April 22, 2019, 10:26:37 PM


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Messages - Jonathan S. Clough

I guess we've never run with just an 010 and not also a 100 year storm.  I think it's fair to say that this portion of the model has only been utilized by our team and is not deeply user friendly.  I'll look into the code to understand the requirements.
Using SLAMM / Re: Storm Surge Raster datum
April 01, 2019, 03:47:44 PM
Yes, if you have no correction factor for NAVD88 then using the MTL datum would be correct.  This is because, while the model will try to convert data from NAVD88 (which has been the format we generally received data in) it would use the zero conversion factor, so there would be no change.
Using SLAMM / Re: Surge Inundation Frequency Legend
April 01, 2019, 03:45:54 PM
Sorry about the deficiency in documentation.  This is from some metadata we created when running the model:

Inundation maps were created by running SLAMM for 5 different inundation elevations (H1-H5 in the subsite parameters)

Raster values are: 0 (zero) - open water, 1 - inundated at H1 level (we often set this to the 30-day inundation level), 2 - inundated at H2 (we have used 60 days), 3 - inundated at H3 (90 days) 4 - inundated by H4 (we often set this to the 10 years storm), 5 - inundated at H5 (100 years storm), 6 - above H5,  7 - below H5 but not connected, 8 - protected by dikes, -99 no data/blank
Using SLAMM / Re: Error Reading Headers
March 07, 2019, 10:32:01 AM
I downloaded the executable and sample files and was unable to reproduce your problem.   

Are you unzipping all of the files rather than trying to run out of the compressed folder?   
What happens when you press the "Set Map Attributes?"  Do the map and editing tools appear?
What happens under the file-setup window?  Are files showing as red -- invalid or are the list of NRows and NCols shown under each one.
In some cases you must point the file system to the correct file, but this may not be required if the files are in the same directory as the SLAMM6 file.

Good luck!  -- Jonathan
Sorry I misspoke.  The code must be compiled on Delphi XE3 -- my version is Embarcadero┬« Delphi┬« XE3 Version 17.0.4625.53395

I cannot port the code to other development platforms at this time.
Using SLAMM / Re: Error Reading Headers
March 01, 2019, 06:56:37 AM
Sorry you are having difficulty with the sample files.  I'm out of my office until Monday and I will look at your question then.
Hi Scott:

First of all, please note that there is a difference in datum used for the two parameters (which is probably not an ideal design.)   GT is expressed as meters between MLLW and MHHW.  The salt elevation is expressed as height above MTL (the mid point between MLLW and MHHW), so is a lower value than the GT generally.

As you have likely seen in some of our reports, this is based on "frequency of elevation" analysis from observed-data analysis so that it takes into account wind tides as well as astronomical tide cycle data.  I can point you at one of these analyses at some point if you'd like.   If you calculate a daily high water level using NOAA data for several years and then calculate the 0.967 percentile of those data that pretty much will get you there.

Best!  -- Jonathan
Sorry -- the forum stopped notifying me of new posts apparently and I completely missed this until today.

The accretion and historical SLR and uplift subsidence equations and considerations haven't changed since the previous version.

Elevation data can be output as MTL or NAVD88.

You are using a different development platform than the model was created on.  Things have changed, see:


Looks like it should be a quick code fix if you'd like to make it.  Otherwise you should be able to download [Embarcadero Delphi XE3] as a licensed user of the more recent version.   [edit- fixed version required at this time]

Best regards-- Jonathan
This category is usually changed as a function of the "salt elevation" parameter which has units of meters above MTL.  Make sure that parameter is properly set within the "Site Parameters" screen.  It is often approximately 133% to 140% of MHHW (relative to MTL). 

To examine the distribution of dry-land cell elevations you can go through "elevation analysis" (you must go through the "set map attributes" button first to load all cells and elevations for analysis.)  Select run elevation analysis and you can view statistics and histograms about each land-classes elevation.  There's more information about this screen in the users manual (context sensitive help).

I hope this gives you a hint as to how to proceed, otherwise please post again!
Using SLAMM / Re: Introduction
May 03, 2018, 08:40:44 AM
Sorry I let this thread go cold.  I have not seen this type of response.  Wonder if you figured it out.  You may want to check the "marsh collapse" parameter that could cause this problem if mis-set.
Tidal ranges affect SLAMM in many ways.  Certainly the model predicts significantly enhanced resilience to SLR for larger tidal range sites.

For one thing, a fixed change in tide levels (due to SLR) is a much higher percentage of the tide range in a microtidal site than a macrotidal.  This means that a marsh (that exists within the "tidal frame") can have much more elevation capital in a macrotidal site.

But with regard to the question at hand.  The SLAMM model does not directly model sediment inputs but those inputs come into account in the relationship between marsh accretion rate and marsh elevation.   See for example Figure 4 in this document.  https://www.sciencedirect.com/science/article/pii/S1364815216302705 ; This figure was derived based on the calibration of a model that does explicitly model sediment inputs (MAM3) 

We recognized that a model such as MAM3 generally predicts a single parabolic accretion-rate response to SLR (if you hold sediment inputs and tide range constant over time).  (The parabola has accretion rates on the y axis and marsh elevation relative to MTL on the x axis)  Therefore we allow for an input of this type of parabola to SLAMM.  A site with a larger tide range has more elevation capital to work with and will generally accumulate more sediment over a period of SLR.  MAM3 also predicts increased sedimentation rates in sites with larger tide ranges.

To generate the required parabola a site-specific empirical data analysis or application of a site-specific mechanistic model should be utilized. 

Hope this is useful and sorry about the long delay in response
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
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