Solutions are determined for normally incident non-breaking linear
gravity waves in a
perfect fluid over a porous plane bed of arbitrary slope α both with
and without bed
friction. For simplicity, computations are restricted to α=π/2m,
m∈N. Modifications
to wave height transformations due to percolation and to friction are determined
for
a variety of slopes and coefficients. The effect on the reflection coefficient
Rf is also
studied and excellent qualitative agreement is found with recent work on
damping
and reflection by permeable structures. In particular, for a choice of
parameters, the
Rf response is determined in closed form.