Diaz Beach: The rush to restore it

MOSSEL BAY NEWS - With structures and homes precariously positioned along the crumbling dunes of Diaz Beach, a local landscape architect has emphasised the rush to repair the damage on the primary dune and restore it before the situation worsens.

The Mossel Bay Municipality officially closed the beach to the public on Wednesday 20 May, citing the hazardous conditions on the beach as the reason for the immediate closure.

A week of unrelenting rain and strong winds battered Mossel Bay's coastline between 6 and 12 May, causing devastation along a stretch of almost 2km of beach on Diaz, including massive dune erosion, collapsing stairs and structures' foundations being eroded.

Speaking to Mossel Bay Advertiser about the damage, Aiden Beck, a landscape architect and environmental consultant in the Garden Route, raised his concerns about the damage and the continued erosion to the primary dune system. He said if steps are not urgently taken to mitigate the current damage, "catastrophic structural damage" could potentially occur.

Beck said the damage along this stretch of coastline is a clear demonstration of the immense power of the ocean and the vulnerability of developed coastal areas when natural primary dune systems are disturbed.

The exposed foundation of a deck along the dunes of Diaz Beach. Photo: Chelsea Pieterse

The primary dune along Diaz Beach acts as the coastline's first line of defence against storm surges and high seas, and its effectiveness depends heavily on deep-rooted indigenous vegetation, such as coastal thicket species, which assist in dune-binding.

Watch Beck explain the situation in detail: Diaz Beach dune damage explained: Enviromental Expert warns of further coastal collapse in Mossel Bay

"Primary dunes move, and the natural vegetation that grows on them actually helps stop sand movement to a degree. Without these root systems holding the loose sand together, the dune becomes highly susceptible to erosion and collapsing," said Beck.

The adjacent areas where the natural vegetation remained intact experienced significantly less damage, which strongly suggests that healthy primary dune ecosystems provide better long-term protection than exposed or hardened areas alone.

Beck said a primary dune is a natural moving structure, and after this storm, nature will now want to try to recreate a talus slope of 45 degrees on these exposed sand cliff faces.

The beach was officially closed to the public on 20 May. Photo: Chelsea Pieterse

He said, should we not assist in recreating this slope with associated breakwater structures, the erosion of the rest of the dune will continue rapidly, and we could potentially see these houses collapse and wash into the sea.

Beck suggested that the new talus slope should be moved back to its original position and an engineered reinforced breakwater structure created. "This rehabilitation of the dune is an emergency, so it will need a structural breakwater feature, like concrete tetrablocks used at the harbour jetty," he said.

Beck also suggested that the eventual rehabilitation plan must include wind hedgerows (protection for pioneer plants) and the planting of pioneer coastal vegetation before secondary species like milkwoods.

"Trying to fix a dune as a static structure is rarely successful when it comes to water. The goal should be to work with natural coastal processes rather than against them," he said.

The recent rains and wind caused devastating damage along Diaz Beach. Photo: Chelsea Pieterse

A tenant of La Palma, an estate along the Diaz dunes, said while she acknowledges the situation is a problem, she feels the photos being shared on social media have made it look like the homes are right at the edge of the dune, which she said is not the case at all.

The tenant, who requested anonymity, said she had faith that the matter would be sorted out soon before the situation worsened, and warned people against fear-mongering.

She said the Mossel Bay community should take a step back and let the relevant authorities attend to the matter.

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