Hurricane Preparedness, Rio Grande Valley: Inland Flooding

Prior to Hurricanes Katrina in 2005 and Ike in 2008, more people died from inland flooding than from storm surge, tornadoes, and high winds combined during the last half of the 20th century. While the percentages changed dramatically after 2005, inland flooding remains a major threat to communities near and far from the immediate Texas coast when torrential rains inundate communities of all sizes.

Intense rainfall is not directly related to the Saffir Simpson Hurricane Scale. The most copious rainfall ever recorded in Texas occurred with tropical storms, not hurricanes, that drifted slowly or stalled out a bit inland from the coast.

Significant Inland Flood Producers
In 1979, Tropical Storm Claudette stalled over Southeast Texas, dumping a whopping 45 inches of rain on Alvin. 42 inches fell in 24 hours, which remains a U.S. record for rainfall over a day long time frame. Flooding deemed "unprecedented" occurred in and near Alvin, where some creeks did not return to their banks for nearly a week. In 2001, Tropical Storm Allison dumped extremely heavy rainfall across southeast Texas and southwest Louisiana, resulting in catastrophic flooding in the Houston metropolitan area. As Allison drifted to the east and then northeast, heavy rainfall and flooding spread from Louisiana through the Tennessee Valley into the Carolinas, Mid Atlantic, and as far north as Massachusetts. More than 30 people died in the Houston area, with damage costs of nearly $5 billion.

For the Rio Grande Valley and Deep South Texas, Beulah remains the storm of record for inland flooding, from September 20th through 22nd of 1967. Beulah dropped more than 20 inches of rain in a swath from Starr County northeast to Brooks County, including northern and western Hidalgo County. These rains, combined with even heavier rainfall in northern Mexico and previously saturated ground from a wet August, stressed the levee and floodway system along and near the Rio Grande River. From east of Rio Grande City to Penitas...the river flooded at a width of 3 to 5 miles, inundating largely agricultural lands. The worst flooding occurred farther downstream, when increased flows well above design capacity overspilled the Arroyo Colorado in Harlingen. Numerous homes flooded; several had water up to their rooftops!

More than 25 inches fell north of Falfurrias toward Alice. Officially, nearly 23 Inches fell in Falfurrias, which overwhelmed Palo Blanco Creek and Cibolo creek, inundating the town.

In July 2008, heavy rains associated with Hurricane Dolly resulted in widespread flooding over much of the Rio Grande Valley. The highest reported rainfall totals for the duration of the storm were concentrated over Hidalgo, Cameron, and Willacy Counties where rainfall ranged from 12 to 18 inches. An unofficial report from the Cameron and Willacy County line north of Combes suggested more Than 20 inches fell. The floods closed many roads and caused substantial agricultural losses, especially to the Lower Rio Grande Valley cotton crop. Fortunately, no injuries or deaths were directly attributed to the flooding.

Hurricane Alex in 2010 proved once again that the exact track and intensity of a storm may be inconsequential compared to impacts produced from far away effects. While 4 to 8+ inches of rain caused generally nuisance urban flooding in the Lower Rio Grande Valley, an estimated 50+ inches flowing into the Rio Grande basin from the Sierra Madre during the first half of July required dam releases which resulted in flooding of the Lower Rio Grande between Falcon Lake and Los Ebanos (Hidalgo County), and forced the Flood Control Project (floodways) into action. For much of July and August, the Rio Grande had turned from a gentle flowing channel into a 2 mile wide fast flowing river beyond levee improvements; the floodway had between 6 and 8 feet of fast flowing water within its levees from Pharr through Mercedes/Weslaco, northeastward along the Cameron/Willacy County line before exiting into the Laguna Madre near the Arroyo Colorado entrance.

What You Can Do
The following are steps you can take to protect life and property in the event of inland flooding.