Data Management Plan

High tide flooding is the overflow or excess accumulation of water that covers typically dry coastal land and occurs during high tides. As relative sea levels rise, high tide flooding (HTF) is occurring more frequently, even on sunny days. HTF creates short term impacts like road closures, overflowing storm drains, and temporary business closures. Over the long term, recurrent HTF causes more severe impacts like damage to below-ground infrastructure and degraded wetlands.

Through NOAA's National Ocean Service (NOS), the Center for Operational Oceanographic Products and Services (CO-OPS) and its predecessors have gathered oceanographic data along our nation's coasts for over 200 years to protect life, property, and the environment. Serving both the public and other government agencies, CO-OPS is the authoritative source for accurate, reliable, and timely water-level and current measurements that support safe and efficient maritime commerce, sound coastal management, and recreation. As part of those roles, CO-OPS offers a suite of interactive products that helps communities understand when, where, and how often high tide flooding may occur along the coast to better inform their coastal flood planning and mitigation efforts. The suite includes a summary of historical HTF days as well as Monthly and Annual HTF Outlooks which are produced for specific stations.

Lineage Statement:
CO-OPS updates high tide flooding likelihoods monthly using a methodology based on Dusek et al. 2023 (see URL 1 above). Flooding likelihoods are derived from a probabilistic model that incorporates tide predictions, sea level rise trends, and seasonal changes in coastal sea level to predict the potential that a higher than normal high tide may exceed established NOS flood thresholds. During these periods, high tide flooding may occur in flood-prone areas.

Process Steps:

• Verified water level data from a water level station (the verified 6-minute data, and the secondary datasets of highs and lows (except for Great Lakes stations), hourly heights, daily means (Great Lakes stations only), and monthly means) are made available roughly one month after collection. This is a 2-step process where one person reviews the data, and if necessary, removes erroneous data or fills gaps by either using data from the station's back-up sensor, predictions for that station, or similar data from proximal stations. With exception of the corrected errors or filled gaps, most preliminary (raw) 6-minute data become the verified 6-minute data. Secondary datasets are also generated during this step. Then a second person reviews the work of the first, and when satisfied, marks the data in the database as "verified." The order in which the 300+ water level stations are processed each month is random, to prevent the same stations or geographical locations from always being first or last. Verified water level data are made available on a monthly basis for the previous month's data.
• Water level gauges mounted along the U.S. coastlines (including Pacific and Caribbean Islands) employ acoustic or microwave technology (with pressure sensors as the back-up sensor). Historic stations employed paper trace rolls (marigram and ADR rolls) until the late 1990's. The type of sensor used today depends on the station's environment. The lack of infrastructure may prevent the use of the desired sensor type at that location.