The Response of Riparian Vegetation to Flood Inundation Patterns and Channel Incision

Keywords: incision, riparian vegetation, flood inundation, channel morphology
Session Type: Virtual Poster Abstract
Day: Saturday
Session Start / End Time: 2/26/2022 09:40 AM (Eastern Time (US & Canada)) - 2/26/2022 11:00 AM (Eastern Time (US & Canada))
Room: Virtual 37

Abstract

Geomorphology, hydrology, and ecology are tightly related components of river systems. We investigate the influence of channel morphology on channel-floodplain connectivity and riparian vegetation on the Fremont River in southern Utah. In Capitol Reef National Park, road construction resulted in a cutoff meander and the development of a knickpoint on the Fremont River, which may be causing changes in channel morphology and riparian vegetation. We conducted topographic and vegetation surveys and produced 1D HEC-RAS models in four 1 km-long reaches: a reach 5 km upstream of the knickpoint that is less impacted by the knickpoint (Reach 1), a reach immediately upstream of the knickpoint (Reach 2), a reach 0.7 km downstream of the knickpoint (Reach 3), and a reach in the cutoff meander (Reach 4). Our results indicate that differences in channel morphology influence flood inundation patterns, which in turn influence riparian vegetation. The channel in Reach 2 is significantly deeper than in Reach 1, resulting in a lower channel-floodplain connectivity, lower average total plant cover, and a greater presence of xeric (dry-adapted) species. Reach 1 had greater channel-floodplain connectivity, greater average total plant cover, and less xeric species. These relationships suggest that increased channel incision just upstream of the knickpoint is driving riparian vegetation cover and species composition through its control on flood inundation patterns. Results from this study will help inform natural resource management decisions in Capitol Reef National Park and enhance our understanding of the influence of hydrogeomorphic characteristics on riparian vegetation.