How our Blue Ridge Mountains enhance flooding in the region

Safety in the Storm

(WFXR) — Tropical systems, including hurricanes, are the largest storms on the planet. They cause significant damage each year. Originating in the warm tropical waters of the world, hurricanes are easily associated with coastal damage, coastal flooding, significant winds, storm surge, spin-up tornadoes and major devastation.  But for western Virginia, the main issue with hurricanes is classified as inland flooding.

Once these monster storms lose the ability to gain strength from the warm ocean waters and come inland, they drop significant rain as they deteriorate to tropical storms, tropical depressions and finally a remnant low-pressure system.  By the time the storms get to Western Virginia, they have little left in the tank, but for our region, a little can go a long way that results in major flooding.  The reason is our topography — or more simply put — the mountains.

Our lovely Blue Ridge Mountains help to squeeze out some of the remaining moisture from the remnant low by what is called upsloping winds.  In other words, as the winds associated with the remnant low circle around the center of the storm, they encounter our mountains. The winds at the surface ride up the face of the mountain and into the cooler air high in the sky.  The air, with a great deal of moisture in it, cools and condenses and rain is developed and enhanced.  

If the storm were over flat land, it would gradually release the tropical moisture obtained from the ocean and although there may be some widespread flooding issues, the ferocity of the rain may be much less.  In our region, the water is released quickly in a more concentrated area, which leads to flooding and flash flooding thanks, in part, to the upsloping winds.

But that is not the only issue facing our region with respect to flooding, and not the only issue with our mountains.  The mountains also act to channel the water as it flows down the hills to the lower valleys. The valleys below get overwhelmed by the swift-moving water that has been focused, or constricted, into the canyons.  Streams are quickly overwhelmed by the fast introduction of the water and the water flows via the path of least resistance to the lower elevations.  Low-lying regions are overrun and flooded, larger rivers become swollen and flooding and flash flooding becomes widespread.

Inland flooding due to the rapid release of the rainwater enhanced by upsloping winds and the channeling of the water from the mountains to the valleys overpowers the region quite frequently. Even three to four inches of rain leftover from a deteriorating hurricane can cause significant damage and devastation to the area. 

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