NWI Data Tool

Setup

MacOS

1. Install direnv, Node.js, GDAL, gettext (for envsubst), and PostgreSQL with PostGIS:

brew bundle

2. Install Node.js dependencies:

npm install

3. Copy sample.env to .env (and update it if necessary):

cp sample.env .env

4. Enable direnv (to set environment variables and to update PATH):

direnv allow

Data Preparation

1. Obtain and load AW reaches table
2. Load Watershed Boundary Dataset (WBD) 4-digit hydrologic units
3. Pick a 4-digit hydrologic unit from the WBD Subregions Map, e.g. 1709 (the Willamette).
4. Create an HU4 reaches table by intersecting WBD with reaches to filter for access points in that HU4
5. Download and import nhdflowline nhdarea, nhdwaterbody, and nhdplusflowlinevaa for the selected 4-digit hydrologic unit.
6. Import nhdfcode (if not already imported).
7. Create snapped reach put-ins (snapped_putins) with nhdplusid, fdate, number of candidate flowlines, point on closest flowline, point on associated polygon, original point, and link from original to snapped location.
8. Create snapped reach take-outs (snapped_takeouts) with nhdplusid, fdate, number of candidate flowlines, point on closest flowline, point on associated polygon, original point, and link from original to snapped location.
9. Adjust put-in locations for reaches immediately downstream from other reaches so that they match the upstream reach's take-out location. (Take-outs are snapped to downstream NHD segments using put-in information.)
10. Generate candidate reach geometries based on put-in and take-out locations (if take-outs were incorrectly snapped, these geometries will be capped by distance)
11. Re-snap take-outs to candidate reach geometries (to ensure that they don't involve traveling upstream)
12. Stitch linework together and crop between put-ins and take-outs to form reach_segments.

These steps can be executed for a given HU4 (e.g. 1709) using:

make -j $(nproc) wbd/1709

This will download 3GB or more of data from USGS, depending on the hydrologic units processed.

Step 9 can be repeated as necessary:

make db/correct_putins

Steps 10-12 can also be repeated, in case snapped put-in or take-out locations have been corrected:

make db/reach_segments.1709

Questionable Reach Segments

Questionable reach segments (i.e. where the segment is something other than a LineString, where snapped flowline points are not on the generated segment, or where snapped put-ins are downstream of take-outs) are marked using the questionable column on reach_segments.

TODO

• Report generation, e.g. # of points that didn't snap per watershed, distance breakdowns