April Flood Among Houston’s Most Severe Non-Tropical Cat Events

Major flooding in the Houston metropolitan area that began on Sunday, April 17, 2016, and continued throughout the week is expected to result in billions of dollars in losses, both insured and uninsured.

According to catastrophe modeling firm, RMS, the flooding on April 18 alone may end up being one of the most severe flooding events not caused by a tropical cyclone in Houston to date and is certainly the largest flood event since Tropical Storm Allison in 2001. That storm, which brought 39 inches of rain in the hardest hit areas and impacted multiple states, caused $5 billion in damages — $3.5 billion of which were insured, the Associated Press reported.

“Unlike Tropical Storm Allison, which brought prolonged rains over several days, this event was characterized by extremely heavy rainfall over a short period. As a result, the main cause of flooding was pluvial, or surface flooding,” said RMS meteorologist and model product manager Jeff Waters in a statement released by the company. “This type of flooding is common in large urban areas, like Houston, where the majority of surfaces are paved and thus contain minimal water absorption capacity. During high intensity rain events, water quickly accumulates on the surface, often leading to widespread flash flooding. Thus, events like these signify the importance of understanding all sources of flood risk — not just coastal and riverine — especially in population centers with significant amounts of exposure.”

From Sunday through Monday, 10 to 20 inches of rain fell “in parts of southeastern Texas, reaching rates as high as 4 inches an hour,” according to Daniel Rees, senior analyst at AIR Worldwide.

The April 18 downpour virtually shut down the city of Houston. Dozens of Houston subdivisions flooded and at least two interstates — I-10, the main east-west freeway, and I-45, the major north-south freeway — were under water near downtown, the AP reported. More than 1,000 homes were flooded, many for the first time, and eight people have died.

AIR noted that flood damage and associated losses are not quickly assessed due to factors such as the length of exposure to flood water, how quickly mitigation is undertaken and the extent of business interruption. In addition, losses can vary greatly by exposures, so impact to the insurance industry will become more clear as flood waters recede.

At press time, no solid numbers on commercial and residential properties losses from the April 18 flooding had been reported. However, Mark Hanna, a spokesman for the Insurance Council of Texas, said as many as 40,000 vehicles had been affected and the insurance industry is expecting around $400 million in insured auto losses.

Texas Gov. Greg Abbott issued a disaster declaration for Austin, Bastrop, Bosque, Colorado, Fayette, Fort Bend, Grimes, Harris, Liberty, Milam, Montgomery, Palo Pinto, Parker, San Jacinto, Waller and Wharton Counties following the severe weather and flooding that inundated Texas in April.

Topics Texas Flood