The prediction of groundwater level fluctuation due to tidal waves propagation in coastal aquifers is
important for the planning and management of water resources in coastal areas. A two-dimensional
(2-D) analytical solution is derived to describe the tidal groundwater fluctuation in an aquifer bounded
by three water–land boundaries that form a U-shaped coastline. Two opposite sides represent estuary–
land boundaries on which the amplitude attenuation and phase shift of the tidal movement in the estuary
are considered while the third side is an ocean–land boundary. The effects of wave interaction due to the
propagation of oscillating oceanic tides in the cross-shore direction inland and the transmission of the
two opposite estuarine tides in the along-shore direction are investigated. Three existing headfluctuation
solutions can be considered as special cases of the present solution; one is for onedimensional
flow and the other two are for 2-D flow. A transition distance ranging from 10 to 15 times
of tidal propagation length along the shoreline can be estimated based on the solution. This distance can
be used to judge whether the interaction among tides is significant. The influences of hydraulic properties
on the tidal fluctuations within the aquifer can therefore be assessed quantitatively. Based on sensitivity
analyses, one can conclude that the tidal head is most sensitive to the transmissivity and storativity of the
aquifer, and least to the damping coefficient of tidal amplitude and wave number along the estuary. The
sensitivities of head fluctuation to the changes of transmissivity and storativity depend on the shoreline
length and whether the interaction among waves is significant. On the other hand, the sensitivities of
head fluctuation to the changes of damping coefficient and wave number increase with diagonal distance
from the entry of estuary and reach the largest magnitude near the estuary far away seashore.