  Neutrinos of astrophysical origin could be detected through the
electromagnetic radiation of the particle showers induced in the atmosphere by
their interaction in the Earth. This applies in particular for tau neutrinos of
energies $E>10^{16}$eV following Earth-skimming trajectories. The
$\sim1^{\circ}$ beaming of the radio emission in the forward direction however
implies that the radio signal will likely fly above a detector deployed over a
flat site and would therefore not be detected. We study here how a non-flat
detector topography can improve the detection probability of these
neutrino-induced air showers. We do this by computing with three distinct tools
the neutrino detection efficiency for a radio array deployed over a toy-model
mountainous terrain, also taking into account experimental and topographic
constraints. We show in particular that ground topographies inclined by few
degrees only induce detection efficiencies typically three times larger than
those obtained for flat areas for favorable trajectories. We conclude that the
topography of the area where the detector is deployed will be a key factor for
an experiment like GRAND.
