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SMS - Calculate Stillwater Volume


Matt_Bilskie
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How would I get a stillwater volume from an observation arc across a river channel?

Matt,

I'm not sure if I understand your question, but I'll give it a shot. You ask about a stillwater volume, but then you reference an arc. An arc would not be associated with a volume, but could be associated with a area (under the arc). If you want a volume you want and area in plan view such as a polygon or elements. In SMS you can select elements or cells and the system reports the area selected. You can also enable the "Info Options" in the File menu to display a volume. The volume is computed based on the area of the selected objects multiplied by their respective scalar values. Normally, this would be a "depth". If you don't have a depth, but you do have a ground elevation, compute a depth using the data calculator (Data menu) by subtracting ground elevation from the still water elevation. Then make that depth the current data set and select the elements in the region you want the volume for.

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Matt,

I'm not sure if I understand your question, but I'll give it a shot. You ask about a stillwater volume, but then you reference an arc. An arc would not be associated with a volume, but could be associated with a area (under the arc). If you want a volume you want and area in plan view such as a polygon or elements. In SMS you can select elements or cells and the system reports the area selected. You can also enable the "Info Options" in the File menu to display a volume. The volume is computed based on the area of the selected objects multiplied by their respective scalar values. Normally, this would be a "depth". If you don't have a depth, but you do have a ground elevation, compute a depth using the data calculator (Data menu) by subtracting ground elevation from the still water elevation. Then make that depth the current data set and select the elements in the region you want the volume for.

Dr. Zundel: Thank you for the response. What I would like to accomplish is to use an observation arc across a river channel and have it compute the amount of volume (per unit width, so perhaps area) of the stillwater area. (area under the curve that is wet). If I look at the cross-section geometry across the observation arc, I want to know the area that is below my datum (NAVD88). I hope this is a better description than what I previously stated. Thanks!

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Dr. Zundel: Thank you for the response. What I would like to accomplish is to use an observation arc across a river channel and have it compute the amount of volume (per unit width, so perhaps area) of the stillwater area. (area under the curve that is wet).

Easiest way I can think of is to export the values to excel and calulate the area as a sum of rectangles (area of a rectangle is base*height/2). This is straight forward if there are no dry areas in the cross section (i.e. wse is above bottom at all points). With min/max functions in excel, also these dry areas could propably be handled with. If there is a dry area, easiest way is to treat the two wetted areas as separate sections.

Here's a simple example:

post-25-129845010644_thumb.jpg

Edited by heimo
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