Check dams matter: Six years of particle tracking experiment in a check-dam-managed and near-natural pool-riffle stream

Abstract

A widely applied approach to stabilizing mountain streams and reducing bedload transport rates involves the systematic construction of transverse structures, such as check dams or bed sills, often in combination with bank stabilization measures. However, the precise quantification of their impact on downstream sediment transport, particularly in comparison to unmanaged conditions, remains insufficiently explored. To address this gap, we conducted a six-year field study utilizing passive integrated transponder (PIT)-tagged gravel and cobble particles to assess sediment transport dynamics in a check-dam-managed reach (Bystry) versus a neighboring near-natural pool-riffle reach (Bastice) with similar catchment-scale characteristics in the Czech Western Carpathians. Based on 14 transport-effective flow events (with critical flow durations of 7–78 h and peak unit stream power ranging from 32 to 402 W/m²), Bystry exhibited higher mobilization rates and travel distances nearly twice as long as those in Bastice, whereas Bastice demonstrated greater sediment retention, particularly within bar units. The study underscores the key role of hydrological drivers—including peak discharge, unit stream power, and cumulative geomorphic work derived from excess critical stream power—in regulating coarse sediment transport, with stronger correlations observed in the near-natural reach. These findings support earlier observations of limited sediment trapping by low transverse structures and align with conceptual models predicting enhanced sediment transport in unconfined valley settings subjected to artificial channel straightening and stabilization through consolidation check dams. The study also provides critical insights into the long-term geomorphic effects of torrent control works and their implications for evaluation of sediment (dis)connectivity at the catchment scale.