Hypothetical Coastal Floodplain Diagram (with caption)

A cross-sectional view of a hypothetical coastline showing one possible arrangement of the three Federal Flood Risk Management Standard (FFRMS) floodplain elevations (Climate-Informed Science Approach, the Freeboard Value Approach, and the 0.2% Annual-Chance Flood Approach) above the current Base Flood Elevation, i.e., the 1% annual-chance flood elevation. The 1% annual-chance flood or 100-year flood refers to a flood event that has a 1% chance of being equaled or exceeded in any given year. The relative elevation of these three FFRMS floodplains can vary from site to site and among projects with different service lives at a particular site. Importantly, a project’s Climate-Informed Science Approach (CISA) floodplain, which is determined from the best available information about plausible future climate scenarios over the course of its service life, does not necessarily lie at a higher elevation than the floodplains determined through the Freeboard Value Approach and the 0.2% Annual-Chance Flood Approach. Under CISA, the 1% annual-chance flood elevation may change over time and, consequently, may vary for different actions in the same location. Floodplains labeled in gray are not included in the Federal Flood Standard Support Tool. The 0.2% annual-chance flood approach floodplains are not currently available for coastal locations due to the paucity of information of such extreme wave heights at most coastal locations. 

Alternative text description of the diagram: Water-colored cross-section of a coastal landscape at the top with a line diagram version below it, representing the Federal Floodplain Risk Management Standard floodplain elevations under a hypothetical situation. The water-colored cross-section shows waves down at sea level in the lower left, with a house on stilts up shore from the wave line, and some trees and another house without stilts further inland. The elevation from shore rises up and to the right. In the line drawing, the same shoreline, wave line, and houses are present, overlaid by hypothetical flood elevations. The Base Flood Elevation (BFE, 1% annual-chance flood) is shown about half-way up to the first house on stilts, the Freeboard Value Approach (+ 2 feet for non-critical actions and + 3 feet for critical actions) is show above the BFE at about the base of the house's stilts. Further inland, the 0.2%-Annual-chance flood approach elevation line and the Climate-informed Science Approach (CISA) are drawn, both with a flat stillwater line (surge only) and a more dynamic line above it for the surge plus waves line. The 0.2% Annual-chance flood approach elevation sits at about the base of the house with stilts, and the CISA line goes further inland about where the non-stilted house sits.