Classify Fluvial Mesohabitats from Depth and Velocity // Classifies hydraulic conditions into nominal fluvial mesohabitat categories using water depth and velocity. It implements the eight-class scheme in the preprint by Cordero and Harris doi:10.2139/ssrn.7100727, supports validated rectangular custom schemes, and works with tabular and spatial data through 'terra'. Outputs describe hydraulic classes and do not by themselves establish biological habitat quality or species occurrence.