I am trying to update the choropleth layer on top of a leaflet map in D3. However, when it is animated the base map "flashes" as it updates as well. I suspect there is a way to only update the choropleth layer, but didn't have much luck.
This is an example where a polyline is revealed and the base map is unchanged: https://bl.ocks.org/gwene/f3929040cca81742c29af297efeda7ab
However, the map.getPanes().overlayPane does not work.
My code and animation is here: https://observablehq.com/@tommlogan/resilience-florence