A hydrodynamic device for removing sediment and other materials from storm water runoff is provided. An exemplary embodiment of this device includes: a first substantially cylindrical chamber a second substantially cylindrical chamber concentrically disposed within the upper portion of the first chamber, a first baffle concentrically disposed within the second chamber, and a second baffle disposed within the lower portion of the first chamber. A water inlet is attached to or formed integrally with the second chamber; a water outlet is attached to or formed integrally with the first chamber; and an optional bypass outlet is attached to or formed integrally with the first chamber.