State of disaster declared after major flooding in Texas

The state of Texas, which experienced one of its wettest springs on record, received additional heavy rainfall during the last two weeks, causing major flooding throughout the state, according to catastrophe modelling firm AIR Worldwide.

The floods significantly impacted the areas around Austin, San Antonio, Houston, College Station and Dallas.

As rivers rose beyond their flood levels and flash floods raced through bayous and low-lying areas, residences, commercial properties, vehicles, agricultural land, and drilling fields were swamped, while roads were shut down and even washed out, and bridges were damaged.

Governor Greg Abbott has declared a state of disaster in 31 counties, due to the severe weather.

“During the last two weeks of frequent, intense, and often slow-moving storm systems, extraordinarily high rainfall amounts were recorded in many communities in Texas,” said Marc Marcella, senior scientist at AIR Worldwide. “Many areas recorded very heavy rainfall amounts, 10 to 20 inches in a 24-hour period. Flash flooding ensued due to the very high intensity of downpours, as high as 3 inches per hour in some locales.”

AIR has said the storm systems responsible for the massive flooding have now dissipated, along with flood levels in most places. Flood damage and clean-up will, however, persist for some time. Parts of other states, such as Oklahoma and Louisiana, were also drenched by the storm systems affecting Texas, although flooding has not been as severe and dramatic in those areas.

Marcella continued: “Recently a slow-moving, weak, upper-level low traversed the Southern Plains. The circulation around the upper-level low aided in streaming tropical moisture from the Gulf of Mexico northward over the Southern Plains. Numerous thunderstorms tracked over the same locations, leading to heavy rainfall and increasing the threat of flash flooding over the Southern Plains and the lower Mississippi Valley.”

“The strong southerly feed of low-level moisture from the Gulf of Mexico, responsible for severe thunderstorms across the lower Midwest and Midlands, was driven back by the rain-soaked and hence cool air from the Central Great Plains and Southern Plains. This moisture, forced into Texas, fuelled several mesoscale convective systems (MCSs) that produced torrential rain from May 26 to May 27. In Brenham, for example, a town between Austin and Houston, 16.62 inches of rain fell in one day with most rainfall occurring in the 12-hour period between noon and midnight Thursday, May 26.”

According to AIR, the upper low slowly trekked toward eastern Texas by Friday and then stalled out before drifting southwest. Eventually, the low dissipated and was carried out by a stronger upper trough moving through the eastern United States. As a result, the possibility of multiple rounds of heavy thunderstorms with torrential rain continued in the central and eastern portions of the state.

Over the last two months, Texas has received substantial amounts of rain, 3 feet, for example, in some eastern parts of the state, as much as 20 inches in some areas around the long Memorial Day weekend, and as much as 8 inches in the Dallas area between May 1 and 2. For some municipalities, such as Austin, College Station, and San Angelo, 2016 has been the wettest spring on record; for others, such as Houston, the second wettest.

“With many rivers already high, the torrential rain of the last two weeks pushed them beyond flood state,

Residential flood insurance is typically offered to homeowners only through the National Flood Insurance Program (NFIP).

Because flood damage and associated losses can result from time-related elements (eg length of exposure to floodwater, how quickly mitigation is undertaken, and extent of business interruption), and can vary greatly by exposure (eg 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.

AIR has said it will monitor the situation and will provide updates as warranted.