Hi 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? Thanks
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.
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?
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
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