Posted Thu, 27 Aug 2015 14:28:39 GMT by samsamia22

I am modeling a flood wave across a large 3D model. The model is a square with 2500m sides.
My wave should affect the whole model equally, a rise of the water table of 3m then a decrease to the original level. So far, I used two different approaches:

1) I added on the bottom layer of my model an inflow and calibrated it to reproduce the wave (rise of 3m then decrease).

2) I simulated a wave on the uphill and calibrated it so I get the response of 3m at my observation well, but across the whole model the wave is not calibrated. I have a damping effect.

The problem with the first method is that it doesn't represent what is really happening on the site and I have vertical flow across the whole model.
The problem with the second is the damping effect.

Any ideas on how I can simulate this???

Thank you
Posted Fri, 28 Aug 2015 13:56:26 GMT by Björn Kaiser
I suggest to represent the river with a 3rd kind Boundary Condition (Cauchy-BC). A Cauchy-BC applies a pre-defined reference head combined with a conductance parameter (transfer-rate).

Then, you could impose several time-series of the water levels as reference heads. Usually, measured time-series are available from local gauges. To regionalize water levels along the river you could use a 1D interpolation. The 1D linear interpolation is a method for interpolating linearly along line features provided by a map.

Floodwaves are damped by natural or artificial retention. To mimic the impact of floodwaves and retention on the groundwater you could take a time-dependent interpolation into account in addition to the spatial 1D-interpolation along the river.

However, this approximation is pure mathematical interpolation. If you are interested to represent the “real” physics of retention (including hysteresis) I suggest to couple FEFLOW with another numerical simulator, which is capable to solve the shallow water equations (St-Venant equation). In this context, an interface between FEFLOW and MIKE11 exists.

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