Nahoon Beach – storm surge event

Nature is proving the hypothesis that increased annual storm surges will be experienced along the South African coastline in years to come. The museum has recorded events over the past two decades and it has been noted that apart from big storm surges every few years (the last being in 2015) mini storm surges are increasing annually.

The biggest annual event occurred last night and a photographic record from Nahoon Beach illustrates just how large the impact was on the coastal primary dune adjacent to the internationally known beach.

A spring tide and days of windy coastal conditions (probably from storm centers south of the SA coast) produced heavy seas with large high energy waves displacing onto the shoreline. Areas where these waves were focused by a bay or promontory (such as Nahoon Point) received a battering and, in particular, the primary dune at Nahoon Beach.

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In recent times there has been no embryonic dune formation with concomitant stabilisation by pioneering dune plants and the effects of these waves erodes directly at the base of the primary dune. The caused massive dune slumping with tons of sand being eroded out to be deposited elsewhere.

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A hint of what was to come was noted on Monday 21st August 2017 when museum scientist Kevin Cole visited Nahoon Beach to document the beginning of an erosive coastal event. It was noted that concrete plinths used to stabilise a sewer connector pipeline had been exposed (for the first time in decades) indicating a low base erosion event along the beach.

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The dune slumping which had occurred along the primary dune at Nahoon Beach was not higher than 3m (as illustrated by the two ladies standing in the photo below taken on Monday 21st August 2017).

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The storm surge last night and this morning has further eroded the dune system, almost to the vegetation line (illustrated below- top photo Monday 21st August 2017, bottom photo Thursday 24th August 2017).

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Additional concrete plinth bases have also been exposed which run a line to the Nahoon River mouth. At the mouth on a very low tide the remains of the sewer pipe can be seen (in part) under the water crossing the river.

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As expected some other interesting specimens which have been buried will be found. A case in point is that a young visitor from KwaZulu-Natal found an animal tooth (which still has to be identified) at the Nahoon corner car park this morning.

tooth nahoon corner

A site visit will be made to Nahoon tomorrow as more dune erosion is expected to take place at high tide later today and tomorrow morning.

 

About East London Museum Science

Conservation Biologist East London Museum South Africa
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