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Messages - Elena V

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 / Re: Bruun rule and beach erosion
December 09, 2012, 08:52:51 PM
I installed the updated version you sent me, and I no longer have the problem of the beach disappearing in 2030. It still disappeared when I kept the "use Bruun rule" box checked, so that was indeed the problem. I have some follow up questions but I'll start a new question. Thanks a lot!
Using SLAMM / Re: Bruun rule and beach erosion
December 03, 2012, 01:27:51 PM
Unfortunately I'm not using the overwash function (frequency of overwash = 0), so I don't think that could be causing the beach to disappear.

Thanks for the files - I'll get the new version installed and respond with what I learn. Thanks!
Using SLAMM / Re: Bruun rule and beach erosion
November 30, 2012, 07:30:52 PM
Thanks for the quick response! I do not see the "Use Bruun Rule for 'ocean beach' Erosion" button on the execution screen (see attached screenshot). I'm using version 6.0.1 beta -- is this the wrong version to be using? I thought this was the most up-to-date version.

According to the elevation analysis, essentially all of the "Ocean Beach" elevations are above minimum elevation for Ocean Beach (see attached figure), so I don't think that's what's causing the erosion...

On the other hand, I'm not sure that the Bruun rule is causing this either. According to the output .csv file there is 0.26 meters of SLR by 2030. The Bruun rule would cause 100*0.26 meters = 26 meters erosion, right? In some places the beach is eroding >200 meters between my 2010 and 2030 output rasters. At least half of this beach is well above the highest observed water level.

Is there something else that might be causing this?
Thanks for your help!
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.