MONITORING THE EFFECT OF HURRICANE ISABEL IN THE SURFICIAL AQUIFER WITH SHALLOW MONITORING WELLS ON BOGUE BANKS, NC

Isabel, a class 2 hurricane, made landfall near Bogue Banks, NC, at 12:00 PM on the 18th of September, 2003. On September 16th, five shallow wells in the water table aquifer between Salter Path and Pine Knoll Shores were equipped with sonic water level data loggers that recorded water table elevations every five minutes until September 25th. The effects of a large, low pressure system on water levels in the surficial aquifer were monitored using these wells.

On September 17th, water levels quickly rose in the wells at 17:46 prior to Isabel’s landfall, even though low tide was at 18:53. Maximum water table elevations were recorded in each well between 13:45 on September 18th (well TCW04) and 2:00 on September 21st (well TCW05). The maximum water levels appear first in the wells closest to Bogue Sound on the northern edge of the island and latest in the wells on the southern, oceanward side.

Maximum head values in each well appear at different times because of the effects of several factors, such as normal tidal oscillations, the storm surge and low atmospheric pressure associated with Isabel, and rain water infiltration. The uniform rise in water levels that began on September 17th peaked between 12:00 and 14:52 on the 18th, and was most likely associated with the passing of the western edge of Isabel’s eye. When the low pressure system passed, wells close to Bogue Sound (TCW3 and TCW4) quickly returned to pre-Isabel water levels, and exhibited a higher amplitude tidal signal than the wells located in the interior of the island (TCW2, TCW5, and TCW7), which all showed a muted tidal signal. Water levels in wells TCW2, TCW5, and TCW7 remain elevated for a week after the storm which probably is related to rain water infiltration.