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

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Example processing of a flood tide and ebb tide cross-sectional transect at Noosaville is shown in Figure
2-2 and Figure 2-3.

The right panel of the WinRiver II interface provides a summary of the measurement including:

• Total Q (flow, m3/s) which is the sum of the ‘Measured Q’, ‘Top Q’ and Bottom Q. The ‘Top Q’ and
   ‘Bottom Q’ are estimates of the flow components not directly measured by the ADCP due to instrument
   blind spots at the top and bottom of the water column. Similarly, the WinRiver II software estimates the
   ‘Left Q’ and ‘Right Q’ which correspond to the flow components at the left and right riverbanks that
   cannot be directly measured with the boat-mounted instrument.

• The width (m) of the transect and the cross-sectional area (m2) and estimates of the cross-sectional flow
  speed (m/s)

The ‘Stick Ship Track’ illustrates the transect and the magnitude and direction of the flow. The ‘sticks’
pointing upstream in Figure 2-2 indicate flood tide conditions. The ‘sticks’ pointing downstream in Figure
2-3 indicate ebb tide conditions.

The cross-sectional plot at the bottom of the WinRiver II interface shows the vertical bins at an instant in
time (the instantaneous ensemble) as the boat-mounted instrument is towed across from the right to left
riverbank (or vice versa). Together, the combined bins provide a quasi-instantaneous snapshot of the cross-
sectional flow velocity. This data is the basis for calculating the ‘Measured Q’.

Timeseries plots of the quasi-instantaneous ‘Measured Q’ at Dog Beach, Noosa Sound, Munna Point and
Noosaville are provided in Figure 2-4 and Figure 2-5. For reference, the indicative water level at Munna
Point is also shown on the plots (based on Maritime Safety Queensland predations and published tidal
planes). In tidal estuaries and at a given location, the peak flood or ebb flow rates will coincide with the
transition from high to low water (or vice versa). The flow rate will be close to zero at times of peak high or
low water level (commonly referred to as ‘slack water’).

The cross-sectional ‘Measured Q’ and ‘Total Q’ collected with the boat-mounted ADCP will provide
important data for calibrating the hydrodynamic model developed for the SEMP. The data will be used to
validate the volume of water in the estuary between high and low tide.

The measured cross- and long-sectional flow velocity and direction will also be used for model
calibration/validation purposes. The long-sections will also provide important information on the peak spring
tide currents at Dog Beach.




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