Environmental Engineering Reference
In-Depth Information
Fig. 2.6
Erosion (
arrowed
) of the Ninety Mile Beach, on the outer barrier of the Gippsland
Lakes in SE Australia, with accretion (
+
) on either side of the Lakes Entrance breakwaters.
© Geostudies
because of ecological changes such as the destruction of shell fauna by pollution,
or because increased growth of seagrasses or other marine vegetation has impeded
shoreward drift and trapped sediment offshore.
2.4 Reduction of Sand Supply from Inland Dunes
Some beaches have been supplied with sand blown from dunes spilling from the
land on to the shore. If the sand supply runs out, or the backshore dunes become
stabilised, either by the natural spread of vegetation, or from the planting of
grasses or shrubs, the spraying of bitumen or rubber compounds, or sealing of the
dune surface by built structures, these beaches may start to erode. On the south-
facing Cape Coast of South Africa, where the prevailing westerly winds are driv-
ing dunes over headlands to supply beaches on the lee shore, dune stabilisation has
resulted in beach erosion, as at Port Elizabeth.
Where beach erosion is due to the reduction of sand supply from inland
dunes this could be the result of successful conservation measures, such as the
