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

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. Plain Language Summary: Gravel bed rivers frequently show spatial width variations. Accompanying these variations, the riverbed presents topographic lows and highs, such as pools and riffles. We have developed an analytical model to quantify pool‐riffle topography in relation to specific width configurations. For gravel bed rivers, this model requires various estimable parameters, including water discharge, flow resistance, riverbed slope, and spatial width variation. River restoration projects often aim to restore rivers to their natural state. Our proposed model can provide crucial insights for comprehending and replicating the natural state of rivers. Key Points: The analytical model linking bed level perturbations with width variations is based on the conservation of mass and energy in water flowThe model demonstrates that bed level perturbations are positive when local width exceeds the average, and negative when it is lessWith larger water discharge, the height of riverbed perturbation increases [ABSTRACT FROM AUTHOR]