Running two different sea level rise scenarios on cbc model, one with SLR and without but getting same exact output rasters

NatCap Software Support
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I am running two separate scenarios, one with 5FT of sea level rise and one with no sea level rise, however I am getting the same exact output rasters with the same carbon sequestration values for each. The input rasters I am using for both of the InVEST CBC runs are different, yet have the same baseline raster. I am not sure why I am getting the same exact outputs although I think it may have to do with the fact that I am using the same baseline input rasters for each?

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Welcome to the forum @Owen! -

When you say that you’re running two separate scenarios, how are you entering them into the CBC model? Are they both being used as what the model calls “snapshots”, in addition to your “baseline”? Are the scenarios being used in the same model run, or in different runs? And what is the difference between the scenarios in terms of land cover that is considered blue carbon habitat?

If you’re doing two separate model runs, each of which includes a baseline plus one scenario “snapshot”, and those scenarios are different in terms of the quantity of blue carbon habitat and/or different in terms of the change due to disturbance, then you should get different results.

~ Stacie

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Hi Stacie, thank you for your reply.

I am running two separate scenarios (two separate runs of InVEST) with the base raster being existing marshes and the other snapshot being the tidal habitats with sea level rise (loss of marshes/change due to disturbance). In the no Sea level rise scenario, the two rasters are the same. For some reason it looks as if InVEST is not analyzing the future snapshot - I tried running a scenario with the base raster being existing marshes and the future snapshot being 100% sea level rise (all LULC codes change into open water) and my outputs were still showing carbon sequestration rather than emissions.

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Hi @Owen , could you provide your logfiles and also your snapshots CSVs from both of the two runs so we can get a better sense of what the model is doing?

Thanks,
James

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Hi James,

Attached are the Logfiles and snapshot CSVs
NO SLR InVEST-Coastal-Blue-Carbon-log-2023-02-13–14_10_42.txt (313.2 KB)
NO SLR snapshot.csv (208 Bytes)

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5FT SLR InVEST-Coastal-Blue-Carbon-log-2023-02-14–15_02_03.txt (171.0 KB)
snapshot5FT.csv (112 Bytes)

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Thanks for your inputs @Owen !

I see that there are a few transitions in the NO SLR snapshots CSV. In which transition year is the complete conversion to open water?

One potential issue here is that I see you do not have an analysis year set. If you are using the same 2022 baseline raster for both scenarios and the lulc indicating the transition to open water is at the year 2100, the model will only compute years between 2022 and 2100, nothing beyond. If you were to define an analysis year of 2150, the analysis would continue running the timesteps out to the year 2150 and you would see that open water transition affecting your carbon emissions.

Another potential reason for the behavior you describe may be your transition table: be sure to mark the transition from marshes to open water as a disturbance. If that transition is a disturbance, you’ll see carbon emissions in the model outputs after the year transition takes place.

Hope this helps and let us know if you have any questions!
James

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