1. "ASTER DEM standard data products are produced with 30m postings, and have Z accuracies generally between 10 m and 25 m root mean square error (RMSE)." I'm afraid that that Z accuracy is not going to be compatible with modeling the effects of 1-2 meters of SLR on marsh systems. You will need LiDAR or ifSar. I would say you wouldn't want a vertical RMSE of above 25 cm.
2. In US applications we get MHHW and MLLW data from NOAA gauges. You can use whichever type of tide gauge or water level monitoring data that you have available -- long term data are best.
3. The SLAMM model usually assumes that tidal flats have a lowest elevation at MLLW. That means that you would need aerial imagery that is tidally coordinated (taken at low tide)
i got 2 queries, 1. how to produce NWI data ( i was looking for a more clear answer as i am not that expert in GIS)? 2. If I use ASTER GDEM data other than LiDAR, will I face any problem with my result?
Last post by rodlammers - May 22, 2019, 09:05:38 AM
Thanks for the reply. I have soil saturation turned off, the dike layer is correctly rendering in the "Set map attributes", and I'm defining the entire area protected by dikes.
I've sent you an email with some screen shots showing my execution options, the dike layer rendering, and the output showing land cover change even in the diked areas.
A potential work around to this problem is changing the diked areas to "Developed Dry Land" and running the simulation with the "Protect Developed Dry Land" option. This takes some additional pre-processing and post-processing of the rasters but it does work.
SLAMM actually tracks partial conversions of cells over time -- it was originally created many years ago when computers were much less powerful and cell sizes were therefore much larger (150-500meter). For this reason it has always tracked multiple land types in each cell. For this reason the tables of output are not always precisely what you would get when adding up the area of the raster maps. After erosion to tidal flat, the elevation of the cell would be set to the elevation of the flat or MTL if there is no adjacent flat.
Last post by rodlammers - May 15, 2019, 12:24:51 PM
I'm running some simulations of SLAMM with and without the classic dike layer (specifying land protected by dikes). Aren't these dikes supposed to keep land cover from changing? Per the technical guide: "In the traditional model, if a cell is defined as protected by a dike or levee it is not permitted to change."
When I run the simulations, land cover is changing even in cells protected by dikes. If I compare this diked-scenario with the same simulation but with dikes turned off, the only differences between the two results are in areas "protected" by dikes. So clearly the dikes are having some effect on land cover change, but not the effect I expected. I thought they would completely prevent any land cover change in the diked area.
Am I incorrect in my interpretation of how the dike layer works? I'm using the most recent version of SLAMM (6.7 beta).
So glad you solved the problem! I will make a note for the next version to override the Windows settings so that a decimal point is used in either case, so this does not pose a problem in future versions. Thanks -- Jonathan