LAUSR

Motivated by need to study supercritical overbank flows on floodplain, we experimentally investigate if initially supercritical flow in a rectangular flume would maintain its state throughout. Varying upstream gate opening, flow rate and angle of the slope, a total of 37 experimental cases were carried out. The experimental results are compared to two existing theories: an inviscid theory based on nonlinear shallow water equations and jump conditions and a hydraulic theory that takes friction into account. The experimental data are consistent with the two theories. Flows on downward slope were stable, while those on upward slope had unstable hydraulic jump and transformed into subcritical flow. The reported results should serve well in designing a laboratory flume with the supercritical inflow and in conducting hydraulic model experiments on overbank flows.