GMS User

Hydraulic characteristic in Horizontal Flow Barrier (HFB)

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I've read the HFB pacakge description found in http://www.xmswiki.com/wiki/GMS:HFB_Package but I'm still not understand which is the correct valure for HC.
From the barrier fact sheet:
-hydraulic conductivity equivalent: 1E-10 m/s 
-thickenss : 0.01 m

The thickness is in the direction of the flow as described in http://www.xmswiki.com/wiki/GMS:HFB_Package.
I get HC = K/T = 1E-8 m/s/m

How Modlfow (LFP) use HC in resolving the flow equations without the barrier thickness?

Why not set HC to the hydraulic conductivity equivalent value?

 

Thank you

daniele

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The HFB changes the cell to cell conductance on the face where it is placed.

As to why... you would have to ask the MODFLOW developers why they choose this particular implementation.

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As I can't insert any thickness in the HFB coverage, the HC 1E-8 seems to me too permeable for a sheet pile. Isn't it?

Do you suggest me to set the HC to 1E-8 m/s ?

Thank you

daniele

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I don't know if that is too permeable for a sheet pile or not. Hopefully you have some head data to help calibrate the value of HC, otherwise you will have to use your professional judgment to determine the value of HC.

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Hi, I don´´ t know if HFB is the right "topic" for my issue: I have a one grid layer steady sytate modflow model of an esker. The problem is that in the middle of modeling (esker)area there is a bedrock outcrop  that arises above groundwater level (or sometimes even above mineral ground surface). If I have understood right it is not allowed to "flag" those finite difference grid cells (inside modeling area) as "inactive" (IBOUND) or "isolate" them. I´d woiuld be very pleased to know how to deal with that before mentioned situation, where the esker has accumukated over impermeable crystalline berdrock and the bedrock surface arises above adjacent esker´s groundwater level (or even outcrops) in the middle of the esker.( = in the middle/or centre of the modeling area) ?

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