Understanding Ocean Surges and Possible Signals over the Nigerian Coast: A Case Study of the Victoria Island Bar – Beach Lagos

Abstract

Eighteen different occurrence of ocean surge events over the beach of the Victoria Island in Nigeria were recorded between 1990 to 2002 and each with its devastating consequences resulting from the massive flooding and erosion. Statistical analysis and parametric wind-wave model were used to investigate the ocean atmospheric interactions in terms of their characteristics, especially before during and after every surge event from 1990 to 2002. It revealed that all ocean surges apart from the surge of March 2002 were experienced in summer months of April to October, but more frequent in August. Coastal atmospheric pressure was generally transiently low and observed to coincide with high tides. However, pressure varies from one event to another, between 1008 – 1013millibar. The lowest pressure was observed during the 30th May 1998 event and the highest was observed during the 14th September 2001 event. Also, pressure during any event was generally lower by about 0.8mb than the pressure two days before the event. Further investigations revealed that the ocean surges are influenced by moderate winds (between 15 - 18kts in strength on the average) over the fetch (Lat. 10oS – 20 oS and Long. 0 oE – 10 oE). These winds were observed to be generally strongest three to two days before the event. They can generate wave height of about 1.8m and with favourable cross equatorial flow, the swell may reach the coast in about 2 – 4 days and when they coincide with high tide they can inundate the beach.