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mestan

TUFLOW 1D Network

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Hi everyone,

I got a warning from Tuflow.

I enter manning n value 0.012 for channel from channel attributes window, but I get a warning everytime like -- "WARNING - Manning's n value of 0.00084 for channel nii_0002 is unusually low or high."-- (but I didn't enter n value 0.00084). This warning causes an error like " UNSTABLE 2999 - Above 61.0m at [115;335]. Time = 8:47:42; Water Level = 102.0; 2D Domain = Domain_001"-- If I enter n value "1", everything is ok.

Manning n value of channels is 1 in tuflow tutorials. If I change it to 0.012, tutorial model give same warnings and errors also.

Please let me know.

Thanks,

Mestan

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Hi,

Sorry for the confusion. This issue comes about because of there are multiple methods for working with Manning N with TUFLOW/SMS.

Manning N values can be based upon materials in a 1D cross-section coverage and the n values specified in the material set. For pipe networks or if materials are not specified for cross-sections, the n value for the channel needs to be specified. For channels using materials, TUFLOW allows you to modify the n value with a multiplier for calibration purposes.

The problem is that the 1D network coverage does not know if you are going to associate it with a cross-section coverage that has materials specified or not. If you have a cross-section coverage with materials, the manning n edit field contains a multiplier for the material definition (default of 1.0 for unchanged). If you have a culvert or 1D channel not using materials, you enter the actual manning value there.

The problem looks like it is taking the value in the channel attributes dialog and multiplying it by the value specified for the material.

I will put some thought into ways we could make this more clear to the user.

Cheers,

Rusty

Hi everyone,

I got a warning from Tuflow.

I enter manning n value 0.012 for channel from channel attributes window, but I get a warning everytime like -- "WARNING - Manning's n value of 0.00084 for channel nii_0002 is unusually low or high."-- (but I didn't enter n value 0.00084). This warning causes an error like " UNSTABLE 2999 - Above 61.0m at [115;335]. Time = 8:47:42; Water Level = 102.0; 2D Domain = Domain_001"-- If I enter n value "1", everything is ok.

Manning n value of channels is 1 in tuflow tutorials. If I change it to 0.012, tutorial model give same warnings and errors also.

Please let me know.

Thanks,

Mestan

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