  Utilizing the unique and reliable ultrasmall--$x$ predictions of the
dynamical (radiative) parton model, nominal event rates and their detailed
energy dependence caused by a variety of cosmic UHE neutrino fluxes are
calculated and analyzed. In addition, maximal Regge--model inspired small--$x$
structure functions are employed for obtaining optimal rates which do not
necessarily require `new' physics interpretations. Upward $\mu^+ +\mu^-$ event
rates are estimated by taking into account total and nadir--angle dependent
regeneration effects due to neutral current interactions. For exploring
extragalactic neutrino sources at highest energies
(\raisebox{-0.1cm}{$\stackrel{>}{\sim}$} $10^8$ GeV) with modern (future)
ground--level telescopes, we analyze horizontal air shower event rates and
shower events caused by Earth--skimming tau--neutrinos, in particular their
detailed shower-- and cosmic neutrino--energy dependence. As an illustration of
`new physics' implications we estimate the relevant horizontal air shower event
rates due to spin--2 Kaluza--Klein `graviton' exchanges in neutral current
neutrino--quark and neutrino--gluon interactions at low TeV--scales.
