Figure 4. The Bruun Rule. Beaches follow a characteristic profile shape based on the wave climate and the types of sediments. When sea level rises, the initial effect is inundation; but eventually enough material will be deposited offshore to re-establish the profile at the higher elevation. Thus, the shore retreat will be based on the slope of the entire beach profile, which is usually flatter than the slope just above the shore. Source: Titus (1986).
The Shore Retreats More than Inundation Alone

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Higher quality version of this figure brief discussion putting the Brrun Rule within the larger context of coastal erosion caused by sea level rise
See also More Sea Level Rise Reports