Deposition potential and flow-response dynamics of emergent sandbars in a braided river

Water Resources Research
By: , and 



Sandbars are ubiquitous in sandy‐braided rivers throughout the world. In the Great Plains of the United States, recovery and expansion of emergent sandbar habitat (ESH) has been a priority in lowland rivers where the natural extent of sandbars has been degraded. Recovery efforts are aimed at protection of populations of the interior least tern (Sterna antillarum) and piping plover (Charadrius melodus). But quantitative observations of deposition and erosion dynamics of populations of sandbars across long segments of rivers are rare. We present a three‐part case study which used Bayesian regression models to examine relations between hydrology, channel morphology, and ESH responses in the Platte River, eastern Nebraska. Logistic regression indicates presence of ESH is positively related to the Parker, (1976) stability criterion and a gradient in sediment transport mode, and negatively related to presence of vegetation. Hierarchical linear regression modeling shows direct coupling between sandbar top‐surface height and formative flood magnitude, but the gap between formative flood stage and sandbar top‐surface increases with increasing discharge. Finally, linear regression modeling of sandbar erosion demonstrates rates of ESH erosion are on the order of 10−1 ha/day during high‐flow periods and 10−2 during low‐flow periods, but sandbar persistence is largely a function of sandbar starting size. The collective observations highlight the importance of large floods (>3‐year recurrence) in creating very large sandbars that persist as high‐quality ESH over periods of years whereas lower‐magnitude, more‐frequent flood events create lower‐quality ESH that typically does not persist into the following nesting season.

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Publication type Article
Publication Subtype Journal Article
Title Deposition potential and flow-response dynamics of emergent sandbars in a braided river
Series title Water Resources Research
DOI 10.1029/2018WR024107
Volume 56
Issue 1
Year Published 2020
Language English
Publisher American Geophysical Union
Contributing office(s) Columbia Environmental Research Center
Description e2018WR024107, 23 p.
Country United States
State Nebraska
Other Geospatial Platte River
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