CGRG Bibliography of Canadian Geomorphology
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Author : Church, I.; Haigh, S.; and Hughes Clarke, J.-E.
Date : 2007.
Title : Applying predicted tides from a local hydrodynamic model to multibeam bathymetry: a solution for seabed monitoring in remote locations.
Publication : ArcticNet 2007 Annual Scientific Meeting. December 11-14, 2007. Collingwood, Ontario.
Issue : Programme.
Page(s) : 36.
Abstract
There has been an increased interest in monitoring seabed transformation from geological processes, such as ice-scouring, mass-wasting, tidal scouring and bedform migration, in remote locations of the Canadian Arctic. The CCGS Amundsen and the CSL Heron have the capability of collecting survey data in these areas for geological interpretation with their EM300 and EM3002 multibeam sonar systems, respectively. To monitor seabed change over time multiple survey datasets are compared, but direct comparison requires a stable common vertical reference datum. The often decimeter level relative vertical precision that is required to detect alterations in the morphology is difficult to obtain in remote locations. One specific project is monitoring the evolution of pro-glacial deltaic sediments in Oliver Sound, within Sirmilik National Park. Traditionally, a tide gauge would be installed in the vicinity of the study area to record water levels during a survey period. In this case, logistics, time constraints and conditions prohibit the installation of such a device. If a gauge could be established, the individual deltas are spread out over several 10’s of kilometres along constricted waterways and there is no prior knowledge of the likely propagation of the tidal wave. Other, non conventional methods of establishing a vertical reference datum must be considered. Ship based globally corrected RTG GPS observations (CNav) are available, but for the requirements of these surveys are not accurate enough and suffer from severe reliability issues due to the steep fjord walls. The Arctic-wide WebTide tidal prediction model would be an option for the more open waters, but does not resolve the fjords. Predicted tides from nearby benchmarks could also be used, but they are far from the survey area and separated by complex and restricted bay geometries. In order to overcome these hurdles, a local nested hydrodynamic circulation model has been developed. The model delivers predicted tidal amplitude, phase and current information at any location within its domain for the two principal semidiurnal constituents (M2 and S2) and diurnal constituents (K1 and O1). Applying these predicted tides to multibeam survey data removes the effects of the tide, thus allowing them to be related to a common vertical datum. The model can be tested against CNav GPS observations, which can confirm correct model phasing of high and low water.
Bibliography of Canadian Geomorphology