Fig. 65—A tidal delta built up until it is partly above water: Popes Creek, Virginia, on the right bank of the lower Potomac River, 4 miles southeast of Colonial Beach, as seen obliquely from a height of 4,000 feet at 3:30 P.M., August 31, 1920. The tidal currents from the Potomac have built hook-shaped bars nearly across the outlet of the creek, and the inflowing currents have built a delta from the mouth of the creek upstream.
It is fortunate for those engaged in the study of shore features and the mapping of coasts that, being flat, shore features are particularly well adapted to representation by air photographs, for on coasts exposed to the wind and waves the channels, shoals and bars are continually changing. Air photography offers a quick and convenient means of keeping charts up to date. The intricacies of the water line in some places makes accurate charting by the ordinary survey methods a slow, laborious process. When bluffs or relatively steep slopes, like those of York River, Virginia, near Gloucester Point, shown in Figure 60,
Fig. 66—A double tidal delta at Barnegat Inlet, New Jersey, as photographed from a height of 10,000 feet. To the east (right) the breaking waves and shadowy depths indicate the position of shoals. West of the surf belt are the light-colored beach sand, shading off from the conspicuous hook at the southern end of Island Beach into underwater shoals and bars, and older surfaces made dark-colored by the growth of plants. South of the hook are the inlet leading into Barnegat Bay and the northern end of Long Beach, at the point of which stands a lighthouse whose long shadow is to be seen across the beach sand. The mottled appearance of the bay to the left is due to shoals slightly submerged or perhaps exposed at low tide, where dark-colored drainage lines appear, and shading off to deeper water, where the submerged land forms have a shadowy appearance. The distribution of the shoals indicates that this is a double tidal delta, an infacing part west of the inlet and an ocean-facing part to the right. Scale, about 1:17,000.
Fig. 67 Fig. 67—A tidal inlet through the barrier beach south of Beach Haven, N. J., connecting the Atlantic Ocean to the right (east) with Little Egg Harbor to the left. The beach sand south of the inlet is little above water level and is frequently washed by waves, which shift the sand and produce the clouded appearance of the sandy surface. The light-colored ragged belt at the right is surf; the continuous narrow belt, beach sand; the clouded areas, recently washed wet or slightly submerged sand. (The ordinary tidal variation here is 4.2 feet.) This inlet does not appear on the 1914 edition of U. S. Coast and Geodetic Survey Chart 1216, and sand hooks had little more than begun to form then. Scale, about 1:14,000.