Rock weirs (porous dam-like structures) are used to construct nature-like fish passages (NLFPs) in order to reestablish river connectivity and allow fish to continue migratory journeys. There is currently no formula to predict whether an NLFP will produce complex flow patterns to attract fish to the passages. My work seeks to accurately predict attraction flow by determining specific weir coefficients that can account for rock weir shape and porosity using a computational and experimental design.