Contract awarded to remove dredge spoil from uMfolozi river

5th February 2016

By: David Oliveira

Creamer Media Staff Writer

  

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The iSimangaliso Wetland Park Authority signed a R10-million contract last month with local tailings storage facility specialist Cyclone Engineering Projects to remove about 100 000 m3 of dredge spoil obstructing the natural course of the uMfolozi river, in KwaZulu-Natal.

A further R20-million has been allocated to continue the work and additional funding will be sourced to complete the restoration.

Dredge spoil was artificially deposited in the natural course of the river to separate it from the St Lucia estuary to protect the estuary from silt inflows. This significantly reduced freshwater flowing from the uMfolozi river, the largest of five rivers entering the estuary. It also interfered with the natural regulation of opening and closing the estuary mouth.

The impacts of this approach are still evident. With current rainfall levels the lowest in 65 years, the lake system has compartmentalised. Presently, only about 30% of the lake’s surface area has water and species recovery is slow.

“Freshwater from the uMfolozi river is critical – even more so in times of drought. The restoration of the uMfolozi’s natural course is important for the hydrological functioning of Lake St Lucia [and], without this, [the lake] . . . will not recover,” says iSimangaliso CEO Andrew Zaloumis.

He asserts that signing the contract with Cyclone Engineering is as significant to the conservation of the lake as former President Nelson Mandela and his Cabinet’s preventing dune mining in 1996, which would have severely impacted on the lake.

“It is the culmination of five years’ work by iSimangaliso and Ezemvelo staff, and marks the beginning of nature’s renewal and a return to wholeness for the Lake St Lucia system. . . I would like to thank the Global Environmental Facility, the World Bank and the Department of Environmental Affairs for their support.”

Historically, red flags had been raised about the possible impacts of silt on the estuarine system – a consequence of the canalisation of the uMfolozi river by sugar cane farmers and the now abnormally functioning flood plain. To mitigate the risks to the system, measures were taken to partially separate the uMfolozi river from the St Lucia estuary in 1952 by depositing dredge spoil between them and artificially breaching the uMfolozi river into the sea at the south, near Maphelane.

However, this management approach was brought into question during the drought of 2002 to 2012, as the impact of starving Lake St Lucia of the uMfolozi’s freshwater led to high salt levels in the lake’s system, resulting in the extinction of a number of indigenous species. Fisheries suffered heavy losses, natural resources available for subsistence use decreased significantly and tourism was negatively affected.

iSimangaliso contracted a multidisciplinary research team in 2010 to concretise solutions for the hydrological problems facing the Lake St Lucia system.
The new research debunks the myth that siltation and sediments are problematic for the system. Silt is an important component of the estuary benthos – the life-giving organisms that inhabit the bed of the estuary – and provides nutrition for fish, besides other species. It also concludes that the uMfolozi river is a significant contributor of freshwater to St Lucia and, importantly, the powerhouse that drives the mouth dynamics of the St Lucia estuary.

The study strongly recommends that nature be left to its own devices and the uMfolozi be allowed to pursue its natural path northwards, subsequently allowing the river to contribute about 60% of the lake’s freshwater, as it did before.

Subsequently, iSimangaliso launched its publicly consulted management strategy in 2011/12 for the St Lucia estuary that entailed minimum interference, the re-establishment of the natural river course and a one-mouth policy.

The first intervention, frequently referred to as the spillway, was completed in 2012. It entailed the removal of small quantities of dredge spoil to facilitate the flow of the uMfolozi river into the estuary along its natural course.

Edited by Martin Zhuwakinyu
Creamer Media Senior Deputy Editor

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