Own History volume-compare membership in the storm catalogue

api/config/storms.py

@@ -7,6 +7,10 @@
   - "impact" — curated floodplain polygon (impact_geometry) + bbox envelope
   - "none" — no flood-bound overlay (e.g. summer control)
 
+volume_compare:
+  - true — included in History Event volume · compare (lake-owned membership)
+  - volume_compare_rank — display order (ascending; Chandra = 1)
+
 impact_geometry is a GeoJSON FeatureCollection (hand-curated v0).
 impact_bbox remains the envelope for clients that only clip by bbox.
 """
@@ -31,6 +35,8 @@
         "severity": "high",
         "impact_summary": "Muchelney cut off for weeks; A361 approaches flooded.",
         "bounds_mode": "impact",
+        "volume_compare": True,
+        "volume_compare_rank": 3,
         "notes": (
             "Somerset Levels winter flooding; Muchelney isolation peaked mid-February. "
             "as_of is the mid-event evaluation instant (not early January onset)."
@@ -76,6 +82,8 @@
         "severity": "high",
         "impact_summary": "Named storm; Parrett corridor under pressure before Dennis.",
         "bounds_mode": "impact",
+        "volume_compare": True,
+        "volume_compare_rank": 4,
         "notes": "Storm Ciara weekend; Dennis followed a week later.",
     },
     {
@@ -90,6 +98,8 @@
         "severity": "high",
         "impact_summary": "Named-storm peak; corridor hindcast golden eval.",
         "bounds_mode": "impact",
+        "volume_compare": True,
+        "volume_compare_rank": 2,
         "notes": "Named storm window used for golden analogue eval.",
     },
     {
@@ -121,6 +131,8 @@
             "impassable; major incident 27 Jan–18 Feb after Storm Chandra on saturated Levels."
         ),
         "bounds_mode": "impact",
+        "volume_compare": True,
+        "volume_compare_rank": 1,
         "notes": (
             "Product impetus event. Met Office named Storm Chandra (UK impact 26–27 Jan 2026) "
             "inside a longer wet spell; Somerset Council closed the A361 from ~25 Jan with "
@@ -149,6 +161,13 @@
 def _enrich_storm(raw: Dict[str, Any]) -> Dict[str, Any]:
     storm = dict(raw)
     storm_id = str(storm["id"])
+    storm["volume_compare"] = bool(storm.get("volume_compare"))
+    if storm["volume_compare"]:
+        rank = storm.get("volume_compare_rank")
+        storm["volume_compare_rank"] = int(rank) if rank is not None else 99
+    else:
+        storm.pop("volume_compare_rank", None)
+
     evidence = warning_evidence_for(storm_id)
     if evidence:
         storm["warning_evidence"] = evidence
@@ -176,6 +195,22 @@ def list_storms(corridor: Optional[str] = None) -> List[Dict[str, Any]]:
     return sorted(rows, key=lambda s: s.get("as_of") or "", reverse=True)
 
 
+def list_volume_compare_storms(corridor: Optional[str] = None) -> List[Dict[str, Any]]:
+    """Golden History volume-compare set — lake-owned membership and order."""
+    rows = [
+        s
+        for s in list_storms(corridor)
+        if s.get("volume_compare")
+    ]
+    return sorted(
+        rows,
+        key=lambda s: (
+            int(s.get("volume_compare_rank") or 99),
+            str(s.get("as_of") or ""),
+        ),
+    )
+
+
 def get_storm(storm_id: str) -> Optional[Dict[str, Any]]:
     for storm in STORMS:
         if storm["id"] == storm_id:

api/routes/predictions.py

@@ -8,7 +8,7 @@
 from api.config.corridors import list_corridor_ids
 from api.config.hipims import get_hipims_pilot, list_hipims_pilot_ids
 from api.config.place_bboxes import get_place_bbox, list_place_ids
-from api.config.storms import get_storm, list_storms
+from api.config.storms import get_storm, list_storms, list_volume_compare_storms
 from api.services.predictions import predict_corridor
 from api.services.volume import list_dtm_tiles, resolve_dtm_resolution
 
@@ -76,6 +76,10 @@ def get_prediction_corridors() -> Dict[str, Any]:
 @router.get("/v1/storms")
 def get_storms(
     corridor: Optional[str] = Query(None, description="Filter by corridor id"),
+    volume_compare: Optional[bool] = Query(
+        None,
+        description="When true, return only lake-curated History volume-compare storms (ordered)",
+    ),
 ) -> Dict[str, Any]:
     if corridor and corridor not in list_corridor_ids():
         raise HTTPException(
@@ -86,6 +90,8 @@ def get_storms(
                 "known": list_corridor_ids(),
             },
         )
+    if volume_compare is True:
+        return {"storms": list_volume_compare_storms(corridor)}
     return {"storms": list_storms(corridor)}
 
 

docs/accuracy-ladder.md

@@ -39,6 +39,7 @@ Use this when adding a place or storm:
 - [ ] Flood Watch History mounts Event volume panel; Live/Transport do not
 - [ ] Panel shows Low confidence / gauge-rise or percentile method (no mock fill)
 - [ ] History compare table lists Chandra / Dennis / 2014 / Ciara volume metrics
+- [ ] Compare membership is lake-owned (`volume_compare` on storms / `?volume_compare=true`)
 - [ ] Map draws A361 depth strip from `road.samples` (lng/lat/depthM) in History
 
 ### Historic warnings (AfA435)

tests/test_volume_compare_storms.py

@@ -0,0 +1,53 @@
+"""Tests for lake-owned History volume-compare storm membership."""
+
+from __future__ import annotations
+
+import unittest
+
+from api.config.storms import get_storm, list_volume_compare_storms
+from fastapi.testclient import TestClient
+
+from api.main import app
+
+
+class VolumeCompareStormsTests(unittest.TestCase):
+    def test_golden_four_flagged_and_ordered(self):
+        rows = list_volume_compare_storms("a361-muchelney")
+        ids = [s["id"] for s in rows]
+        self.assertEqual(
+            ids,
+            [
+                "place-2026-01-chandra-levels",
+                "eval-2020-02",
+                "eval-2014-01",
+                "place-2020-02-ciara",
+            ],
+        )
+        for storm in rows:
+            self.assertTrue(storm["volume_compare"])
+            self.assertIsInstance(storm["volume_compare_rank"], int)
+
+    def test_control_and_wet_spells_excluded(self):
+        self.assertFalse(get_storm("eval-stable-summer")["volume_compare"])
+        self.assertFalse(get_storm("place-2019-11")["volume_compare"])
+        self.assertNotIn(
+            "place-2014-01-onset",
+            [s["id"] for s in list_volume_compare_storms("a361-muchelney")],
+        )
+
+    def test_storms_endpoint_volume_compare_filter(self):
+        client = TestClient(app)
+        res = client.get(
+            "/v1/storms",
+            params={"corridor": "a361-muchelney", "volume_compare": "true"},
+        )
+        self.assertEqual(res.status_code, 200)
+        body = res.json()
+        ids = [s["id"] for s in body["storms"]]
+        self.assertEqual(ids[0], "place-2026-01-chandra-levels")
+        self.assertEqual(len(ids), 4)
+        self.assertTrue(all(s.get("volume_compare") for s in body["storms"]))
+
+
+if __name__ == "__main__":
+    unittest.main()