Written by the TreasureGuide for the exclusive use of the Treasure Beaches Report.
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| Vero South Beach Monday Morning. Photo by DJ. |
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Here is some good research on coastal erosion that was published in the Journal of Coastal Research - Beach Erosion Potential for Severe Nor'easters by Keqi Zhangt, Bruce C. Douglas§, Stephen P. Leatherman in Coastal Research, 2001.
It contains a lot of academic jargon. I'll post a few brief excerpts below. Here is one.It has long been speculated that the semi-monthly tidal cycle plays a role (WOOD,
1982), but proof based on quantitative measurements has
been lacking. In addition, beach erosion caused by storms is
a complicated process. Erosion induced by a storm at a particular site can also be affected by the pre-storm beach profile
and geological conditions. Large storm waves are the major
agents of erosion, but the storm tide determines the position
(and elevation) where storm waves attack beaches and dunes...
I've talked about all of those factors before, but not using the same terminology.
Beach erosion caused by storms is indeed a complex process. Erosion at a particular site does depend upon the condition of the beach before a storm event. That is one way that knowing the state of various beaches helps. Some beaches will have more sand and be more protected than others. Some detectorists think only the most current photos are useful, but they are missing some important information.
I've also talked about the combined effect of the tides and waves. Higher tides move more water onto the beach and provides a higher base upon which the waves are moved. Waves on top of high tides results in more water on the beach and moves the wave impact farther back on the beach. You might remember the combined high tides and big surf we had in November of 2020, which eroded dunes that are not hit very often, and that resulted in some great finds.
Here is another good excerpt.
The severity of coastal erosion and damage induced by
storms is determined by a combination of storm tide, wave
energy, storm duration, and the character of the beach and
shoreface. Storm waves determine the destructive potential
of a storm, but storm tide dictates the onshore spatial range
influenced by storm waves. At low tide, even large waves will
have relatively minor impact on beach and dunes. When a
storm coincides with high tides, especially spring high tides,
storm waves can cause significant erosion and property damage because the waves experience less attenuation..
There are two major types of storms that affect the U.S. East Coast: hurricanes and nor'easters. Hurricanes are tight and strong low pressure systems with high wind speed. They usually influence a relatively small area, about 150 kilometers. Saffir and Simpson ranked hurricanes into five categories in terms of central pressure, wind speed, storm surge height, and damage (SIMPSON, 1974). This classification has been used extensively in both scientific and public arenas. By contrast, nor' easters are diffuse and weaker low pressure systems with wind peak speed seldom greater than those of the weakest hurricane (about 70 knots). However, nor'easters occur more frequently and are much larger in size. They can continue for several days and affect almost the entire U.S. East Coast...
Nor'easters are more important than hurricanes in causing beach erosion because of their long duration, large lateral extent, and greater frequency...
Thus, beach erosion induced by storms is not only related to the strength and duration of a storm but also depends critically on the astronomical high tide. A large storm coinciding with perigean spring tides will severely impact beaches...
The bias of the SEPI to large storms is reasonable since one great storm often causes much more severe beach erosion than the contribution of many small storms, especially if they do not impact the dune...
While the paper presents a lot of great information, there are some limitations. For one thing, the study is concerned with very large areas. Detectorists are interested in smaller areas, and in some cases specific areas of particular beaches.
Thus, beach erosion induced by storms is not only related to the strength and duration of a storm but also depends critically on the astronomical high tide. A large storm coinciding with perigean spring tides will severely impact beaches...
The bias of the SEPI to large storms is reasonable since one great storm often causes much more severe beach erosion than the contribution of many small storms, especially if they do not impact the dune...
Erosion is not perfectly correlated with finds either. There can be a lot of erosion and few finds. On the other hand, there can be less erosion, but if it is well placed and timed, it can produce a lot of finds. A beach can get wiped out, but if there is nothing of interest there, it does not matter much.
The paper does not discuss some of the important factors that I often discuss because of their focus on such large areas.
They also mention wave tank data, which is often not totally realistic for a variety of reasons. For example, wave tank waves always hit straight on instead of at angles. That is just one of many factors that limit the value of wave tank observations.
I could go on with this at length, but I will leave it to you to review the paper if you want to. It is useful. You will find mention of several specific storms
Here is the link.
https://journals.flvc.org/jcr/article/download/81292/78431
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| Source: MagicSeaweed.com |
Expect a bigger surf Wednesday. Unfortnately the tides are not big and the wind direction won't be great.
Happy hunting,
Treasureguide@comcast.net