No abstract

No abstract

Acoustic Doppler Current Profilers (ADCP) are increasingly used for velocity and discharge measurements in riverine environment capitalizing on operation efficiency and rugged configuration. Part I of the paper investigated the potential of the moving-boat ADCP measurements to appropriately describe mean velocity field in river cross sections. It was concluded that the ADCP data collected during transects for estimation of discharges is not readily usable for estimation of the mean velocity distribution over the depth. Given the increased demand of the latter data for studies such as sediment transport, ecohabitat restoration, and for supporting numerical simulations, measurements with ADCP at fixed locations are evaluated from the same perspective.The paper reviews first general instrument requirements to accurately measure mean and time-resolved characteristics of turbulent river flows and subsequently formulates practical guidelines for conducting measurements of this kind. Next, the paper analyzes a set of ADCP data collected at fixed river locations using long sampling times. The effect of sampling time length on the accuracy of the mean velocities and turbulence intensities profiles is investigated using several statistical criteria. Time-resolved turbulence characteristics, such as autocorrelation and power spectrum, are also analyzed to verify ADCP capabilities to capture finer details of the turbulence in riverine environment. Additionally, the paper reviews the potential of ADCP fixed-location measurements to measure depth and to quantify near-bed layer velocities. 

There is a need for a simple, accurate soil density measurement system that does not require extensive calibration or significant health and safety measures for compaction quality control. This research describes the invention of a photogrammetric technique for obtaining the volume of an excavated hole in soil. This procedure requires a series of 8 to 16 digital photographs with a standard digital camera around the perimeter of an excavated hole with a reference scale in the scene. Algorithms convert the digital photographs into a colorized three-dimensional point cloud, which is automatically rotated into a plan view and displayed via the Matlab graphical user interface. Once the reference scale dimensions are input, the volume of the hole is calculated via a user selected ground plane. Once the mass of the excavated soil is input, the wet density of the soil is calculated by dividing by the volume of the hole. This procedure has been validated against both the nuclear density gauge and the sand cone apparatus and found to be equivalent in accuracy to both. This procedure enables soil density determination within 15 min with no replacement material, no specific excavated hole dimension, and no safety or health risks.

Bedforms are a consequence of flow of sufficient magnitude over a mobile sediment bed. They are a primary component of the drag acting upon a moving stream, yet are infrequently explicitly treated in numerical models of fluvial sediment transport. This study aims to document the collection of bathymetric data in the Mississippi River in an area of persistent and dynamic bedforms over a range of flow conditions, statistically examine bedform geometry, and parameterize results for inclusion in numerical models. Bathymetric data were collected several times to measure rates of bedform transport. Linear profiles of the bedforms were extracted from the bathymetry and analyzed for roughness and dune population statistics. These statistics are compared with the flow conditions under which the bedforms were observed. Bedforms increase in size with discharge and decrease in steepness (height:length ratio). At extremely high discharges, bedforms begin to decrease in size. In comparing results with methods for calculating form drag coefficients, it was observed that the dunes at higher river stages, despite their greater size, may present less resistance to flow due to their reduced steepness and reduced relative heights (dune height:flow depth). DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents.