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QGIS Plugin#

The NWM Coastal QGIS plugin provides an interactive graphical workflow for defining coastal model domains. It loads National HydroFabric (NHF) data and NOAA CO-OPS station layers as a basemap, lets you sketch and refine an area-of-interest (AOI) polygon, snap the polygon boundary to NHF watershed divides, and export the result as GeoJSON for use with the create command.

Experimental

The QGIS plugin is experimental (v0.1.0) and requires QGIS 3.34 or later.

Installation#

The plugin lives in the qgis_plugin/nwm_coastal/ directory of the repository. To install it into QGIS:

  1. Locate your QGIS plugin directory:

    • Linux: ~/.local/share/QGIS/QGIS3/profiles/default/python/plugins/
    • macOS: ~/Library/Application Support/QGIS/QGIS3/profiles/default/python/plugins/
    • Windows: %APPDATA%\QGIS\QGIS3\profiles\default\python\plugins\

  2. Symlink or copy the plugin folder:

    ln -s /path/to/nwm-coastal/qgis_plugin/nwm_coastal \
    ~/.local/share/QGIS/QGIS3/profiles/default/python/plugins/nwm_coastal

  3. Restart QGIS, then enable NWM Coastal in Plugins > Manage and Install Plugins.

After activation, an NWM Coastal toolbar appears with five buttons.

Required Data#

Before using the plugin, prepare two data files:

File Format Contents
National HydroFabric GeoPackage (.gpkg) Must contain flowpaths and divides layers. gages and nexus layers are loaded if present but are optional.
CO-OPS Stations Parquet (.parquet) NOAA CO-OPS tide-gauge station locations with a geometry column.

Toolbar Buttons#

1. Add Basemap#

Opens a dialog to select the NHF GeoPackage, CO-OPS parquet file, and a minimum stream order filter. On confirmation the plugin loads:

Layer Style Source
OpenStreetMap XYZ raster tiles openstreetmap.org
divides Transparent fill, black outline (0.1 width) GeoPackage
flowpaths Blue lines (width 1), filtered by stream order GeoPackage
gages Red circles (size 3) GeoPackage (optional)
nexus Green circles (size 2) GeoPackage (optional)
coops Orange stars (size 7) Parquet

The dialog validates that the GeoPackage exists and contains the required flowpaths and divides layers before accepting.

2. Draw Polygon#

Creates a temporary in-memory polygon layer (sketcher_polygon) and activates the Add Feature tool so you can immediately sketch a polygon on the map canvas.

  • Left-click to place vertices.
  • Right-click to finish the polygon.
  • The sketcher layer uses a semi-transparent orange fill so underlying basemap layers remain visible.

3. Edit Polygon#

Activates the Vertex Tool on the sketcher layer, allowing you to move individual vertices to refine the polygon shape.

4. Union with NHF Divides#

Computes the geometric union of the sketcher polygon with all intersecting NHF divide polygons. This snaps the AOI boundary to watershed boundaries, producing a hydrologically meaningful domain.

  • The original sketcher layer is preserved so you can edit and re-run the union.
  • The union result appears in a separate merged_polygon layer with a semi-transparent green fill.
  • Interior holes are removed and multipart results are collapsed to the largest polygon.
  • CRS differences between the sketcher and divides layers are handled automatically.

5. Save Polygon#

Exports the polygon to a GeoJSON file via a file-save dialog. If a merged layer exists it is saved; otherwise the sketcher polygon is used.

The exported GeoJSON can be passed directly to the create command as the aoi parameter:

aoi: my_domain.geojson
output_dir: ./my_sfincs_model

grid:
  crs: EPSG:32617

coastal-calibration create create_config.yaml

Typical Workflow#

flowchart TD
    A["Add Basemap"] --> B["Draw Polygon"]
    B --> C["Edit Polygon"]
    C --> D["Union with NHF Divides"]
    D --> E{Satisfied?}
    E -- No --> C
    E -- Yes --> F["Save Polygon"]
    F --> G["coastal-calibration create"]
  1. Add Basemap -- load NHF data and CO-OPS stations to orient yourself.
  2. Draw Polygon -- sketch a rough AOI around the coastal area of interest.
  3. Edit Polygon -- fine-tune vertices as needed.
  4. Union with NHF Divides -- snap the boundary to NHF watershed divides.
  5. Repeat steps 3--4 until the domain looks right.
  6. Save Polygon -- export as GeoJSON.
  7. Use the exported GeoJSON as input to coastal-calibration create to build a SFINCS model.