Complex sentence: The Bahr al Jabal runs to the north-northwest and therefore in an angle to the gradient of the flood plain, which slopes down to the north, while north of Juba the river flows in an incised trough.
Split into simpler sentences: The Bahr al Jabal runs to the north-northwest and therefore in an angle to the gradient of the flood plain which is sloping down to the north. While north of Juba the river flows in an incised trough.