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Messages - marco.propato

Using SLAMM / Re: dry land
February 06, 2013, 05:07:14 PM
Hi Magdeline,

(1-2) SLAMM skips the cells that are blank. In other words elevations are not updated, inundation and wetland conversion are not executed. So basically nothing happens for those blank cells while if they were initially dry land they could convert to wetlands as sea level rises.
(3) In the latest version you have, SLAMM 6.2, there should be a conversion button, "blank" to "dry land", in the Edit Cell menu. This will fill ALL blank cells as undeveloped dry land unless you have also an impervious raster in your project. If this is the case, then some cells may be converted to developed dry land if the pct. impervious is greater than 25. Such button only works if you are tracking ALL the cells in your project.

Hope this helps.
Using SLAMM / Re: Shifting Swamp elevation
August 13, 2012, 03:09:50 PM
For what concerns the tidal information we usually use it because it is a verified datum and it is definitively better than guessing.

To derive the elevation correction you can try to use the VDATUM software from NOAA at It normally covers only coastal areas but it maybe sufficient for your application


Using SLAMM / Re: Shifting Swamp elevation
August 10, 2012, 01:56:35 PM
Hi Rich,
initially, SLAMM simulates the "time zero" step, in which the consistency of model assumptions is validated with respect to available wetland coverage information, elevation data and tidal frames. Due to simplifications within the SLAMM conceptual model, DEM and wetland layer uncertainty, or other local factors, some cells may fall below their lowest allowable elevation category and would be immediately converted by the model to a different land cover category (e.g. an area categorized in the wetland layer as swamp where water has a tidal regime according to its elevation and tidal information will be converted to a tidal marsh). These cells represent outliers on the distribution of elevations for a given land-cover type. Generally, a threshold tolerance of up to 5% change is allowed for in major land cover categories in SLAMM analyses (e.g. we allow the conversion to happen if it is not more than 5%)

So you can try to change the min/max allowable elevations in the elevation analysis window. However, this shift may be due to other reasons, for example the available elevations in those areas are very low and the tides data show that water there is tidal .... therefore a swamp can't be there for the model. So maybe is the tidal information that needs to be re-evaluated or the elevations around are too low and allow water to enter ....

Hope this helps,
Using SLAMM / Re: Getting the layers to line up?
July 09, 2012, 01:09:57 PM
if your cell size is significantly bigger than a meter, there should be no problem to reset the starting corner. The projections will be affected very little by this shift.

Hope it helps,