Question: How many meters is Riverbank State Park elevated above the river that the Manhattan grid plan is aligned with rather than cardinal directions?

full_context: Document 1: List of numbered streets in Manhattan: The numbered streets carry crosstown traffic. In general, even-numbered streets are one-way eastbound and odd-numbered streets are one-way west. Several exceptions reverse this. Most wider streets carry two-way traffic, as do a few of the narrow ones.
Document 2: Central Park: Central Park is an urban park in Manhattan, New York City, U.S. state of New York. It comprises 843 acres (341 ha) between the Upper West Side and Upper East Side, roughly bounded by Fifth Avenue on the east, Central Park West (Eighth Avenue) on the west, Central Park South (59th Street) on the south, and Central Park North (110th Street) on the north. Central Park is the most visited urban park in the United States, with 40 million visitors in 2013, and one of the most filmed locations in the world.
Document 3: New York City: New York City is located on one of the world's largest natural harbors, and the boroughs of Manhattan and Staten Island are (primarily) coterminous with islands of the same names, while Queens and Brooklyn are located at the west end of the larger Long Island, and The Bronx is located at the southern tip of New York State's mainland. This situation of boroughs separated by water led to the development of an extensive infrastructure of bridges and tunnels. Nearly all of the city's major bridges and tunnels are notable, and several have broken or set records.
Document 4: List of numbered streets in Manhattan: Although the numbered streets begin just north of East Houston Street in the East Village, they generally do not extend west into Greenwich Village, which already had streets when the grid plan was laid out by the Commissioners' Plan of 1811. Streets that do continue farther west change direction before reaching the Hudson River. The grid covers the length of the island from 14th Street north.
Document 5: New York City: There are seven state parks within the confines of New York City, including Clay Pit Ponds State Park Preserve, a natural area which includes extensive riding trails, and Riverbank State Park, a 28-acre (110,000 m2) facility that rises 69 feet (21 m) over the Hudson River.
Document 6: The Bronx: The Bronx's highest elevation at 280 feet (85 m) is in the northwest corner, west of Van Cortlandt Park and in the Chapel Farm area near the Riverdale Country School. The opposite (southeastern) side of the Bronx has four large low peninsulas or "necks" of low-lying land that jut into the waters of the East River and were once salt marsh: Hunt's Point, Clason's Point, Screvin's Neck and Throg's Neck. Further up the coastline, Rodman's Neck lies between Pelham Bay Park in the northeast and City Island. The Bronx's irregular shoreline extends for 75 square miles (194 km2).
Document 7: New York City: New York City has over 28,000 acres (110 km2) of municipal parkland and 14 miles (23 km) of public beaches. Parks in New York City include Central Park, Prospect Park, Flushing Meadows–Corona Park, Forest Park, and Washington Square Park. The largest municipal park in the city is Pelham Bay Park with 2,700 acres (1,093 ha).
Document 8: List of numbered streets in Manhattan: 23rd Street is another main numbered street in Manhattan. It begins at FDR Drive and ends at Eleventh Avenue. Its length is 3.1 km/1.9m. It has two-way travel. On 23rd Street there are five local subway stations:
Document 9: List of numbered streets in Manhattan: 220th Street is the highest numbered street on Manhattan Island. Marble Hill is also within the borough of Manhattan, so the highest street number in the borough is 228th Street. However, the numbering continues in the Bronx up to 263rd Street. The lowest number is East First Street—which runs in Alphabet City near East Houston Street—as well as First Place in Battery Park City.
Document 10: List of numbered streets in Manhattan: This article covers numbered east-west streets in Manhattan, New York City. Major streets have their own linked articles; minor streets are discussed here. The streets do not run exactly east–west, because the grid plan is aligned with the Hudson River rather than with the cardinal directions. "West" is approximately 29 degrees north of true west.
Document 11: Appalachian Trail: New York's 88.4 miles (142.3 km) of trail contain very little elevation change compared to other states. From south to north, the trail summits many small mountains under 1,400 feet (430 m) in elevation, its highest point in New York being Prospect Rock at 1,433 feet (437 m), and only 3,000 feet (910 m) from the border with New Jersey. The trail continues north, climbing near Fitzgerald Falls, passing through Sterling Forest, and then entering Harriman State Park and Bear Mountain State Park. The lowest point on the entire Appalachian Trail is in the Bear Mountain Zoo 124 feet (38 m). It crosses the Hudson River on the Bear Mountain Bridge. It then passes through Fahnestock State Park, and continues northeast and crosses the Metro - North Railroad's Harlem Line. This track crossing is the site of the only train station along the trail's length. It enters Connecticut via the Pawling Nature Reserve. The section of the trail that passes through Harriman and Bear Mountain State Parks is the oldest section of the trail, completed in 1923. A portion of this section was paved by 700 volunteers with 800 granite - slab steps followed by over a mile of walkway supported by stone crib walls with boulders lining the path. The project took four years, cost roughly $1 million, and was officially opened in June 2010. The project was done by the New York -- New Jersey Trail Conference. The New York -- New Jersey Trail Conference maintains and updates the Appalachian Trail in New York.
Document 12: New York City: The city's land has been altered substantially by human intervention, with considerable land reclamation along the waterfronts since Dutch colonial times; reclamation is most prominent in Lower Manhattan, with developments such as Battery Park City in the 1970s and 1980s. Some of the natural relief in topography has been evened out, especially in Manhattan.
Document 13: The Bronx: The Bronx street grid is irregular. Like the northernmost part of upper Manhattan, the West Bronx's hilly terrain leaves a relatively free-style street grid. Much of the West Bronx's street numbering carries over from upper Manhattan, but does not match it exactly; East 132nd Street is the lowest numbered street in the Bronx. This dates from the mid-19th century when the southwestern area of Westchester County west of the Bronx River, was incorporated into New York City and known as the Northside.
Document 14: New York City: Gateway National Recreation Area contains over 26,000 acres (10,521.83 ha) in total, most of it surrounded by New York City, including the Jamaica Bay Wildlife Refuge in Brooklyn and Queens, over 9,000 acres (36 km2) of salt marsh, islands, and water, including most of Jamaica Bay. Also in Queens, the park includes a significant portion of the western Rockaway Peninsula, most notably Jacob Riis Park and Fort Tilden. In Staten Island, the park includes Fort Wadsworth, with historic pre-Civil War era Battery Weed and Fort Tompkins, and Great Kills Park, with beaches, trails, and a marina.
Document 15: List of numbered streets in Manhattan: 20th Street starts at Avenue C, and 21st and 22nd Streets begin at First Avenue. They all end at Eleventh Avenue. Travel on the last block of the 20th, 21st and 22nd Streets, between Tenth and Eleventh Avenues, is in the opposite direction than it is on the rest of the respective street. 20th Street is very wide from the Avenue C to First Avenue.
ground_truth: 21
sub_queries: What is the grid plan aligned with rather than the cardinal directions? Answer: Hudson River
How many meters is Riverbank State Park elevated above Hudson River ? Answer: 21