Observations of Seiching and Tides Around the Islands of Mauritius and Rodrigues

Abstract

Short-period sea level changes around the islands of Mauritius and Rodrigues in the
central Indian Ocean have been analysed to determine the favoured seiche periods. The largest
amplitudes are found inside the harbours of Port Louis, Mauritius (7 and 20 minutes) and Port
Mathurin, Rodrigues (25 minutes), but these amplitudes are much smaller just outside the harbours,
and the characteristic periods are found only locally, confirming that local topography controls
the periods of the seiching. The extent and energising of these seiching phenomena calls for
further investigation. Associated seiche currents, potentially much stronger than tidal currents,
could influence harbour shipping movements. Analysis of the sea level data showed that there are
significant spatial variations in the amplitudes and phases of the tides around Mauritius Island,
but the around-island tidal variations are much smaller for Rodrigues Island.