AIR Worldwide: Storms in Texas Brought Up to 600% of Long-Term Average Rain Amounts

Catastrophe modeling firm, AIR Worldwide, reports that over the last several weeks, much of Texas has experienced 400 percent to 600 percent of long-term average rainfall amounts.

The storms have subsided for now, but during the recent storm period many areas of the state recorded very heavy rainfall amounts, 10 to 20 inches in a 24-hour period, AIR said. In Brenham, a town between Austin and Houston, 16.62 inches of rain fell on May 26, with most rainfall occurring in the 12-hour period, according to AIR.

Major flooding has occurred throughout the state, with areas around Austin, San Antonio, Houston, College Station, and Dallas significantly impacted. Flood damage and cleanup will persist for some time in many of the affected areas.

Texas Governor Greg Abbott has declared a state of disaster in 31 counties.

Due to high water in the Colorado River, officials closed Lake Austin, Lady Bird Lake, and the river itself downstream of Longhorn Dam in Austin. Outside Austin, Colorado River flooding affected Bastrop and La Grange.

Aside from far northern and far western areas of Texas, most of the state has been affected by the recent weeks of heavy precipitation. The flooding impacts have been substantial, from property damage to closed highways (including interstates and other major roadways), affecting both travel (nearly 200 flight cancellations in Dallas and Houston) and commerce. Hundreds of water rescues have taken place, and some communities — such as Kingdom Heights, west of Houston — have been isolated since highways became impassable.

According to AIR, the vulnerability of buildings to flood damage depends on many factors, including construction and occupancy, and building height and age. In general, damage due to inundation tends to be nonstructural, affecting interior finishes, such as drywall, plaster, insulation, and flooring, in addition to building contents. In severe inland flood events, high-velocity flood and debris can compromise the structural integrity of a building, which can lead to the collapse of foundations and the displacement of structural walls.

AIR reports that in Texas, more than 8 percent of the residential construction is wood and an estimated 5 percent having basements. The presence of a basement increases the risk for contents and building damage.

Over half of the commercial buildings are steel and concrete. Unlike residential structures, commercial buildings often are engineered and built to stricter standards, and are thus less vulnerable than single-family homes. Still, mechanical, electrical and plumbing (MEP) systems can experience severe damage, which results in high losses.

In the Houston area, officials began asking residents and business owners during the period of heavy precipitation to report flood damage to help facilitate obtaining federal disaster assistance.

Because flood damage and associated losses can result from time-related elements (e.g., length of exposure to floodwater, how quickly mitigation is undertaken, and extent of business interruption), and can vary greatly by exposure (e.g., physical location of utilities in a structure, construction materials used, and occupancy), the impacts to the insurance industry will become clearer as floodwaters recede and assessments can be conducted.

Source: AIR Worldwide