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

Noosa Spit SEMP Final Report                                                                                                                                                                                                                                                                   11
Noosa Spit Shoreline Erosion


 Imagery                                                                         Observed Changes                                          Wind Climate              Notable         Orientation         Northern Spit      Southern Spit      Dominant Flow       High Tide         High Tide
   Date                                                                        (since previous image)                                   Compared to Average          Rainfall       and Condition         Length and         Length and          Channel          Recreational      Recreational
                                                                                                                                           (since previous             (since          of Mouth            Condition          Condition                              Beach            Beach
                                                                                                                                                image)               previous                                                                                    Availability at   Availability at
                                                                                                                                                                      image)                                                                                     central Doggie      eastern
                                                                                                                                                                                                                                                                     Beach         Doggie Beach


September                                          Growth of the northern spit appears to have reversed, with the spit narrowing        Double Island Point:      Nil. Dryer than   Multiple     N-S     Average, wide,     Short,             Multiple          Limited           Average
2016                                               and adopting a more westward N-S alignment. There is no change in the                Summer        2015/16     average. 2016     channels             submerged          submerged          channels
                                                   development of the northern channel.                                                 stronger   SE      than   lowest rainfall                        shoals to west                        through shoals
                                                                                                                                        average, & Winter 2016    on      station                        and south
                                                   The southern and central channels have fragmented across the flood-tide delta,
                                                                                                                                        lighter N than average    record
                                                   developing multiple disconnected channels. Dual N-S channels have developed
                                                   through the ebb-tide delta, one connecting to the southern channels and another      Tewantin:
                                                   running along the seaward face of the northern spit.                                 Typical winds

                                                   Minor narrowing of the centre of Doggie Beach is visible, but no loss of
                                                   vegetation is apparent.

                                                   There is limited change in development of the southern spit, with approximately
                                                   12,500m3 intercepted by the sand shifter.




February                                           Southward growth of the northern spit has resumed, further blocking the central      Double Island Point:      Nil. Dryer than   Shore-parallel       Long,      wide,   Minimal   above    Multiple          Limited to none   Average
2017                                               channel and forcing the remaining fragmented channels to consolidate                 Summer 2016/17 more       average.          west            of   western   side     HWM, average       channels
                                                   southwards. Increased inundation of dune grasses on the western face of the          N-NE than average                           coastline,   then    partially          submerged          through shoals
                                                   northern spit indicates potential for breaching.                                                                                 N-S                  submerged          shoals to north-
                                                                                                                                        Tewantin:
                                                                                                                                                                                                                            west
                                                   Vegetation loss along central Doggie Beach has resumed as the southern               Typical winds
                                                   channel migrates southward against Noosa Spit. The submerged geobag
                                                   groyne has been partially covered with sand from the adjacent sand shoal.

                                                   Although the scour pocket at the Noosa Woods training wall still controls flows,
                                                   the southern channel no longer exits alongside the training wall, instead running
                                                   in a shore-parallel direction before exiting closer to Noosa North Shore. The
                                                   southern spit extent remains small above high-water, although the submerged
                                                   portion has notably increased as the channel exit moves north away from the
                                                   training wall.




December                                           While vegetation on the northern spit continued to establish, the spit itself does   Double Island Point:      Wetter     than   Shore-parallel       Average, wide      Minimal above      Southern     –    Limited to none   Limited
2017                                               not appear to change significantly, and inundation of the spit along the upstream    Typical winds             average.          west           of    but     patchy     HWM, average       Hard up against
                                                   (western) face of the spit appears to be increasing, with overtopping visible                                                    coastline,   then    overwash           submerged          Doggie Beach
                                                                                                                                        Tewantin:                 Highest March
                                                   where the split northern channel re-joins. The central channel continues to be                                                   NE-SW                                   shoals to north-
                                                                                                                                        Typical winds             rainfall    on
                                                   blocked by the spit.                                                                                                                                                     west
                                                                                                                                                                  station record
                                                   Southward merging of the multiple channels between the northern spit and                                       (ex-TC Debbie).
                                                   Doggie Beach is complete, with the southern channel now the sole channel.                                      Significant
                                                   Notable loss of vegetation along Doggie Beach is a direct result of the proximity                              rainfall     in
                                                   of this dominant channel.                                                                                      October   and
                                                                                                                                                                  November.
                                                   The southern spit has grown notably below the high-water mark, despite more
                                                   than 8,000 m3 of material being intercepted by the sand shifter in the preceding
                                                   month. The spit growth has forced the channel towards the northern spit before
                                                   exiting near Noosa North Shore.




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