Hydro-sedimentological drivers of fine sediment ingress in a gravel-bed river

[Display omitted] •In-situ investigations of fine sediment ingress in gravel-bed rivers remain limited.•Ingress rates and directional mechanisms of accumulation were investigated across a range of flow conditions.•Three designs of sediment traps (>250 traps in total) were used.•Linear mixed effects models showed that the ingress of cohesive particles were well explained by mean hydro-sedimentological parameters.•Observed results have important implications on the legacy effects that can originate from ingressed particles. Most studies investigating fine sediment ingress in gravel-bed rivers have been conducted at the laboratory scale, and even fewer have explored the ingress processes of flocculated particles. Here, an extensive in-situ sampling programme was undertaken to investigate hydro-sedimentological drivers of interstitial fine sediment accumulation and to evaluate fine sediment ingress directional mechanisms in a gravel-bed river located on the eastern slopes of the Rocky Mountains in southern Alberta. Three sediment trap designs were installed across seven deployment cycles at four sites along the river. Instantaneous discharge, suspended solids concentration, and particle size distributions (of suspended and ingressed particles) were measured, while relevant hydraulic parameters were modelled with a flow model (MOBED). Distinct patterns of ingress dynamics between non-cohesive and cohesive fractions of fine sediment were observed. While the assessed hydro-sedimentological parameters did not statistically explain the ingress rates of non-cohesive 0.5 – 2 mm particles, the opposite was observed for