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Topics - Elena V

I recently noticed that accretion is not occurring as expected in areas defined as "freshwater influenced."

I first ran my model with an inverse linear relationship between accretion and elevation (low = 2 mm/year, high = 6 mm/year) in a region that was "freshwater influenced". All categories without the empirical relationship were assigned accretion of 3 mm/year.

Then I ran the same model, but with 2x the accretion rates and found no difference between the model outputs within the region of freshwater influence. There were differences outside the freshwater region.

To confirm, I ran the low/high accretion scenarios without freshwater influence and saw a major difference.

Am I implementing the freshwater influence module incorrectly? Or is it just a bug since this option is still relatively new in SLAMM?
Hi again,
Based on my understanding, the Elevation Analysis only uses global water level parameters to assess the vegetation/elevation relationship. Are there plans for future SLAMM versions to run this analysis using spatially varying MTL-NAVD, Salt Elev, and GDTR? This would be helpful in systems where there is tidal damping.

I know a lot of WPC's studies have used spatially varying tide ranges - how did you assess the compatibility of your changing tide ranges with the topography? It would be neat to be able to run the Elevation Analysis on a specific sub-site where the parameters are being modified from the global value.

The Tech Doc (6.2) says the following habitat-switching function is implemented when an area of freshwater influence is specified:

Swamp --> Tidal Swamp --> Tidal Fresh Marsh --> Irregularly Flooded Marsh

However, according to the Tech Doc the default lower elevation of the first three habitats is the salt elevation. Are the defaults different when freshwater influence is specified? Or do they simply switch once per timestep?

And a sidenote - if I do want to change the lower elevation, can this be done in the user interface or should I run SLAMM from the command line? Is editing the value in the Elevation Analysis window sufficient to change the minimum elevation for model runs?

thanks once again!
A few questions about implementing accretion feedback curves:

1. Timestep: I was expecting to run at a much smaller timestep because of the feedback between two variables, but when I ran the same model with 10- and 5-year timesteps I saw only very slight differences. Is SLAMM tracking elevation/accretion between timesteps? Or am I running the model incorrectly? If "Use Model" is set to True, this overrides the constant accretion rate specified above, correct? I'd expect that with a large timestep, a low-lying wetland cell would accrete very rapidly for the long timestep, overshooting and reaching a much higher elevation by the next timestep.

2. Wetland Types: Is there a reason this model is only available for four habitat types (Irreg Flood, Reg FloodTidal Flat, Tidal Fresh)? Are those categories actually generalized and include multiple SLAMM habitats? Seems like you would want to have the option for Transitional Salt Marsh and maybe Swamp/Tidal Swamp/Mangrove?

3. Are there any published examples of this model being implemented? I am selecting a reasonable low and high value and assuming an inverse linear relation between elevation and accretion.

I'm using SLAMM 6.2 beta.
Using SLAMM / Save a copy of model inputs
August 05, 2013, 03:10:52 PM
Is there a capability in SLAMM that automatically saves a copy of the inputs (not the source files themselves, but the file paths), site parameters, and execution options?
Hi again,
I'm using SLAMM version 6.2 (which has some really neat new features!). I just ran an elevation analysis on the same input data as I was using in version 6.1 and it looks like the value corresponding to "no data" (-9999 in this case) might now be included in the elevation analysis. This mainly shows up in the results for the dry land categories (the mean elevation is ~ -6000 m NAVD) since these areas are at the edges of my study area where I don't have topo data.

Just wanted to confirm that this is what's happening because I want to be aware of any skew it might be introducing to the other veg categories (where there are fewer "no data" points so it might not be as obvious).
According to my understanding, Ocean Beach (12) converts to Open Water Subtidal (17) if the elevation drops below MLW, which should then convert to Open Ocean (19) if connected to the ocean in the offshore direction and within 500 meters of the ocean. The offshore direction is set as South. I've attached an example of a (very initial) input/output habitat layer at one my sites (the mouth of the Ventura River in Ventura, CA) as well as the input topography.

Why do some cells clearly connected to the ocean convert to Open Water Subtidal while others convert to Open Ocean? I see this in my other sites as well.

Other comments:
- I am using v6.1 beta
- Bruun erosion is disabled for Ocean Beach erosion
- Using a 10 year time step
- All erosion parameters are set to 0.2 m/yr and accretion to 1 mm/yr
- Overwash is disabled

Please disregard the names of the habitats in the legend -- they don't match directly with the official SLAMM names as we've adapted them to our habitats.

Model Formulation & Parameters / ocean beach erosion
December 09, 2012, 09:14:15 PM
1. In version 6.1 beta, is there a way to specify an erosion rate for ocean beach? As I mentioned in another thread, the Bruun rule was over-predicting beach erosion, so I have stopped using it. I have done fairly extensive shoreline change analysis for my study area in southern CA, and I would like to incorporate those values into SLAMM. It would be ideal if there was another parameter called "Ocean Beach Erosion" that let me put in the erosion rates I've calculated using historic shorelines.

2. If the Bruun rule is turned off, is there any default erosion occurring for ocean beach? Or is the change I'm seeing solely due to sea level encroaching on the beach?

I see that there's a Beach Sed Rate, which I guess I could use to counter erosion in areas that are accreting by assuming a representative beach geometry in each subsite...

Using SLAMM / Bruun rule and beach erosion
November 15, 2012, 04:12:53 PM
In some of the SLAMM documentation I read that the Bruun rule for ocean beaches is optional in SLAMM. How do I implement this optional rule? Also (this may or may not be related), I'm noticing that all the beaches in my study area disappear in 2020 for all my model runs, even when my input erosion rates are low (0.2) and wouldn't account for that much erosion by 2030. The beaches are present in the 2005 and 2010 maps, which makes me think this is not a conflict between the SLAMM map and topography.