Sandy 2012 inundation specialist + .gitattributes LFS for *.geojson

Empirical extent of Hurricane Sandy storm-tide inundation, published
by NYC Open Data from FEMA MOTF surge modelling. This is the
historical-observation layer — what actually went under in October
2012 — and serves as the empirical floor when the forward-modelled
DEP scenarios disagree with lived experience.

The 91 MB GeoJSON ships pre-baked; *.geojson now routes through LFS.

.gitattributes

@@ -1,3 +1,7 @@
+# Riprap-specific LFS tracking
+*.geojson filter=lfs diff=lfs merge=lfs -text
+
+# Hugging Face's standard LFS rules (kept for forward-compat with model assets)
 *.7z filter=lfs diff=lfs merge=lfs -text
 *.arrow filter=lfs diff=lfs merge=lfs -text
 *.bin filter=lfs diff=lfs merge=lfs -text

app/flood_layers/sandy_inundation.py

@@ -0,0 +1,34 @@
+"""NYC Sandy Inundation Zone (empirical 2012 extent, NYC OD 5xsi-dfpx)."""
+from __future__ import annotations
+
+from functools import lru_cache
+
+import geopandas as gpd
+
+from app.spatial import DATA, load_layer
+
+DOC_ID = "sandy_inundation"
+CITATION = "NYC Sandy Inundation Zone (NYC OpenData 5xsi-dfpx, empirical 2012 extent)"
+
+
+@lru_cache(maxsize=1)
+def load() -> gpd.GeoDataFrame:
+    g = load_layer(DATA / "sandy_inundation.geojson")
+    return g[["geometry"]]
+
+
+def join(assets: gpd.GeoDataFrame) -> "gpd.pd.Series":
+    """Return a boolean Series indexed like assets: True if inside Sandy zone."""
+    z = load()
+    # spatial join avoids fragile unary union over messy public polygons
+    hits = gpd.sjoin(
+        assets[["geometry"]].assign(_aid=range(len(assets))),
+        z[["geometry"]],
+        how="left",
+        predicate="intersects",
+    )
+    flagged = hits.dropna(subset=["index_right"])["_aid"].unique()
+    s = assets.geometry.copy().astype(bool)
+    s[:] = False
+    s.iloc[list(flagged)] = True
+    return s.reset_index(drop=True)

data/sandy_inundation.geojson

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:2d5b899acc144a422ca340eabe100c91c5fe110e2b13e62216e61fdc07b00200
+size 91392952