FEMA creates and uses flood maps to identify a community’s flood risk. The maps are based on the collection of statistical data (flow, storm tides, hydrologic/hydraulic analyses, rainfall and topographic surveys) that many contend is outdated and inaccurate in the determination of a property’s actual flood risk. And that leads to property owners being ill-prepared to prevent uninsured losses or to add value to their respective real estate investments. As outlined in a previous post, flood maps provide broad-brush strokes, which depict geographical areas, not individual structures, and do not take into consideration structures built above the community’s base flood elevation to mitigate flooding.
LiDAR (Light Detection and Ranging) offers a more precise method of collecting data and in the post, Flood Risk Planners Await Next-Generation Laser Mapping, Patrick Marshall explains the application of this new technology to flood risk mapping.
While there have recently been revolutionary improvements in the accuracy of flood maps and in the predictive power of hydrologic modeling, by 2012 only a fraction of the country had been mapped using the newer technologies.
“The biggest change in the accuracy of flood zones and flood hazard maps in general is due to LiDAR,” said Marie Peppler, flood and hazards program coordinator at the U.S. Geological Survey.
Prior to LiDAR – from the early 1900s to the early 21st century – most elevation maps were created using manual surveying methods. The old contour maps have a margin of error in elevation accuracy as high as plus or minus 20 feet. “So we’re going from plus or minus 20 feet to 9.25 centimeters,” DeMulder said.
And when it comes determining flood risk, elevation measurements are the most critical factor, according to Peppler. “The accuracy of the map is 110 percent dependent on the accuracy of your elevation data,” she said. “As we get better elevation data sets we can do better modeling on top of that.”
This story matters to both residential and commercial property owners alike and underscores the importance of being proactive about flood risk. If you own, manage or represent property subject to flood insurance requirements, be diligent about flood risk:
- Stay informed of flood insurance rate map changes in your area.
- Contact your legislative representatives and tell them unequal treatment of property owners is unacceptable.
- Conduct a flood risk evaluation, a proactive strategy to mitigate flood risk, protect the real estate investment and verify whether the structure is built to minimize the risk of flooding.
Contact AmeriFlood Solutions for more information including a complimentary flood risk evaluation performed by an expert team of flood risk professionals.