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ABSTRACT A depth-averaged linearized meander evolution model was calibrated and tested using the field data collected at the Quinn River in the Black Rock Desert, Nevada. Two approaches used to test the model were: (1) simulating meander evolution and comparing the results with the observed 38 year migration pattern; and (2) fitting the model parameters to present bank asymmetry (the ratio of the maximum bank gradients on opposite sides of the channel). The data required as input were collected in the field during a high flow in May 2011 and from aerial photographs and LiDAR data. Both approaches yielded similar results for the best fit parameter values. The bank asymmetry analysis showed that the bank asymmetry and the velocity perturbation have high correlation at close to zero spatial lag while the maximum correlation between the bank asymmetry and maximum bend curvature is offset by about 25 m. The model sufficiently replicated 38 years of channel migration, with a few locations significantly under- or over-predicted. Inadequacies of the flow model and/or variation in bank properties unaccounted for are most likely the causes for these discrepancies. Flow through the Quinn River was also simulated by a more general 3D model. The downstream pattern of near-bank shear stresses simulated by the 3D model is nearly identical to those resulting from the linearized flow model. Topographic profiles across interior bends are essentially invariant over a wide range of migration rates, suggesting that the traditional formulation that cut bank erosion processes govern migration rates is appropriate for the Quinn River. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The article presents a study approximating the hyporheic activity of Truckee River in Nevada via its restored and unrestored reaches. It notes the observed increase of surface-subsurface interaction which is believed to have caused by the rocky riffles induction and the ascension of the channel bed elevations. The tracer being used in the determination of the hyporheic exchange is the fluctuating chloride concentration signal and the model known as OTIS is also utilized as model for solute transport. Results from the study indicates the great average of the transient storage zone cross-sectional area and the smaller exchange coefficient.

The efficacy of in-stream nephelometric turbidometric as a surrogate for total suspended solids (TSS) and total phosphorus (TP) concentrations was evaluated for use in low turbidity (<50 NTU) subalpine watersheds at Lake Tahoe, California-Nevada, USA. Continuous turbidity records for the 1999, 2000 and 2001 snowmelt seasons and data from water quality samples (1982-2000) were examined to determine watershed sediment delivery dynamics. Strong correlations were found between turbidity and both TSS and TP concentration. The strong correlation indicates that turbidity can serve as a good surrogate for direct measurement in these watersheds. The watersheds displayed clockwise hysteresis: sediment flushing and depletion, on daily, seasonal and decadal time-scales. The hysteresis curves had strong concave shapes, indicating a sensitive response to peak flow. A pronounced seasonal trend was observed for the ratio of suspended sediment concentration (SSC)/discharge over time, indicating early season flushing of available sediment. Significant linear relationships (p < 0.051 were found for 12 of 17 years. Comparison of annual sediment rating curve coefficients indicated smaller coefficients during high sediment loading years and in the years following. The smaller coefficients are evidence of sediment depletion during high flow years. The effect of hysteresis on monitoring methods was illustrated by comparing turbidity estimates of TSS load with sediment rating curve estimates of SSC. After accounting for differences in SSC/TSS methods of analysis, daily loads calculated with turbidity methods were 58-98% of rating curve estimates for the spring snowmelt seasons of 1999-2001. [ABSTRACT FROM AUTHOR]

1. We investigated the impacts of saltcedar invasion on organic matter dynamics in a spring-fed stream (Jackrabbit Spring) in the Mojave Desert of southern Nevada, U.S.A., by experimentally manipulating saltcedar abundance. 2. Saltcedar heavily shaded Jackrabbit Spring and shifted the dominant organic matter inputs from autochthonous production that was available throughout the year to allochthonous saltcedar leaf litter that was strongly pulsed in the autumn. Specifically, reaches dominated by saltcedar had allochthonous litter inputs of 299 g ash free dry mass (AFDM) m−2 year−1, macrophyte production of 15 g AFDM m−2 year−1 and algal production of 400 g AFDM m−2 year−1, while reaches dominated by native riparian vegetation or where saltcedar had been experimentally removed had allochthonous litter inputs of 7–34 g AFDM m−2 year−1, macrophyte production of 118–425 g AFDM m−2 year−1 and algal production of 640–900 g AFDM m−2 year−1. 3. A leaf litter breakdown study indicated that saltcedar also altered decomposition in Jackrabbit Spring, mainly through its influence on litter quality rather than by altering the environment for decomposition. Decomposition rates for saltcedar were lower than for ash ( Fraxinus velutina), the dominant native allochthonous litter type, but faster than for bulrush ( Scirpus americanus), the dominant macrophyte in this system. [ABSTRACT FROM AUTHOR]

In December 2010, a 40‐year flood occurred in the lower Virgin River (SE Nevada, southwestern United States), 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 light detection and ranging‐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. 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. [ABSTRACT FROM AUTHOR]