Because of delays to the finalizing of the continuing flood prevention plan, Shetzu Island, a sandbar formed by the alluvium deposited by the Tamsui and Keelung Rivers, became designated as a "flood district" because of its low-lying terrain, low population (only 2,000-3,000) and low economic value. Development was prohibited, and the island became an area of green fields used only for agriculture.
由於後續防洪計畫遲遲未定案，因此，由淡水河及基隆河挾帶泥沙所沖積而成的沙洲地社子島，便以其低窪的地勢、稀少的人口﹘﹘不過二、三千人，經濟價值低等因素，被列為「洪氾區」，實施禁建，只能作為農業用地及綠地。