Impacto das ondas oceânicas nas praias da Cidade da Beira : uma contribuição para a erosão costeira

Abstract

The beaches of the city of Beira present very serious erosion problems caused by various processes that are acting and responsible for coastal dynamics, among which waves, ocean currents, precipitation and tides stand out. Ocean waves act as important energy transfer agents, generating different types of currents and different patterns of sand transport along the coastline, thus constituting one of the main causes of coastal erosion. In this work, the ocean waves and their impact on the beaches of the city of Beira were studied. For four months the waves were observed using two methods: direct method; based on the measurement of wave amplitude through Theodolite and Level and the indirect method that focused on measuring the local wind speed through a manual anemometer. The collected data were subjected to statistical analysis. The results of the work indicate that during the study period there was a significant variation in wave height, from 0.22m to 3.64m; of the wave period, from 1.22s to 7.99s; of the wave energy, from 9,911.67 jm'2 to 86.20 jm'2 and of the wave frequency, from 0.129Hz to 0.82Hz The main conclusions of the work point out that the dissipated energy of waves in the studied beaches is very high for sandy beaches such as those in the city of Beira; thus, the waves constitute one of the main forces causing coastal erosion.(TRADUÇÃO NOSSA)