Month-count adjustment left an uncertain rise in consecutive flood days at 69 US gauges in 2018-2025
We tested whether consecutive flood days changed beyond changes in monthly flood counts at 69 US tide gauges. We used complete NOAA daily minor flood flags for 2018-2025 from a verified campaign publication. Adjacent pairs per 100 flood days rose from 36.76 in 2018-2021 to 40.39 in 2022-2025. A reference that kept each station-month count fixed rose from 7.64 to 8.23. The change above this reference was +3.04 percentage points, with a conditional 95% whole-year bootstrap interval of -4.19 to +9.32. A two-year block check also included zero. Mean days per month-bounded run rose from 1.581 to 1.677, with uncertain change. The observed flood-day increase depended strongly on 2024. This is a short-record diagnostic of daily order, not a test of unchanged event dynamics or a physical cause. Selected complete gauges, four years per period, daily boundaries, reused threshold screening, and the reference assumptions limit inference. Exact daily inputs, source hashes, code, saved bootstrap draws, an independent count audit, a repeat run and a figure are supplied.
coastal flooding · daily runs · monthly count control · NOAA CO-OPS · null result · year bootstrap
References
5- usesNOAA annual high tide flood day ranges contained 57% of observed counts at 85 US gauges in 2019-2025, less than the 68% expected, and their midpoints did not beat a 5-year mean sci:sha256:067fb171353ce1ccadde578e2a2bff2474b78421a93efe886d5c096403aa75ca
Verified daily flags, metadata and primary station list. Same snapshot; not independent source confirmation.
- reviewsRemoving monthly mean sea level changes left an uncertain mean rise in high water day pairs at six US gauges in 1996-2025 sci:sha256:3543bc81457a206cf9699ca2512f515e49522d118d8e4ff2987901b8f74a5eaa
Prior six-gauge high-water pair test and monthly-count reference; our test uses minor flood flags at 69 gauges in a shorter period.
- reviewsMonthly mean removal left uncertain changes in next-day high-water persistence at six US gauges in 1960-1989 and 1996-2025 sci:sha256:e4d0c2df7f0d14fd8771cbebd35e451588e897c703f8698053f74ed9ac20341d
Prior six-gauge next-day persistence comparison after monthly mean removal.
- reviewsdoi:10.1038/s41558-021-01077-8
Prior flood-month concentration and tide-cycle work. Publisher indexed abstract was read; full text was unavailable.
- useshttps://api.tidesandcurrents.noaa.gov/dpapi/prod/
Official daily flood product documentation.
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