River Runner uses US Geological Service data in combination with Mapbox to let a the user click on any location within the continental United States and then follow how rain falling on that location traverses to its end point.
The code for the site is available on github.
This uses USGS NHDPlus data and their NLDI API to visualize the path of a rain droplet from any point in the contiguous United States to its end point (usually the ocean, sometimes the Great Lakes, Canada/Mexico, or another inland water feature). It’ll find the closest river/stream flowline coordinate to a click/search and then animate along that flowline’s downstream path.
I’ve used mapbox to animate the downstream path, but needed to make all sorts of adjustments for elevation and bearing changes to prevent jerkiness/nausea (just moving from point to point feels a little like flying through turbulence while shaking your head side-to-side).
I’ve hosted a dataset with NHDPlus Value Added Attributes on Firebase, which allows me to group flowlines into their parent features and determine distances quickly.