Sea Level Trend
Table in mm/yr
Sea Level Trend
Table in feet/century
Extreme Water Levels
Please click on the arrow to access additional information about that station.
Extremely high or low water levels at coastal locations are an important public concern and a factor in coastal hazard assessment, navigational safety, and ecosystem management. Exceedance probability is the likelihood that water levels will exceed a given elevation based on a statistical analysis of historic values. The Product provides annual and monthly exceedance probability statistics for select CO-OPS water level stations with at least 30 years of data. When used in conjunction with real time station data, exceedance probability statistics can be used to evaluate current conditions and determine when a rare event is occurring. This information may also be instrumental in planning for the possibility of dangerously high or low water events on a local level. Because these statistics are station specific, their use for evaluating surrounding areas may be limited.
The extreme levels measured by the CO-OPS tide gauges during storms are called storm tides which are a combination of the astronomical tide, the storm surge, and the wave setup caused by breaking waves. They do not include wave runup, the movement of water up a slope. Therefore, the 1% annual exceedance probability levels shown on this website do not necessarily correspond to the Base Flood Elevations (BFE) defined by the Federal Emergency Management Administration (FEMA), which are the basis for the National Flood Insurance Program. The 1% annual exceedance probability levels on this website more closely correspond to FEMA's Still Water Flood Elevations (SWEL). The peak levels from tsunamis, which cause high-frequency fluctuations at some locations, have not been included in this statistical analysis due to their infrequency during the periods of historic record.
Frequently Asked Questions
Data and Resources
For additional information, please contact CO-OPS.