ABSTRACT
Flood water in an urban area must be quickly carried away by streets and channels. Design of flood channel takes into consideration both the channel hydraulic capacity and the future maintainability. Open-channel flows are analyzed by the empirical formulas that calculate the cross-sectional average flow velocity and hydraulic parameters. Grade control by drop structure is a common practice to design a channel on a steep slope. A drop structure creates a vertical fall within a short horizontal distance along the channel longitudinal alignment. The purpose of a drop structure is to reduce the flow velocity and to satisfy a set of design criteria on permissible flow Froude number. Riprap linings are flexible and generally less expensive than rigid linings. Riprap lining is a good choice if the channel is expected to experience frost heave and/or swelling of the underlying soils that can change the shape of the channel lining.
