The beach water table as a response variable of the beach-ocean-atmosphere system
Fluctuations of the water table in a marine beach over a rising half-tide cycle were investigated as a function of variations in local still water level, swash runup distance, distance of a sampling station from the shoreline, and atmospheric pressure. The data were taken from a 30-day time series o...
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| Format: | Others |
| Language: | English |
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W&M ScholarWorks
1970
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| Online Access: | https://scholarworks.wm.edu/etd/1627407592 https://scholarworks.wm.edu/cgi/viewcontent.cgi?article=7170&context=etd |
| Summary: | Fluctuations of the water table in a marine beach over a rising half-tide cycle were investigated as a function of variations in local still water level, swash runup distance, distance of a sampling station from the shoreline, and atmospheric pressure. The data were taken from a 30-day time series of observations of environmental variables taken at Virginia Beach, Virginia, during August and September, 1969. Sequential linear multiple regression analyses were used to rank the process variables in order of importance in each of 13 water-table monitoring wells spaced along a transect transverse to the shoreline . Results showed that tidal fluctuations exert the strongest influence in all except the two seawardmost wells and the most landward well. Distance from the shoreline is the most important variable in the seawardmost wells because of the exponential decay of the input wave and the resultant large range of water table fluctuations near the beach face. Atmospheric pressure becomes the dominant variable influencing water-table fluctuations in the most landward well, due to the relatively slight contribution of the tide and wave inputs. The amplitude of the water table fluctuation decreases exponentially in a landward direction and the lag time of the input tide wave increases linearly with the distance from the shoreline.The time lag is found to be approximately 60 minutes per 18 meters of beach penetrated. This value is somewhat less than that determined by Emery and Foster (1948), who found a lag time of from one to three hours at distances between 20 and 40 feet (approximately 6 to 13 meters) from the shoreline. This dissertation is from the Joint Program Degree from the College of William & Mary and University of Virginia and awarded by the University of Virginia. |
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