April 19, 2018, 11:00:05 PM


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Recent Posts

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Model Formulation & Parameters / Does the model simulate sedime...
Last post by Pat Prado - April 04, 2018, 06:42:19 AM

I was wondering if someone could clarify if SLAMM takes into account that higher sediment inputs seem to happen in systems with greater tydal ranges, which could lead to enhanced resilience to SLR compared to systems with lower tydal ranges. Is the model calibrated to simulate this effect?

Many thanks in advance!!
The input files look good but there was one key issue.  The CRS units for SLAMM projects must be meters.  I am sorry if that has not been made clear enough through the GUI and/or users guide.  I will specify that on the file-input GUI for the next version .

Best regards -- Jonathan
Using SLAMM / Re: Data Set
Last post by pse1999 - February 24, 2018, 10:25:56 PM

I think one way you can do it is when you convert the polygon (NWI shp) to a raster through the tool you can set the processing extent the already created DEM raster through the "environments.." button to match your other rasters. There should be a box you can click where it will snap to the raster.
Using SLAMM / Regularly Flooded marsh conver...
Last post by pse1999 - February 24, 2018, 10:21:41 PM
I am curious if anyone else who has used SLAMM to evaluate elevations has noticed when a cell converts to regularly flooded marsh that elevation decreases exponentially more than other classification types?
data derived from the below example is sourced from the GCPLCC dem and NWI ASCII files

for example (all elevations relative to MTL):

2006 2037 2068 2100     '06    '37    '68       '00
5   5      7      8         1.96    1.8     1.52   -1.19
5   5      7      8          2.11    1.9    -2.84  -3.25
3   3      7      8          1.93    1.66   1.28   -1.44
5   5      7      8          1.77    1.6      1.33   -1.39
5   5      7      8         1.82    1.65   1.38   -1.34

"8" is classified as "Regularly flooded marsh" and as seen it gradually decreases at first to essentially falling down a hole in the latter time steps. Is this common? is it the time step interval that is too large?

Any help would be very much appreciated.

If you are using a dike layer I would turn that off as a test.

Next thing to do is look at the elevation analysis -- Set Map Attributes, Elevation Analysis button towards middle of Analysis Tools tab.  Then "Run Elevation Analysis (This Site)  Double click on the category names to sort, sorting by n cells can be useful.  The 5th percentile for wetland classes should be around the minimum elevation. 

See the help file text for more information on interpreting the matrix on that page.  Also you can see this reference:


If you want to email me the SLAMM6 and spatial files I will take a look at it, or you can just email the elevation-analysis matrix after exporting to Excel for now.

Good luck!  -- Jonathan
Model Formulation & Parameters / Model runs but shows change in...
Last post by Hartney - February 12, 2018, 08:50:42 AM
Hi all,

I have been running a model for the Pearl River LA/MS region.  The model runs smoothly but there is never any wetland change, even with 6m of SLR and no accretion values.  I have been able to run other models with parameters based on journal studies, including Pascagoula, and those models do show wetland change.  Some things I have double checked (based on answers to similar posts on this forum) include elevation data units, DEM/NWI date, and the NAVD88 to MTL conversion (based on the Bay Waveland Yacht Club, MS tidal station: https://tidesandcurrents.noaa.gov/datums.html?units=1&epoch=0&id=8747437&name=Bay+Waveland+Yacht+Club&state=MS ).  My accretion values are based on Louisiana's Coastwide Reference Monitoring System (CRMS).  What other parameters should I be looking at to fix the issue? At this point, it feels like I'm missing something obvious so I'm hoping for an extra set of eyes to help me brainstorm what the issue may be. 

Thank you!
I ran multiple tests and, for my study files, when there is no dike input raster map, the maps produced have been identical whether "use dikes" is checked or not.  Are you willing to share your input files so that I can look into this further?   Regards -- Jonathan
Model Formulation & Parameters / Re: Differences between Includ...
Last post by maryramirez - November 13, 2017, 10:57:45 AM
Using the most recent version available (SLAMM 6.7 beta).
If you do not have a dike file specified, the results should be identical.  Please let me know which version you are using and I'll run a test and ensure there is not a software bug causing this problem.
Using SLAMM / Re: Data Set
Last post by Jonathan S. Clough - November 10, 2017, 02:14:58 PM
As you know, NRow and NCol and "lower left corner attributes" must match precisely.

In the QGIS world we use GDAL WARP to ensure that this is the case.

It is best to set the attributes precisely when converting from NWI polygons into a raster because re-projecting or moving raster files can result in data loss.

I cannot speak to the ESRI world -- anyone else?

Best regards -- Jonathan
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