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Rising sea level inundates low-lying areas, converts wetlands to open water, erodes beaches, exacerbates flooding, and increases the salinity of estuaries and aquifers. Here are some reports that examine how shores may erode as sea level rises.

the Bruun Rule of erosion caused by sea level rise

The Bruun Rule

A rise in sea level immediately results in shoreline retreat due to innundation, as shown in (a) and (b). However, a one-meter rise in sea level implies that the offshore bottom must also rise one meter. The sand requires to raise the bottom (X') can be supplied by bach nourishmemt. Otherwise, the beach and dunes will supply that sand (X) as shown in (c).
Source: The Cost of Holding Back the Sea

Rising sea level erodes beaches by more than the loss of land from inundation alone. Since 1962, coastal geologists and engineers have often used the Bruun Rule to explain why. The figure to the right shows the general idea. A rise in sea level directly inundates a relatively small portion of tbe beach (b). However, the cross section of a given beach tends to follow a given profile relative to the sea. As storm waves erode the beach and deposit sand nearby and the summer swell rebuilds the beach, the offshore area tends to retain a particular depth. As sea level rises, the nearshore bottom must rise as well to keep that profile and unless sand is brought in from elsewhere, the beach and dunes provide the land that elevates the bottom.

Some geologists dislike the Bruun Rule as a predictive tool, but whether it is a complete explanation of erosion caused by sea level rise, it is one of the best teaching tools because a simple reflection of the three boxes illustrate why shore erosion should be greater than just inundation alone.

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