The relentless struggle between sea and shore

Text and Photos by Hu Berry | Main photo ©Paul van Schalkwyk

| This article was first published in the Flamingo January 2009 issue.

Change is a constant. This inescapable fact illustrates itself vividly on Namibia’s desert coastline where the sea advances, swallowing lagoons, and retreats, leaving shipwrecks stranded in the desert.

A n immutable law of nature is that the erosion and weathering of the earth’s surface occur constantly and at differing tempos. In the process, land masses are unceasingly corroded and returned to the sea in a timeless geological cycle. Water and wind are indisputably the most potent of the natural elements. Driven by sun energy, unequal heating of the earth’s surface spawns ocean currents and wind strength. The ocean absorbs most of this incoming radiation and its estimated 1 320 billion cubic metres, which comprise 97% of all the planet’s water, starts a giant ‘heat’ engine that sends waves crashing against thousands of kilometres of coastline. Curling in concert they either hurl sand onto beaches or gnaw away at the edges of continents. Along Namibia’s 1 400-kilometre-long shoreline rocky outcrops wear slowly but the softer beaches yield easily and quickly to wave energy. The powerful Benguela Current drifts incessantly northwards, feeding on soft sand and driving the tidal wash higher and further inland.

Seafarers a century ago could have not imagined that the safe haven offered by Sandwich Harbour would virtually disappear under a relentlessly encroaching surge. Where great sailing ships rode safely at anchor as they waited for bird guano to be loaded, the sea has moved landward and the channels of the harbour have shrunk, forming a shallow, unstable lagoon. As Sandwich became less friendly to seafarers, the scene slowly reverted to its original desolation. Where lush reed beds, fed by fresh water that seeped beneath the dunes, once cradled nests of egrets and herons, the beachfront retreated, burying both reeds and an ancient human cemetery with a broad blanket of pale sand. The huts of early guano collectors collapsed under a twofold attack of advancing dunes and encroaching sea. The once lush wonderland of freshwater pools and the extensive lagoon system are now merely a memory to those of us who visited there then.

South of Sandwich lies the notorious ‘Lange Wand’ (German for Long Wall) of dunes that slope into the sea, affording a narrow strip of exposed beach along which four-wheel drive vehicles may pass at low tide only. High water washes waves onto the dunes, sucking in any vehicle that has not completed the dangerous passage in time. It is along this stretch of sloping sand that the freighter Shaunee, came to rest in 1976. Her bow is berthed under a towering dune and she now earns her last voyage as an attraction for tourists in aircraft on scenic flights. In contrast, further south near Conception Bay, the Atlantic retreated when the bay’s head closed against the shore. One hundred years ago, on a lonely stretch of beach close to Conception Bay, the 2 272-ton freighter Eduard Bohlen ran aground in thick fog, adding to the numerous shipwrecks of the Skeleton Coast. Now she lies, stern raised defiantly against the south-westerly wind, 400 metres from the waves that washed her ashore. Advancing and retreating, this lonely coastline personifies the instability of Namibia’s edge against the sea.

Marking the entrance to Walvis Bay’s modern harbour, Pelican Point’s lighthouse bears witness to the inexorable northward march of sand. Built in 1932 at the tip of a barren sand spit that juts into the open ocean to form a natural bay, the redundant lighthouse overlooks a beach head that has lengthened the point by two kilometres to the north, equivalent to about 25 metres a year. The future of the extending sand spit and the destiny of Walvis Bay are difficult to predict. Nevertheless, given the fate of similar systems further south, the arrowhead spit points forebodingly to the shore. Eventually, with time, it may encase the present bay to form a shallow lagoon, as happened with Sandwich Harbour, Conception Bay and Meob Bay to the south.

This theory is supported by reputed geologists who point out that Walvis Bay owes its formation to the course of the Kuiseb River, which developed a broad delta, creating a wind and sea current ‘shadow’. By geological chance, the presence of a strong, ephemeral river that regularly discharged sand and gravel into the ocean permitted the bay’s creation. Such favourable circumstances for people can be of short duration unfortunately. Human ingenuity has blocked the Kuiseb’s flow by the building of a flood barrier across its northern arm to prevent flooding of the low-lying town. At the same time the increased abstraction of large volumes of ‘fossil’ water (which has taken up to 40 000 years to accumulate) has killed much of the natural, riverine vegetation that prevented sand movement across the delta. It does not take much imagination to project the consequences of this. Starved of its floodwaters, the Kuiseb can no longer sluice the accumulated dune sand from the delta nor can it feed the bay with productive sediment.

Walvis Bay Lagoon already faces silting and drying, convincing evidence that the bay is progressively developing into a large lagoon. Pelican Point’s beach head drift will probably eventually cut Walvis Bay off from the Atlantic with an advancing coastline. If this happens, in the final phase, all sea water evaporates and the depression becomes a huge, salt-filled pan – and part of the Namib Desert. To support this course of events, look south where previously the Tsauchab River entered the sea at Meob Bay; where the Tsondab River did likewise at Conception Bay, and a southerly arm of the Kuiseb fed Sandwich Harbour. All three rivers were cut off by the unstoppable advance of the dunes, causing the bays to close and become shallow lagoons or disappear. Will Walvis Bay follow the same fate?

To the north of these dramatic changes lie, until recently, the relatively stable sandy shores stretching 200 kilometres along Namibia’s mecca for holidaymakers and retired people. Added to these pleasant pursuits are the booming businesses of mining together with the entire spectrum of social and auxiliary support services, which make the central coast a rapidly developing hub of activity. As they sip sunset cocktails on the beach, visitors and residents alike can see coastal erosion taking place. Sturdy concrete pillars that in 1915 supported a railway bridge across the Swakop River stand awry in the tidal wash. In 1931 a flood scoured away the river’s delta, allowing the sea to encroach and form a bay, in a manner similar to the birth of Walvis Bay.

Driving northwards toward the Skeleton Coast, reminders of sea power show. Some housing units perch uncomfortably close to high tides, especially when Atlantic storms create strong swells that whip waves to crest and fling spray onto gardens and windows. At Mile 14, a favourite angling area, the toilets have succumbed to high tidal washes and toppled into the sea as wave energy scours the back beach and gravelled camping area. Prime property beachfront homes on Henties Bay’s south and north dune overlook surf that eats away at the dune bases. The owners can only guess whether and when their erven or even their houses may be reclaimed by a hungry sea. Continuing past numerous fishermen’s haunts provides a hint of what may yet come – the sea has breached the main coastal road in many places, driving tides across low-lying salt pans which have become part of the tidal zone.

Nobody can predict what will happen because we are dealing with global ocean currents and wind regimes set against an unprecedented change in climate. The evolution of Namibia’s coastline was always dynamic and incessant. In the future it has to deal with worldwide weather transformations, including sea level rise. Are we naïve enough to think our ingenuity and engineering can prevail against the might of water and wind?