Hi, i have two questions regarding the bathymetry input in the coastal vulnerability model.
What is the optimal resolution for the bathymetry. For example, in earlier versions examples(claybark) the bathymetry had a 20 m resolution and in the latest it has 3500 m. Are the basic bathymetries for coarse scale modelling (450 m resolution) ok for the implementation of the model in a 100 km coastline?
Why do the bathymetry in the latest version is needed to extend to the maximum fetch distance while in previous if it was only inside the aoi there was no problem?
The results of this model are not overly sensitive to the resolution of the bathymetry. The model averages bathymetry values found under the fetch rays and uses that average depth in subsequent calculations. So the variation in a higher resolution bathymetry is lost in that averaging anyway. More details here at Equation 10 and below: http://releases.naturalcapitalproject.org/invest-userguide/latest/coastal_vulnerability.html#wave-exposure
As a general rule, I would suggest bathymetry resolution on the same order of magnitude as your choice for the model resolution. Also, in prior versions of the model and sample data, the same DEM was used for the bathymetry and above-ground relief layers. The model results are probably more sensitive to the resolution of the relief, and the sample data provided now reflects that.
I could be wrong, but I think the model has always needed bathymetry coverage underneath the fetch rays. It could be the requirement for the AOI that has changed? Anyway, please see above for why bathymetry is required.