River Derwent (Tasmania)

The Derwent is a river in Tasmania, Australia.

While obviously named after one of the English River Derwents, the name - which apparently means "valley thick with oaks" - is especially appropriate. When first explored by Europeans, the lower parts of the picturesque valley were clad in thick she-oak forests, remnants of which remain in a few places.

180 km long with flows ranging from 50 to 300 tonnes per second, its large estuary forms the Port of the City of Hobart - often claimed to be the deepest sheltered harbour in the Southern Hemisphere; some past guests of the port include the USS Enterprise and USS Missouri.

Until the construction of several hydroelectric dams between 1934 and 1968, it was prone to frequent flooding. The State of Tasmania is now almost entirely powered by hydroelectricity. A substantial part of the dam construction work was performed by Polish and British migrants after World War II.

On the 5th of January 1975, the Tasman Bridge over the Derwent, just north of the port, was struck by the bulk ore carrier Lake Illawarra, causing a massive section of concrete to fall from the bridge and sink the ship. Seven crewman and five motorists were killed. The depth of the river at this point is so great that the wreck of Lake Illawarra lies on the bottom, with concrete slab on top of it, without presenting a navigation hazard.