The devastating flood that made a Maryland town look like the set of a disaster movie was unexpected and almost unprecedented. According to the National Weather Service, 5.52 inches of rain fell in a 90 minute period. 3.16 of those inches fell just in the first thirty minutes of the storm. The NWS classified the event as a 1,000 year event, meaning the statistical odds of this kind of deadly flood happening are about .1% in any year.
Was the storm a result of climate change? That remains to be seen, the experts are still duking it out over numbers and scientific reports. There are a couple of reasons why the flooding was so dangerous. As cities and towns continue to sprawl out into more rural areas, there are more impervious surfaces…concrete and asphalt roads don't soak up rainwater like undeveloped ground can. Another factor that has been discussed is water run off management. Storm drains, catch basins and other water management structures were built when rainfall amounts were lower. There's more rain now, which is attributable to climate change and the systems most cities and towns have are not equipped to deal with the run-off.
