  We present (3+1)D dynamical simulations of asymmetric nuclear collisions at
the Relativistic Heavy Ion Collider (RHIC). Employing a dynamical initial state
model coupled to (3+1)D viscous relativistic hydrodynamics, we explore the
rapidity dependence of anisotropic flow in the RHIC small system scan at 200
GeV center of mass energy. We calibrate parameters to describe central
$^3$He+Au collisions and make extrapolations to d+Au and p+Au collisions. Our
calculations demonstrate that approximately 50% of the $v_3(p_T)$ difference
between the measurements by the STAR and PHENIX Collaborations can be explained
by the use of reference flow vectors from different rapidity regions. This
emphasizes the importance of longitudinal flow decorrelation for anisotropic
flow measurements in asymmetric nuclear collisions, and the need for (3+1)D
simulations. We also present results for the beam energy dependence of particle
spectra and anisotropic flow in d+Au collisions.
