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SLAMM sensitivity to Salt Elevation

Started by jmkassak, March 15, 2011, 11:13:39 AM

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In testing the sensitivity of SLAMM to the salt elevation parameter I came across a situation that I'm having trouble understanding. At our tropical site, we had been using a salt elevation of 0.325 m above MTL and a GDT of 0.05 m. To test the sensitivity of the model to salt elevation, we reduced it by 25% to 0.244 and ran the model again to compare our results in 2100.  As expected, as compared to the base run, we saw increases in most fresh habitats and much less mangrove creation, as fresh habitats were now allowed to persist to a lower elevation.  However, the majority of the decrease in area of mangroves created was offset by a large increase in the amount of estuarine water created. I cannot understand how this would have happened.  (It was not because more inland open water was turning into estuarine water, and it clearly appears to be an issue of area once converting to mangroves now instead converting to estuarine water).

Any ideas?


Jonathan S. Clough

Nothing obvious off the top of my head...

Two questions, are you using the elev. pre-processor in these sites?

Can you send me some maps of these results to help me visualize what is going on?

Thanks -- Jonathan


Hi Jonathan,

We are not using the pre-processor here, but did make some alterations to the conceptual model as follows:

•   Tidal Fresh Marsh – changed to 40 percent of salt elevation.

•   Tidal Swamp -  changed to 40 percent of salt elevation.

•   Inland Fresh Marsh – changed to 50 percent of salt elevation.

•   Irregularly Flooded Marsh – Due to the unique tidal regime that characterizes the estuary, traditional "Regularly flooded marsh" that are inundated and exposed on a daily basis do not exist as they do in other east coast estuaries. We allow this habitat type to persist to the mean tide level (i.e., 0 meters relative to MTL=0) at all sites.

I did not create maps for this run, but could send you the tabular results.  Would that be helpful?


One more point.  It is interesting to note that from 2004 - 2060 the difference between the amount of estuarine water in our base run and our revised SE run are negligible (i.e., most of the difference in mangrove area is accounted for my increases in fresh water habitats).  It is in 2070 that we suddenly see over 1,000 ha more Estuarine water than we did in the base run, as though some sort of threshold is being crossed between 2060 and 2070.