Timber Flotation

a form of water transport of logs that uses the buoyancy of the wood. As an industrial process, timber transport is the final stage of logging operations; its purpose is to deliver prepared timber to points of consumption or transfer to another type of transportation. Flotation is an extremely cheap form of large-scale timber transport; in some areas it is the only kind available. In the USSR, 105–120 million cu m of timber is transported by water annually, using 80,000 km of waterways. Timber may be driven, rafted, or cribbed.

In driving, usually done during the spring high-water period, loose logs are floated downstream. Driving is used in the primary river network when other types of transport are impossible; it is prohibited on navigable rivers and on rivers with commercial fish. Guiding structures (boomsticks) are built to direct the movement of the timber along the flotation route, and timber-restraining structures (floating pens) are built for temporary or final detention at certain points along the river. Since some of the timber sinks as it loses buoyancy, causing logjams, driving logs is forbidden or limited on many rivers.

In rafting, the logs are bound into bundles or other forms of transportation units that form rafts (with a volume of 27,000 cu m or more), which are towed by diesel-powered ships. Rafting is used on permanently and temporarily navigable routes. The logs can be joined in the water (in basins of flotation-and-rafting sites) or on shore (at raft-joining sites) by mechanized joiners and joining-transport units. Timber-pass structures are used to pass the logs through dams and other hydraulic engineering structures in driving or rafting.

In cribbing, unjoined logs are transported by diesel-powered ships in special floating barriers (cribs) made of logs. Cribbing is done on a small scale on lake systems and also over short distances along lakelike sections.

In order to preserve the buoyancy of timber of deciduous species (such as birch and aspen) during flotation, the logs are dried and their butts are covered with waterproofing compounds. Logs can be transported on vessels whether or not the wood is buoyant and along waterways with complex in-route conditions (through sluiced navigable and temporarily navigable rivers, water reservoirs, lakes, canals, and seas). Timber freighters are used to transport logs. Timber flotation is organized and conducted by timber floating or logging enterprises with the participation of steamship companies.