The purpose of this report is to characterize Delaware Atlantic Coast beach sand on the basis of sand texture data in order to identify geologic material suitable for beach nourishment.
On December 10, a low pressure system moved rapidly north-northwest from eastern North Carolina and Virginia, up the Chesapeake Bay to a position just west of Chestertown in Kent County, Maryland by 0700 on December 11. The system then moved irregularly to the southeast, stalled for several hours over Georgetown, Delaware, and proceeded offshore early on December 12. Approximate locations of the storm's track are shown on Figure 1. The storm had associated rain that contributed to some local stream flooding and high winds that created strong surf and waves. The waves were compounded by an astronomical high tide (full moon) to produce coastal flooding along Delaware Bay and some breaching of the dunes along the Atlantic coast. The position of the storm offshore blew north-northeast winds onto the coast and abnormally high tides continued through December 15.
On January 4, 1992 an intense storm moved from the east across the Delmarva Peninsula and the Chesapeake Bay. Its track was the result of the low pressure being pulled westward by a strong cold-cored upper low moving across Georgia and South Carolina. The storm exhibited tropical/subtropical characteristics on radar. Satellite photos indicate that an "eye" to the storm formed just prior to landfall. Landfall occurred over the southern Delmarva Peninsula just prior to the time of high tide (0648 at Ocean City, Md). The storm weakened rapidly as it moved over land areas with a secondary area redeveloping farther out to sea later in the day on the 4th. Approximate locations of the storm's track are given on Figure 1. As the storm moved across the Delmarva Peninsula perpendicular to the coast, Delaware was in the right-foreward quadrant to the north of the "eye" of the storm. This position typically produces the highest winds associated with a tropical storm. These winds created high waves that in conjunction with an astronomical high tide (new moon) produced strong surf and abnormally high tides along the shore. Rainfall from the storm in Delaware was not heavy enough to cause flooding of streams. Coastal flooding of marshes and low-lying areas did occur along the Inland Bays and along Delaware Bay.
Coastlines are not static features. They are shaped by the daily effects of wind, current, and wave activity. Over time, a coastline may move landward due to relative sea-level rise or low sediment supply, or seaward due to relative sea-level fall or an overabundance of sediment. Perhaps the most striking example of shoreline movement in Delaware is at Cape Henlopen which has grown northward approximately one mile in the last 160 years. Maps and aerial photographs show these changes.
The need for locating additional sources of ground water for the Delaware Atlantic seashore, a predominantly recreation-oriented area, is indicated by an expanding population in the belt between Philadelphia, Pennsylvania and Washington, D.C., combined with increasing leisure time. Present water use in the shore area is approximately 4 million gallons per day and will reach 9.3 million gallons per day by the year 2000. A new geologic interpretation of the occurrence of deep aquifers in the Delaware Atlantic seashore area is presented. Recent data from deep wells has enabled the construction of a more accurate geologic framework upon which the hydrologic data are superimposed. Correlation of Miocene sands concludes that the Manokin aquifer lies at greater depths in southeastern Delaware than previously thought.
The core of much DGS work culminates in the release of data and findings in official DGS publications, including Open File Reports, Reports of Investigations, Geologic Maps, Hydrologic Maps, and Bulletins.