At the end of January the cyclone Domoina came inland over Moçambique and Swaziland and thence over the Eastern Transvaal and Natal regions of South Africa. This caused very high rainfall over a few days and the run-off down the Pongola River was of such proportions that at the peak of the hydrograph it had far exceeded the regional maximum flood (R M F) calculated value. The flood was absorbed into the Pongolapoort Dam which has a full supply storage of 2 500 m3 and which was 13 per cent full at the start of the flood.
The threat of cyclones along our east coast is always with us and should obviously not be ignored in the design of important structures. Extrapolation of the probability distribution (Gumbel) based on the historical record of peak discharges in the Mfolozi would indicate that the return period of the 1984 flood was of the order of 500 years.