experiments/08_nycha_developments/RESULTS.md

Phase 8 — nycha_development_exposure specialist (first output)

Status

First end-to-end output on Red Hook (Brooklyn) validates. Same join pattern as the MTA-entrance specialist, but for polygon assets: the metric of interest is "% of the development's footprint that intersects the flood layer" rather than point-in-polygon.

What it does

Per queried (lat, lon), returns up to N NYCHA developments whose centroid is within radius_m (default 2 km — developments are sparser than subway entrances), enriched with:

Field	Source	Tier
development, tds_num, borough	data/nycha.geojson (NYC Open Data, 218 developments)	reference
centroid_lat/lon, distance_m, footprint_km2	computed	computed
rep_elevation_m, rep_hand_m	USGS 3DEP DEM + derived HAND, sampled at the polygon's representative interior point	proxy
pct_inside_sandy_2012	area-fraction overlap with data/sandy_inundation.geojson	empirical
pct_in_dep_extreme_2080 (any depth)	area-fraction overlap with NYC DEP 3.66 in/hr / 2080 SLR scenario	modeled
pct_in_dep_extreme_2080_deep	area-fraction overlap with DEP Flooding_Category=3 ("Deep Contiguous, >4 ft") only	modeled
pct_in_dep_moderate_2050 (any depth)	area-fraction overlap with NYC DEP 2.13 in/hr / 2050 SLR scenario	modeled

Plus rollup counts: n_majority_inside_sandy_2012, n_with_dep_2080_overlap.

All overlap math runs in EPSG:2263 (NYC State Plane, feet) so area arithmetic is correct citywide.

First output — Red Hook (40.6745, -74.0090)

{
  "n_developments": 2,
  "n_majority_inside_sandy_2012": 2,
  "n_with_dep_2080_overlap": 2,
  "developments": [
    {
      "development": "RED HOOK WEST",
      "footprint_km2": 0.0761,
      "rep_elevation_m": 3.16,
      "rep_hand_m": 4.39,
      "pct_inside_sandy_2012": 84.49,
      "pct_in_dep_extreme_2080": 8.33,
      "pct_in_dep_moderate_2050": 1.91
    },
    {
      "development": "RED HOOK EAST",
      "footprint_km2": 0.0808,
      "rep_elevation_m": 3.37,
      "rep_hand_m": 4.6,
      "pct_inside_sandy_2012": 59.83,
      "pct_in_dep_extreme_2080": 16.1,
      "pct_in_dep_moderate_2050": 4.73
    }
  ]
}

The Red Hook campuses are exactly the asset-level claim the work plan calls for: 84% of Red Hook West's footprint sits inside the 2012 Sandy Inundation Zone (empirical evidence — water actually came in here), at a representative interior elevation of 3.16 m, and the same campus has 8% overlap with DEP's modeled Extreme-2080 extreme-rainfall scenario. Red Hook East is similar — 60% Sandy overlap at elev 3.37 m.

These are NYCHA's most-mentioned Sandy-affected campuses, and the specialist surfaces the empirical + modeled exposure cleanly with a single doc-message-shaped JSON object per development.

Honest scope

• Exposure, not damage forecast. "84% of the development's footprint sits inside the 2012 Sandy zone" is a structural claim about the shape of the flood that day — not a prediction that the next storm will flood the same area to the same depth.
• Polygon overlap is the right unit, not building count. A development is many buildings on a campus; the % overlap conveys "how much of the campus footprint is exposed" without overstating per-unit impact. Building-level inundation requires a separate join against MapPLUTO + DOB footprints.
• 30 m DEM resolution. rep_elevation_m is sampled at the polygon's representative_point(). Useful for borough-level comparisons; not building-by-building precision.
• No NYCHA-internal Sandy-recovery records yet. The 2014 NYCHA Sandy Recovery Plan and HUD CDBG-DR allocations name specific developments; folding those citations in is a follow-up before app/ integration.

Reproduce

.venv/bin/python experiments/08_nycha_developments/specialist.py \
    --lat 40.6745 --lon -74.0090 --radius 1500 --max 4
# Red Hook West + Red Hook East (Brooklyn)

.venv/bin/python experiments/08_nycha_developments/specialist.py \
    --lat 40.5760 --lon -73.9836 --radius 1500 --max 4
# Coney Island Houses (Brooklyn)

Open work (before app/ integration)

1. MapLibre rendering. Filled polygons color-graded by pct_inside_sandy_2012, dashed outline if no DEP overlap.
2. Doc-message emitter. nycha_dev_<tds_num> doc_id format, one per development; reuse the dev_check phrasing patterns.
3. NYCHA Sandy Recovery Plan (2014) citations. Per-development recovery dollars (or program tiers) folded in as a second evidence layer.
4. Coney Island / Hammel / Carleton Manor validation runs. Three sites that should produce the most demo-friendly outputs.
5. Hollis silence test. Hollis (no NYCHA in 2-km radius) should return available=False, n_developments=0 cleanly.
6. FSM wiring. Add step_nycha to app/fsm.py parallel-fanout block, gated on whether the planner classified the query as single_address / neighborhood / development_check.
7. pytest integration test. Lock the Red Hook result shape; skip if data/nycha.geojson is missing.

Sharp edges encountered

• Sandy GeoJSON had a hole-orientation issue that blew up unary_union with TopologyException. buffer(0) fixes it without changing the footprint at sub-foot precision.
• DEP column is Flooding_Category (int16), not depth_class. Documented; Flooding_Category == 3 is "Deep Contiguous (>4 ft)".

License: NYC OD NYCHA developments + NYC OEM Sandy + NYC DEP stormwater + USGS 3DEP DEM — all public-record, civic-tech-clean, already in use elsewhere in Riprap.