Floods
13 Jan 2010

FLOODS

Owen McGee

Possibly the worst storm ever recorded in Pietermaritzburg occurred on Tuesday 14 January 1947. A total of 230 mm of rain fell in the 19 hours between 14h00 on the Tuesday and 21h00 on the Wednesday. At the Purification Works 117 mm fell within one 45-minute period.

Other violent storms were experienced in October 1917, 'King Sol only making his appearance after a week of heavy rain', and in March 1939, but the 1947 storm probably holds the record. Certainly the Natal Witness gave its readers a very full twopence worth of detail. The advertisements were appropriate, one appealing for entries to a bathing beauty contest: 'Support Maritzburg's Efforts to Drown Mrs Sleepy Hollow Grundy'.

In September 1987 not a storm but prolonged and heavy rains, producing nearly 400 mm in 36 hours, brought devastating floods to the Msunduze floodplain. The floods were widespread over southern Natal and were labelled the worst in living memory.

At the height of the flood the Camp's Drift Road, West Street, Lindley and the N3 bridges across the Msunduze had to be closed to traffic. The City was therefore virtually cut in two with only the Commercial Road bridge open to traffic. The Edendale Road bridge was partially washed away and reopened three months later.

Houses in low-lying areas of Edendale were washed away, and much of Sobantu Village was inundated by waist-high water. Many of the City's sports facilities which are located on the floodplain were severely damaged. The Sax Young cycle track became a 'duck pond', and the Kershaw Park tennis courts were ruined. The Maritzburg Rugby Sub-Union, which only a week earlier had requested top soil for their four fields, saw their entire complex flooded, and when the water subsided their fields were covered by as much as 20 cm of silt. At the height of the flood the crossbars on the main stadium goalposts were under water, which meant that the water was 3 m deep. The playing fields of Merchiston School were flooded and Longmarket Girls School had to be evacuated.

Floods of this severity are fortunately rare and are invariably associated with low pressure regions in the general circulation pattern. The low which caused the September flood was 'cut-off' from the normal west to east drift of our weather systems. It stalled over the OFS and Natal as a deep and intense system drawing in moisture-laden air from the oceans. What aided this air movement was a high pressure system over the Indian Ocean from which air was being expelled. The resulting 'push-pull' effect produced a strong onshore air flow - with low-level air converging and rising. Heavy cloud, rain and snow was the result.

Flood-producing rains over Natal are rare, requiring as they do the simultaneous occurrence and suitable positioning of a deep and intense inland low and a strong high to the south. Thus not every thunderstorm or heavy rainfall, however severe, should be taken as a potential flood threat.

CAPTION: A flood-devastated home in Edendale, September 1987.

SOURCE: Pietermaritzburg 1838–1988: a new portrait of an African city, edited by John Laband and Robert Haswell (Pietermaritzburg: University of Natal Press and Shuter & Shooter, 1988), p 11.