Page 19 - LandscapeSAIssue113

FEATURE

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).

he heavy February rains – mainly
in the Eastern Cape and KwaZulu-
TNatal but also in the Free State
and North West provinces – destroyed
property and infrastructure, and
led to over 80 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 Xanthe Adams, principal Urbanisation is a significant factor in increasing Municipalities must upgrade
and infrastructure from flooding is the engineer at SRK Consulting the size of floodplains and the velocity of floods culverts and drainage infrastructure
regulated floodline alongside rivers in (Image: City of Tshwane) whenever necessary
urban areas – below which any building (Image: SRK Consulting)
or development is not permitted.
Among the efforts by local government to to furnish a floodline as part of the permitting
What is a floodline? address rising run-off levels is to ensure that process,” she said. “In fact, planning any
“A floodline is an imaginary line on the ground developments design water attenuation activity in or near a river – such as building
that denotes the edge of the water during a facilities into new projects. These dams, a bridge or installing a pump – may require
flood,” said Xanthe Adams, principal engineer ponds and wetlands will act to slow down a water use licence that includes a floodline.”
at SRK Consulting. “The floodplain is the area the flow of water and allow more of it to
alongside a river that will be expected to be percolate into the ground. She noted that while the recent flooding
under water during a flood, with the upper seemed out of the ordinary, this would still
edge of this floodplain being designated as Emergency plans have to be confirmed by detailed studies.
the floodline.” At the most basic level, however, It was also difficult to know the extent to
municipalities must ensure that any new which climate change contributed to the
The National Water Act requires these developments are outside the floodline and magnitude of these rainfall events, as there
floodlines to be shown on plans for housing must also upgrade culverts and drainage were many different global climate models –
and other developments, which show the infrastructure whenever necessary, as part of each with a range of predictions.
highest level that a flood could reach every their emergency planning.
100 years – the most common stipulated Protection measures
time frame. All buildings then need to be “Other situations where a floodline is “More important will be the country’s ability
above this floodline, to avoid the danger of required include mining operations which to develop flood protection measures
flooding. might encroach on rivers or streams,” said alongside floodline studies, as it is likely to be
Adams. “Holders of water use licences might impractical to move houses and infrastructure
Adams highlighted that municipalities are also need to determine floodlines, as their which today lie within floodplains,” she said.
responsible for enforcing compliance with work may potentially disturb the area within “Flood management on the catchment scale
floodlines as part of reducing flood risk the floodline.” is another relevant field of enquiry which can
to communities and infrastructure. Their significantly reduce flooding so I wouldn’t be
planning must mitigate and manage the It is likely that a floodline will be required by surprised to see more regulations focusing on
effect of urbanisation, which generally law if a developer or other entity is planning catchment scale management of floods.”
means more rainfall run-off and greater risk to build on a property that has a river or
of flooding. stream running across it, she said. It might Floodline studies remain a highly specialised
also be a legal requirement if a river is within task, and they need to be properly signed
“Urbanisation is certainly a significant factor a few hundred meters of the property being off before a local authority will accept the
increasing the size of floodplains and the developed. floodline determination. This sign-off must
velocity of floods,” she said. “We see its effect be done by a professional engineer registered
frequently as we determine floodlines, EIA’s and water use licences with the Engineering Council of South Africa.
especially in older urban areas, where we “Companies that require a full environmental
often find that some of the infrastructure is impact assessment (EIA) or even a basic Information and photos supplied by SBPR on
actually already within the floodline.” environmental assessment may be required behalf of SRK Consulting. n

Landscape SA • Issue 113 2022 17