SLAMM Forum

General Category => Model Formulation & Parameters => Topic started by: hachinamio on June 12, 2015, 08:03:18 PM

Title: Erosion and Accretion rates
Post by: hachinamio on June 12, 2015, 08:03:18 PM
Hi all,

I have a question about erosion and accretion rate. Are they (erosion and accretion) always taken into account no matter a cell is inundated by SLR or not, right? or they are only taken into account when a cell is inundated?

Thank you very much.
Title: Re: Erosion and Accretion rates
Post by: marco.propato on June 15, 2015, 06:54:42 PM
Both Technical Documentation and User's Manual have lots of information that may help in answering many questions.

Erosion: As it is written in the technical documentation: "Erosion is only predicted to occur at a land-cover to open water interface".

Accretion: the cell accretes no matter inundation. However, if accretion is defined on a cell covered by marsh and this is not inundated then the overall model land-cover, elevation and tides may be at least questionable.

Title: Re: Erosion and Accretion rates
Post by: hachinamio on June 18, 2015, 02:12:17 PM
Hi Marco,

Thank you very much for your response.
Based on the technical documentation, "Erosion is only predicted to occur at a land-cover to open water interface... The marsh erosion parameter pertain to the interface between open water and regularly- and irregularly-flooded marshes as well as transitional marshes.", in my simulation, Irregular.Flooded Marsh is adjacent to Open Water. The obtained results show that Irregular.Flooded Marsh is always inundated and converted to Regularly.Flooded Marsh then converted to Tidal Flat (this conclusion is drawn based on the table 3, showing that Inundation occurs dominantly) even though I already set 0.14m, or 1, or even 10m for erosion rate of marsh, this also means marsh erosion rate is not taken into account. I did try many cases, moved irreg. Flooded marsh to higher or lower elevation and other positions, but it's still inundated and converted to Regularly.Flooded marsh after simulated. I'm wondering whether the problem is my input data or SLAMM because I've read a lot of topics related to this problem in the forum. Thank you very much.

PS: My DEM resolution is 1m.
Title: Re: Erosion and Accretion rates
Post by: marco.propato on June 18, 2015, 02:47:46 PM
There was a recent discussion about this topic that may be helpful to your problem also. In any case, one reason that observed marsh erosion is limited may be due to the fact that when marsh is eroded, land cover is converted to tidal flat. As a result, the marsh behind will not be connected to open water, and thus not eroding anymore, until the fringe of tidal flat is gone (permanently submerged or eroded away). So you may want to increase tidal flat erosion rate or change the code as suggested in the erosion issue discussion I was mentioning above.
Title: Re: Erosion and Accretion rates
Post by: hachinamio on June 25, 2015, 10:01:23 PM
Thank you Macro.
I think I may not increase tidal flat erosion rate as well change the erosion function of marsh to open water instead of tidal flat, this is not reality although this is a possible solution to manage erosion problem so far. I think the best solution is that marsh erosion rate should be taken into account within the tidal range rather than be adjacent to open water, erosion should be trigger under the effects of tidal (including SLR).