Sand in movement

Panoramic photo taken on Tuesday at Beach 1 showing some erosion occurring to the fore-dune. Notice the water pooling in the bottom right.

This next photo is facing SE at the same site and the undulating effect from the pooling water extends to the horizon.  Truly a dynamic environment!

COASTAL FLOWERS OF THE DUNES

With the great weather we've been having lately it might be time to get outdoors and enjoy the flowers.

The Daisy Bushes Olearia sp. are colouring the dunes with their white flowers.

While the Seaberry Saltbush Rhagodia candolleana red berries attract the eye as well as providing food for the native animals.

There is also an invader from southern Africa hiding in the coastal vegetation. Purple Groundsel Senecio elegans gives itself away with its purple and yellow flowers. It is drought tolerant and can often be found scattered behind the foredunes.

Two Generations of Erosion

At many location along the Venus Bay beaches, you can see two generations of erosion on the one dune face. The upper erosion scarp (a geological term for the small vertical face, escarpment, created when waves washed away some sand)  has itself been partly eroded. As the sand face dries out it becomes unstable and collapses along wind picks up other dry sand and piles it infront of the face. Re-grown of saltbush grasses help stabile the sand collecting infron of the dune. Eventually the scarp itself will dissapear and the dune just have a steep front face. The recent erosion can be seen at the base as a new vertical face, with a areas where blocks of unstable sand have already tumbled from the sand faces above.

REMEMBER: These sand faces are remain very unstable, even if they sometimes look dry and stable.Even just a single square meter of wet sand will weigh close to 2 tonnes enough to fatally bury an adult. So children (even grown up ones) must be discouraged from playing on such erosion scarps

Tumbling Tumble Weed

Australia doesn’t really have the true (by which I mean the American Western Movie Style) tumble weed but the seed of the humble Spinifex, Spinifex sericeus comes very close. This grass also known as the beach spinifex is crucial for dune stability. It usually forms tussocks and has long rhizomes that spread out through the sand and hold the dunes in place. It can easily be propogated from rhizome cuttings planted in damp sand. Interestingly this spinifex has separate male and female plants. The above photo shows the dried flower, from a female plant, now holding the fertile seed. It blows along the beach following the shifting sand and thus populating newly formed dunes. A very clever design!

The introduced marram grass, is now competing with native spinifex all along the Venus Bay beach and may eventually replace all the native spinifex. The marram grass also helps stabilize the dunes, that is why it was originally introduced, but its dense growth may contribute to steeper dunes by entrapping more sand, at the expense of the upper beach zone (ie summer berm) This may be one factor in an increased susceptibility to direct wave erosion.  The dense grass mat also inhibits other dune pioneer plants and may reduce the traditional nesting and foraging habitat available for some small animals and birds. For example at Summerland Beach on Phillip Island the change in dune shape bought about by marram grass replacing spinifex has meant special temporary penguin tracks have had to be constructed up the dunes to give access to the little penguins breeding areas.