Erosion vulnerability and risk on Amazon estuarine beaches (Marajó Island, Brazil)

As the coastal zone is dynamic and subject to change from both natural and anthropogenic drivers, coastal vulnerability assessment is an essential tool for marine spatial planning, adaptation and mitigation of impacts. The eastern coastal environments of Marajó Island, the largest river-estuarine island in the world, are partially anthropized and vulnerable to erosion due to global (changes in sea level) and local (high-energy conditions on a tide-dominated coast) processes. It hosts diverse traditional communities which rely on the ecosystem services provided by the coast, as well as growing touristic activity and urbanization on the east coast. Here, vulnerability to erosion (Low: 0 to 5; Moderate: 6 to 10; High: 11 to 16) and risk level was assessed on two distinct estuarine beaches on the eastern coast of Marajó Island: Praia Grande and Barra Velha. A semi-quantitative analysis considered human occupation and natural parameters using remote sensing and in situ data collection techniques. Results indicated that Barra Velha beach has moderate vulnerability to erosion (value 10) in the northwestern sector and high vulnerability (value 11) in the southeastern sector, due to high erosion rates. These results were more evident by a shoreline analysis over a 16-year period (2003 to 2019: ~10 m/year). Praia Grande has moderate vulnerability to erosion (value 9) and is a more stable beach. Coastal risk to property and infrastructure was low at Praia Grande and at the southeastern sector of Barra Velha, where urbanization is incipient (15% to 17%; and absent, respectively). Moderate coastal risk was detected for the northwestern sector of Barra Velha where coastal development takes the form of controlled occupation (7% occupancy) due to its location in an environmental conservation area.