More NHDPlus with GRASS GIS

Here is the flow accumulation grid from the NHDPlus dataset

Here, I take the log of the accumulation again:

r.mapcalc 'log_fac=log(abs(fac)+1)

Extract the streams and convert them to vector:

r.mapcalc 'inf_rivers=if(log_fac>6)'

r.thin input=inf_rivers out=thin_rivers

r.to.vect -s thin_rivers out=inf_rivers