Methodology: Flash-flood event records & seasonality
Every figure carrying this label on a county page is computed exactly as described below, from public government data. Nothing is estimated or editorialized.
| What it measures | NOAA-recorded event REPORTS in the county (episodes contain multiple records) |
|---|---|
| Unit | event records |
| Source dataset | NOAA — Storm Events Database |
| Data version / accessed | through 2026-03 (cube build 2026-07-21b, generated 2026-07-21) |
| Exact source fields | EVENT_ID, EPISODE_ID, EVENT_TYPE, BEGIN_YEARMONTH, STATE_FIPS, CZ_TYPE, CZ_FIPS, CZ_NAME |
| Formula | COUNT(fct_storm_event) per county_fips x month x hazard x sub_hazard |
| Predicates / filters | EVENT_TYPE = 'Flash Flood', bucketed by EVENT BEGIN MONTH (BEGIN_YEARMONTH), 2020 onward. The county is assigned from the county/zone fields: CZ_TYPE = 'C' (county entries; zone entries are not county-assigned) with STATE_FIPS + CZ_FIPS forming the 5-digit county FIPS (CZ_NAME is the label). These are NOAA EVENT RECORDS dated by when the event BEGAN — never a 'date of loss'. Seasonality = the fewest calendar months covering >=50% of the county's records; shown only at >= 3 records. |
| Date semantics | event BEGIN month (BEGIN_YEARMONTH); windows end at complete_through |
| Window boundaries | 2020-01 through 2026-03 (last complete NOAA month), bucketed by event begin month |
| Rounding | none |
| Suppression rule | seasonality hidden below 3 qualifying records |
| Minimum sample (min_n) | 1 |
| Geography | US county (FIPS) |
Internal build query
This query runs against our internal data cube (private cube_*/fct_* tables built from the public sources below). It is exact but not runnable by a reader — use the public reproduction recipe that follows.
SELECT COALESCE(SUM(storm_event_records),0)
FROM cube_county
WHERE county_fips = :fips AND sub_hazard = 'Flash Flood'
AND month >= '2020-01';Reproduce from the public source
This recomputes the figure from the raw public dataset. Public data is live and may run ahead of our snapshot (see the data version above); numbers can differ by rows added since our ingest vintage.
NOAA Storm Events Database — ncdc.noaa.gov/stormevents (bulk CSV
StormEvents_details-*.csv):
keep EVENT_TYPE = 'Flash Flood', STATE_FIPS = 48, CZ_TYPE = 'C',
BEGIN_YEARMONTH >= 202001; county FIPS = STATE_FIPS*1000 + CZ_FIPS.
Count records; bucket by BEGIN_YEARMONTH month for seasonality.Worked example: Harris County: 34 recorded flash-flood event records since 2020 (event begin month).
Change log
2026-07-21 (r3) — window boundaries corrected (no windowed metric reads "not windowed"); LIMIT/ordering/geography/status predicates documented; the query relabeled the internal build query and paired with a public raw-source reproduction recipe.
2026-07-21 — record published with source URL, exact fields, predicates, window boundaries, rounding, suppression, and a worked example. Prior records disclosed a formula only.
Corrections
Spotted an error? Corrections: [email protected]. We publish the fix and note it in this change log.
Independent professional (adjuster/restoration) review of the guidance built on these figures is pending and blocks release (D2). This record documents the data method only; it is not insurance, legal, or engineering advice.