During the several years of travel in the western Sahel of Africa, Mungo Park kept detailed records of the geography as well as of the people and flora and fauna of the areas through which he traveled.
In this brief entry, he describes the construction of a floating bridge that must yearly be re-built following the rainy season, and which he sketches in the following print. In this picture, he also draws in himself (lower right corner) in the act of doing the sketch of the bridge.
This may be the earliest description of a toll bridge – at least, in Africa.
Two tall trees [bamboo stalks], when tied together by the tops, are sufficiently long to reach from one side to the other, the roots resting upon the rocks, and the tops floating in the water. When a few trees have been placed in this direction, they are covered with dry bamboos, so as to form a floating bridge, with a sloping gangway at each end, where the trees rest upon the rocks.
This bridge is carried away every year by the swelling of the river in the rainy season, and is constantly rebuilt by the inhabitants of Manna, who, on that account, expect a small tribute from every passenger.
Source: Mungo Park – Travels in the Interior Districts of Africa in the years 1795, 1796, 1797 – Volume 2. London 1816.
The bamboo that Park discusses would have been Oxytenanthera abyssinica, a drought tolerant, lowland bamboo that is found across the southern Sahel from Senegal in the west to Eritrea in the east, and down into Kenya, Tanzania, as bell as in the east of Burundi.
The condition of O. abyssinica stands in Sudan is discussed in the following blog, which summarizes work conducted with colleagues from the Kenya Forestry Research Institute and from the Sudan Forestry Corporation. This work was supported by the National Academy of Sciences – BOSTID, and led to further regional activities with participants coming from several east African countries on similar subjects but with a larger grant base.