Rivers generally are relatively short and flow from interior mountains towards the sea. The Kapuas (1,140 km long), Barito (900 km), and Mahakam (770 km) are among the longest, but their importance for transport is greatly reduced by sandbars across their mouths. Papua, most of which receives heavy rainfall, is drained by several large rivers, including the Baliem, the Mamberamo, and the Digul.