SUDD, or SADD (an Arabic word meaning "to dam"), the name given to the vegetable obstruction which has at various dates closed the waters of the Upper Nile to navigation. It is composed of masses of papyrus and urn suf ( Vossia procera) and the earth adhering to the roots of those reeds. Mingled with the papyrus and um suf (Arabic for " mother -of-wool " ) are small swimming plants and the light brittle ambach. The papyrus and um suf grow abundantly along the Nile banks and the connected lagoons between 7 N. and 13 N. Loosened by storms these reeds drift until they lodge on some obstruction and form a dam across the channel, converted by fresh arrivals into blocks that are sometimes 25 m. in length, and extend 15 to 20 ft. below the surface. These masses of decayed vegetation and earth, resembling peat in consistency, are so much compressed by the force of the current that men can walk over them everywhere. In parts elephants could cross them without danger. The pressure of the water at length causes the formation of a side channel or the bursting of the sudd. (For sudd cutting see NILE.)
In the Bahr-el-Ghazal the sudd, being chiefly composed of small swimming plants, is of less formidable nature than that of the main stream.
Consult, O. Deuerling, Die Pflanzenbarren der afrikanischen Flusse (Munich, 1900), a valuable monograph; and the bibliography under NILE, especially Captain H. G. Lyons, The Physiography of the Nile and its Basin (Cairo, 1906).
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)