  We investigate the one-dimensional propagation of waves in the Anderson
localization regime, for a single-mode, surface disordered waveguide. We make
use of both an analytical formulation and rigorous numerical simulation
calculations. The occurrence of anomalously large transmission coefficients for
given realizations and/or frequencies is studied, revealing huge field
intensity concentration inside the disordered waveguide. The analytically
predicted s-like dependence of the average intensity, being in good agreement
with the numerical results for moderately long systems, fails to explain the
intensity distribution observed deep in the localized regime. The average
contribution to the field intensity from the resonances that are above a
threshold transmission coefficient $T_{c}$ is a broad distribution with a large
maximum at/near mid-waveguide, depending universally (for given $T_{c}$) on the
ratio of the length of the disorder segment to the localization length,
$L/\xi$. The same universality is observed in the spatial distribution of the
intensity inside typical (non-resonant with respect to the transmission
coefficient) realizations, presenting a s-like shape similar to that of the
total average intensity for $T_{c}$ close to 1, which decays faster the lower
is $T_{c}$. Evidence is given of the self-averaging nature of the random
quantity $\log[I(x)]/x\simeq -1/\xi$. Higher-order moments of the intensity are
also shown.
