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Using SLAMM / changes in wetlands categories
Last post by azarcos - June 25, 2020, 09:59:35 AM

I am modelling the initial conditions for time-zero and I found some issues in the wetland's conversion. My initial land cover (based on Lidar data) starts with the categories: Dry land >> Transitional >> Irregularly flooded >> Regularly flooded >> tidal flat. I assumed a scenario of protection for all dry land.

The final land cover (after time-zero) ends with the categories: Dry land >> Transitional >> Irregularly flooded >> Regularly flooded >> tidal flat >> Estuarine Open Water.
I have a very significant loss of the transitional marsh and a significant gain in estuarine open water category. There are almost no changes in the Regularly flooded and Irregularly flooded categories.
According to the manual changes in the transitional marsh should be expected "when it falls below its lower elevation boundary, this category generally converts to "Regularly-Flooded Marsh. (...)"
Any idea about what is happening with to the transitional marsh and Estuarine Open Water?

Using SLAMM / Viewing MLLW, MTL, MHHW on the...
Last post by JackieRaw - June 23, 2020, 02:09:23 AM
Hi SLAMM forum  :) ,

I am hoping you will be able to help me. 

When I view the map from the "Set Map Attributes" tab, select 3D graphing and view MLLW, MTL, MHHW on the map, the MLLW is not visible.
I know that changing the MTL = 0 correction as well as the GT (great diurnal tide) changes this, but when I use the known values for these parameters it still does not work. 
As I am working with an estuary, I have figured out that I will have to change the MTL correction for the upper reaches (as compared to the estuary mouth). Currently the DEM is relative to a land levelling datum so there are elevation values for the estuary surface. The difference between the land datum and the MTL at the nearest tide gauge is 0.204 m. And the GT at the estuary mouth is 1.6 m.

So I think my questions is - is it okay that I can't see the MLLW on the map viewer, or does this mean that SLAMM thinks the estuary is empty at MLLW? Should I try to change the MTL correction so that MLLW is visible, or is it more important that the MHHW is correct. I am quite confident in the tide ranges along the estuary as they come from in-situ water level recordings. 

I also wanted to know whether it is possible to get a map of the MLLW, MTL, and MHHW for the whole study site as an output. I have seen the option to save inundation maps from the "Execute" window, but I am not sure this is exactly what I am looking for.


Using SLAMM / Re: Model calibration
Last post by Jonathan S. Clough - June 22, 2020, 08:28:52 AM
Hi:  The SLB files are a SLAMM Binary format, not readable by GIS.  You need to either re-run and export to non-binary format (ASCII Rasters readable by ESRI and QGIS) or convert the binary files.

See the users manual, page 14-15 under "Data to Save" (GIS files options on the file execution screen) to do the former. 

To convert the binary files go to SLAMM File Setup and click the "Conv Binary Files to ASCII" button.  You can then drag the SLB file to the interface and it will convert to an ASCII Raster.

The output CSV is indeed in hectares,  (an embarrassing omission from the users manual!)

Best regards -- Jonathan

Using SLAMM / Re: Model calibration
Last post by azarcos - June 18, 2020, 05:44:27 AM
Dear Jonathan,

Thanks for your reply and advices, will do. The inundation files are the ... _Inund_Freq_GIS.SLB. How do I open these rasters?

At the end of the simulation a csv file is generated, named with the start and end date, and containing the summary of the modelled scenario. Are the values distributed in columns for each category in ha?

Using SLAMM / Re: Model calibration
Last post by Jonathan S. Clough - June 16, 2020, 06:22:33 AM
The time-zero run is a very important step.  To the extent possible, it should not be any different than the model's initial conditions.  It tests that the conceptual model, the wetland coverage, the elevation data, and the tide range data are all consistent.  In the results the initial condition is shown as "0" and the "time zero" result is shown as the first date of the simulation.

From the tech doc:
SLAMM can also simulate a "time zero" step, in which the conceptual model can be validated against the data inputs for your site. The time-zero model predicts the changes in the landscape given specified model tide ranges, elevation data, and land-cover data. Any discrepancy in time-zero results can provide a partial sense of the uncertainty of the model. There will almost always be some minor changes predicted at time zero due to horizontal off-sets between the land-cover and elevation data-sets, general data uncertainty, or other local conditions that make a portion of your site not conform perfectly to the conceptual model. However, large discrepancies could reflect an error in model parameterization with regards to tide ranges or dike locations, for example, and should be closely investigated.

I would suggest setting up the model to run for a couple of years (photo date, photo date + 1, photo date + 1) with minimal or zero SLR.  Any changes predicted should be understood as much as possible in terms of data error (issues with the tide model, DEM, or wetland coverage), lack of dike or seawall accounting, etc.  You should also examine the inundation frequency maps to ensure that the wetlands are being regularly wetted.  You can consider using the results from the time-zero run as your initial condition for your projection runs to ensure that the effects that you are seeing in the simulation are from the SLR signal and not uncertainty or lack of precision in your input data sets.

Sorry about the long delay in response.  -- Jonathan
Using SLAMM / Model calibration
Last post by azarcos - June 02, 2020, 04:27:05 AM
Hi Jonathon,

I am new to SLAMM. I want to conducted model calibration by running the "time zero" step, following the same methodology in Clough et al. (2016). I know already that no sea-level rise, accretion or erosion should be considered, but I am not sure about what to introduce in the last year of simulation. For how long should I run the model?
In the SLR scenarios to run' should I apply 0m by 2100? Can you please provide more details on the calibration procedure?
Thanks for your help

Using SLAMM / Re: Run the model using Classi...
Last post by Jonathan S. Clough - April 27, 2020, 07:22:05 AM
Yes, it's the first question you are asked when creating a new SLAMM simulation.

"Use California Categories?"  Answer "no" to use "classic" SLAMM categories.

Using SLAMM / Run the model using Classic SL...
Last post by SAM - April 25, 2020, 08:22:01 PM
Dear Jonathan,

Is it possible to run the model in SLAMM 6.7 using classic SLAMM categories?
Here are some references:

Start Date End Date Rate Source N
1900 2000 1.7 mm/year +-0.5 IPCC 2007a §
1961 2003 1.8 mm/year +- 0.5 IPCC 2007a §
1993 2003 3.1 mm/year Grinsted et al. (2009).  Historical Data
1993 2003 3.3 mm/year Grinsted et al. (2009).  Satelite Altimetry

Also see

So maybe assume 1.8 mm/year from 1948-2003 and then 3.3 mm/year from 2003-2015?  So something like 2.1 mm/year for 1948-2015 perhaps?

There may be some newer references-- I haven't done a literature search recently.
Model Formulation & Parameters / Re: Historic Trend and Histori...
Last post by SAM - April 14, 2020, 11:36:46 PM
Thank you Jonathan for your informative reply.

The time period in my region given by the tide gauge station is from 1948 to 2015.
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