How to simulate river level rise in R - r

Question

I need to make a simulation to see what areas would be affected if the sea level rises in X meters. Could anyone give me tips were to start? I've search for tools embedded in the google maps API but didn't find any workaround.
The idea is to create a function such as this:
isAffected <- function( coordinate, metersRised)
---- return True if it is affected, false otherwise
Thanks in advance!

Answer 1

First reaction is I can't see there being any quick straightforward solution with off the shelf R libraries/data sets on top of which to build a function like that. Second is wondering if you'd like to model it or rely on already developed products, or something in the middle. The most rigorous would be applying a hydrodynamic model and the other bookend is sampling someone else's grid of anticipated results.
Just for context, For river level affected by sea level rise near the coast, you may want to consider variable river stages if they vary quite a bit. If the rivers are running high due to recent storms or snowmelt events, it will worsen flooding from sea level rise alone. So maybe you could assume a limited number of river heights (say rainy season - high, dry season - low). Tides complicate things too, as do storms and storm surge - basically above average ocean heights due to the temporary very low pressure. An example worst cast scenario with those three components is, how much of x city (regional coastline) would be flooded, say New Orleans or Australian coast, during storm surge, a high tide, and the local river very full from spring snowmelt, with 5 feet more extra sea level added, so lots of data needs to consider - eg you may want some sort of x,y,z data for those river height assumptions. Lots of cities have inundation maps where you can get those river stage elevations. The bigger the sea level rise assumption, the less the rivers might matter. Eg, a huge sea level rise scenario could easily inundate the whole city as it is today, no matter how high the river is, with the mouth of the river moving miles inland.
Simplyifying things, I'd say the most important data will be the digital elevation model (DEM), probably a raster file of x,y,z coordinates, with z being the key piece - the elevation of a pixel at every xy location above some certain datum. Higher resolution DEMs will give much more detailed and realistic inundation. Processed LiDAR data is maybe ideal - very high resolution data that some else has produced - raw LiDAR data is a burden. There's at least some here for New Zealand - http://opentopo.sdsc.edu/datasets - but I'm not sure of good warehouses for data outside the US.
A basic workflow might be, decide what hydraulic components you'll consider and how many scenarios. Eg, you'll ignore tides by using an average sea level and have just two sea level rise scenarios, and assume the river is always at __ feet, or maybe __ ft and __ ft. Download/build DEM, and then add your river heights to the digital elevation model (not trivial, but searching GIS Stack overflow a good start). That's a reference baseline elevation to combine sea water with. With an assumption of sea level rise, say 10 feet, that's incorporated into another DEM, one approach is raster math centric, subtracting one from the other and the result will show the new inundation areas. Once you've done the raster math, you could have a binary xy grid with either flooded or not flooded, to apply that final xy search function: is xy 1 or 0, but by far the trickiest part is all before that. There's maybe more straightforward or simplified approaches, but the system is so dyanmic so the sky is the limit for how complicated your model will be. Here's more information on the river component, that might help visualize the river starting points to which you'll add your sea water scenario(s) https://www.usgs.gov/mission-areas/water-resources/science/flood-inundation-mapping-science?qt-science_center_objects=0#qt-science_center_objects
The library raster might be a good start, that will read in downloaded raster/grid files, like .tif, and also perform the raster math you'd need - adding/subtracting same size rasters together. Or forgetting all this processing, maybe you could just read in pre-processed rasters of such scenarios done by others, then do your search on them. There's probably a good number for certain sea level rises, but it just gets much trickier if you want to assume both sea level and river elevation scenarios.