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Started by YUROK1, April 22, 2015, 05:21:14 PM

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I have recently located some local uplift data showing a range   of .1 to 1.0 mm/year here in Klamath CA. I do not have a layer representing this value and I am wondering how I can use the historical Trend Parameter to increase the accuracy of the model?  Would you recommend that I use an average, .5 mm/year, in the Historical trend box? 

Jonathan S. Clough

Hello and welcome to the SLAMM Forum.

This would be a misinterpretation of the historical trend parameter, though you are correct that it can be related to local subsidence.

The historical trend parameter was designed to accept data from local NOAA gauges measuring long term SLR trends.  This input would then be compared to eustatic long term SLR trends.  If you assume a global (eustatic) historic trend of 1.7 mm/yr global historic trend based on IPCC (2007), then a site with no local subsidence or uplift or other local factors affecting SLR (water temperatures or regional weather patterns) would be expected to have a historical trend that is also 1.7.    Please see equation (2) in the Technical Documentation..

In other words, in SLAMM 6.2, if you add a historic trend parameter of 1.7 mm/year then local and global SLR would be assumed to be equal in projections.

If you have uplift of 0.5 mm/year in your location then you would expect a local gauge to have registered a long-term SLR of closer to 1.2 mm/year.  Therefore, if you want to reflect uplift of this extent you should use that value in the parameter.

I hope this is useful.  -- Jonathan


Thanks for your reply, Does using an uplift raster in the file setup offer any advantages over using an adjusted historical trend?

Jonathan S. Clough

The advantage to the uplift raster is the capability to model spatially variable uplift on a cell-by-cell basis, if you have that type of data.  Otherwise using the historical trend parameter (that can be varied by "sub-sites" that are polygons drawn within the study area) will give you the same results.  Best -- Jonathan


If I were to use the Historical Trend parameter, how does this effect the SLR scenario that is chosen(execution options)? Is a custom rate then required?

Jonathan S. Clough

The local historic trend is compared to the global trend and global SLR scenarios are adjusted into the future ("localized") based on the difference between the local historic trend and the global trend.  Therefore, any eustatic SLR projection may be used.