Hurricane Irene is headed to the American Southeast coastline as we speak.  With hurricanes comes flooding, both storm surge and inland. Storm surge flooding happens right along the coast, and comes mostly from the winds of the hurricane pushing water around and causing the level to rise.

Inland flooding, on the other hand, happens far away from the coastline.  Remember, hurricanes carry a huge amount of water in their storm body.  When the hurricane hits land, it starts to dump that water in the form of rain.  Depending on the particular storm (tropical cyclone/hurricane/tropical storm), it can drop as much as a foot of rain in just a few hours. 

The effect that this amount of rain will have on an area depends on several factors.  Is the ground already saturated?  How fast is the storm moving?  Is the area hilly or mountainous?  What other weather is the storm running into?  Is the area urban or more rural?

If the ground is already saturated from earlier rain, the water from the tropical storm will have nowhere to go, and will start flooding rivers, streams, lakes, streets, storm drains.  If the storm is moving slowly, it will drop more rain over a given area than if it is moving faster.  Hilly and mountainous areas push the storm higher, causing it to intensify somewhat.  The collision of multiple storm systems disrupts them both, but making them both dump rain and possibly spawn strong and chaotic winds. 

Inland flooding is particularly dangerous in urban areas, where there are a lot of streets, parking lots, and other man-made flat features.  The natural drainage around these areas can be seriously changed by land development.  To put it one way, there is not much place for the excessive water to go.  This can cause streets to become flooded with water.

Flood safety

  • First, listen to your NOAA weather radio for storm and flood information.
  • Second, NEVER DRIVE THROUGH FLOOD WATER.  It only takes a couple of inches worth of water to lift up a car and wash it downstream.  This can end up with you dead.  Also, moving water can wash out the road and you will probably not see if there is roadway missing. Turn around, don’t drown.
  • Third, if you are on foot, do not cross water that is more than ankle-deep.  Moving water is incredibly strong, and can sweep your feet out from under you amazingly fast.
  • Fourth, do not let children play in around streams, creeks, storm drains, or high water when there is a flood.  These are all dangerous areas.

If you end up being caught outside when there is danger of a flood, stay away from low-lying areas and areas likely to flood.  STAY OUT OF DRY CREEK BEDS.   If possible, get to higher ground quickly.  If you are driving and your car stalls, get out and find higher ground right away.

The National Weather Service has some great information resources about flooding in general and hurricane-related flooding in particular.  I urge you to spend a while perusing their site and learning a little more about your own area.  What you learn might just save your life.

Stay safe!