Geology topics

Bruce K. Orr

Publications and source records attributed to Bruce K. Orr.

4 recordsLinked to original sources

USGS2020

Final report: Southwestern Willow Flycatcher (Empidonax traillii extimus) and Western Yellow-billed Cuckoo (Coccyzus americanus occidentalis) surveys and habitat availability modeling on the Santa Clara River, California, 26 March 2020

Our project aimed to conduct population surveys for Southwestern Willow Flycatcher (Empidonax trailii extimus; SWFL) and Yellow-billed Cuckoo (Coccyzus americanus; YBCU) in 2018 and 2019, apply existing habitat models to illustrate and predict past, current, and future habitat suitabilities for these two species, and update and standardize classification and mapping of riparian vegetation to reflect recent conditions along the lower 50 miles of the Santa Clara River. Models developed by Hatten and Paradzick (2003), Hatten, et al. (2010), Hatten (2016), and Johnson et al. (2016) were applied to the SCR to provide California Department of Fish and Wildlife (CDFW) and the U.S. Fish and Wildlife Service (USFWS) with useful tools for management of resources for SWFL and YBCU.

California↗

USGS2019

Short-term geomorphological and riparian vegetation responses to a 40-year flood on a braided, dryland river

In December 2010, a 40-yr flood occurred in the lower Virgin River (SE Nevada, southwestern U.S.), a braided river segment with riparian vegetation largely dominated by invasive shrubs in the genus Tamarix. We assessed geomorphological and vegetation responses to this large magnitude disturbance event by comparing pre- and post-flood remote sensing and field survey data in four river reaches. Analyses of orthophotos and LiDAR-derived topography showed that both the active channel area and channel width increased between ~80 and 258%, representing an increase from 13% to 30% of the total river corridor area. Erosion predominated in the outer bends of the enlarged channel and deposition in the pre-flood channel, causing local avulsions of the low-flow channel. Field-based topographic data recorded before and after the flood in 385 plots also showed that deposition occurred in parts of the floodplain that were not eroded. Two thirds of woody vegetation cover (mainly dominated by Tamarix, with some native shrub Pluchea sericea) was lost in areas that eroded (~20% of the river corridor). In the remaining ~80% of stable river corridor (aggrading or no change in elevation) Tamarix remained dominant. Following erosion, but also where sediment deposition predominated under the Tamarix canopy, the most common colonizing vegetation in the understory was comprised of annual plants, especially Salsola tragus. Overall, our study supported previous studies describing large floods in braided rivers: we documented the first phase of a cycle of channel widening and increase in vegetation heterogeneity that is commonly followed by narrowing and vegetation homogenization. We underscore the importance of rivers with mostly unregulated flood regimes as laboratories for understanding eco-hydrologic feedbacks.

Nevada↗

USGS2019

Recovery planning in a dynamic system: Integrating uncertainty into a decision support tool for an endangered songbird

Along the Santa Clara River in California, populations of the federally and state-listed Least Bell's Vireo ( Vireo bellii pusillus ) are recovering from near extirpation. Habitat protection and restoration, as well as controlling rates of brood parasitism, are thought to be the primary drivers of this recovery. Continuing successful management of this population faces multiple challenges due to the highly dynamic and unpredictable nature of the system, lack of clearly defined and measurable recovery criteria, parametric and stochastic uncertainty, and data limitations. Many of these management challenges are not unique to Least Bell's Vireo and require careful balancing of limited resources into the future. We developed a decision support tool as a user interface for exploring the underlying uncertainty in a population viability analysis under an array of different management scenarios. The tool was designed to assist with the planning and coordination between conservation partners in the region in three distinct aspects of the decision-making process: defining the problem and setting clear goals and objectives, exploring the consequences of potential alternative actions, and identifying criteria for ongoing evaluation and monitoring. The general framework for the design of this decision support tool is broadly applicable to many management and decision-making scenarios that share these common challenges.

California↗

USGS2014

Riparian restoration framework for the Upper Gila River, Arizona

This technical report summarizes the methods and results of a comprehensive riparian restoration planning effort for the Gila Valley Restoration Planning Area, an approximately 53-mile portion of the upper Gila River in Arizona (Figure 1-1). This planning effort has developed a Restoration Framework intended to deliver science-based guidance on suitable riparian restoration actions within the ecologically sensitive river corridor. The framework development was conducted by a restoration science team, led by Stillwater Sciences with contributions from researchers at the Desert Botanical Garden (DBG), Northern Arizona University (NAU), University of California at Santa Barbara (UCSB), and U.S. Geological Survey (USGS). All work was coordinated by the Gila Watershed Partnership of Arizona (GWP), whose broader Upper Gila River Project Area is depicted in Figure 1-1, with funding from the Walton Family Foundation’s Freshwater Initiative Program.

Arizona↗