Measurement and modeling of moisture content above an oscillating water table: implications for beach surface moisture dynamics

Namikas, Steven L.

doi:10.1002/esp.3418

Cited by 12 publications

(12 citation statements)

References 43 publications

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“…To illustrate our approach (see also Namikas et al. , and Schmutz and Namikas, ), Figure shows predicted moisture profiles for three water table depths ( h = 1.0 m, 0.4 m and 0.1 m), all with w res = 2 % , w sat = 25 % , α = 3.5 m −1 and n = 3.19, where the latter two values were based on Tuller and Or (). For h = 1.0 m (Figure a) the moisture profile contains an approximately 0.10–0.15 m thick capillary fringe

false(w_{s}^{'} \approx w_{sat} false)

and a roughly 0.5 m thick layer where the moisture content gradually reduces to w res .…”

Section: Methodsmentioning

confidence: 98%

“…Here, hysteresis effects with higher surface moisture content with falling than rising tide for the same water table depth may be substantial. This was illustrated from laboratory experiments with a vertical sand (130 μ m) column and an oscillating water table (Schmutz and Namikas, ) and from field measurements on an upper beach (also 130 μ m; Padre Island National Seashore, USA) under spring tidal conditions when the groundwater depth was less than about 1 m (Schmutz, ). It is likely that the importance of hysteresis to surface moisture variability diminishes with increasing grain size (e.g., Yang et al.…”

Section: Introductionmentioning

confidence: 90%

“…Just above the low-tide level, where the groundwater table is shallowest (h < 0.1 0.2 m), the sand remains saturated. In this case, the capillary fringe above the water table intersects the surface (e.g., Namikas et al, 2010;Schmutz and Namikas, 2013). On fine-11grained low-sloping beaches the water table can remain close to the surface for most of the tide and, accordingly, the persistently saturated part of the beach can extend well landward of the swash zone (Atherton et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

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Tide‐induced variability in beach surface moisture: Observations and modelling

Brakenhoff

Smit

Donker

et al. 2018

Earth Surf Processes Landf

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The moisture content ws of a beach surface strongly controls the availability of sand for aeolian transport. Our predictive capability of the spatiotemporal variability in ws, which depends to a large extent on water table depth, is, however, limited. Here we show that water table fluctuations and surface moisture content observed during a 10‐day period on a medium‐grained (365μm) planar (1:30) beach can be predicted well with the nonlinear Boussinesq equation extended to include run‐up infiltration and a soil–water retention curve under the assumption of hydrostatic equilibrium. On the intertidal part of the beach the water table is observed and predicted to continuously fall from the moment the beach surface emerges from the falling tide to just before it is submerged by the incoming tide. We find that on the lower 30% of the intertidal beach the water table remains within 0.1–0.2 m from the surface and that the sand is always saturated (ws≈20%, by mass). Higher up on the intertidal beach, the surface can dry to about 5% when the water table has fallen to 0.4–0.5 m beneath the surface. Above the high‐tide level the water table is always too deep (>0.5 m) to affect surface moisture and, without precipitation, the sand is dry (ws < 5 − 8%). Because the water table depth on the emerged part of the intertidal beach increases with time irrespective of whether the (ocean) tide falls or rises, we find no need to include hysteresis (wetting and drying) effects in the surface‐moisture modelling. Model simulations suggest that at the present planar beach only the part well above mean sea level can dry sufficiently (ws < 10%) for sand to become available for aeolian transport. ©2018 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.

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false(w_{s}^{'} \approx w_{sat} false)

and a roughly 0.5 m thick layer where the moisture content gradually reduces to w res .…”

Section: Methodsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Tide‐induced variability in beach surface moisture: Observations and modelling

Brakenhoff

Smit

Donker

et al. 2018

Earth Surf Processes Landf

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“…[] observed strong hysteresis effects near a fluctuating capillary fringe with different flux and pressure boundary conditions, and water content varied more in the case of slow fluctuation. Schmutz and Namikas [] measured the surface moisture content above an oscillating water table and simulated the response of surface water content to water table oscillation using the Hydrus‐1D program [ Simunek et al ., ] with both hysteresis and nonhysteresis approaches. Comparisons between measured and simulated surface water content showed that hysteresis exerts significant influence on surface moisture content dynamics, especially when the water table is close to land surface.…”

Section: Introductionmentioning

confidence: 99%

Validation of finite water‐content vadose zone dynamics method using column experiments with a moving water table and applied surface flux

Ogden

Lai

Steinke

et al. 2015

Water Resources Research

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Data from laboratory experiments on a 143 cm tall and 14.5 cm diameter column, packed with Wedron sand with varied constant upper boundary fluxes and water table velocities for both falling and rising water tables are used to validate a finite water-content vadose zone simulation methodology. The onedimensional finite water-content Talbot and Ogden (2008) (T-O) infiltration and redistribution method was improved to simulate groundwater table dynamic effects and compared against the numerical solution of the Richards equation using Hydrus-1D. Both numerical solutions agreed satisfactorily with time series measurements of water content. Results showed similar performance for both methods, with the T-O method on average having higher Nash-Sutcliffe efficiencies and smaller absolute biases. Hydrus-1D was more accurate in predicting deponding times in the case of a falling water table, while Hydrus-1D and the T-O method had similar errors in predicted ponding times in the case of a rising water table in six of nine tests. The improved T-O method was able to predict general features of vadose zone moisture dynamics with moving water table and surface infiltration using an explicit, mass-conservative formulation. The advantage of an explicit formulation is that it is numerically simple, using forward Euler solution methodology, and is guaranteed to converge and to conserve mass. These properties make the improved T-O method presented in this paper a robust and computationally efficient alternative to the numerical solution of the Richards equation in hydrological modeling applications involving groundwater table dynamic effects on vadose zone soil moistures.

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“…To study moisture, Robin and his students (I. Delgado-Fernandez and I. Darke) designed innovative methods to quantify moisture (e.g. Darke et al, 2009;Delgado-Fernandez et al, 2009).In this collection, Edwards and Namikas (2013) introduce an infrared sensor to measure beach surface moisture, and Schmutz and Namikas (2013) examine the influence of tidal oscillations of the water table and the relationship with beach moisture.…”

mentioning

confidence: 99%