In the aftermath of Tropical Storm Allison, the Federal Emergency Management Agency (FEMA) and the Harris County Flood Control District began a multi-year initiative called the Tropical Storm Allison Recovery Project (TSARP) that comprehensively assessed the flood risks associated with the major flooding sources within Harris County.
FEMA and the District have worked closely together in the past to identify major flooding sources and associated flood risks within Harris County, but never on such a scale.
For TSARP, both agencies used innovative scientific techniques to determine the current flood risks posed by streams and bayous throughout the county's approximate 1,700 square mile area, including 22 watersheds and 35 communities. The information developed as a result of TSARP has been provided to the public, government officials and numerous other Harris County stakeholders, so that they can make informed, scientifically based flood management decisions about the places in which they work and reside.
Better Tools for Drainage and Flood Damage Reduction Planning Each of Harris County's 35 communities is responsible for planning and regulating new land development projects within their municipal boundaries. TSARP has provided access to more accurate flood risk information, and it allows community planners and engineers to make decisions based on up-to-date technology and conditions. This is critically important as the population of Harris County continues to grow and new land development projects are considered, planned and constructed. In addition, the District will be able to use the TSARP products as new tools for planning and design of new flood damage reduction projects within Harris County.
Comprehensive Remapping of Harris County's Floodplains FEMA's Flood Insurance Rate Maps, commonly referred to as FIRMs or floodplain maps, show which areas of the county are at a higher risk of flooding than others.
Periods of heavy rain regularly occur in Harris County, an area prone historically to flooding. As a result, it is very important that citizens possess the best possible knowledge of their flood risks for their homes and businesses. The District and FEMA believe that the citizens of Harris County want to and should know what these risks are so that they can plan accordingly.
During the late 1970s and early 1980s, the first comprehensive effort was undertaken to map the floodplains for major flooding sources in Harris County. Since that time, updates for particular areas have occurred to reflect changes in conditions resulting from things such as new land developments and the completion of flood damage reduction projects. These map updates were made with reference to the original data from the first comprehensive effort.
As a result of TSARP, not only have Harris County's floodplains been entirely remapped, but brand new and more accurate data and computer models have also been created using important advances in science and technology.
The Science Behind TSARP TSARP was a massive undertaking involving extensive use of a sophisticated laser technology called Light Detection And Ranging, commonly referred to as LiDAR, to map the ground's topography.
Developed by NASA, this laser technology has already been successfully employed by FEMA on other important projects, including recovery efforts at Ground Zero after the 9-11 attacks.
The use of LiDAR for the Tropical Storm Allison Recovery The use of LiDAR for the Tropical Storm Allison Recovery Project involved directing millions of laser beams toward the ground from low-flying aircraft, and measuring the time it took for that light to bounce off the earth and back to the recording equipment on the plane. The measurable differences in the laser's bounce time represent different heights, or the relief, of the land.
The information generated by this laser technology, along with many other parameters, was used in computer models to estimate flood elevations. Flood elevations were then mapped on base topographic maps, also produced from the laser technology. This information became the basis of the new FEMA Flood Insurance Rate Maps.
The Impact of New FEMA Flood Insurance Rate Maps FEMA's National Flood Insurance Program (NFIP) - of which every community in Harris County is a member - underwrites flood insurance for the entire nation. FEMA uses Flood Insurance Rate Maps (also called FIRMs or floodplain maps) to help determine flood risk zones and associated rates for flood insurance policies.
Example of some features of a FEMA Flood Insurance Rate Map. Note: Not taken from an actual FIRM. For representation only.
For many, the new FEMA Flood Insurance Rate Maps have little or no impact on their flood zone designation and associated policy rate, and for some, their status may have actually improved. However, it is possible that the maps may show new boundaries that would require a homeowner to purchase flood insurance for the first time.
FEMA and the NFIP are mindful that such changes can be unwelcome. For that reason, the NFIP has a "Grandfather Rule" that allows alternative rating rules for certain structures. Contact an insurance agent for more information.
If the new flood insurance rate maps that resulted from TSARP reflect a change in flood zone status with which a home or property owner does not agree, the owner has the right to appeal the change to FEMA by getting an Elevation Certificate. An Elevation Certificate is a detailed survey of a structure’s elevation to see if it is above or below the base flood elevation. An Elevation Certificate can be used to reduce the cost of flood insurance or even remove a particular structure from the 1% (100-year) floodplain.
The Importance of Flood Insurance Consider these facts: Tropical Storm Allison dropped up to 35 inches of rain in some parts of Harris County, with 28 inches falling in 10 hours. As a result, approximately two-thirds of the areas that flooded were outside the 1% (100-year) floodplain. That is a floodplain occurring from rainfall that has a 1% chance of being equaled or exceeded in any given year, as depicted on the FEMA Flood Insurance Rate Maps (or floodplain maps). Additionally, approximately 62,000 property owners who did not carry flood insurance during Tropical Storm Allison experienced flooding.
A storm like Tropical Storm Allison will happen again. It's only a matter of when... and where.
Put simply, even if you have never flooded before, or if the new FEMA Flood Insurance Rate Maps do not identify you as being at a high risk, it is strongly recommended that you purchase flood insurance. Contact an insurance agent for more information.
