Del. Code tit. 22, § 707

Upon final action by the proper authorities in laying out, altering or relocating a proper way or in discontinuing the whole or any part thereof or in establishing or enlarging a public park or closing thereof in whole or in part, the lines and notations showing such improvement, discontinuance or closing, as so established or effected, shall, without further action by the city council or town commissioners, be made a part of the official map, if any, of the incorporated city or town in which such public way or park is located.