1) Nile growth 
The Sudd (a s-Sudd or al-Sudd) is a vast swamp in South Sudan, formed by the White Nile`s Baḥr al-Jabal section. The Arabic word sudd is derived from sadd (سد), meaning ‘barrier’ or ‘obstruction.’ The term ‘the sudd’ has come to refer to any large solid floating vegetation island or mat. The area which the swamp covers is one of t....
mass of floating weed blocking the Nile River
• (n.) A tangled mass of floating vegetal matter obstructing navigation.
(from the article `Africa`) In addition to the major types of vegetation described above, a special vegetation called sudd (literally meaning `barrier`) occurs in the great ...
Sudd (sŭd) noun [ Arabic sadd barrier.] A tangled mass of floating vegetal matter obstructing navigation. [ Central Africa]
The sudd is a floating mass of vegetable matter that forms in the White Nile and obstructs navigation.
(in the White Nile) floating vegetable matter that often obstructs navigation.
Barrier or obstruction; with lower case the term designates clumps of aquatic vegetation that block the Nile channel; with upper case, the term is used loosely for the entire White Nile swamps.