Flood Protection and Atlas 14
The National Weather Service issued a rainfall study that aims to help state and local officials better understand potential flood risk in their areas. The study, known as Atlas 14, shows that the frequency of major storms that can take place in Fort Bend County and Sugar Land is expected to increase.
The Atlas 14 rainfall values are used for infrastructure design and planning activities under federal, state, and local regulations. They also help to determine flood risk, manage development in the floodplains, and forecast flooding threats for the entire state of Texas.
How is Sugar Land responding?
Sugar Land is adopting the Atlas 14 rainfall frequency estimates for Texas. This will result in modifications to the city’s Development Code and Design Standards, the city-adopted guidelines that provide guidance for the review of requests to alter or develop new property within the city.
Changes resulting from the Atlas 14 adoption will apply to new development and redevelopment areas within the city and its extraterritorial jurisdiction (ETJ).
The city is in the process of updating city-wide ponding maps using the new Atlas 14 rainfall information. The updated maps will show areas where potential street ponding might occur due to an increase in the frequency of intense rain events.
What are some of the expected changes?
- New buildings will be required to have higher finish floor elevations and new roads will be designed and constructed in order to accommodate the new standards.
- In areas located inside the current FEMA floodplain (until FEMA issues updated maps for Fort Bend County), new buildings will be required to have a finish floor elevation 2.0 feet above the current FEMA 500-yr elevation, 1.5 feet above natural ground, or 1.0 ft. above top of curb, whichever is the more restrictive.
- In areas protected by levees, new buildings will be required to have a finish floor elevation 2.0 feet above the coincidental ponding elevation determined by the Levee District using Atlas 14 rainfall volumes.
- What is Atlas 14?
- Why is it necessary to adopt the Atlas 14 rainfall frequency values?
- Who is affected by the implementation of Atlas 14?
- What is coincidental ponding?
- Are homes built to the new standards going to produce flooding in adjacent properties?
- What is the City doing to mitigate the impact of increased rainfall frequencies?
Atlas 14 - Quick Fact
Before the study, Sugar Land had a 1 percent chance to receive 12.5 inches of rain to fall in 24 hours (1 in 100) at any given time. The Atlas 14 study shows that this amount of rainfall is now likely to occur more frequently - a 4 percent chance for 12.5 inches of rain to fall in 24 hours (1 in 25) at any given time.
Areas located inside the current FEMA floodplain boundaries and areas protected by levees might see an increased risk of street ponding due to the Atlas 14 rainfall values.
Jorge L. Alba, P.E., CFM
Senior Engineering Manager
2700 Town Center Blvd. N.
Sugar Land, TX 77479
Ph: 281-275-2780 | Fx: 281-275-2771