Wetland Restoration in Urban Settings: Studies of Vegetation and Seed Banks in Restored and Reference Tidal Freshwater Marshes

This study examined the seed bank and vegetation of a restored tidal freshwater marsh located in Washington, D.C. and compared it to an older restored marsh, a natural urban marsh, and a natural non-urban marsh. A study examining the effects of a beaver impoundment on the vegetation and edaphic factors in the natural non-urban reference site was also conducted. The number of seedlings, vegetation cover, taxa density, evenness, and diversity of vegetation were compared among sites in these studies. The restored marshes were more similar to the natural urban wetland than to the natural non-urban wetland with regard to the seed bank and vegetation. Duration of flooding from the beaver impoundment was found to be an important factor affecting vegetation composition at the non-urban reference site. Findings included: urban restoration projects should likely have urban reference sites; and natural disturbances may have similar influences upon both natural and restored systems

CROSSTEX: A Description of the Experimental Condtions, Wave Climate, and Inner Surf Zone Hydrodynamics

Edwin A. Cowen (Todd), Phillip L-F Liu, Charles H. K. WilliamsonThe Cross Shore Sediment Transport Experiments (CROSSTEX) are a group of experiments examining sediment transport processes in the near shore environment with the goal of improving process based models for sediment transport. This is accomplished via large scale lab experiments utilizing advanced instrumentation and controlled, repeatable wave conditions as well as a natural sand beach. One section of these experiments examined sediment transport in the swash zone, the alternating wet and dry portion of the beach. Velocity data was collected from outside the breaker line into the surf zone, along with free surface measurements throughout the tank. Additional instrumentation to measure optical backscatter, sediment grain velocity and water pressure was deployed in the near shore. Waves consisted of regular, 5th order Stokes waves with wave heights ranging from 12 cm to 30 cm, two runs with a simple bi-chromatic wave train and one run with random waves. An analysis of wave climate stability and wave repeatability indicates the wave tank approaches a steady, repeatable wave climate after approximately 5 minutes although bathymetry changes ultimately affect repeatability in the near shore. Comparison of the time averaged mean free surface with empirical estimates shows good agreement with other studies conducted in both the field and wave tanks. Phase averaged velocity profiles taken in the offshore by an Acoustic Doppler Current Profiler (ADCP) indicate a 2-D flow environment with minimal along shore flow and repeatable wave conditions. An alternate processing scheme was developed for the ADCP data to allow redundant estimates of each velocity component which was used to assess flow uniformity. Phase averaged velocity data in the surf zone taken from Acoustic Doppler Velocimeters (ADVs) revealed occasional strong along shore flow and more complex flow structure, but supports wave repeatability. Analysis of the bathymetry data in the surf zone revealed strong along shore gradients, which contribute to the more complex flow seen in the surf zone. Surf zone turbulence obtained by applying a linear predictive filter to velocity signals and differencing the filtered and original signals indicates plunging to weakly plunging breaking conditions as well as providing order of magnitude estimates of turbulent dissipation in the surf zone. Recommendations for the conduct of future large scale experiments (field or lab) in the surf zone and in general, and future work on the present data are provided.National Science Foundatio

Improvements in acoustic doppler velocimetery

Proceedings of the Seventh International Conference on Hydroscience and Engineering, Philadelphia, PA, September 2006. http://hdl.handle.net/1860/732Acoustic velocimeters have become popular for measuring turbulent and mean flows in fluid mechanics laboratories. A series of tests were conducted to evaluate the performance of several acoustic velocimeters at low signal to noise ratios (SNR) to assess the accuracy of mean flow estimates, and at typical SNR in response to tilting of the velocimeter head with respect to the flow. Tests were conducted in an open channel flow with Particle Imaging Velocimetery (PIV) measurements made for comparison and assessment of flow disturbance around the head. While limited in the scope of its assessment, this study shows large improvements have been made in the performance of acoustic velocimeters since their introduction in the early 1990s

Turbulence, instream wood and fish: ecohydraulic interactions under field conditions

This is the pre-peer reviewed version of the following article: Trinci, G, Harvey, GL, Henshaw, AJ, Bertoldi, W, Hölker, F. Turbulence, instream wood and fish: Ecohydraulic interactions under field conditions. Ecohydrology. 2020;e2211. https://doi.org/10.1002/eco.2211 , which has been published in final form at https://doi.org/10.1002/eco.2211. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions

Gender differences in chronic liver diseases in two cohorts of 2001 and 2014 in Italy

Background: Gender differences in chronic liver disease (CLD) have been partially investigated. To extend the present knowledge, we evaluated 12,263 patients with CLD enrolled in two national surveys (9997 in 2001 and 2557 in 2014). Methods: The two surveys prospectively recruited patients aged â¥Â 18 referring to Italian liver units throughout the country using a similar clinical approach and analytical methods. Results: The overall male to female ratio (M/F) was 1.4 (7138/5124). Compared with females, males were significantly more likely to be younger (52.9 vs. 58.7 yrs.), with HBV infection alone (13.2% vs. 9.2%) and with alcoholic liver disease alone (11.4% vs. 6.9%), but less likely to show HCV infection alone (48.0% vs. 67.9%). A male preponderance was observed in HBV-related cases (1.99) and in alcoholic-related cases (2.3), a preponderance observed both in the 2001 and in 2014 cases. In HCV-related cases, however, females predominated in 2001 (M/F 0.9) and males in 2014 (M/F 1.5).The rate of cirrhosis in alcohol-related etiology was close to 36% in both genders, a finding much higher than that observed for both sexes in HBV and HCV etiologies.Both males and females enrolled in 2014 were older (p < 0.001) and with a higher rate of cirrhosis and/or HCC (p < 0.001) than those investigated in 2001. There was a remarkable increase over time in the proportion of male abstainers (36.7% in 2001 and 64.3% in 2014). Conclusion: This study highlights important inter- and intra-gender differences in the characteristics and etiological factors of patients with CLD in Italy

Turbulence In Low Energy Lacustrine Environments At The Sediment-Water Interface

The sediment-water interface is an important region where biological, chemical, and physical processes occur. Fluid flow determines the ability of organisms to utilize the bottom sediments for food, shelter, and reproduction, the amount and rate of mass transfer between the sediment and bulk fluid, and the deposition, re-suspension and transport of sediment. Field experiments carried out in three medium sized basins, one a heavily polluted lake and the other two drinking water reservoirs, are used to describe typical turbulence levels during the mid to late stratified season (July through October) in a low energy lacustrine bottom boundary layer. Using these measurements, a turbulence chamber was developed for use in turbulent scalar flux studies. The chamber was characterized using particle image velocimetery (PIV), characterizing the near bed turbulence and dissipation levels. The chamber successfully reproduces the range of turbulent energy levels observed in the field, allowing a more direct comparison of results obtained in field and laboratory studies of scalar fluxes. Results from the two reservoirs were used in laboratory cohesive sediment erosion and resuspension tests of a mono-disperse kaolin clay and natural sediment cores obtained from various bottom and shore locations in one of the reservoirs. This testing showed the small bed stresses typical of the lacustrine bottom boundary layer were not sufficient to erode or resuspend significant quantities of sediment. Higher stress levels caused erosion and resuspension, but it was heterogeneous in nature and appeared to be tied to flow structures associated with the facility used to carry out the experiments. Even at higher stress levels, very short settling times (only 1-2 hours) were needed for observable erosion to occur. A method for estimating erosion utilizing images of the sediment-water interface and tracking the interface as an intensity peak over time was developed. Initial results show this is a reliable means to gauge the sediment-water interface position when optical access is available