It soon becomes the boundary for a while between the departments of the HautesAlpes and of the Basses-Alpes, and receives successively the considerable Ubaye river, flowing from near the foot of Monte Viso past Barcelonnette (left), and then the small stream of the Luye (right), on which, a few miles above, is Gap. It enters the Basses-Alpes shortly before reaching Sisteron, where it is joined (right) by the wild torrent of the Busch, flowing from the desolate region of the Devoluy, and receives the Bleone (left) (on which Digne, the capital of the department, is situated) and the Asse (left), before quitting the department of the Basses-Alpes just as it is reinforced (left) by the Verdon, flowing from the lower summits of the Maritime Alps past Castellane.
After passing through some narrow gorges near Sisteron the bed of the river becomes wide, and spreads desolation around, the frequent overflows being kept within bounds by numerous dykes and enbankments.
The department is divided into five arrondissements (Digne, Barcelonnette, Castellane, Forcalquier, and Sisteron), 30 cantons and 250 communes.
It is poorly supplied with railways (total length 1091 m.), the main line from Grenoble to Avignon running through it from Sisteron to Manosque, and sending off two short branch lines to Digne (14 m.) and to Forcalquier (9 m.).