Floodplain hectares beside each segment, from a catalog item's floodplain
Source:R/floodplain_ha.R
knw_floodplain_ha.RdThe stac-floodplains-bc catalog publishes, per watershed group, a whole-network
floodplain (all_ff04) and its attribution by blue line
(all_ff04_by_blue_line_key): exact 30 m BC Albers cells, each blue line
claiming the cells of its own valley, so the claims overlap where valleys
meet. This rasterises all_ff04 on that same 30 m grid (no reprojection; the
cell count times 0.09 ha reproduces the polygon's area), takes the blue-line
polygons as the claims, and gives every floodplain cell one owner with
flooded::fl_valley_join(): the nearest segment among the claiming blue lines'
segments (nearest, one owner per cell, so hectares add up). Each segment's
hectares are its cells times 0.09; graded hectares are hectares times the
segment's grade, so 500 ha beside grade-0.9 habitat is 450 and the same 500 ha
beside grade-0.3 habitat is 150.
Arguments
- gpkg
character(1)the item'sfloodplain.gpkg.- segments
an
sfof the group's link segments in EPSG:3005 withid_segment,blue_line_key, logical flag columnsflags, andgrade.- flags
characterthe logical columns (habitat under each rule,accessible) to carry;fl_valley_join()takes logical columns only.- scenario
character(1)the floodplain layer and the attribution layer's prefix.
Value
A list: segments, segments with fp_ha and fp_graded_ha added;
summary, one row per flag: hectares beside segments where the flag holds,
graded hectares, and hectares by grade class; check, fl_valley_join()'s
cell accounting plus the polygon area and the raster's area in km².
Examples
if (FALSE) { # \dontrun{
seg <- sf::st_read(conn, query = "SELECT id_segment, blue_line_key, geom FROM fresh_default.streams
WHERE watershed_group_code = 'LARL'")
seg$rearing_default <- ...; seg$rearing_tuned <- ...; seg$grade <- ...
fp <- knw_floodplain_ha("larl_floodplain.gpkg", seg, c("rearing_default", "rearing_tuned"))
fp$summary
} # }