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Salt Elevation

Started by cpapiez, September 07, 2010, 11:32:16 AM

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cpapiez

Jonathan,

How do you calculate the salt elevation parameter?  Is it MHW or MHHW minus the MTL?  So far the model outputs are looking good with the LiDAR and new accretion calculation...its great to have a comparison (Maryland NWF study) to see the differences you've made to the model.

Thanks!

Chelsie

Evan Larson

We typically multiply the GT by the percentage of MHHW where water reaches at least once every 30 days, and divide by 2.  So, for the Chesapeake Bay region -- where this percentage is around 133% -- the calculation would be (GT)(1.33)/2.

I hope that answers you question.

Evan

cpapiez

Thanks for clarifying Evan.  I have one additional question about the NWI breakout for the NWF study.  What is the description of Riverine Tidal wetlands?  It's listed in the final wetland conversion chart but I can't find a description for it.  We used the same NWI breakout so a description would be super helpful.

Thanks,

Chelsie

Jonathan S. Clough

Which final wetland conversion chart?  Do you mean Riverine Tidal Open Water?

cpapiez

The wetland classification is in the National Wildlife Federations SLAMM report for the Chesapeake Bay.  We used the same NWI breakout as them and I just want to know what the "Riverine Tidal" class is.  I believe Jonathan ran the model for NWF so maybe he knows what "Riverine Tidal" is.  It may not be a wetland type but rather a form of water body.  Here's the link to the report:  http://cf.nwf.org/sealevelrise/pdfs/sealevelriseandcoastalhabitats_chesapeakeregion.pdf


Evan Larson

We treat Riverine Tidal as open water.  Jonathan may be able to further clarify our definition.

Evan

cpapiez


kfreeman

Quote from: elarson on September 07, 2010, 11:49:38 AM
We typically multiply the GT by the percentage of MHHW where water reaches at least once every 30 days, and divide by 2.  So, for the Chesapeake Bay region -- where this percentage is around 133% -- the calculation would be (GT)(1.33)/2.

I hope that answers you question.

Evan

The technical documentation states that the salt boundary is defined as the elevation that is inundated by salt water less than every 30 days.  So, as an example, if I download tide data from NOAA and calculate that elevation to be 1.1 meters, I would then put 1.1 in as the Salt Elevation parameter.  The formula stated above is different than what is in the documentation.  Would you please clarify the calculation for salt boundary?  If there is more than one method, how does one choose what is most appropriate?

Jonathan S. Clough

The formula, as an estimation procedure, was essentially derived from the type of analysis that you are discussing.  We can tie this to MHHW in many locations.  For the Chesapeake, based on "frequency of inundation analyses" the elevation inundated every 30 days is approximately 133% of MHHW.  We therefore use this formula throughout the site. 

See page 107 of http://cf.nwf.org/sealevelrise/pdfs/sealevelriseandcoastalhabitats_chesapeakeregion.pdf

This estimation of salt elevation as a function of tide range can then be used in areas where real-time tide data are not available.  It doesn't take into account the differential effects of wind tides, however.

-- Jonathan

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