Catchment area
Catchment area
(OP)
There seems to be various methods for calculating the catchment area. And each method gives an area which varies in around 10% to other method. Can anyone give me which method is more appropriate and why?
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RE: Catchment area
RE: Catchment area
RE: Catchment area
RE: Catchment area
RE: Catchment area
To confirm the drainage area I would go into the field to verify and or modify the area based on what I've seen in the field. I've seen many cases where DEM and base mapping data has not picked up roadway culverts, ditch geometry and drainage divides which have increased and/or reduced drainage areas by a substaintial amount. Before going into the field, identify key areas where you would want to spend some time.
Hope this helps.
RE: Catchment area
Civil Development Group, LLC
Los Angeles Civil Engineering specializing in Hillside Grading
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RE: Catchment area
However, an accurate electronic map (confirmed as Ryb01 suggests) will be far better than using a planimeter.
Now-a-days, I only use a planimeter for measuring off paper maps that don't scan well. If they scan OK, I drop them into Autocad, scale them, and make closed plines to get areas. Well, actually, I have other people do this for me.
RE: Catchment area
RE: Catchment area
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"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill
RE: Catchment area
RE: Catchment area
Within 10% on any design job is usually cloes enough unless you are designing F15 wings.
RE: Catchment area
I agree that if you could estimate actual conditions to within 10% of the actual values you are doing well. However, if you start a basic process like measuring area and has a variance of 10 % you are in trouble. If you let your errors add up the chances are that your estimated final condition will be several orders of magnitude away from an engineering estimate.