Analytical and Experimental Investigation of a Side-Weir Detention Basin in Flood-Level Reduction in the Main Channel

To design the off-stream detention basin by the sides of rivers or channels, flood-level reduction in main channels should be evaluated under unsteady flow. Flow discharge diverted to the side weir from the main stream can be calculated practically by the standard weir or lateral weir equations. In this study, experimental and numerical modeling with a side-weir detention basin was conducted for unsteady flow. The experimental results were compared with the numerical backwater profile calculation considering the water discharge overflowed into the basin from the channel. The overflowed discharge was estimated by the standard weir and lateral weir equations for various flow types at the side weir. The standard weir equation accurately predicted flow discharge diverted to the side weir for free overflow condition. The lateral weir equation calculated a precise flood level and time of peak flow for the condition modeled, especially when the various flows, including free and submerged overflows, were developed at the side weir.