2019-12-16 GC Agenda - Item 5 - Attachment 1 - Noosa Spit Shoreline Erosion Management Plan-Part 2

Comparison to Existing Bathymetry and Future Surveys
Comparison of the 2019 data set to existing bathymetry across the survey area was
somewhat limited. The internal check between the 2019 swath bathymetry and 2019 SBES
bathymetry showed a mean difference of around 10cm which was deemed acceptable by NC.
The raw 2010 SBES data were not made available for this study but charts showing derived
contours were provided as PDFs. Selected sections of these PDFs were converted to Geotif
format and imported to a Fledermaus Scene for comparison against the 2019 swath
bathymetry. The charts were registered at selected contour heights within the Scene and
compared to the contours extracted from the swath bathymetry. In both upstream and
downstream locations where presumed minimal erosion or deposition had occurred (e.g., in a
protected marina) the two data sets aligned well. As such, our AHD reduction closely matches
that used for the 2010 data set.
The 2019 swath bathymetry data set should be an invaluable tool for evaluating future
changes in the Noosa River waterway, complimenting existing Lidar data across the region.
Alternative techniques to acoustic sonars may be more economically proficient for future
large-scale mapping of the river system (e.g., LIDAR systems affixed to drones, Satellite
Derived Bathymetry) but the swath techniques employed as part of this survey could be used
for more local monitoring of “problem” areas within the river or areas undergoing
development.




21                           Noosa Council - Noosa River Survey                   20.06.2019