TIDES

The mean tidal range at Wilmington is 2.5 feet, and at the ocean bar 4.5 feet, while the extreme tidal range is 4.1 feet at Wilmington and 6.7 feet at the ocean bar.

TIDAL CURRENTS

The tidal currents on the ocean bar run with considerable velocity, and as a rule set nearly in the direction of the channels; but on the last of the flood and first of the ebb they tend more or less across the shoals. Abreast of Southport the estimated velocity of the ebb at strength of spring tides is 2.5 to 3.5 knots. At ordinary times a strong flood is felt for a considerable distance above Wilmington, where it runs 54 hours to nearly 7 hours of ebb.

Freshets.-Low-water stages prevail in the rivers above Wilmington from 2 to 4 months during the summer, and freshets usually occur as often as once a month during the remainder of the year, but with no regularity.

ANCHORAGES

The best anchorage is off the town of Southport, about 21⁄2 miles above Bald Head Lighthouse, where the depth ranges from 4 to 6 fathoms. This basin has an area of 2,100,000 square feet. At this point the holding ground is good, but on account of the strong tidal currents vessels should anchor with a good scope of chain. This anchorage is sometimes used in winter as a harbor of refuge by coasting vessels. Abreast the southern end of Wilmington, on the easterly side of the river north of Alligator Creek there is a limited anchorage basin with a depth of 30 feet. This basin is approximately 2,000 feet long and has an average width of 1,000 feet.

Vessels are cautioned not to anchor on or near a line from Bald Head Lighthouse to Fort Caswell, on account of the Government submarine cable.

WEATHER CONDITIONS

Open season for navigation.-The channels of this harbor are navigable throughout the year.

Prevailing winds. The prevailing direction of wind for a period of 60 years has been northeast during the months of September, October, and November, and southwest or west during the remainder of the year.

Fogs. Fogs are most prevalent during the winter and fall. The average number of foggy days per month is two.

Precipitation. The average annual precipitation computed from the Weather Bureau records of 50 years is 46.93 inches. The table below gives the precipitation for each month.

Temperature. The mean daily minimum temperature for 46 years is 54.5° and the mean daily maximum temperature for the same period, 71.8°.

Meteorological data

Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Annual

37.1

37.6 43.4 53.3 63.3 69.6 71.1 69.1 64. 4 56.7 47.6

Maximum hourly rate of the wind velocities and direction for 60 years 1

There are three bridges across the channel within a radius of 2 miles of Wilmington; two across the Northeast Branch and one across the Northwest Branch. The first bridge across the Northeast Branch is a steel State highway bridge and crosses about 1 mile above the mouth. This bridge has a double-leaf bascule channel span with a clear opening of 150 feet. The second bridge on the Northeast Branch is a steel railroad bridge with a clear channel span of 95 feet, and is located about 11⁄2 miles above the mouth. The bridge on the Northwest Branch is a steel State highway bridge, has a double-leaf bascule channel span with a clear opening of 120 feet, and is located about 1,000 feet above the mouth of the Northeast Branch.

There are six other bridges from 264 to 56 miles above the mouth of Northeast Branch, all of which are opened for boats. On Black River there are six bridges located from 14 to 53 miles above the mouth, 5 of which are opened for boats. On the Northwest Branch there are two other bridges, one located 34 miles above the mouth near Navassa, and the other at Elizabethtown, 102 miles above the mouth.

For detailed information in regard to these bridges see table, page 118.