Theoretical Solution Linking Channel Width and Pool‐Riffle Bed Level Perturbations

Abstract Gravel bed rivers often display pool‐riffle morphology. Downstream changes in channel width are often correlated with pool‐riffle topography. Considering self‐formed, alluvial, straight and single‐thread gravel‐bed rivers, here we provide an analytical solution for their equilibrium pool‐riffle morphology in the presence of spatially varying widths. Our analytical model, based on mass and energy conservation for water flow, shows how bed level perturbations are closely linked to downstream width variations under the influence of water discharge. The analytical model is validated against experimental data and applied to reconstruct the natural pool‐riffle bed profile. The validated model shows how increasing water discharge (i.e., water depth and flow velocity) enhances the amplitude of pool‐riffle sequences. The proposed model can provide valuable guidance for river restoration projects.