When performing floodplain delineation with HEC-RAS, what specific input parameter directly controls the calculation of water surface elevation for a given flow rate?

The specific input parameter that directly controls the calculation of water surface elevation for a given flow rate in HEC-RAS is the Manning's roughness coefficient, commonly referred to as Manning's 'n' value. This parameter quantifies the resistance to flow experienced by water as it moves through a channel or over a floodplain. This resistance originates from the friction between the flowing water and the wetted perimeter of the channel, including its bed and....