Active mechanisms controlling morphodynamics of a coastal barrier: Ilha Comprida, Brazil

Gyrlene Aparecida Mendes Da Silva,Mayara Santana Silva,Carlos Conforti Ferreira Guedes,Gilberto Pessanha Ribeiro

doi:10.1590/2675-2824069.20-338mss

Gyrlene Aparecida Mendes Da Silva, Mayara Santana Silva + Show 2 more

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https://doi.org/10.1590/2675-2824069.20-338mss

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Abstract

Abstract The Cananeia-Iguape lagoon-estuarine system, where the Ilha Comprida barrier (IC) is located, is one of the most dynamic coastal areas on the southeastern Brazilian coast. IC island is a 63 km-long barrier and it is limited by the Icapara inlet to the north, and the Cananeia inlet to the south. This system has been affected by intense changes in its morphology since the opening of the Valo Grande artificial channel in 1852 A.D., connecting the nearby Ribeira de Iguape river to the Mar Pequeno lagoon. In this context of anthropogenic disturbance on the coastal systems, the objective of this study is to understand the active mechanisms, both natural and anthropogenic, controlling the morphological changes of the northeastern portion of the IC, from monthly as well as centenary timescales. We analyzed successional addition and erosion of beach ridges using a multi-temporal dataset obtained by Optically Stimulated Luminescence, aerial photos (1962 and 2000), satellite images (1980-2016) and GNSS surveys (2015-2017). The results were compared to climatic (rainfall and waves) data. Northeastward migration rates of the IC ranged from 15.5 m/y, on the GNSS surveys, to 154 m/y, calculated based on OSL rates. Changes on rates on the northeastward inlet migration barrier are related to anthropogenic interference, mainly the Valo Grande opening and climate changes. Sediment accumulation occurred mainly during the summer on the baymouth spits. This depositional scheme is consistent with the highest values of Ribeira de Iguape river flow and the low synergy of waves coming from the South. By contrast, the retrogradation of the coastline occurs in the winter, when the wave power is stronger than in the summer. This seasonal configuration is controlled both by the bidirectional longshore drift and by the fluvial discharge.

Highlights

Coastal barriers can be defined as a range of emergent depositional landforms separated from the mainland by a lagoon, bay, or marsh (Davidson-Arnott, 2010)
Barrier dynamics are directly influenced by the availability of sediments, relative sea level, and processes related to the ocean-atmosphere interaction, such as anomalies related to El Niño/La Niña (Davidson-Arnott, 2010; Masselink et al, 2014)
The region is remotely influenced by anomalies, such as El Niño events, the anthropogenic influence on barrier evolution was the focus of the study

Summary

Introduction

Coastal barriers can be defined as a range of emergent depositional landforms separated from the mainland by a lagoon, bay, or marsh (Davidson-Arnott, 2010). Barriers are common landforms associated to wave-dominated coasts (Roy et al 1994). Submitted on: 11-May-2020 Approved on: 05-January-2021 Associate Editor: Eduardo Siegle lagoons and barriers are highly dynamic and vulnerable systems, modulated by the complex interaction between the hydrosphere, lithosphere, atmosphere, and biosphere (Masselink et al, 2014). Barrier dynamics are directly influenced by the availability of sediments, relative sea level, and processes related to the ocean-atmosphere interaction, such as anomalies related to El Niño/La Niña (Davidson-Arnott, 2010; Masselink et al, 2014).

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