Durban harbour entrance silting up

Due to a lack of maintenance dredging of the sand trap outside the Durban port South Pier, sand has again built up across the entrance.

According to a source, the lack of dredging was a result of the main dredger in Durban harbour, ISANDLWANA requiring repairs. A spare part needed to keep the vessel in service had to be sourced in Europe, which took time, leaving the dredger unable to perform its duties.

As a result the port has been forced to place an additional red buoy in the channel marking a width of some 40 metres of the channel as un-navigable.

The dredging of a sand trap, essentially a deep hole on the south side of the South Pier, has traditionally been the means of preventing sand from spilling over across the entrance channel.

What it does is to catch most of the sand being moved northwards by the littoral drift (a counter current which runs northwards close in to the coast, carrying sea sand along with it). The sand falls into this trap which is usually constantly being dredged, thus preventing any spill over across the channel entrance.

Much of this ‘trapped’ sand is then transferred via the sand bypass system onto the city’s beaches on the north side of the entrance channel.

The port of Durban has had a number of groundings recently – two in the entrance channel and several in the port, which were a result of a lack of maintenance dredging. In addition, ISANDLWANA lacks a suction spout on her bows and has to rely on her trailing suction pipe, which prevents the dredger from setting her anchor with the bows of the dredger facing close to the walls of the breakwater to clear debris and excess sand.

The older dredgers now taken out of service were able to do this.

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