This paper examines the scattering of a train of small-amplitude harmo
nic surface waves on water by one-dimensional topography, using the mi
ld-slope equation. The associated boundary value problem is converted
into a pair of integral equations whose solutions are approximated by
variational techniques, which also supply error bounds. Excellent appr
oximations to the reflection and transmission coefficients and to the
free surface shape are produced with only 2- or 3-dimensional trial sp
aces, by choosing these spaces to be problem dependent. The bed profil
es considered include localised humps and taluds which join two horizo
ntal planes at different depths.