Great project! I’m interested in adjusting some settings in the hydrology of the Sandbox (I’m working on describing trying to describe various flood risk and management aspects with the Sandbox) and I am keen on getting into the hydrology side of things (I want to see how you could implement surface roughness amongst other things). I was wondering if you have a published model of the shallow water equation solution that you’re using that you could link? And where do your epsilon and attenuation come into it?
The paper on which the water simulation is based is referenced in the AR Sandbox project page. The epsilon value going into flux and derivative calculation is explained in that paper.
Attenuation is my addition; it’s a simple way to remove energy from the water mass over time. For serious hydrology applications you want to replace that with a proper (bedding) friction term, which would include surface roughness as one parameter. There’s a simple friction term that has been evaluated against gauge data from the 1959 Malpasset dam failure in this SIAM presentation by Andre Brodtkorb.