. Logistic regression models indicate that the performance of restoration structures depends strongly on drainage area, slope, local vegetation cover, and the recency of large-scale commercial grazing. In total, only ~30% of the 92 in-channel structures evaluated (mostly ≤4 years old) were both intact and produced visible geomorphic change. Structures in piping-dominated headwaters remained intact but rarely trapped sediment, whereas those in larger catchments were more likely to initiate local geomorphic change, despite having higher odds of destruction during peak flows. These findings highlight the need to match restoration strategies with the geomorphic processes driving channel adjustment and call into question the extent to which commonly implemented structure-based interventions in grassland systems are truly process-based.