[5pt] CatFIM site mapping some stages but not others without error messaging

[EmilyDeardorff]

The stage-based CatFIM for site PACI1 only has inundation for the moderate and record stages. However WRDS has stage values for action and minor as well, but they do not have any mapped CatFIM. The site status reflects that there is no stage data for major, but does not explain why action and minor stages are not being mapped.

Investigate why these stages are not being mapped and either fix the bug so it maps them or improve the error handling so the status reflects why they do not have mapped CatFIM.

This issue was originally highlighted in Vlab ticket #127460.

[EmilyDeardorff]

Action and Minor flood stages for site PACI1 are not inundating because the hand_stage variable is negative (see math example below).

This is because the adjusted water surface elevation (datum_adj_wse_m) for Action and Minor stages is lower than the LID elevation value (lid_usgs_elev). This is causing them to not map. This is also probably why Moderate and Record stages are SO weirdly small.

In our workflow, we discard any sites where the lid_usgs_elev and lid_altitude are more than 10 feet different. In this site, the lid_usgs_elev is 9.2 feet higher than the lid_altitude, so it’s almost to that threshold but not quite.

There are a few options to fix this issue:

• We could experiment with lowering that 10 ft threshold, but that would require a lot of testing to determine what a better threshold would be.
• In the meantime, I think it would be useful to add logging that returns the elev difference and add a check that returns a more descriptive error if the hand_stage is negative.
• If we can't find a way to fix this elevation disparity or catch this error with filtering, we should probably add this site to the restricted sites list.

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Math example for site PACI1, action stage (example has a negative hand_stage value, preventing inundation)

Process inputs:

• stage_val: height of river inundation level (from WRDS)
• datum_adj_ft: amount to adjust elevation based on vertical datum (from code)
• lid altitude: site elevation (USGS elevation, taken from WRDS
• lid_usgs_elev: site elevation (DEM-adjusted elevation, taken from usgs_elev_table.csv)

1. Calculate the datum-adjusted water surface elevation (WSE) by adding the stage value, the datum adjustment, and the site elevation (the USGS value from WRDS).

datum_adj_wse = stage_val + datum_adj_ft + lid_altitude
Example: 2544.5 = 8.0 + 0.0 + 2536.5

2. Convert the datum-adjusted water surface elevation from feet to meters.

datum_adj_wse_m = datum_adj_wse * 0.3048
Example: 775.5636 = 2544.5 * 0.3048

3. Calculate the stage to be used by the HAND model by subtracting the site elevation (from our DEM-adjusted elevation values in the usgs_elev_table.csv) from the datum adjusted water surface elevation. Notice that hand_stage_m is negative in this example. This is why it is not properly inundating.

hand_stage_m = datum_adj_wse_m - lid_usgs_elev
Example: -0.3684= 775.5636 - 775.9321

4. Round the final stage value.

hand_stage = round(hand_stage_m * 1000)
Example: -368 = round(-0.3684 * 1000)