Extreme Events

March 2007 coastal erosion event

A storm swell, coinciding with a saros spring high tide, struck the KwaZulu-Natal coast on 19–20 March 2007. At its peak, the storm produced swells of ~8.5 m, caused significant coastal erosion and unprecedented damage to coastal property, estimated at more than one billion rand. Property damage resulted from unwise urban planning during the coastal building boom of the last two decades. Local exacerbating factors included construction too close to the high water mark, adverse coastal profile, and coastal modification. The town of Ballito, north of Durban, presented all these aspects and was the worst-hit area. The storm also destabilized the coast, consequently chronic coastal erosion will continue until a new equilibrium is achieved (Smith et al, 2007).

September 1987 floods

Between 28 and 30 September, the central and southern part of Natal were ravaged by floods that were amongst the most devastating to have occurred in South Africa. The destruction of property was catastrophic, nearly 400 people were killed and about 50 000 were left homeless. Damage to agriculture, communications, infrastructure and property amounted to R400 million (De Villiers et al, 1994).

The bigger rivers (Mgeni and Mvoti) had flood duration periods of up to 24 hours and this caused dramatic erosion. In the Mgeni, the island near the mouth was totally removed and scour of generally about 2m took place. In the Mvoti, the river channel, normally 35m, widened to about 900m and deposited large quantities of sediment over this flood plain. Many bridges were washed away but the destruction of the Mdloti and Tugela river bridges caused the greatest disruption (Badenhorst et al. 1989).

January and February 1984 tropical cyclones Domoina and Imboa

Cyclone Domoina developed on 16 January 1984 along the northeastern coast of Mozambique and struck the African continent on 27 January. The storm moved south and for the following five days torrential rain fell over Mozambique, northern KwaZulu-Natal, Mpumalanga and Swaziland, reaching as far south as Durban. The cyclone caused widespread flooding; left thousands of people homeless and 242 deaths were recorded in southeastern Africa. In South Africa alone damage of more than R100 billion was caused to agriculture, communications and nature reserves (Kovács et al, 1985). The rainfall peaked during this storm at 950 mm and most river basins were flooded. The most rain ever recorded to fall in one day at one point in South Africa was at the St Lucia Lake (597mm) (Grobler, 2003).

On 18 February, less than three weeks after cyclone Domoina, cyclone Imboa reached the Zululand coast. Imboa caused high winds and dropped heavy rainfall, over 350 mm in some locations, causing flooding along the Mhlatuze and Mfolozi rivers. Fortunately the cyclone Imboa changed course on the same day and moved away from the East coast of Africa (Kovács et al, 1985).