This Paper presents a simple closed-form mathematical solution to grou
ndwater variations arising from one-dimensional laminar flow through s
tructures in tidal areas. Finite-difference methods are used to study
the groundwater response to tidal variations for a non-laminar flow co
ndition where the discharge is proportional to the square root of the
differential head. The study highlights the significance of small open
ings in marine structures on the water pressures and flows through the
boundary. It also shows that, for the same openings and ground condit
ions, the water pressure response for non-laminar flow through the bou
ndary can be significantly greater than that determined for laminar fl
ow. Examples of the practical application of these findings are includ
ed to show the effect on the groundwater response to tidal variations
of placing natural and geosynthetic filter layers on confined and unco
nfined gravel aquifers, and of grouting masonry quay walls.