Mkhuseli Jack: Maintenance an essential
LACK of maintenance can have expensive consequences. I was brought up on the farms around Oyster Bay so I know that area.
These days I am shocked by the destruction of public areas and private houses by sand and water. Dunes are blowing onto houses. Houses are falling into the Slang River. Luckily for me I have a friend who is an earth scientist dealing with these sand dunes. I hauled Werner Illenberger off to Oyster Bay so he could explain what is going on. This is how I understand the situation: In the beginning, God made the world. He made the wind, he made the sand, he made the rivers, he made the sea. Everything was good, wind blew sand, waves washed sand along the beaches, rivers flowed from the land to the sea. Then he made people. Perhaps a bad move. People saw the beautiful sandy beach, dunes, sea, waves, rivers and coast at Oyster Bay, and thought they might like to have a holiday house next to the river overlooking the sea. Or perhaps along the beach behind artificially stabilised dunes. The dominant south-westerly wind blows sand off the Oyster Bay beach. Dunes used to move eastward across a relatively flat area (where Oyster Bay village is now located). These dunes continued moving eastward into the main body of the Oyster Bay dunefield and eventually arrived at St Francis Bay, where they were blown into the sea. The Department of Forestry embarked on a programme of stabilisation in the area around Oyster Bay from 1917. (It was subsequently realised that this programme was misguided, because it interfered with the natural wind-blown movement of sand, eventually resulting in big problems.) This resulted in the accumulation of sand to form an artificial dune ridge parallel to the shore. The pictures, above, illustrates the situation in 1942 (the first available aerial photograph) and in 1971, by which time the western half of Oyster Bay was laid out. This dune ridge continued to grow over the years, till eventually it was too big to keep on being stabilised. In 1980 the ridge was removed by bulldozing it into the sea along the Oyster Bay beach.
This may seem a drastic action, but nature actually has no problem coping with such things, as nature is ever-changing and big pulses of sand often arrive on beaches when a river brings down a lot of sand in a big flood. Illenberger recommends that the dunes are reduced and then artificially stabilised with drift fences and dune vegetation. Walkways should be created, and the ablutions block and parking area rebuilt. In addition to this, dunes need to be artificially stabilised and reduced when they build up too much. They need to be reduced every 10 years or so. Dunes moving eastward tend to block the Slang River. Normally during the wetter winters the Slang River starts to flow and erodes away the encroaching dune sand, washing it out to sea. However, during drought periods the river flow may not be strong enough to breach the dunes blocking its path. Farm dams in the catchment of the Slang River also contribute to reducing its flow. In addition, during the last 10 years or so the dunes on the beach west of the Slang River have started moving in bulk as they are no longer being artificially stabilised. All these factors combined to cause a huge volume of water to dam up behind the dunes in 2011. The same thing has happened many times in the past, but the 2011 event was particularly big and damaging. There are photos on the Oyster Bay Residents Association web page (http://www.oesterbaai.info/duinedam.html). A simple management strategy is needed: the dune should be artificially breached every time there is a build-up of water above a pre-determined level. Lack of maintenance is the problem. It can be seen in the Sardinia Bay sand dunes. Those dunes were artificially stabilised 100 years ago but have not been stabilised for the past 15 years. The sand has swamped the road and car park. The Kouga Municipality is preparing a dune management plan to address encroachment of windblown dunes onto the Slang River estuary as well as private properties and Brander Street. Everything needs maintenance, even sand dunes, it seems. If they are not monitored, and reduced and stabilised, public and private property is destroyed and access to beaches restricted. It takes a lot more money to rebuild and move huge mounds of sand than if the dunes had been maintained. It’s the story of our lives in South Africa. But well done to the Kouga Municipality, through the Ratepayers Association, for commissioning the study and intending to act on it. For more information, see http:// sites.google.com/a/illenberger.biz/oyster-baydune-management-plan-eia-process , in particular the dune management plan and specialist reports.
