What are the two components that make up the BFEs for coastal studies?

The correct answer identifies the two critical components that define Base Flood Elevations (BFEs) in coastal studies: stillwater elevations and wave runup.

Stillwater elevations represent the height of water during a flood event without the influence of wave action, including effects from tidal conditions and storm surges. These elevations provide a baseline for flood risk assessment.

Wave runup, on the other hand, refers to the additional height that waves reach as they run up on the beach or coastal structure. This phenomenon can significantly affect flooding scenarios, especially during severe storms or hurricanes when wave action can exacerbate flooding beyond what stillwater elevations predict.

Together, these components give a more comprehensive understanding of flood risk in coastal areas; they account for both the static water level and the dynamic influence of waves, which is essential for effective floodplain management and appropriate planning for flood resilience. Other components mentioned in the incorrect options do not accurately capture these crucial factors or their relationship to assessing flood heights in coastal environments.