  We use radiation hydrodynamic simulations to examine two models of solar
flare chromospheric heating: Alfv\'en wave dissipation and electron beam
collisional losses. Both mechanisms are capable of strong chromospheric
heating, and we show that the distinctive atmospheric evolution in the
mid-to-upper chromosphere results in Mg II k-line emission that should be
observably different between wave-heated and beam-heated simulations. We also
present Ca II 8542A profiles which are formed slightly deeper in the
chromosphere. The Mg II k-line profiles from our wave-heated simulation are
quite different from those from a beam-heated model and are more consistent
with IRIS observations. The predicted differences between the Ca II 8542A in
the two models are small. We conclude that careful observational and
theoretical study of lines formed in the mid-to-upper chromosphere holds
genuine promise for distinguishing between competing models for chromospheric
heating in flares.
