Myths and Misconceptions about Flooding in Huntsville
Many people believe that if they are not in the floodplain they won’t have flooding or drainage problems. This is a commonly held misconception. In fact, floodplains are normally only determined for the largest streams, and do not include smaller drainage channels and streams. Between major floods in Huntsville, more than 90 percent of drainage complaints come from residents not in the floodplain. Many of these drainage issues occur on properties located on the sides of local mountains.
The National Oceanic and Atmospheric Administration (NOAA) has determined that the probable maximum rainfall that could occur in Huntsville is 40 inches in 24 hours. Though this amount of rainfall will probably not fall in our lifetime, if even half that much fell, almost every drainage channel and street in Huntsville would flood including those on top of Monte Sano Mountain. Many homes not in the 100-year floodplain would also flood.
Another common myth is that ‘100-year floods’ only occur once in 100 years. The term “100-year flood” is commonly used to refer to those big event floods that statistically have a 1-percent chance of occurring in any given year. For example, some living in Aldridge Creek might think that because they experienced the June 28, 1999 flood, they shouldn’t expect another similar flood until 2099. In fact, another ‘100-year flood’ could occur tomorrow. Remember, a ‘100-year flood’ has a 1% chance of occurring in any given year. However, it is quite possible to experience 3 ‘100-year floods’ in a single year.
Some believe that Aldridge Creek is Huntsville’s only major flooding concern. In March 1973, you could ride a boat down Memorial Parkway from Governor’s Drive to Drake Avenue. According to the Federal Emergency Management Agency (FEMA) flood maps for Huntsville, the Hall Avenue Bridge over Broglan Branch would go almost six feet under water during a 100-year flood. By comparison, FEMA maps indicate that Lily Flagg Road bridge over Aldridge Creek would go less than 1 foot under water in a 100-year flood. At Hall Avenue, the floodplain is almost a mile wide and the floodplains for Pinhook Creek and Broglan Branch merge. The City is currently evaluating several projects that would alleviate some of these issues. The remedies will require a watershed computer model to determine the most effective measures.
Any resident of Huntsville who has a question regarding flood mitigation progress in Huntsville can call (256) 427-5300 for more information.