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Supplementary materials associated with “The Transience of Channel-Spanning Logjams in Mountain Streams”




Wohl, Ellen
Iskin, Emily

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We use 11 years of annual surveys in streams of the Southern Rockies of Colorado, USA to examine the persistence and geomorphic effects of logjams. Each year’s survey includes ~300 logjams along more than 21 km of 4 mountain streams in primarily old-growth subalpine forest. Streams alternate longitudinally between laterally confined reaches with a single channel and wider reaches with multithread channel planform. We distinguish logjam persistence and site persistence. Logjam persistence is the median timespan over which an individual jam is present. Site persistence describes the tendency for jams to disappear and then re-form at the same site. We hypothesize that (i) site persistence is greatest in multithread reaches; (ii) logjam persistence is greatest in multithread reaches; and (iii) average backwater storage at each jam is greater in multithread reaches. We find that spatial and temporal metrics of site persistence differ significantly between single and multithread reaches. Individual logjam persistence does not differ significantly. Backwater storage is significantly greater in multithread reaches. Varying combinations of riparian forest age and average logjams per channel length explain variation in jam and site persistence and backwater storage via multivariate linear regression analyses. Over the 11 years of survey, a total of 429 distinct logjams were observed. Only 2.1% of the population was present for all 11 annual surveys. Median jam persistence is 1-2.5 years; median site persistence is 6-10 years. Despite the transience of most channel-spanning logjams in the population, these jams create persistent effects in channel planform and backwater storage.


The supplemental files include (1) details of each statistical model used to analyze the data, (2) supplemental figures to illustrate issues discussed in the main text, (3) basic supporting data in an Excel file that contains worksheets with geographic coordinates of each of the logjams, reach-scale averaged variables over the period of study, reach-scale annual variables over the period of study, the data organized for individual logjam persistence, and the data organized for statistical analysis of logjam persistence. These supplemental materials can be used to more fully understand the dataset and analyses and to conduct independent analyses of the original data.
Department of Geosciences

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Southern Rockies
geomorphic effects
mountain streams
Rocky Mountain National Park


Associated Publications

Wohl, E., & Iskin, E. P. (2022). The transience of channel-spanning logjams in mountain streams. Water Resources Research, 58, e2021WR031556.