Sea-Level Calculator for Non-NOAA Long-Term Tide Gauges

Consideration of future sea level change has been a requirement for USACE projects at coastal sites since 1986. EC 1165-2-212 (pdf, 845 KB) and its successor ER 1100-2-8162 (pdf, 317 KB) specify the equations to be used in computation of possible future sea level scenarios, based on an observed historical rate of sea level change. This rate of change has been established for NOAA tide gauges, and a web tool has been established to facilitate computations using these gauges.

For areas without a nearby NOAA tide gauge, establishing a historical rate of sea level change for the purpose of generating future sea level scenarios may be difficult due to changing datums, riverine influences, and intermittent data records. This on-line Sea Level Change Calculator computes the amount of predicted sea level change using constants from EC 1165-2-212 (pdf, 845 KB) and its successor ER 1100-2-8162 (pdf, 317 KB) using a base year of 1992, which is the midpoint of the most recent (1983-2001) National Tidal Datum Epoch, for those non-NOAA tide gauges where historical rates have been established

The historical rate of sea-level change is the rate for the "USACE Low Curve."

The rate for the "USACE Intermediate Curve" is computed from the modified NRC Curve I considering both the most recent IPCC projections and modified NRC projections with the local rate of vertical land movement added.

The rate for the "USACE High Curve" is computed from the modified NRC Curve III considering both the most recent IPCC projections and modified NRC projections with the local rate of vertical land movement added.

The three local relative sea level change scenarios updated from EC 1165-2-212 (pdf, 845 KB) and its successor ER 1100-2-8162 (pdf, 317 KB), Equation 2 are depicted in the Figure to the right of the table.

Engineering and Construction Bulletin (ECB) 2013-27 was issued on September 9, 2013 to provide guidance related to the use of non-NOAA tide gauge records for computing relative sea level change. Detailed procedures for computing relative sea level change at non-NOAA tide gauges can be found in the Atlas of U.S. Army Corps of Engineers Historic Daily Tide Data in Coastal Louisiana. (pdf, 15 MB) As historical rates of relative sea level change are computed for additional (non-NOAA) tide gauges, those gauges will be added to this calculator, creating an increasingly comprehensive tool for sea level scenario projections.

This calculator has been updated to reflect the 2015 calculated rates contained in the Updated Atlas of U.S. Army Corps of Engineers Historic Daily Tide Data in Coastal Louisiana MRG&P Report No. 14, November 2017 (pdf, 6 MB) to reflect the newest reference document.

Equation Used by this Calculator

EC 1165-2-212, Equation 2 is as follows:

E(t) = (0.0017+M)t + bt²

Where:
E = Change in RSL in m
t = timespan (years) between Base Year or beginning date and projected year
M = Rate of local land movement in m/yr
b = Constants provided in Engineering Circular        

The year 1992 is used as the base year because that is the midpoint of the most recent tidal epoch for which mean sea level has been established (1983-2001). If scenarios of projected relative sea level change between two future years are needed, the difference in change since 1992 for those two years should be subtracted.