The national National Day fireworks are in Taitung on Saturday, October 10, not in Taipei. The site is the south bank of the Beinan River mouth, with the main ground near the international landmark by Haibin Park. The theme this year is an Austronesian ark. The show is scheduled for 8 p.m. and runs about thirty minutes. Taipei 101’s separate performance starts two hours later. You cannot do both in person.
Taiwan Railways is the ordinary way east. High-speed rail ends at Taipei, Banqiao, or Taoyuan for anyone coming down the west; the east coast is a TRA ride through Yilan and Hualien, or a connection at those stations. A holiday Saturday evening in Taitung is not a walk-up ticket. Reserved seats on the limited express go first. If you are still in Taipei on Saturday morning, assume you are watching the tower, not the river. Leave Friday, which is already the substitute holiday, and stay the night.
The useful ground is the south bank and the park around the landmark. A bridge control is expected from about 6:30 p.m. to 9 p.m. on Zhonghua Bridge, which is the road toward Fugang fishing harbor. Boat operators out of Fugang have been selling a sea viewing at about NT$850, through the harbor ticket desks of the Green Island ferries, and those sailings depend on weather notices two days out. Do not build the night around a boat until that notice is up.
After 8:30 p.m. the station will be a crowd trying to leave a small city. A same-night sleeper back to Taipei is a rumor unless you already hold the ticket. Sunday trains are the realistic return. Hotels in central Taitung and near the station are the practical base; the firing ground is a shuttle or a taxi problem, not a stroll from most rooms. Check reserved-seat inventory on the Taiwan Railways booking site before you promise anyone the east coast.