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

Executive Summary
Two surveys were conducted for the Noosa Council across a section of the Noosa River
extending from the Noosa Ferry crossing to offshore of the Noosa River entrance: a
multiphase echo sounder (MPES) swath survey and a single beam echo sounder (SBES) /
land transect survey. The latter focussed on shorelines and sand banks around the entrance
to the river not surveyed by the swath mapping system. Both surveys were completed without
any safety incidents and in a timely manner.
The MPES produced both bathymetry and backscatter (sidescan sonar) data. The emphasis
for this survey was the bathymetry data in support of a shoreline erosion study being
conducted by coastal engineering consultants. However, the backscatter data were also
logged for possible future use in other Noosa Council projects and a small sample of the
processed data is presented in this report.
Positioning accuracy (horizontal and vertical) for all survey data were 1-2cm, with all data
reduced to AHD. Approximately 2.0 km2 of river area were surveyed with 100% swath
coverage, a considerable amount considering the bulk of the river depth is around 2m AHD.
The MPES and SBES data were combined and interpolated to produce a composite digital
terrain model (DTM) for the entire survey area. A highly detailed view of river and entrance
features was obtained, and the swath coverage should assist in the engineering modelling
efforts being undertaken by the Noosa Council.
The backscatter data, although not a focus of this report, can be used in the future for such
objectives as seabed characterisation and detection of small features on the riverbed or along
the river banks (e.g., anthropogenic debris, rocks, soft sediment areas, etc.).
In turn, the combined data set, when imported into a 3D/4D Scene, should provide the Noosa
Council with a useful marketing tool to highlight dynamic nature of the river and the complex
topography hidden beneath the main water body.




3                             Noosa Council - Noosa River Survey                    20.06.2019