Grassroots Vol 22 No 2 | Page 37

NEWS

Figure 2 . Roland Schulze , Professor Emeritus of Hydrology at the University of KwaZulu-Natal ’ s Centre for Water Resources Research . ( Photo : Supplied )
municipality civil engineer Geoff Tooley , he noted that these shallower-rooted plants were washed away more easily than slower-growing and deeper-rooted indigenous vegetation .
As these plants were uprooted , the exposed soils were washed away rapidly , with alien plant debris and growing volumes of litter adding to the blockage of stormwater culverts .
How did the 2022 floods compare with previous storms in KZN ?
Between 9 and 12 April , Durban and other parts of the KZN coastline were hit by three days of very heavy rain due to a cut-off low-pressure system .
The heaviest rain ( more than 300 mm ) fell on 12 April onto already saturated soils due to the preceding two days of rainfall between . By the fourth day , Virginia Beach in Durban had measured an accumulation of 411 mm while Pennington measured 464 mm .
Just six weeks later , there was a “ double-blow ”, when the coast was struck by further heavy falls of between 160 mm
Figure 4 . Vehicles were stranded next to the Umfolozi River bridge which was severely damaged . ( Photo : Department of Water Affairs )
and 240 mm over consecutive days ( 21 to 22 May ).
Dramatic as they are , these falls have been exceeded several times since rainfall collection records began from the 1850s onwards .
To compare the severity of the recent floods , Schulze extracted data from a variety of sources , including a South African Weather Bureau document titled “ A History of Exceptional Weather Occurrences in South Africa : 1500-1990 ” ( which Schulze translated from Afrikaans to English ).
Schulze also notes that similar heavy rains fell over the KZN coast in May 2017 , November 2019 and November
2020 , but does not elaborate on the rainfall volumes recorded during these events .
Why are comparisons important ?
Schulze says that — devastating as it was — April 2022 had to be seen in the context of previous similar floods and storms .
The scale of devastation had prompted the senior government and statelinked officials ( including President Cyril Ramaphosa ) to suggest “ unequivocally ” that climate change was behind these floods .
“ A key question is whether such statements and sentiments related to climate change are backed up with certainty by science , especially when scientific experts at the South African Weather Service , commenting on this particular April 2022 cut-off low-pressure system , could not with any ‘ quantifiable precision ’, attribute it to climate change .”
Figure 3 . Rainfall data for the 2022 Durban floods showing the total volumes after four days – ( Source : Roland Schulze )
Further questions that arose were “ whether rainfalls and associated floods of the magnitude of the ones in April 2022 are necessarily related directly to climate change , or whether statements such as those above are signs of conveniently jumping on to the climate change bandwagon by blaming climate change for possibly unrelated naturally
Grassroots Vol 22 No 2 July 2022 36