O Rio Oiapoque

Resumo

In 1956, the author headed the Brazilian team of the Franco-Brazilian Joint Comission on Frontier Demarcation between Brazil and French Guiana, put in charge of determining the thalweg of the River Oyapock, known in Brazil as the Rio Oiapoque.

            This mission led to the definition of sovereignty, Brazilian or Guianan, over hundreds of islands lining this border river from its mouth in Oyapock Bay up to the mouth of the River Ingarari on the right bank.

            In his report upon conclusion of the mission, the author analyses the physical and human characteristics of the river, which is divided into three sections: the upper, middle and lower Oyapock.

            The author assigns to the River Oyapock a watershed of 30,000 sq. km. (11,583 sq. miles) and a length of 352 km. (219 miles), of which 186 km. (116 miles) corresponds to the upper, 102 km. (63 miles) to the middle and 64 km (40 miles) to the lower course.

            Furthermore, the present study shows that the width of the River Qyapock varies from 20 to 5,000 meters (65 to 16,500 feet) and the general gradient of its course is very gentle (0.04%).

            The report itself is divided into chapters entitled "Physiographic Observations", "Islands and Archipelagoes", "General Conditions of Navigability" and "Riverside Populations and boatmen of the Oyapock". In this last chapter, the author praises the skill, courage and endurance of the men that thrust their canoes up past 'the shoals, waterfalls and rapids that are strung out along the middle or upper courses of the rivers that rise in the mountains along the northern frontier of Brazil.

            In the "Physiographic Observations", the author _goes into a comprehensive explanation of the tectonic origin of the Oyapock basin and the formation of the falls, rapids and transverse reefs, due to intrusions or dykes, respectively of alkaline and magmatic rocks, that rejuvenate many stretches of the river in its middle and upper course, making navigation only possible in canoes or dugouts.

            Moreover, the author examines the process of decomposition of the rocks in the bed of the Oyapock; the formation of potholes; "fluviometric" rocks; the conglomerate at Clevelândia do Norte; the Pleistocene formation of Oyapock Bay; and the rocks that are typical of the basin.

            After evaluating the mineral resources, the author discusses the relief, climate, flora, forest products and fauna of the Oyapock basin, stressing the Amazonian aspect of the various manifestations of vegetable and animal life.

            In the chapter on "Islands and Archipelagoes of the River Oyapock", the author proceeds to a detailed study of these features, describing the most important islands from the standpoint of their distribution in the higher upper, lower upper, middle and lower course of the river.

            The author also presents. a substantial contribution to a knowledge of the "General Conditions of Navigability of the River", reviewing each of the major sections into which the course of the Oyapock is divided; after alluding with admiration to the prowess of the boatmen in the more turbulent waters of the Amazon basin, the author concludes his report with practical observations on the "Riverside Populations", pointing out the unbroken nature of the forest along the banks of the Upper Oyapok, with only an occasional clearing for the communal hut of a tribe of Oyapi Indians; the difficulties in the· way of settlement in the region of the Middle Oyapock; and the restrictions imposed on demographic occupation by the relief in the valley of the Lower Oyapok.