Connecting the dots: building a sediment-ecological connectivity framework to link tributary erosion to downstream floodplain forest establishment in a large river network
Abstract
Sediment loads are declining across the Colorado River Basin as a result of disruptions in sediment connectivity between tributaries and main-stem rivers due both to dams as well as land management in the headwaters designed to mitigate erosion. Cottonwood floodplain forests, ubiquitous but declining basin-wide, are disturbance-driven ecosystems dependent on sediment-laden floods for establishment. In order to further understand the role of sediment connectivity in governing ecological processes such as floodplain forest establishment, here we investigate the linkages between tributary erosion and downstream cottonwood floodplain forest establishment in the Little Snake/Yampa River Basin of northwestern Colorado and southwestern Wyoming. Inspection of historical documents and aerial photographs suggests that three key tributaries of the Yampa underwent significant historical erosion via arroyo incision in the late 19th to early 20th century. Dendrochronology results indicate establishment dates of cottonwood forests in several downstream locations along the mainstem Yampa and Green Rivers lag behind this period of arroyo incision by several decades. Taken together, the above findings suggest that sediment wave(s) of sand-sized sediment initiated by historical headwater erosion were transported >100 km downstream over multiple decades and resulted in construction of geomorphic surfaces necessary for forest replenishment. We propose that the demonstrable link between headwater morphological processes (e.g. extreme erosion) and distal downstream ecological processes (e.g. forest establishment) shown here substantiates the key role of sediment connectivity in governing ecological processes such as riparian forest establishment and growth. 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 in order to ensure the maintenance of vital riparian ecosystems.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMEP056..05K
- Keywords:
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- 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCES;
- 0481 Restoration;
- BIOGEOSCIENCES;
- 1825 Geomorphology: fluvial;
- HYDROLOGY;
- 4327 Resilience;
- NATURAL HAZARDS