Dunes Wonderland Trail #6: Disappearing Dunes
The cache, previously called Skildersgatkop's Disappearing Dunes, has now been incorporated as the 6th cache on the DWT trail, for details of which see GCA3BT8 DWT#1.
The small camo-taped tablet pot, is hidden in a rocky/bushy island towards the middle of the main remaining visible (‘bare sand’) part of the dune system in the lovely lower Silvermine Valley.
The area is an amazing otherworldly place of pristine white sand dunes with beautiful shapes and wind ripple patterns, and well worth visiting. Sadly, they are disappearing with 80% less now than in 1945. So, make the effort to see them before they are gone – and grab a cache or two in the process!
To Reach the Cache Location:
a) Shortest route (approx 1km/30 mins): follow Clovelly Road past the golf club buildings and park at the end of the car park @ S 34 7.284 E 18 25.537. From here continue down the jeep track to around S 34 7.104 E 18 25.072 then head down across the grass and the footbridge across the Silvermine River to the corner of the golf course @ approx S 34 7.118 E 18 25.012. Then make your way the approx. 350m up and across the more or less vegetated dune slopes using any ‘path’ of least resistance to the cache location. You may find/decide to use a more direct approx. 175m Route 1 approach from the edge of the golf course after surveying the terrain on site!
Whichever route you choose, you will need to do some slip/sliding up and down the loose sandy dune slopes and some relatively minor bundu-bashing as you make your way around/through the largely alien and ever-encroaching dune vegetation.
b) Longer route A (from Clovelly Golf Club side – approx 2.4km 60 mins): follow a) above but continue along the jeep track to S 34 7.118 E 18 25.012 where the track crosses over the river and also the start of a sandy trail heading south winding its way across and up the gentle slope to the western end of the main dune area. Follow this and continue heading straight up the dune ‘valley’ to the cache location.
To Return, either retrace your steps or use route a) in reverse to regain the jeep track.
c) Longer route B (from Silvermine Sunbird Centre side – approx 1.4km 40 mins): after parking at S 34 6.706 E 18 24.488 follow the jeep track to the river crossing and then follow route b) as above.
d) Longer route C (from Fish Hoek) – approx 1.4km 40 mins): after parking at S 34 7.652 E 18 25.549 use any of the many small tracks which may still be found to make your way through the scrub and up the dune slopes by the route of least resistance to the eastern end of the remaining bare sand dune and walk down the dune valley to the cache location. (Note: this route is visible on Google Earth 2021 imaging and has been used in the past to access the dunes and the existing cache there. However, info on the current status of the rampant invasive alien overgrowth – and therefore the viability of this route is not (yet) available.
The remaining clearly visible (ie. predominantly pure sand) dune area in the lower Silvermine Valley stretches for some 700m from NW to SE where it meets the Clovelly golf course. It is approx. 100m across at its widest point.
In the past (see photos) the dune-field was much more extensive, stretching all the way from the coastal dunes along Fish Hoek & Clovelly beaches up to the current western end where the sandy access trail starts/ends. The sand has become progressively covered with vegetation – a mixture of grasses, shrubs and small trees – unfortunately the latter dominated by the alien Rooikrans (Acacia cyclops).
Originally from Australia, it was brought to Cape Town as an ornamental plant in the 1800s, and later used for dune stabilisation on the Cape Flats. It reaches 5m and its seeds are dispersed by birds (long distance) and ants (short distance) and are able to lie dormant in sand for 40 years.
Its detrimental effects are that it uses large amounts of water compared to fynbos, creates a canopy impenetrable by sunlight over natural vegetation leading to the death of the natural vegetation, stabilises dunes, out-competes natural vegetation and contributes to a loss in biodiversity.
It makes nitrates available to the soil which our natural vegetation cannot tolerate and creates a serious fire hazard due to a massive fuel load and highly flammable oils. As these are present in living trees, they are just as flammable as a dead ones.
Some QI dune facts:
A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or complex. A large dune complex is called a dune field, while broad, flat regions covered with wind-swept sand or dunes with little or no vegetation are called ergs or sand seas.
Dunes occur in different shapes and sizes, but most are longer on the stoss (upflow) side, where the sand is pushed up the dune, and have a shorter slip face in the lee side. The valley or trough between dunes is called a dune slack.
They are most common in deserts, where lack of moisture hinders the growth of vegetation that would otherwise interfere with their development. However, sand deposits are not restricted to deserts, and dunes are also found along sea shores, along streams in semiarid climates, in areas of glacial outwash, and in other areas where poorly cemented sandstone bedrock disintegrates to produce an ample supply of loose sand. Subaqueous dunes can form from the action of water flow (fluvial processes) on sand or gravel beds of rivers, estuaries, and the sea-bed.
Some coastal areas have one or more sets of dunes running parallel to the shoreline directly inland from the beach. In most cases, they are important in protecting the land against potential ravages by storm waves from the sea and artificial dunes are sometimes constructed to protect coastal areas. The dynamic action of wind and water can sometimes cause dunes to drift, which can have serious consequences.
Dune habitats provide niches for highly specialized plants and animals, including numerous rare species and some endangered species. Due to widespread human population expansion, dunes face destruction through land development and recreational usages, as well as alteration to prevent the encroachment of sand onto inhabited areas.
See here for a comprehensive 1982 report on the Lower Silvermine Valley and estuary with details on inter alia flora and fauna.
See here for a fascinating 2006 thesis on Geomorphic Changes to a Dune System In The Cape Peninsula: Fish Hoek – Noordhoek Dune Corridor which highlights the extent of the huge reduction in bare sand since 1945 and explains the main reasons for these changes – namely invasion of alien plants and interference with the dune system through various forms of urban development - in particular, at the eastern end, by extensive works relating to the railway, which resulted in most of the source sand for the dune system being removed from Fish Hoek beach.
Some Record Dunes:
Tallest dune (world): Duna Federico Kirbus, Argentina 1,230m
Tallest coastal dune: Mt. Tempest: Moreton Island, Australia 285m
Tallest dune (Africa): Dune 7, Walvis Bay, Namibia 383m
Largest dune (South Africa): Dragon Dune, Mossel Bay 170m – also at 350m the longest sandboarding run in the country
Largest sand dune desert: Simpson Desert Dunes, Australia – 168,000 sq.km. This is also the location of the world’s longest parallel dunes which are up to 160 km long.
