General Category => Using SLAMM => Topic started by: Jonathan S. Clough on April 24, 2009, 09:25:52 AM

Title: SLAMM Users Guide
Post by: Jonathan S. Clough on April 24, 2009, 09:25:52 AM

In this topic, I hope to post some frequently asked questions about applying the SLAMM Model.  Please feel free to add a new topic if you do not see your question listed here:

GIS Projections:  It is recommended that an equal-area projection is utilized to avoid the potential for error in calculating surface area statistics.  

Site Data:

1.) I am having trouble understand the "water depth" input.  Could you clarify how one would develop this input?  In the documentation, you say "meters below MTL".  How would you estimate this?

This is not an important input to the model unless you are modeling a system in which sea level is falling.  We have not modeled such a site in many years.  (Projected Sea Level Rise almost always is greater than equal to projected rates of isostatic rebound)  To answer your question, though, this would be the depth of water two meters from shore (the depths in-between are interpolated.)  However, we haven't tested this accretion code in many years now.  Also, this should be replaced by code to read bathymetry data in the mid-term future.  You should find the model to be completely insensitive to this (vestigal) parameter.

2) We are having some trouble finding information on Mean High Water Spring.  Any thoughts as to the best source for this information.  The COOPS data does not appear provide MHWS.

This is an interesting issue.  In recent years and model applications I have replaced the concept of MHWS with the concept of frequency of inundation.  I usually define MHWS as the elevation above MTL that is expected to flood less than one time per month.  This usually lines up fairly closely with the dry-land/wetland boundary.  

"Spring Range" is available as part of NOAA tide table data (  However, this "MHWS" is actually the mean high water (not MHHW) on the dates of new moon or full moon and it is often quite close to the MHHW-MLLW range.  What we are really looking for is an elevation that floods infrequently enough so that we predict dry land above that elevation and wet lands below.  Based on consultation with wetland scientists a frequency of once per month was deemed as appropriate.  

You can use either NOAA tide predictions to try to derive this value or NOAA historic tide data.  Or, you can use a regional relationship, often something like 1.33 to 1.5 times the Great Diurnal Tide Range.

When the model is re-worked some of these parameters will need to be renamed for clarity sake.  (and some removed altogether!)

Frequency of Large Storms:  This parameter reflects the frequency of overwash for

Tide Range Inland vs. Tide Range Oceanic: These parameters were split up when the model was run with a single site record.  The inland tide-range reflects the tide range in a location where dry land is prevalent.  However, we generally keep these two parameters the same and parameterize gradients in tide ranges using the model's sub-site capabilities.

Do not forget that these "site" parameters can become "subsite" parameters by defining subsites in the set-map attirbutes mode.  Each of these parameters can be assigned to an individual polygon instead of a whole site.

Salinity Module:  

Title: Re: SLAMM Users Guide
Post by: Jonathan S. Clough on March 11, 2010, 02:12:01 PM
Most of you are probably aware that there is a more formal SLAMM Users guide here: