The East Coast is under siege this week with widespread flooding. Seasonal flooding is common, but what’s unusual about this week’s storms is the sheer size of the area they cover; nearly 700 miles of coastline and cities farther inland are affected. As in other floods over the past several years—Houston comes to mind—the water is high enough that some residents have needed to be rescued from buildings and vehicles. Flash flood warnings are in effect for several states, and the rain will continue for much of this week. Some areas have received as much as 10 inches of rain so far.

At least three deaths have been reported, two of them caused by falling trees. And, dangerous as the floods themselves are, the trees are a risk that remains long after the water recedes.

Farther west, storms have also caused flooding and closed roads, particularly in Colorado and New Mexico. Most of the western US, though, is still dry, with many cities hitting record-high temperatures and some states still considered to be in drought conditions.

Here’s where the two conditions converge, in an unlikely way—with the trees. The states that have had long-term drought are experiencing large die-offs of trees, which are first weakened by lack of water and then sometimes finished off by parasites or storms. California alone has lost more than 100 million trees, according to surveys done by the US Forest Service.
Trees that are damaged by wind or that have had their root systems weakened by flood waters are at risk even after the storms themselves are over. As this University of Missouri Extension guide shows, the steps we take to fix the damage are often misguided at best, and more likely to make the tree or its limbs fall at some unexpected time in the future. For example, topping a damaged tree—that is, drastically cutting back its branches as many people do after a storm because they think it will avoid falling limbs during the next high wind—makes it more likely that the tree will either die because it doesn’t have enough foliage, or will grow several small, weak branches at the site of the cuts.