Restoration is frequently aimed at the recovery of target species, but also influences the larger food web in which these species participate. Effects of restoration on this broader network of organisms can influence target species both directly and indirectly via changes in energy flow through food webs. To help incorporate these complexities into river restoration planning, we constructed a model that links river food web dynamics to in-stream physical habitat and riparian vegetation conditions. We present an application of the model to the Methow River, Washington, USA, a location of on-going restoration aimed at recovering salmon. Three restoration strategies were simulated: riparian vegetation restoration, nutrient augmentation via salmon carcass addition, and side channel reconnection. We also added populations of nonnative aquatic snails and fish to the modeled food web to explore how changes in food web structure mediate responses to restoration. Simulations suggest that side channel reconnection may be a better strategy than carcass addition and vegetation planting for improving conditions for salmon in this river segment. However, modeled responses were strongly sensitive to changes in the structure of the food web. The addition of nonnative snails and fish modified pathways of energy through the food web, which negated restoration improvements. This finding illustrates that forecasting responses to restoration may require accounting for the structure of food webs, and that changes in this structure, as might be expected with the spread of invasive species, could compromise restoration outcomes. Unlike habitat-based approaches to restoration assessment that focus on the direct effects of physical habitat conditions on single species of interest, our approach dynamically links the success of target organisms to the success of competitors, predators, and prey. By elucidating the direct and indirect pathways by which restoration affects target species, dynamic food web models can improve restoration planning by fostering a deeper understanding of system connectedness and dynamics.

Supergranulation is one of the most visible length scales of solar convection and has been studied extensively by local helioseismology. We use synthetic data computed with the Seismic Propagation through Active Regions and Convection (SPARC) code to test regularized-least squares (RLS) inversions of helioseismic-holography measurements for a supergranulation-like flow. The code simulates the acoustic wavefield by solving the linearized three-dimensional Euler equations in Cartesian geometry. We model a single supergranulation cell with a simple, axisymmetric, mass-conserving flow.The use of simulated data provides an opportunity for direct evaluation of the accuracy of measurement and inversion techniques. The RLS technique applied to helioseismicholography measurements is generally successful in reproducing the structure of the horizontal-flow field of the model supergranule cell. The errors are significant in horizontalflow inversions near the top and bottom of the computational domain as well as in verticalflow inversions throughout the domain. We show that the errors in the vertical velocity are due largely to cross talk from the horizontal velocity.

Fouling communities living on hard surfaces in harbors are model systems for studying larval recruitment and ecological succession. Although they live in protected harbors, fouling communities are exposed to waves due to wind chop and ship wakes. We studied how superimposing waves onto unidirectional currents affects hydrodynamic stresses experienced by larvae settling into different microhabitats within rugose fouling communities. We exposed fouled plates in a flume to turbulent water currents and waves mimicking those measured across fouling communities in Pearl Harbor, Hawaii, USA, and used laser-Doppler velocimetry to measure water velocities on the scale of larvae (500 µm from surfaces) at specific positions within each community chosen to represent a wide range of microhabitat types. These data were used to determine in stantaneous hydrodynamic stresses encountered by larvae and to calculate larval settlement probabilities. Local topography was more important than successional stage in determining hydrodynamic stresses on the scale of larvae. Increasing current velocity reduced settlement probabilities, with the largest effects on a flat unfouled surface and on microhabitats on the tops of fouling organisms. Wind chop and ship wakes reduced the probability of larval settlement at all current speeds and in all microhabitats, with the most pronounced effects on sites atop fouling organisms. Episodic peak stresses can be orders of magnitude higher than mean stresses, so using instantaneous stresses to calculate settlement probability yields a lower value than is predicted using mean stress. The factor by which the use of mean stress overestimates settlement probability depends on both microhabitat and flow conditions.

