Characterization of Suspended Frazil and Surface Ice in Rivers Using Sonars

  • Author / Creator
    Ghobrial, Tadros I.R.
  • This research describes laboratory and field experiments aiming at developing techniques for obtaining quantitative measurements of suspended frazil ice and surface ice characteristics in rivers using sonars. A series of laboratory experiments were conducted to correlate the sonar backscatter signal from a high (546 kHz) and low (235 kHz) frequency units with direct measurements of frazil concentration. The sonar measurements showed that the high frequency unit is more sensitive to the presence of suspended frazil particles than the low frequency unit, especially at lower concentrations. A strong correlation was found between the acoustic relative backscatter from both sonar units and the measured concentrations. This calibration was conducted over a range of frazil mass concentrations between 0.012 and 0.135 % and the majority of observed frazil particles were disk shaped, varying in diameter from 0.25 to 4.25 mm. An algorithm has been developed to measure surface ice characteristics using field data from the high and low frequency sonars, a 2 MHz current profiler, and a monitoring station, deployed on the North Saskatchewan River in the north east of Edmonton, AB, Canada, during the 2009/2010 freeze-up season. The validity and the accuracy of these measurements were tested and results are presented. Over the entire season, pans/rafts drafts ranging from 0.1 to 1.0 m and pan/raft lengths ranging from 0.6 to 8.0 m were measured. The sonar proved to be very accurate in detecting the exact surface ice conditions locally above the sonar beam. Acoustic field data gathered during suspended frazil events have been processed and analyzed to provide estimates of frazil concentration and particle sizes using laboratory regression equations and fluid disk scattering model. In total, eight frazil events were detected with the sonars during the field deployment. Preliminary linkages between the meteorological (air and water temperatures) and surface ice conditions measured at the site, and the duration and magnitude of the detected frazil events are presented. Concentrations ranging between 0.01 and 0.05% and disk radii between 0.13 and 0.21 mm have been estimated from the field data.

  • Subjects / Keywords
  • Graduation date
    Fall 2012
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.