11.9: Storm Surge and Tides and Subdivisions of the Intertidal Zone
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Storm Surge and Storm Tides
A storm surge is a wind-driven current of water that piles water into shallow coastal areas and onshore areas with low coastal elevation. A storm surge is a buildup of water created by winds associated with large storms where wind moves water into coastal areas that have no place to drain away.
Storm surges are typically associated with large low pressure tropical cyclones (hurricanes and typhoons) and strong extra-tropical storms that move into shallow neritic zone environments, and often have enhanced effects where coastal geography, such as a shallow bay or estuary, that cause water to accumulate. Storm surge effect are most catastrophic when they occur in association with high tide, and are often the cause of the greatest death & destruction associated with large storms.
A storm tide is when a storm surge coincides with a regular high tide. The effects of storm tides adds to the catastrophic effects of storms associated with cyclones on coastal settings (Figures 11-18 and 11-19).
Fortunately, storm tides can be predicted in association with large storms.
|Figure 11.18. Storm surge associated with a cyclone.||Figure 11.19. Additive effects of storm surge with high tide.|
Subdivisions of the Intertidal Zone
The intertidal zone is the region where land surface is intermittently exposed between the lowest-low water and the highest-high water. The intertidal zone is between the subtidal and supratidal zones (Figure 11.20). Tidal ranges influence the distribution of sediments and the habitats occupied by plants and animals.
The subtidal zone is the submerged region lying below the low-tide mark but still shallow and close to shore.
The supratidal zone is the typically vegetation-free splash or spray zone above the high water line where back-beach dunes accumulate.
A wrackline is an accumulation of shell material and debris that typically marks the location of the last high tide cycle on a beach or after a storm surge (Figure 11.21).
|Figure 11.20. Coastal environments within the intertidal zone extend from offshore bars to inland estuaries and bays.||Figure 11.21. A wrackline consisting of most shell material, pebbles, and flotsam along Plumb Beach, Jamaica Bay, Brooklyn, NY|