“NOAA’s new rainfall frequency values for Texas will help state and local authorities better understand their flood risk and more accurately plan and design infrastructure to minimize the threat of flooding,” said Thomas Graziano, Ph.D., director, NOAA Office of Water Prediction.Ĭurrent standards used for infrastructure design and floodplain regulations will likely be revised based on the new values. They also help delineate flood risks, manage development in floodplains for FEMA’s National Flood Insurance Program and are used to monitor precipitation observations and forecasts that can indicate flooding threats by NOAA’s National Weather Service. NOAA Atlas 14 rainfall values are used for infrastructure design and planning activities under federal, state and local regulations. 100-year estimates around Houston increased from 13 inches to 18 inches and values previously classified as 100-year events are now much more frequent 25-year events. In Austin, for example, 100-year rainfall amounts for 24 hours increased as much as three inches up to 13 inches. The study, published as NOAA Atlas 14, Volume 11 Precipitation-Frequency Atlas of the United States, Texas, found increased values in parts of Texas, including larger cities such as Austin and Houston, that will result in changes to the rainfall amounts that define 100-year events, which are those that on average occur every 100 years or have a one percent chance of happening in any given year. A NOAA analysis released today finds significantly higher rainfall frequency values in parts of Texas, redefining the amount of rainfall it takes to qualify as a 100-year or 1000-year event.

Dfw precipitation totals