Sea-Level Change Curve Calculator Using the Flood Risk Reduction Standard for Sandy Rebuilding Projects
ER 1110-2-8162, Incorporating Sea Level Change in Civil Works programs, requires that USACE incorporate the direct and indirect physical effects of projected future sea level change across the project life cycle in managing, planning, engineering, designing, constructing, operating, and maintaining USACE projects and systems of projects. This ER replaces EC 1165-2-212 (pdf, 845 KB), which was developed with the assistance of coastal scientists from the NOAA National Ocean Service and the U.S. Geological Survey. Both ER 1110-2-8162 and EC 1165-2-212 (pdf, 845 KB) uses the historic rate of sea-level change as 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 scenarios proposed by the NRC result in global eustatic sea-level rise values, by the year 2100, of 0.5 meters, 1.0 meters, and 1.5 meters. Adjusting the equation to include the historic GMSL change rate of 1.7 mm/year and the start date of 1992 (which corresponds to the midpoint of the current National Tidal Datum Epoch of 1983-2001), instead of 1986 (the start date used by the NRC), results in updated values for the coefficients (b) being equal to 2.71E-5 for modified NRC Curve I, 7.00E-5 for modified NRC Curve II, and 1.13E-4 for modified NRC Curve III.
The three local relative sea level change scenarios updated in EC 1165-2-212 (pdf, 845 KB) (see Equation 2) and its successor ER 1110-2-8162, are depicted in the Figure to the right of the table. A link to an Excel version of the calculator is below the table. The Excel version has a drop-down menu to select tide gauges. Below that is a direct link to the NOAA Tides and Currents web site for the selected tide gauge. The Excel version also provides graphical and tabular output in both feet and meters.
Computation of FRRS elevation required for USACE Sandy-related rebuilding or retrofitting projects funded by Public Law 113-2 that include vertical construction infrastructure or flood proofing should follow these steps:
- Is the project located within the designated Sandy recovery area? If yes, continue on to b. If no, the FRRS does not apply.
- Is the project funded by funded by Public Law 113-2? If yes, continue on to c. If no, the FRRS does not apply.
- Using the web tool available here, locate the project site and the nearest long-term tide gauge meeting the requirements of ER 1165-2-8162, “Incorporating Sea Level Change in Civil Works Programs” or ECB 2013-27,“Use of Non-NOAA Tide Gauge Records for Computing Relative Sea Level Change.” Identify the BFE. For example, in the image above, the BFE for a project located at the intersection of Rte 35 and Johnson Road in Mantoloking would be 8 ft NAVD88. The nearest long-term NOAA tide gauge is #8531680, Sandy Hook, NJ, with 75 years of record. Select this gauge using the drop-down menu. Use the link to “Select closest NOAA gauge station” if you are unsure of the closest tide gauge. Enter the BFE elevation in the web tool table.
- The minimum FRRS is 1.0 ft. To determine the local FRRS, the appropriate county and municipal officials shall be consulted to determine whether a more restrictive standard exists. For example, for a project located at the intersection of Rte 35 and Johnson Road in Figure 1, the applicable local minimum standard would be the State of New Jersey’s Flood Control Hazard Act Rules (N.J.A.C 7:13) which state that “The lowest floor of the building is reconstructed or elevated to at least one foot above the flood hazard area design flood elevation.” Therefore, the local FRRS is 1.0 ft, the same as the minimum FRRS. Enter the local FRRS in the web tool and click on the “Calculate Curves” button to calculate the BFE plus FRRS.
- Compare the BFE plus FRRS with the BFE plus USACE sea level change scenarios to determine the required minimum elevation for the first floor of vertical infrastructure or the elevation of the required elevation or floodproofing. In this case, the computed minimum elevation would be 8 +1 = 9 ft NAVD88 for the FRRS or the appropriate value of the sea level change scenarios depending on the vertical construction requirements of the project in question.
If the project is located in the Bronx, Brooklyn, Manhattan, Queens, or Staten Island Borough, use the NPCC calculator available here.