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Input and default values

Started by rich74, February 10, 2010, 09:03:32 AM

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I am new to SLAMM and am working on a project where we want to apply the model to the North Carolina coast. I am trying to familiarize myself with the model and how it works. I have a question about how the input values for the model (swamp erosion, salt marsh vertical accretion . . . etc.) are being generated. I assume users of the model are creating their own unique values, but are there default values for the input categories that are sometimes used when there is no data available for a category and if there are default values, what is the science behind them?

I have looked in the Technical manual, user manual, and the completed samples from Florida and Washington, but have not been able to find an answer to this question. Can someone please point me in the right direction?

Jonathan S. Clough

The SLAMM erosion routine tries to estimate where marsh and swamp erosion will take place by estimating maximum fetch (wave-setup).  When the maximum fetch threshold has been exceeded horizontal erosion starts to occur.

Important note:  erosion of marshes and swamps occurs only at the marsh-water interface.  Beaches and tidal flats are assumed to be protective from erosion (though not inundation).

I recommend site-specific data based on shoreline changes maps or local data if possible.  Basically you should try to determine how many horizontal meters the shoreline is moving per year in the areas that it is receding due to erosion.  These rates can be defined in a spatially variable manner if data are available.  If not, you may have to rely on the nearest available data or regional averages.

I recommend that you play with these parameters as part of a sensitivity or uncertainty analysis as well.

The SLAMM erosion routine remains simple and has not been updated in the time that I have worked with the model (since 1998).  I am hopeful that future development of this portion of the model can take place soon.

There is no database of "default" erosion and accretion rates available at this time however I recommend the following resources for your region:

Benninger, L. K. andJ. P. Chanton. 1985. Fallout of 239,240Pu and natural 238U and 210Pb in sediments of the North River Marsh, North Carolina.  EOS 66:276.

Cahoon, D.R., J. W. Day, Jr., and D. J. Reed, 1999. "The influence of surface and shallow subsurface soil processes on wetland elevation: A synthesis." Current Topics in Wetland Biogeochemistry, 3, 72-88.

Reed, D.J., D.A. Bishara, D.R. Cahoon, J. Donnelly, M. Kearney, A.S. Kolker, L.L.  Leonard, R.A. Orson, and J.C. Stevenson, 2008: "Site-Specific Scenarios for Wetlands Accretion in the Mid-Atlantic Region. Section 2.1" in Background Documents Supporting Climate Change Science Program Synthesis and Assessment Product 4.1: Coastal Elevations and Sensitivity to Sea Level Rise, J.G. Titus and E.M. Strange (eds.), EPA430R07004, Washington, DC: U.S. EPA.

(For a wider perspective) Stevenson and Kearney, 2009, "Impacts of Global Climate Change and Sea-Level Rise on Tidal Wetlands"  in Human Impacts on Salt Marshes a Global Perspective.2009 University of California Press.