Quick summary. During Hurricane Harvey, a chemical plant in Baytown, Texas, was flooded and it spilled. There are more than 2,500 similar toxic chemical depots that are located in areas prone to flooding. Many plants are built near major rivers/ports for the ease of transportation, and with increased risks of flooding, we're probably going to see more chemical spills.

Floods Are Getting Worse, and 2,500 Chemical Sites Lie in the Water’s Path, New York Times, Feb 6, 2018, by HIROKO TABUCHI, NADJA POPOVICH, BLACKI MIGLIOZZI and ANDREW W. LEHREN.

This makes me think that if you live near one of these plants, you just have to bug out, possibly even when your immediate neighborhood is safe from flooding.