Acoustic Doppler velocimetry (ADV) is a popular technique for quantifying turbulent fluid flows in aquatic, marine, and laboratory environments. The technique relies on the Doppler shift principle to measure the velocity of suspended scattering particles that are assumed to move passively with the flow. Descriptions of ADV principles of operation are given by Lohrmann et al. (1994), Sontek (1997), and Voulgaris and Trowbridge (1998. The velocimeter employed in this evaluation is a SonTek 16 MHz MicroADV with the ADVField signal processing hardware enclosed in a splash-proof housing. This is a newer generation instrument that is advertised as having better spatial and temporal characteristics than the original SonTek 10 MHz and 5 MHz Ocean probes. These attributes make the 16 MHz model ideal for laboratory and turbulence measurements; however all of the models are available with ADVField processors enabling the probe to be used in the field. Acoustic instruments have a sampling volume (located at the intersection of the transmitting and receiving beams) that is large compared to the smallest scales of motion in turbulent flows. This limits the resolution and signal-to-noise (SNR) performance of the instrument, particularly in flows with smallscale turbulence and large velocity gradients. Thus, the ADV technique is subject to certain limitations in different flow regions and conditions. In this study, we evaluate ADV system performance by using the instrument to measure controlled laboratory flows. ADV results are compared to laser Doppler velocimetry (LDV) measurements in the same flow and to direct numerical simulations (DNS) of similar flows. The mean flow rates are designed to mimic those typically found in natural marine and aquatic systems so as to provide a useful guide for users interested in field and laboratory study. AbstractAn evaluation of acoustic Doppler velocimetry (ADV) in the near-bed region of turbulent boundary layer flows is presented. Acoustic instruments have large sampling volumes compared with the smallest scales of motion in turbulent flows. This limits the accuracy of the technique, especially when making measurements close to the bed or in flows where large spatial gradients are present. These limitations are quantified by comparing ADV results to laser Doppler velocimetry (LDV) measurements from the same flow, and to direct numerical simulations of similar flows. A SonTek 16 MHz ADVField system was used in the evaluation. Measurements were made in a turbulent boundary layer over a smooth bed in a laboratory flume. The instrument was evaluated in both a fast and slow flow case with free stream velocities similar to those found in many natural environments. Additionally, results from an assessment of ADV sample volume size and position are reported. Mean velocities were within 5% accuracy down to 0.7 cm from the bed for the fast flow case and 1 cm for the slow flow case. ADV-derived Reynolds stresses matched well with those from LDV to within 1-2 cm of the bed, however turbulence intens...

Riparian vegetation provides many noteworthy functions in river and floodplain systems including its influence on hydrodynamic processes. Traditional methods for predicting hydrodynamic characteristics in the presence of vegetation involve the application of static roughness ( n) values, which neglect changes in roughness due to local flow characteristics. The objectives of this study were to: (1) implement numerical routines for simulating dynamic hydraulic roughness ( n) in a two-dimensional (2D) hydrodynamic model; (2) evaluate the performance of two dynamic roughness approaches; and (3) compare vegetation parameters and hydrodynamic model results based on field-based and remote sensing acquisition methods. A coupled vegetation-hydraulic solver was developed for a 2D hydraulics model using two dynamic approaches, which required vegetation parameters to calculate spatially distributed, dynamic roughness coefficients. Vegetation parameters were determined by field survey and using airborne LiDAR data. Water surface elevations modeled using conventional and the proposed dynamic approaches produced similar profiles. The method demonstrates the suitability in modeling the system where there is no calibration data. Substantial spatial variations in both n and hydraulic parameters were observed when comparing the static and dynamic approaches. Thus, the method proposed here is beneficial for describing the hydraulic conditions for the area having huge variation of vegetation. The proposed methods have the potential to improve our ability to simulate the spatial and temporal heterogeneity of vegetated floodplain surfaces with an approach that is more physically-based and reproducible than conventional “look up” approaches. However, additional research is needed to quantify model performance with respect to spatially distributed flow properties and parameterization of vegetation characteristics.