Explain the new rio-shapes logic better.
Explain the new rio-shapes logic better.

njwilson23/rasterio,njwilson23/rasterio,clembou/rasterio,youngpm/rasterio,njwilson23/rasterio,kapadia/rasterio,brendan-ward/rasterio,brendan-ward/rasterio,youngpm/rasterio,perrygeo/rasterio,kapadia/rasterio,perrygeo/rasterio,brendan-ward/rasterio,clembou/rasterio,youngpm/rasterio,johanvdw/rasterio,perrygeo/rasterio,kapadia/rasterio,clembou/rasterio,johanvdw/rasterio,johanvdw/rasterio