Durban - Durban could face fresh battering at the weekend as a cold front approaches the city, weather authorities have warned.
This follows the central Durban beachfront being lashed by heavy waves, which damaged the promenade at Dairy Beach and New Pier on Wednesday.
Further along the beach, authorities had to scramble to open the uMngeni River mouth at Blue Lagoon after erosion caused a sandbank to form.
Thandiwe Gumede, South African Weather Services forecaster, said on Thursday that while most of the province would enjoy fine conditions at the weekend, with only a remote chance of isolated rain and thundershowers, the effects of the cold front would be felt from Saturday night.
“The system is moving eastwards from the south-eastern parts of the country. It brings with it high winds and high tides for Saturday and Sunday.”
Swells could reach heights of 3.5m, she said, making it dangerous for those using the beach.
Gumede urged caution.
She said north-easterly winds not exceeding 15 knots were expected to persist throughout the weekend.
Saturday and on Sunday night, the winds were expected to drop to between five and 10 knots.
University of KwaZulu-Natal marine expert, Dr Deborah Robertson-Andersson, said that generally three factors influenced the formation of waves:
* The strength of the wind;
* The duration of the wind; and
* The distance and direction the wind had been blowing.
Robertson-Andersson stresed that the tides were influenced by the moon’s gravitational pull.
Talking about Wednesday’s destruction on Durban beachfront, she said this was exacerbated during the new moon (or spring tide) when the sun, Earth and moon, in that order, lined up, leading to a “higher high spring tide.”
The new moon period began on January 20 just after 3 pm, according to lunar charts.
The combination of the new moon (which is closest to the earth in its orbit); the sun, earth and moon lining up; and the presence of a high tide and storm all led to the high waves and consequent destruction, she said.
The new moon, when it is closest to Earth in its orbit, coupled with the advent of the spring tide, is referred to colloquially as a “king tide,” a term coined in the South Pacific to describe the occurrence.
eThekwini climate protection scientist Lisa Smith said the cold front from last week, which rained out the SA v West Indies cricket match, together with a tropical cyclone off the east coast, had also influenced the height of the waves.
She said: “The conditions are not expected to be as destructive as they were this week, but we do urge caution on the part of beach users.”
Agreeing with Robertson-Andersson, she said bigger gravitational pull as a result of the moon being closer to earth also influenced tide formation.
Meanwhile, those living in the area expressed relief that the river mouth, following the deposit of sand after heavy swells, had been re-opened by the eThekwini Municipality.
Three excavators were sent to the area and completed the task in less than two hours.
Colin Naidoo, who also goes running in the area, said the phenomenon usually took place once a year.
“We’re just happy the situation has improved. It has been blocked since Monday, which is not healthy for the river or the fish,” he said.
Daily News