Heavy Rains Focus More Attention on Floodlines
The question of floodlines is in the spotlight after the serious flooding in parts of South Africa earlier this year was declared a national disaster by the National Disaster Management Centre ( NDMC )
Xanthe Adams Principal Engineer at SRK Consulting
The heavy rains – mainly in the Eastern Cape and KwaZulu-Natal but also in the Free State and North West provinces – destroyed property and infrastructure , and led to hundreds of lives being lost . While the declaration allowed more direct intervention in recovery efforts by national government and organs of state , the NDMC noted that “ these threatening conditions call for an all-of-society and government approach to promote risk reduction ”.
Among the standard measures in place to protect communities , businesses and infrastructure from flooding is the regulated floodline alongside rivers in urban areas – below which any building or development is not permitted .
What ’ s a Floodline ? “ A floodline is an imaginary line on the ground that denotes the edge of the water during a flood ,” said Xanthe Adams , principal engineer at SRK Consulting . “ The floodplain is the area alongside a river that will be expected to be under water during a flood , with the upper edge of this floodplain being designated as the floodline .”
The National Water Act requires these floodlines to be shown on plans for housing and other developments , which show the highest level that a flood could reach every 100 years – the most common stipulated timeframe . All buildings then need to be above this floodline , to avoid the danger of flooding .
Who Needs One ? Adams highlighted that municipalities are responsible for enforcing compliance with floodlines as part of reducing flood risk to communities and infrastructure . Their planning must mitigate and manage the effect of urbanisation , which generally means more rainfall run-off and greater risk of flooding .
“ Urbanisation is certainly a significant factor increasing the size of floodplains and the velocity of floods ,” she said . “ We see its effect frequently as we determine floodlines , especially in older urban areas , where we often find that some of the infrastructure is actually already within the floodline .”
Among the efforts by local government to address rising run-off levels is to ensure that developments design water attenuation facilities into new projects . These dams , ponds and
14 Heavy Rains