However, recession is the landward movement of a feature, such as an elevation contour or the bluff or dune crest, while erosion is the wearing away of land. Recession is expressed as a distance, or a change in distance, while erosion is expressed as a volume, or a change in volume. Recession can be thought of as a consequence of erosion. To that extent it is reflective of bluff erosion. In addition, bluff recession may be reflective of coastal erosion processes as a whole, if averaged over a sufficiently long period of time.
Bluff recession is the most visible aspect of coastal erosion and receives the most attention.
However, using only bluff recession as an indicator of erosion rates or erosion trends may be misleading because of the length of time, or lag, that usually occurs between erosion and bluff recession. Coastal erosion occurs over the area roughly from the top of the bluff out into the nearshore region to about the 30 foot water depth. In addition, erosion, particularly bluff erosion and recession, do not occur at a constant rate. Over relatively short time periods of days, weeks, and months, the rate of erosion and recession may vary greatly. It is very common for a reach of coastline to have no bluff recession for months or years and then experience severe bluff recession over a period of days or weeks.