A Decade of Rain
Two pages drawn from one record: the HERBS file of U.S. military herbicide
missions over South Vietnam, 1961 to 1971.
- A Decade of Rain (rain.sizheng.me):
a scroll-driven narrative in eight nodes, from the 1961 test sprays to the
1971 reckoning, over a single heat field that fills in as the reader scrolls.
- The Herbicide Atlas of Vietnam (/archive):
an explorer of the same record. A playable decade, three zoom-dependent
encodings of the volume, an agent filter, and a lookup that returns the
individual runs within a radius of a place or the runs of a HERBS mission
number (
?m=4493).
The version submitted to the IDA on 14 September 2026 stays as it was at
adecadeofrain.sizheng.me, served from the
ida branch; everything since, the story-card illustrations first, is at
rain.sizheng.me from master.
Both are static pages: no backend, no accounts, no analytics.
The record
The source is the HERBS file as republished in Andrew Stellman's open
hea-v repository
(data/herbs.json, MIT), pinned to commit cb5948b so that every number here
can be recomputed from the same bytes. It is the record behind Stellman,
Stellman, Christian, Weber and Tomasallo, The extent and patterns of usage of
Agent Orange and other herbicides in Vietnam, Nature 422 (2003).
Measured at that commit:
| |
|---|
| Rows (waypoint records) | 24,604, fourteen fields each |
| Missions | 9,141 |
| Mission + Run pairs | 11,273 |
| Gallons | 19,490,690, all of them on each mission's 1A row |
| Dates | 10 August 1961 to 27 December 1971 |
| Method | fixed-wing 95.4% of the gallons, helicopter 3.8%, ground 0.25% |
The one fact that shapes everything below: the file books a mission's whole
load against the first waypoint of its first track, and records the track
itself as a chain of further waypoints with no volume on them. A map drawn
straight from the fields puts the load in one cell at one end of an 11 km line.
What the pipeline does
- Georeference. The grid references are MGRS-style with the UTM zone
omitted. Each is converted under every candidate zone and band (48 and 49 ×
N, P, Q, R) and the candidate nearest
hea-v's own 0.01° lattice
(gridpoints.json) is kept, within 0.05°. All 24,604 rows convert; none is
dropped. Coordinates are rounded to 0.001°.
- Reconstruct runs as lines. Rows are grouped by
Mission + Run in file
order and split where the leg number changes: 8,753 line segments and 2,831
single-point records.
- Spread the volume. Each mission's gallons are spread along every line
track it flew, in proportion to length. Totals are conserved to the gallon
(19,490,688 out against 19,490,690 in, whole-gallon rounding) and the build
throws if they are not.
- Bin. The Atlas's two dot tiers (0.12° and 0.03° cells) are binned from
the lines in the browser (
src/components/trackGrid.ts); the Story's field
is binned by scripts/build-story-heat.mjs into 0.03° cells by month.
- Draw. Dots take area proportional to gallons; strokes take width
proportional to gallons per kilometre and fade from the first waypoint on
file; the heat weight is √(gallons / ref) with ref the 90th percentile of
the cell-month totals.
Steps 1 to 3 are scripts/build-spray-tracks.mjs (npm run build:tracks);
the point file for the timeline is scripts/build-spray-data.mjs
(npm run build:data). The source is cached under scripts/.cache/ and
fetched from the pinned commit when absent.
What the pipeline does not do
No drift, no swath width, no degradation, no canopy or soil interception, no
population. The maps show where the record says the herbicide was released,
not where it landed or whom it reached. The full list of limits is in
docs/methods.md.
Outputs
All in public/data/, fetched by the pages at runtime.
| File | One entry is | Fields |
|---|
spray.json | one source row | [lon, lat, day, agent, gallons, ctz] |
spray-tracks.json | one line segment (tracks) or one single-point run (marks) | [agent, day, gallons, km, coords, mission, run, fwac] / [agent, day, gallons, lon, lat, mission, run, fwac] |
spray-heat.json | one (cell, month) aggregate | [lon, lat, day, gallons], 23,729 of them |
day counts from 1 January 1961 as day 1, matching hea-v's own engine.
src/data/README.md documents the point file in more detail.
Methods
docs/methods.md: the working methods note, kept
current with the build.docs/methods-paper.md: a longer note written for
the authors of the record, with the field dictionary as observed, every
encoding constant, the checks, the limits, and open questions. Its central
measurement: at a 3 km cell, 59% of all gallons sit in a different place
under the file's own booking than under the along-track reading, and 63% of
cells that received herbicide read as zero.scripts/analyse-binning.mjs (npm run analyse:binning) reproduces the
tables in both notes; scripts/analyse-mission-spread.mjs measures the
per-mission correction; scripts/build-figure-binning.mjs
(npm run build:figures) draws docs/figures/binning-comparison.svg.
docs/ also holds the design-system notes and the map label and zoom studies.
docs/decisions.md is the decision log: what was chosen,
why, what was set aside, and what is still open.
Running it
npm install
npm run dev # http://localhost:5173
npm run build # tsc + vite → dist/
npm run preview
Rebuilding the data, in order: npm run build:data, npm run build:tracks,
npm run build:heat. npm run build:regions rebuilds the province and
military-region layers from geoBoundaries.
Stack
Vite, React and TypeScript. MapLibre GL JS with the OpenFreeMap Positron
style (no key), AWS Terrain Tiles for the optional 3D relief, geoBoundaries
for provinces. Scrollama drives the Story. Geist and Courier Prime are
self-hosted under public/fonts/. Deployed on Vercel.
Licence and citation
The code, the build scripts and the notes in this repository are released
under the MIT licence (see LICENSE). The source data is MIT-licensed by
Andrew Stellman via hea-v; the pages cite it as "the complete record behind
Stellman et al. (2003)". The basemap, terrain and boundary sources carry their
own licences, listed in the pages' sources.
