The idea behind the general theory of ‘hydraulic’-type problems as described by Gill (1977) is applied to an inertial boundary current. The flow considered is a single-layer inviscid fluid flowing under gravity along a rotating, irregular wall. It is shown that owing to variations in the curvature of the wall the boundary current may be controlled in the hydraulic sense at sections along the wall classified as ‘bays’. It is also shown that because of such variations in geometry the flow can be ‘blocked’. The behaviour of the flow in response to variations in the bottom topography, such as a varying lateral slope or a broad-crested weir, is discussed with particular reference to conditions under which the flow is either controlled or blocked.