Spring‐neap tide‐induced beach water table fluctuations in a sloping coastal aquifer

Abstract

[1] Predictions of water table fluctuations in coastal aquifers are needed for numerous coastal and water resources engineering problems. Most previous investigations have been based on the Boussinesq equation for the case of a vertical beach. In this note an analytical solution based on shallow water expansion for the spring-neap tide-induced water table fluctuations in a coastal aquifer is presented. Unlike most previous investigations, multitidal signals are considered with a sloping coastal aquifer. The new solution is verified by comparing with field observations from Ardeer, Scotland. On the basis of the analytical approximation the influences of higher-order components on water table elevation are examined first. Then, a parametric study has been performed to investigate the effects of the amplitude ratio (l), frequency ratio (w), and phases (d 1 and d 2 ) on the tide-induced water table fluctuations in a sloping sandy beach.

Estimations of tidal characteristics and aquifer parameters via tide-induced head changes in coastal observation wells

“…Figure 1 illustrates the groundwater fluctuations in response to tidal variations in a coastal aquifer. Jeng et al (2005) assumed that the flow in a rigid porous medium is homogeneous and incompressible. The tides are assumed to be bichromatic, which can be synthesized by the superposition of two different wave frequencies.…”

“…On the other hand, Teo et al (2003) developed a higher-order analytical solution based on the shallow water expansions for the water table fluctuations induced by the monochromatic tide in a sloping coastal aquifer. Jeng et al (2005) further considered the effect of bichromatic tide in the development of solution for WWL fluctuations in a sloping coastal aquifer.…”

“…In his model, the shoreline boundary condition at the interface of the beach and the ocean was allowed to vary with the tide height; it was however invalid in the situations of flat beach and/or large tidal range that may cause a seepage point deviated from the shoreline. Li et al (2000) overcame this conflict by introducing a moving shoreline condition and considered the tides to be bichromatic, namely, tides can be represented by two different wave frequencies. Both models however treated the beach slope as a part of the perturbation parameter, which restricts the applicability of the models to the case of aquifers with large beach slopes.…”

“…The analytical solution presented by Jeng et al (2005) along with a set of chosen parameter values is adopted to generate the observed WWL data in the hypothetical case. Then, both synthetic and real field WWL data are analyzed to demonstrate the capability and the limitation of proposed method in the determination of the aquifer parameters and tidal characteristics.…”

A simple model for predicting water table fluctuations in a tidal marsh

“…Some [Parlange et al, 1984;Nielsen, 1990;Barry et al, 1996;Li et al, 2000aLi et al, , 2000bLi et al, , 2002Li and Jiao, 2003] have used the well-known Boussinesq equation to model the transient position of the water table in a shallow, rigid aquifer in contact with a sinusoidally oscillating reservoir. Jeng et al [2005] develop an analytical solution to the Boussinesq equation to address spring-neap tide induced fluctuations in a sloping coastal aquifer. More detailed hydrologic models have been derived to describe various individual components of tidal marsh hydrology, such as the vertical flow of groundwater in response to evapotranspiration demand and the piezometric pressure of an underlying aquifer [Hemond and Fifield, 1982], surface infiltration [Hemond et al, 1984], horizontal fluxes [Nuttle and Hemond, 1988], and the stress and pressure changes due to tidal loading of the marsh surface [Reeves et al, 2000].…”