Research about Escalante River

USGS2025

Long-term geomorphic response of a southwestern USA river following establishment and removal of an invasive riparian tree

Invasion of non-native riparian vegetation along southwestern USA rivers is associated with channel narrowing and simplification, prompting numerous and varied removal efforts. Channel width and migration rate often, but not always, increase following treatment. The cause of this variability and the duration of response is poorly understood. Using flow records and aerial imagery we quantified measurement uncertainty, change in channel width and rates of floodplain formation and erosion relative to annual peak flows before and during the invasion of Russian olive ( Elaeagnus angustifolia L.), and following removal, along the Escalante River, Utah, over a fifty-year period. Prior to the invasion, the Escalante River was undergoing a decades-long narrowing process following large, turn-of-the-20th-century floods. Russian olive created a unique geomorphic shift in the observed pattern of channel change. Dense, channel-edge establishment and morphological traits including dense, inflexible branches, resulted in enhanced channel narrowing. Because the initial spread of Russian olive was from upstream to downstream, the Russian olive forest was wider and older upstream than downstream. Consequently, channel narrowing was greater and floodplain erosion rates had already decreased in upstream reaches compared to downstream. Russian olive removal increased channel width and floodplain erosion rates in upstream reaches, where Russian olive was most abundant. In contrast, downstream reaches continued to narrow. Small but detectable increases in rates of floodplain erosion across all reaches, and increased sinuosity in some, suggest the channel is becoming more mobile in the absence of Russian olive. Results indicate channel adjustment to Russian olive removal is spatially variable and may take a decade or more. With continued expansion of native riparian vegetation, future narrowing is likely during sustained low peak flows and large-scale widening is unlikely in the absence of extreme floods or physical removal of existing riparian vegetation.

Arizona, Utah↗

USGS2018

The role of a non-native tree in riparian vegetation expansion and channel narrowing along a dryland river

Along rivers, native and invasive species may establish and persist on active channel bedforms as part of channel narrowing. Using historical aerial photography and dendrochronology, we quantified spatial and temporal patterns of narrowing and vegetation expansion, including native Fremont cottonwood (Populus fremontii) and non‐native Russian olive (Elaeagnus angustifolia), along the largely unregulated Escalante River in south‐western United States. Russian olive establishment was examined with respect to hydrologic and climate variables. Narrowing along the Escalante River was initiated during a mid‐20th century drought. Cottonwood rapidly colonized higher, bar surfaces between the 1950s and 1981. Small numbers of Russian olive established in moist sites during this period as the channel narrowed by nearly 80%. After 1981, there was no obvious cottonwood establishment but low channel bars and banks were rapidly colonized by Russian olive. Hydroclimate predictors were equivocal but exponential growth of this large‐seeded, shade‐tolerant species lagged its introduction by 30 years, apparently because of delayed reproductive maturity, limited seed availability, and widespread availability of favourable establishment sites following initial channel narrowing. Sediment trapping, levee formation, and modification of channel form by dense, channel‐edge bands of Russian olive progressively limited new establishment sites and by 2000, recruitment declined sharply. Our results have implications for management of non‐native tree invasions along arid‐region rivers, including identification of low, moist, active channel bars where the establishment and physical impacts of Russian olive appear to be most pronounced and where focused management efforts are likely to be most effective.

Utah↗