Water Resources Research Act Program

Details for Project ID 2019CO033B

Floodplain Forest Establishment and Legacy Sediment within the Yampa River Basin, Northern Colorado

Institute: Colorado
Year Established: 2019 Start Date: 2019-03-01 End Date: 2020-02-29
Total Federal Funds: $5,000 Total Non-Federal Funds: $2,600

Principal Investigators: Sara Rathburn

Abstract: The Yampa River is the last largely unregulated major tributary in the Colorado River system. In the semi-arid climate of northwestern Colorado, the Yampa is an essential water source for agriculture, power generation, and municipalities as it flows westward from the Rocky Mountains across broad lowlands1. In addition to a vital water supply, the Yampa River floodplain forest, composed largely of cottonwood trees, creates diverse ecosystems that provide essential ecological and human benefits disproportionate to forest size. For humans, riparian forests attenuate floods, offer food and shelter for livestock, and are essential to recreational activities that include hunting, boating, and camping. Ecologically, these forests provide critical ecosystem services such as nutrient cycling and support diverse species habitat2. For its final 70 km, the Yampa River flows through Dinosaur National Monument, an area of major conservation and recreation importance in northern Colorado where cottonwood floodplain forests are in decline due to a disequilibrium with current river processes. Cottonwood floodplain forests exist entirely due to the availability of suitable establishment sites exposed during seed germination season. The extent of establishment areas is dependent upon the processes that shape the river landscape, including variability in water and sediment transport that cause channel migration3. While the impact of flow variability on cottonwood reproduction has been extensively investigated, studies quantifying the importance of sediment variability are relatively sparse. The proposed research will test the hypothesis that: Establishment of cottonwood floodplain forests along the Yampa River in Dinosaur is the result of extreme erosion that deposited a large volume of legacy sediment along the Yampa from the late 19th to mid-20th century. The influence of legacy sediment on cottonwood establishment in relatively unregulated, natural systems remains a critical knowledge gap. Study findings have important research and management implications for numerous stakeholders in the basin facing uncertain sediment regimes needed to establish cottonwood forests along a river of critical economic, ecologic and recreational value.