1998), starting a cascade of deleterious ecological consequences. High river salinity disrupts the ecological integrity of downstream riparian floodplains when soil salinity increases and promotes dislocation of native riparian plants by nonnatives (Glenn et al. ( 1991) documented a decline in river salinity in the Colorado River basin through the early twentieth century, salinity remains a concern because of its negative effect on water quality for municipal and agricultural uses (Gardner and Young 1988). Incised stream channels and migrating headcuts are common in the region’s drainages and are a significant source of sediment and salt (Gellis et al. This is particularly important because southwest Wyoming is a significant headwater area for the Colorado River Basin (DeLong 1977). Southwest Wyoming’s arid climate ( X̅ = 22 cm precipitation year −1) and high-desert vegetation leave soil vulnerable to erosion during heavy precipitation events.
In arid climates, rapidly changing flow volumes and energies, combined with diminished vegetative conditions, can create distinctive vertical drops (Schumm and Hadley 1957). They frequently impact surface features and water tables, with cascading effects on flora and fauna as they retreat upstream (Stavi et al. Headcuts, also known as knick points or drops in stream channel base levels, are points of accelerated erosion. Historical imagery and photogrammetric modeling proved very useful in elucidating stream dynamics associated with this large, dynamic headcut. Ground-based image acquisition took longer and was more costly per unit area, but is an efficient method for small project areas, or areas where aerial imagery cannot be safely or practically acquired. The ground-based imagery model showed more detail, especially on vertical and overhanging surfaces, while the aerial imagery model produced a more realistic orthomosaic and efficiently covered a larger area.
Models created from aerial- and terrestrial-based images differed in volumetric estimates by 2%, indicating that either method could be used for this type of monitoring.
Since 1954, soil loss within the channel has been ~ 98 m 3 year −1 or ~871 t ha −1 year −1since then. From these two models, we measured soil loss downstream of the headcut at ~ 126 m 3 m −1 valley length. Both aerial and terrestrial-based image platforms were used to collect stereo imagery and create 3D photogrammetric models of the headcut in 2016. Channel sinuosity downstream of the headcut is greater than upstream, which we attribute to the presence of the headcut, given that there are no major changes in valley geometry, geology, or soils through this reach. Following installation of a concrete slab structure in the mid-1970s, headcut retreat slowed to ~ 0.5 m year −1.
Aerial photography shows the Bitter Creek headcut retreated > 200 m upstream in 68 years (1948–2016) at ~ 1.4 m year −1. To better understand and address this issue, we undertook a review of the headcut’s upstream retreat, followed by photogrammetric monitoring of the present condition for erosion monitoring. A particularly large and dynamic headcut in southwest Wyoming has affected natural and anthropogenic resources for decades. Headcuts are points of accelerated channel erosion that frequently have ecological consequences.
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