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NOAA-OWP / inundation-mapping

Flood inundation mapping and evaluation software configured to work with U.S. National Water Model.
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[13pt] Test new floor for Manning's slope #1190

Open CarsonPruitt-NOAA opened 3 weeks ago

CarsonPruitt-NOAA commented 3 weeks ago

Our current minimum slope value of 0.001 may be too high for some locations, e.g. Illinois River. Let's make sure to test FIM in these lower slope areas as well as the effect it may have on other areas that don't have that low of a slope.

CarsonPruitt-NOAA commented 3 weeks ago

Matt, I think you're already testing this new slope for low low-relief inland areas, but can you also do a test on a coastal area which might also have low relief? I'm specifically thinking of the Brazoria, TX region that Derek called out yesterday. This area is overpredicting pretty terribly, and I'm curious to see what kind of effect your tests might show here. The HUC is 12070104. Even a 2-yr flow is inundating the floodplain and town pretty badly.

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mluck commented 3 weeks ago

The slope for this area is very low, even below the new floor of 0.000001. However, reducing the slope from the original slope_min of 0.001 only exacerbates the inundation overprediction problem as it decreases the discharge in the Manning's equation. The crosswalking error identified in #1194 is likely responsible for this overprediction.