  Blind 21cm surveys in the local universe have shown that the local HI mass
density, Omega_HI, is dominated by luminous, high surface brightness, spiral
galaxies. On the other hand, surveys for host galaxies of damped Ly-alpha
systems have not always been successful in finding bright spiral galaxies. From
an analysis of 21cm aperture synthesis maps of nearby galaxies we show that
this apparent contradiction can be resolved by realizing that the HI mass
density is dominated by L* galaxies, but the HI cross section near the DLA
threshold is more evenly distributed over galaxies with a large range in
luminosity, gas mass, and surface brightness. The distributions of column
densities and impact parameters of optically identified and non-identified DLA
host galaxies in the literature and the HI maps are qualitatively in agreement.
Due to poor number statistics of low redshift DLA systems, there is no firm
indication that the redshift number count of low redshift DLA systems is
inconsistent with that calculated from the nearby galaxy population.
