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Controls on spatial and temporal variations in sand delivery to salmonid spawning riffles

Milan, David



Fine sediment infiltration into gravel interstices is known to be detrimental to incubating salmonid embryos. Infiltration into spawning riffles can show large spatial variations at the scale of a morphological unit and over time, with significant implications for embryo survival. Furthermore, some process-based infiltration studies, and incubation-to-emergence models assume that fines are delivered to redds via suspension rather than bedload. This process-based 12-month study examined spatial patterns of predominantly sand infiltration into gravels in an upland trout stream, using infiltration baskets. An assessment of Rouse numbers for infiltrated sand indicated that it was transported predominantly as bedload at flow peaks. Clear temporal and spatial patterns existed, with highest rates of infiltration strongly associated with higher discharges (r2 = 0.7, p < .05). Seasonal variations in the delivery of different grain sizes were also a feature, with enhanced contributions of 0.5–2 mm sediment during elevated winter flows and 0.125–0.5 mm sediment during spring and summer; the latter is potentially harmful to the later stages of embryo incubation. Clear spatial patterns were also evident across riffles, with highest rates of infiltration tending to occur in areas of lower relative roughness—the areas competent to transport sand for longer periods. Incubation-to-emergence models should take into consideration spatial patterns of fine sediment dynamics at the pool–riffle scale, to improve prediction.


Milan, D. (2017). Controls on spatial and temporal variations in sand delivery to salmonid spawning riffles. Hydrological Processes, 31(12), 2179-2195.

Journal Article Type Article
Acceptance Date Mar 13, 2017
Online Publication Date May 5, 2017
Publication Date Jun 15, 2017
Deposit Date May 15, 2017
Publicly Available Date Oct 27, 2022
Journal Hydrological processes
Print ISSN 0885-6087
Electronic ISSN 1099-1085
Publisher Wiley
Peer Reviewed Peer Reviewed
Volume 31
Issue 12
Pages 2179-2195
Keywords Bedload; Brown trout embryos; Fine‐grained sediment; Hydraulics; Relative roughness; Siltation
Public URL
Publisher URL
Additional Information This is the accepted manuscript of an article published in Hydrological processes, 2017. The version of record is available at the DOI link in this record.


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