State of the Bay Report 2011-Final.pdf - Anchor Environmental

State of Saldanha Bay & Langebaan Lagoon 2011
Sediments
Southern Oceaneering CC in 2003, to carry out an urgent beach reclamation programme following
intensive investigations into various solutions by coastal engineers, PRDW, and the necessary EIA
approvals granted by DECAS in 2001. This involved the construction of two groynes using Geotextile
Sand Containers (GSCs) and the deposition of large quantities of sand dredged from Saldanha Bay to
extend the beach area (Figure 5.6).
Figure 5.5.
Rock revetments constructed along the beach at Langebaan in an effort to protect coastal
infrastructure.
Different sized GSCs (i.e. 2.5 m³, 12 m³ and 20 m³) were filled with sand collected from two
adjacent areas (Figure 5.6 - Area A or B) where sand was mixed continually with pumped sea water
creating a “slurry” which was then emptied into the bags and stitched closed. The GSC units were
then positioned by crane in the water, assisted by a team of divers. The first 250 m groyne (reduced
from the planned 448 m due to strong currents at the face) was completed in 2005 and the second
360 m groyne in 2007. Critical to the project was the beach replenishment programme which
involved dredging large amounts of sand from areas in the vicinity of groyne 1 (Figure 5.6 – Area C),
and depositing sand north of the 2 nd groyne up to the southern extent of Leentjiesklip No.1 (Figure
5.6-Figure 5.9). Approximately 380 000 m³ of material was dredged until the end of the programme
in November 2008.
Monitoring in the form of bi-annual beach profile surveys are conducted by the Saldanha
Bay Municipality (in collaboration with Prestedge Retief Dresner Wijnberg (PRDW) since completion
of the groynes and reclamation in October 2009. The beach profile survey record extends back to
before 1997 and provides a good basis for long-term monitoring of impacts to the coastline resulting
from the Langebaan Beach Restoration Project.
The beach profile surveys indicate that there is little unseasonal erosion and accretion in the
area. The rock revetments which were supposed to be a temporary solution cannot be removed as
they still serve a critical role in erosion prevention. The revetments to the South have been covered
partially with sand but to the North the main revetment is still exposed. It is not know at this stage
whether further reclamation of the beach to the North will eventually enable the revetment to be
removed. It is more likely that the revetment will remain and will eventually be covered with sand
through artificial deposition and some natural accretion. The beaches south of Groyne 1, adjacent to
the channel, appear dynamically stable (Mclarty, PRDW, pers. comm. 2012). However, there is still
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