Sunday, February 19, 2012

Storm Surges water Quality and Sediment

The Greater St Lucia Wetlands Problem
Facts and Myths about the system

From the mouth parking are facing South. This was taken standing infront of the toilets.
The water directly infront use to be 400m of beach area. 17h00 20 March 2007
St Lucia Estuary is one of the most important Estuarine systems in the World. It is a stop over to a diverse migrating animal population. It is home to many Hippo, Crocodiles and Marine species, but most off all it is the biggest Nursery North of the Aliwal Shelf. Since 2001 it has briefly functioning in 2007 but for most of the 11 years it was dormant and thousands of species had no where to breed or for the fry to grow in relative safety.

Picture of the Estuary Mouth in 1955
Pictures from way back when is circulating the Internet and creating the impression that when the two moths, iMfolozi and Estuary, are joined it will create this oasis of a fishing mecca and wild/marine life will flourish again. Sadly that is not true. For the sediment built up from the flooding iMfolozi has lead to many problems. The origin of this sediment finds its way high up in the catchment area where no soil erosion prevention is done.

Arial Photo showing the St Lucia and iMfolozi Mouths in relation
at the time  when above mentioned photo was taken in 1955

The area shown in the picture above had to be filled up with sediment from dredging operations that followed in the years to come. What prophets of the 1955 photo fails to disclose is that the 1955 photo was taken in a year of a great flood. And that the years between 1951 and 1955 the Estuary mouth was closed.
1955 and 1956 was marked by Great Floods and thus the abundance of water. 1956-1961 Mouth closed and was re-opened artificially on three occasions. 

This is agrivated by habitat destruction through Sugar Cane farming in the iMfolozi flood plains. No where for the sediment that floods down the iMfolozi River to settle except to was straight into the ocean. On the East Coast of Africa tidal movement and ocean action leads to sediment built up along the coast line and this is how the St Lucia Lake system was formed over the past 20 000 years.

Every single square meter of sediment catchment area has been drained and over run with Sugar Cane farming. Thus the proof that habitat destruction is the single most dangerous activity humans can endeavour on earth.  With out the functioning of these thousands of hectares of swamp and wetlands area the evolution of the St Lucia Estuary system has seized and no amount of Beach Driving or hard surface development can safe our Marine Echo-System. 

Some people claim that the major species lost because of St Lucia Estuary not functioning properly is the Tugela Shelf prawns species. Well it is the main source of food and is the basis of the food chain but as a youngster growing up in St Lucia we experienced hundreds of thousands of shad migrating into the system. Large 3 - 4 kilogram specimens. They never took any bait nor spoons. We sat on the boats and watch them swim past to the upper parts of the system. What for is a mystery to me.

For decades the Sport Fisherman has been blamed for the decline of the Fish populations and for decades more nature has been lost to farming and other hard surface developments. One wonders how competent are the Conservation Authorities if they have no specie list of migrating marine fish up and down the lake and concludes that beach driving is harmful to the environment?

by Petrus Viviers
081 342 7371

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