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whether the SLAMM model can be used to simulate the impact of global SLR

Started by zhiliehui1, January 09, 2020, 10:03:38 AM

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zhiliehui1

Dear sir?
      In a study by my research group, it is necessary to predict the change of coastal wetland vegetation and the distribution of ground salinity in the future SLR scenario. We have successfully performed small area studies with SLAMM, and we do not know whether SLAMM is applicable to global scales.I remember the technical documentation mentioning that the coastal zone can be divided into subsites. Whether the global scale can divide multiple sub-areas according to the direction to the sea and set rough model parameters for research. If we want to carry on this research, do you have any good suggestions?
      Look forword to your reply.

Jonathan S. Clough

Hello:

The scale on which SLAMM can be applied is an interesting question.

Early versions of the model (mid 1980s) were designed to be run with very large cell sizes (500m x 500m for example).  Within those cells there would be a classification of strips of wetlands and dry lands characterized as widths.  Each wetland and dry land would have an elevation and slope among other characteristics. 

Set up in this manner (this was pre-GIS, so from what I have heard inputs were entered by hand) an application to 20% of coastal US was prepared along with a report to congress:
http://risingsea.net/papers/federal_reports/rtc_park_wetlands.pdf

Newer version of the model have kept some of that architecture, but with the advent of GIS mapping, smaller cell sizes were desired.  In order to conserve memory the maximum number of classes per cell is now down to 3 in the latest version.  So that would not support larger cell sizes.  On the other hand, it exceeds the computational capacity and memory capacity of most machines to model the entire globe with cell sizes of 30 meters or less.  And that is likely an understatement.

So I guess it would be possible to perform such a run but the source code would need to revert back to an older version that supports larger cell sizes and the processing of data for model inputs would be quite tricky.

Hope this is useful.


zhiliehui1

Dear sir

Thank you for your advice?sincerely.

 How can we obtain the early version (mid 1980s) you mentioned? We couldn't find it on the official website.

 Look forward to your reply.

Jonathan S. Clough

That code predates my involvement with the code which started with SLAMM 3 in 1998.  Even if I had it you would need to find some historical compiler to run it on (probably some version of Borland Pascal)

However, the constructs that govern applying the model to large cell sizes remains in the model.  (The capability to model many categories within a single cell.  SLAMM currently holds up to three land types per cell modeled.  However, as cell sizes tend to be small, model initialization is based on a one category-per-cell assumption.)

You would have to be a coder.  It seems to me that the simplest steps would be to:

increase the NUM_CAT_COMPRESS variable which currently only allows 3 classes per cell.

Then the difficulty would be to initialize the model with minimum elevations, widths, and slopes for each category you wish to model in each large cell.

The mapping and GIS linkages wouldn't be particularly useful as they only display the dominant category per cell.

It would take some work in the code -- I'm afraid this type of application is not supported at this time unless someone wants to pay for model development...

Best regards -- Jonathan

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