Maywood Riverfront Park was built on the site of eight former industrial properties in Los Angeles County. Luis Sinco/Los Angeles Times via Getty ImagesFloodwaters are a growing risk for many American cities, threatening to displace not only people and housing but also the land-based pollution left behind by earlier industrial activities. In 2019, researchers at the U.S. Government Accountability Office investigated climate-related risks at the 1,571 most polluted properties in the country, also