Details

Autor(en) / Beteiligte

• Kemper, John T.
• Thaxton, Richard D.
• Rathburn, Sara L.
• Friedman, Jonathan M.
• Mueller, Erich R.
• Scott, Michael L.

Titel

Sediment‐ecological connectivity in a large river network

Ist Teil von

• Earth surface processes and landforms, 2022-02, Vol.47 (2), p.639-657

Ort / Verlag

Bognor Regis: Wiley Subscription Services, Inc

Erscheinungsjahr

2022

Quelle

Wiley-Blackwell Journals

Beschreibungen/Notizen

• Sediment eroded from the headwaters of a large basin strongly influences channels and ecosystems far downstream, but the connection is often difficult to trace. Disturbance‐dependent riparian trees are thought to rely primarily on floods for formation of the sand bars necessary for seedling establishment, but pulses of sediment should also promote formation of such features. In order to expand understanding of the role of sediment connectivity in governing ecological processes, here we explore the hypothesis that cottonwood forest along the Green and Yampa Rivers in Utah and Colorado are dominated by trees established a century ago during a period of extensive channel migration caused by significant headwater erosion. Analysis of historical documents and aerial photographs suggests that three key tributaries of the Yampa River underwent significant historical erosion from roughly 1880 to 1940. Average width and depth of tributaries with defined arroyos increased two to six times from historical surveys, resulting in the export of ~30 million metric tons of sediment, sizably increasing the sediment load and channel migration rate of the Yampa and Green Rivers. Establishment of major portions of several downstream cottonwood forests occurred during this period of historical erosion, increased sediment loads, and heightened channel migration rates, and the area of forest dating to that time is much greater than can be explained by high flows alone. Viewed collectively, our findings suggest tributary erosion played a vital role in successful downstream forest establishment, a link we contend is best illustrated through a sediment‐ecological connectivity framework. Broadly, this framework facilitates consideration of linkages between morphological and ecological processes at the watershed‐scale. Development and utilization of a watershed‐scale sediment‐ecological connectivity perspective highlights the value of sediment as a critical ecological resource to be managed jointly with flow to ensure the maintenance of vital riverine ecosystems. The sediment‐ecological connectivity framework links downstream ecological processes to upstream morphological processes. Here, as erosional processes upstream inject large amounts of sediment into a system, downstream channels become more dynamic, resulting in heightened rates of downstream riparian vegetation establishment. As rates of upstream erosion then gradually decline, downstream channels begin to stabilize, leading to an overall decrease in riparian vegetation establishment.