Data obtained in the field is the basis for the first nautical charts for the region
By Second Lieutenant (RM2-T) Augusto Rodrigues – Belém-PA
The Brazilian Navy conducted, between November 2022 and April this year, hydrographic surveys in the region of the Breves Straits and the Melgaço, Portel and Bocas Basins, in the Marajó Archipelago, regions of intense water traffic in Pará. The depths of access channels, maneuvering areas, anchoring and mooring berths were recorded over a perimeter of about 500 km2. The data obtained in the field form the basis for nautical charts that have never before been produced for the area, which has only a navigation sketch.
The Marajó nautical charts, 4341 and 4342, are provided for in the III Brazilian Nautical Cartographic Plan, published by the Navy’s Directorate of Hydrography and Navigation. “The continuous hydrographic survey of the rivers requires planning and considerable logistical effort, with a view to increasing the safety of navigation. The Navy has been investing human, material, and financial resources in this activity, which will result in the delivery of new nautical charts to society, which are fundamental for a region that uses the rivers as if they were roads,” says Vice-Admiral Antonio Capistrano de Freitas Filho, Commander of the 4th Naval District.
The surveys were carried out by means subordinated to the Center of Hydrography and Navigation of the North: the Fluvial Hydro-oceanographic Notice “Rio Tocantins” and the Beacon Notice “Denébola”, both equipped with a single-beam echo sounder, in addition to the Inland Waters Hydrographic Launch “Rígel”, which provided logistical support. The hydrographic surveys in Marajó were carried out in partnership between the Brazilian Navy and the National Department of Infrastructure and Transportation.
Marajó Archipelago
With around three thousand islands and islets, Marajó is the largest river-sea archipelago in the world. Located at the confluence of the Amazon and Tocantins-Araguaia rivers, Marajó harbors the Amazon estuary, one of the richest regions in the country in terms of water and biological resources.
The archipelago encompasses 16 municipalities: Afuá, Anajás, Bagre, Breves, Cachoeira do Arari, Chaves, Curralinho, Gurupá, Melgaço, Muaná, Ponta de Pedras, Portel, Salvaterra, Santa Cruz do Arari, São Sebastião da Boa Vista, and Soure. The total area of the archipelago, 104,139.93 km², is larger than the sum of the territories of the states of Espírito Santo and Paraíba. The population is estimated at 557,231 inhabitants.
Larger commercial vessels, as well as smaller boats, will benefit. “The production of nautical charts for the Estreitos region is a relevant increase in navigation safety, especially because of the intense vessel traffic, which contributes greatly to the orderly flow of this very significant route for the Arco Norte. Furthermore, by increasing safety, the riverside population also benefits directly from this initiative, since navigation is the main means of transporting cargo and people in the areas covered by the new charts that will come into force”, says Wellington Guanabara, Navigation Manager of Hidrovias Brasil, a logistics solutions company that operates in waterway transport and also navigates in the region that is being mapped.
What is a hydrographic survey?
A hydrographic survey is a set of activities carried out to obtain bathymetric, geological, tide gauge, fluviometric, top geodesic, oceanographic, and geophysical data in maritime, fluvial, and lake areas, and in natural or artificial channels.
Modern echo sound meters use the physical principles of sound propagation in water to calculate depth. An echo sounder’s signals are emitted by a source towed on the surface or attached to the hull of the vessel. They are in high frequency acoustic waves, which propagate through the water, reach the bottom, and are reflected back to the surface. By knowing the speed of sound propagation in water and the transit time of the signals, it is possible to calculate the depth.
What are nautical charts?
Nautical charts are representations on a flat area of a stretch of water and coastline, which enable the sailor to orient himself on his position on the Earth’s surface and on dangers (banks, submerged rocks, sunken hulls or any other obstacle), depths and aids that enable safer navigation.
The records on depth are fundamental for the precise determination of the clearance under the keel of vessels, i.e., the distance between the deepest point of the ship’s hull and the bottom of the river. In Brazil, all official nautical charts are produced and updated by the Directorate of Hydrography and Navigation.
Learn about the naval resources that participated in the surveys
