COASTAL PROCESSES
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The driving force for the creation of coastal landforms is wave action. Although we commonly think of the devastation produced by hurricanes as being characteristic of our coast, most of the time we have rather benign conditions. The coast is mainly depositional. |
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Almost all of our coastlands are low-lying, so that there is little chance for cliffs to form, even when there are times of erosion. |
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Most of the deposition is the result of sand movement up or along the beach. The upslope movement creates dunes.
Although these are created primarily by wave action, they need to be stabilized by vegetation before they can become a permanent - or at least semi-permanent feature of the shoreline. Vegetation root systems serve to bind the sand particles together into a solid mass, preventing ready removal by storm waves or even by wind action.
Actions which destroy or deplete the dune vegetation can lead to major erosional problems. |
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Indeed, storm waves will always attack the dunes and produce some erosion. In many cases, if the vegetation has been removed or stressed, the result is some removal or sand from the dune front and/or some over wash of sand from the seaward to the landward face. In both cases the effective result is dune retreat. In the case at left, the retreat is clearly indicated by the abandoned boardwalk. In this case the retreat has been as much by sand migrating along the beach, under the influence of prolonged beach drift, away towards the horizon. |
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In many cases where development has taken place close to the shoreline, the result is the undermining of foundation of structures and their potential loss to the ocean. Groins or sandbags (seen at right) may provide a temporary solution, stopping the flow of sand along the beach. This, of course, causes problems for those downstream, who are thus deprived of their source of beach sand.
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The current situation, where deposition dominates, has not always been the case. Small "cliffs" - sown at left - at waters edge in the northern part of the coastal plain indicate a recent period of erosional activity. Further, several thousand years ago, sea level was considerably higher than it is now. Cliffs, maybe not very high or spectacular but cliffs nonetheless, were formed at the old shoreline. Now several of them can be seen with careful observation. The one shown at right is probably one of the clearest, although not the easiest to photograph. This is the rise westward out of the Great Dismal Swamp in Gates County up the slight hill on US Highway 158. |  |
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This area close to the current coastline which was underwater not too long ago is not an exceptionally flat area. It is commonly regarded as part of the outer coastal plain or as the "Tidewater" region. This area if North Carolina is fairly narrow in the south, but covers much of the north-eastern part of the state. |
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Finally, the current smooth depositional coast may be great for beach activities, but they make it difficult to establish decent deep-water ports. Even the port at Wilmington (shown at right), some way up the Cape Fear River, is in an area of deposition. The river has to be dredged almost continuously for keep the port operational. |
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