Geology topics

Research about California, Colorado

Source-linked reports with geographic coverage including California, Colorado.

3 recordsLinked to original sources

USGS2024

Defining the pathobiomes associated with drippy blight in Colorado and drippy nut in California

Drippy blight, an emergent bacterial disease of oaks, was described recently from urban oaks in the Front Range of Colorado, U.S.A. This disease, which causes branch dieback and oozing of bacterial exudates from cankers, is caused by Lonsdalea quercina and primarily affects red oaks, with northern red oak ( Quercus rubra ) being the most susceptible. Drippy nut is a similar, less acute condition that exists in California, U.S.A., and affects acorns of interior live oak ( Q. wislizenii ) and coastal live oak ( Q. agrifolia ). The objective of this study was to compare the microbial communities of drippy blight in Colorado to those of drippy nut in California and to determine whether other pathogenic fungal or bacterial taxa are associated with the diseases. Symptomatic and asymptomatic tissues were sampled in California and Colorado, and metagenomic analyses were performed to describe the fungal and bacterial communities. We found a suite of bacterial species, dominated by taxa within the genus Zymobacter , that were associated with symptomatic tissues for both drippy nut and drippy blight. L. quercina is the main pathogenic associate of both diseases. We found fungal yeasts associated with symptomatic tissues, and although not pathogens, these taxa were present in the pathobiome of drippy nut and drippy blight in California and Colorado. We did, however, identify taxa belonging to Gnomoniopsis , a known pathogen, associated with California symptomatic samples. Our study found an overlapping suite of bacterial associates of drippy blight and drippy nut, though more variation occurred within the fungal genera associated with these oak diseases.

California, Colorado↗

USGS2019

Taking the pulse of debris flows: Extracting debris-flow dynamics from good vibrations in southern California and central Colorado

The destructive nature of debris flows makes it difficult to quantify flow dynamics with direct instrumentation. For this reason, seismic sensors placed safely away from the flow path are often used to identify the timing and speed of debris flows. While seismic sensors have proven to be a valuable tool for event detection and early warning, their potential for identifying other aspects of debris flows (such as sediment concentration) is less studied. Here we use two monitoring sites to investigate the extent to which debris-flow dynamics can be decoded from ground vibrations. One site is a bedrock channel in a steep semiarid basin in central Colorado (Chalk Cliffs), and the other is in a debris-flow channel incised in alluvium in a recently burned area in southern California (Van Tassel). At both sites, seismic data are measured with geophones (4.5 Hz) mounted next to the channels and sampled at high frequencies (500-1000 Hz). Independent constraints on flow dynamics are provided by laser distance meters to record flow stage (at 10 Hz) and high-definition video cameras to record flow velocity and sediment concentration. The observed debris flows at Chalk Cliffs typically consist of a series of short-duration (~30 second) surges with total durations of <40 minutes and have coarse-grained fronts and fluid-rich tails. In contrast, the events at Van Tassel are longer duration flows (>40 minutes) that begin as debris flows and transform into more steady debris floods. The arrangement of sensors at both sites allow us to identify correlations between vertical ground velocity, frequency, flow stage, and qualitative estimates of sediment concentration.

California, Colorado↗

USGS2015

Using hydrophones as a surrogate monitoring technique to detect temporal and spatial variability in bedload transport

Collecting physical bedload measurements is an expensive and time-consuming endeavor that rarely captures the spatial and temporal variability of sediment transport. Technological advances can improve monitoring of sediment transport by filling in temporal gaps between physical sampling periods. We have developed a low-cost hydrophone recording system designed to record the sediment-generated noise (SGN) resulting from collisions of coarse particles (generally larger than 4 mm) in gravel-bedded rivers. The sound level of the signal recorded by the hydrophone is assumed to be proportional to the magnitude of bedload transport as long as the acoustic frequency of the SGN is known, the grain-size distribution of the bedload is assumed constant, and the frequency band of the ambient noise is known and can be excluded from the analysis. Each system has two hydrophone heads and samples at half-hour intervals. Ten systems were deployed on the San Joaquin River, California, and its tributaries for ten months during water year 2014, and two systems were deployed during a flood event on the Gunnison River, Colorado in 2014. A mobile hydrophone system was also tested at both locations to collect longitudinal profiles of SGN. Physical samples of bedload were not collected in this study. In lieu of physical measurements, several audio recordings from each site were aurally reviewed to confirm the presence or absence of SGN, and hydraulic data were compared to historical measurements of bedload transport or transport capacity estimates to verify if hydraulic conditions during the study would likely produce bedload transport. At one site on the San Joaquin River, the threshold of movement was estimated to have occurred around 30 m 3 /s based on SGN data. During the Gunnison River flood event, continuous data showed clockwise hysteresis, indicating that bedload transport was generally less at any given streamflow discharge during the recession limb of the hydrograph. Spatial variability in transport was also detected in the longitudinal profiles audibly and using signal processing algorithms. These experiments demonstrate the ability of hydrophone technology to capture the temporal and spatial variability of sediment transport, which may be missed when samples are collected using conventional methods.

California, Colorado↗