Lithology

Geologic maps and channel statistics by rock type. The statistics come from lsdtt3; these commands draw them:

lsdtt3 run	What it writes	Command
lsdtt-fetch-lithology	<prefix>_macrostrat_units.fgb (Macrostrat geologic map)	— (input to the runs below)
lsdtt-chi-analysis with lithology_fname	k_sn by lithologic unit, <prefix>_lithology_code.tif (write_lithology_code_raster)	lsdviz3-ksn-by-lithology, lsdviz3-lithology-map
lsdtt-chi-analysis with erosion_rate_fname	erodibility calibration (erosion rate against k_sn)	lsdviz3-erodibility-calibration
lsdtt-channel-network-analysis with lithology_fname and channel_bearing_group_by: lithology	bearing and junction-angle statistics by unit	lsdviz3-channel-bearings --group-key lithology (Channel networks)

All three lithology commands accept --unit-colours: a name,colour CSV, or a JSON {name: colour}, fixing each unit's colour by name. Use the same file for every figure of a study so a unit has one colour throughout.

Lithology map (lsdviz3-lithology-map)

pixi run lsdviz3-lithology-map --codes runs/site_lithology_code.tif \
  --dem runs/site_DEM.tif --out figures/site_lithology_map.png

Draws the unit code raster with a legend of unit names, a credit line for the geologic map and the DEM, a scale bar and a north arrow. By default the unit colours are semi-transparent over a hillshade of --dem; --no-hillshade draws flat opaque colours.

• Unit names are found next to the code raster (<prefix>_lithology_units.csv, then the chi k_sn tables), or given with --names (a code,name CSV) or --crosswalk. A unit with no name stops the plot with a message: lsdtt3 writes an empty name for map polygons whose lithology field is empty, so give such a unit a name with --names.
• Channels: --channels overlays a line or point vector, or the chi lithology node CSV (*_chi_ksn_lithology_nodes_mn_*.csv), in one colour, by stream order (--channel-order-column), or by k_sn (--channel-color-by k_sn, which mutes the geology). --network-status draws a channel-network-analysis run's whole network, analysed links thick.
• Regions: --regions outlines region polygons (e.g. physiographic provinces), named by --region-field.
• --hide-unmapped leaves unmapped cells out; --legend-title, --legend-columns, --transparency, --relief and the shared style flags control the look; --credit, --attribution, --dem-source or --no-credit set the credit line.

k_sn by lithology (lsdviz3-ksn-by-lithology)

pixi run lsdviz3-ksn-by-lithology --data-dir runs --prefix site_chi \
  --m-over-n 0.45 --out-dir figures

Reads the lithology tables of a chi run and writes, prefixed <out-prefix>_:

File	Contents
ksn_hist_length.png	Length-weighted k_sn histograms per unit
ksn_hist_count.png	Node-count histograms per unit
ksn_box.png	Per-unit box plots with sample sizes
reach_ksn_box.png	Per-reach k_sn, when the reach table exists
ksn_unit_basin.png	Unit-by-basin dots, when that table exists

--order sets the unit order (auto, median, reach_median, code, name, length); --layout overlays the histograms (up to 6 units by default) or draws them as facets; --raw plots raw length or count instead of each unit's fraction; --box-source takes the boxes from the per-node values or the summary quartiles.

Before reading a difference between units as an erodibility contrast, check the caveats lsdtt3 prints with these tables: a knickzone crossing a unit, or strike-parallel drainage that puts a unit mostly at channel heads, moves its k_sn for reasons other than rock strength.

Erodibility calibration (lsdviz3-erodibility-calibration)

pixi run lsdviz3-erodibility-calibration --data-dir runs --prefix site_cal \
  --m-over-n 0.45 --out-dir figures

For a chi run given basin-averaged erosion rates (erosion_rate_fname), this draws <out-prefix>_erosion_rate_vs_ksn.png (erosion rate against k_sn on log axes, with lsdtt3's fit) and the sample-basin maps <out-prefix>_basin_map_status.png and _basin_map_unit.png (coloured by whether each basin was used, and by its dominant unit). --plots picks scatter and/or map; --map-colour-by picks status, unit or both; the map's hillshade comes from --dem or the run's own DEM.