Flooding and flash flooding may seem to be differentiated by one word. However, the effects of the two can be catastrophically different. A flood is defined by the National Weather Service as “An overflow of water onto normally dry land” whereas a flash flood is ” A flood caused by heavy or excessive rainfall in a short period of time, generally less than 6 hours”.
John Lipe, Senior Service Hydrologist for the National Weather Service Lubbock Office explains. “When we issue flash flood warnings, the flash flood warning is typically reserved for the higher end situations and the main thing is life threatening […] Typically on the South Plains the flooding that we have is not as life threatening. Now it can be very disruptive to traffic and everything else. So we will issue flash flood warnings in Lubbock, and it’s based on level of intensity.”
Here on the South Plains, it may seem as though sometimes there is a flash flood. After all, it just takes a quick 10 minute rain shower for our streets to fill with water. But would you be surprised to know that that’s actually what is suppose to happen by design?
John says, “the drainage here in Lubbock, and really in much of the Southwest, is unique from other parts of the country. If you’re not from here and wonder why does it flood so quickly when we have heavy rains, well storm drains and everything else costs a lot of money and we don’t get that much rainfall. So we use our streets for storm drains. And so when we get even a quarter of an inch of rain, we get flooded intersections and everything else. And that’s because it is the easier way when you don’t get frequent rains is you use your streets for the runoff.”
Even though floods and flash floods don’t happen too often here, it is important to be aware of what to look out for when they do happen.
John explains, “one of the things we emphasize with flooding is that it is more life threatening at night. And the reason is not because the rain is more intense at night, it’s because you don’t see what you are driving into and what you are getting yourself into […] You can be driving 70 mph through these roads and it’s flooded, and the water can be a foot to three feet deep. And if you hit that at a higher rate of speed, you just don’t see it. And same thing anywhere, flash flooding is especially dangerous at night so we lower our criteria level for when we can issue a flash flood warning based on the time of the rain.”