Engineers. It was cut off once again in 2011 by Hurricane Irene. Access to the island was largely limited to boat access only from August to late October until another temporary bridge could be built. Three state highway bridges connect the Outer Banks to the mainland, the Wright Memorial Bridge, the oldest (built in 1930, rehabilitated in 1966), carries US 158 between Point Harbor and Kitty Hawk. William B. Umstead Bridge, the second oldest (built in 1957, rehabilitated in 1966), carries US 64 between Manns Harbor on the mainland and Manteo on Roanoke Island. The newest bridge, the Virginia Dare Memorial Bridge, was completed in 2002 and carries US 64 Bypass between Manns Harbor and Roanoke Island between Manteo and Wanchese. The Melvin R. Daniels Bridge carries US 64 between Roanoke Island and Nags Head. At Whalebone Junction, the three main highways of the Outer Banks (NC 12, US 158, and US 64) all meet. Additionally, NC 615 serves as the main route along Knotts Island in the extreme north; it connects only to Virginia by land. A number of ferries maintained by the North Carolina Department of Transportation Ferry Division also serve the Outer Banks. From north to south, these are the Knotts Island-Currituck Ferry, the Hatteras-Ocracoke Ferry, the Swan Quarter-Ocracoke Ferry, and the Cedar Island-Ocracoke Ferry. Additionally, a semi-regular emergency ferry often runs from Stumpy Point to Rodanthe to serve travelers due to frequent wash-outs of NC 12 between Nags Head and Rodanthe. Additionally, private ferries are commissioned by the National Park Service to access certain islands within the National Seashores along the outer banks, these include ferries to Portsmouth Island, to Cape Lookout Lighthouse, and various locations along Core Banks and Shackleford Banks. Ecology Vegetation The vegetation of the Outer Banks has biodiversity, although it is considered the northern limit for many southern plants such as wild scrub palms. In the northern part of the Outer Banks, from Virginia Beach southward past the North Carolina border to Cape Hatteras, the main types of vegetation are sea grasses, beach grasses and other beach plants including Opuntia humifusa on the Atlantic side and wax myrtles, bays, and grasses on the Sound side with areas of pine and Spanish moss-covered live oaks. Yucca aloifolia and Yucca gloriosa can be found growing wild here in the northern parts of its range on the beach. Dwarf palmettos were once indigenous to the