The entire lower Brahmaputra consists of a vast network of channels, which are dry in the cold season but are inundated during the monsoon. The lower Brahmaputra River basin is susceptible to catastrophic flooding with major social, economic, and public health impacts. There is relatively little rainfall and snowpack information for the watershed, and the system is poorly understood hydrologically. Interannual rainfall variability is low and is a weak predictor of monsoon discharge volumes. The lower Brahmaputra is navigable for more than 800 miles (1,300 km) and is a major means of transport.