Flood — Hidalgo, Texas

2010-08-01 to 2010-08-19 · near Progreso, Hidalgo, Texas

Event narrative

Flooding of the Lower Rio Grande Valley Flood Control Project floodway/levee system (spillway), which includes the Banker Floodway (from near Granjeno to just south of Pharr), the Main Floodway (from just south of Pharr to the split at the Arroyo Colorado just southwest of Mercedes, the Arroyo Colorado itself, and the North Floodway, (which extends from near Mercedes to near La Villa before curving east to northwest Cameron County), continued through a good portion of August, as water continued to be diverted through Anzalduas for several days beyond the time that water was receding upstream of the dam. Continuing water diversion helps reduce the potential for backwater flooding along the improved levee section (Penitas to Anzalduas) as well as unprotected shorelines west of Penitas. At the same time, the diversion maintained several feet of water in the floodways for days to come which receded more slowly. The floodway emptied out for the most part by August 15th, but local high water hazards continued through at least the 18th.

These floodways, protected by a robust system of levees and gates, protected communities outside of the levees by containing up to 50%, or 4 to 8 to feet of fast flowing water, within them into the first third of August. Unfortunately, a number of residences, dozens of paved and unpaved roads with low water bridges, and some agriculture are located within the floodways; significant damage was noted in several locations. Pumping and plugging operations near Weslaco and La Villa successfully kept high water out of poor drainage locations where the potential for freshwater flooding due to heavy rains would have been exacerbated with periodic thunderstorms, which did not materialize in August. Closed roads included FM 493 and FM 1015, each moderately traveled; at least five homes were flooded along the Main Floodway south of Pharr along I Road; 15 to 20 homes were asked to voluntarily evacuate, and at least two other residences were flooded south of Weslaco near FM 88. Floodwaters also submerged portions of the Llano Grande golf course in Mercedes.

Voluntary evacuations were finally lifted along I Road (Capote Farms subdivision) on August 18th at 6 PM CST, where the 15 to 20 homes mentioned above were located. Wet, muddy conditions continued in these areas until the last week of August; damage assessments began on roadways and bridges impacted in the floodway after the waters finally receded. In all, the floodways contained water for more than 6 weeks.

High flowing water along the river covered a large portion of the Lower Rio Grande Valley National Wildlife Refuge (Santa Ana) south and southeast of Pharr, including a number of unpaved roads. Damage to the roads was unknown at this time; the flooding occurred downstream of the Anzalduas Diversion Dam; river gages downstream at San Benito and Brownsville remained in action stage. Floodwaters did not reach public or private structures, nor roadways, between the Refuge and the Main Floodway. The water finally receded back to muddy pockets sometime between August 27th and 28th.

There was one reported fatality in early August; a man drowned after reportedly driving his vehicle accidentally into the fast flowing waters of the floodway late on August 1st or early on August 2nd. His body was found along the south side of the Main Floodway, near S. Jackson and W. Juan Balli Road just west of Pharr.

Several crops may have been destroyed by the flood along the Main and North Floodways, but damage was unknown as of this writing in this area. Property and infrastructure damage may have exceeded [$10] million in these areas. Note: Dollar damage estimated for the flooding are provided in the July report.

Wider weather episode

Torrential rainfall from Hurricane Alex and remains, followed by daily peltings of rain across the front range of the Sierra Madre Oriental, and concluding with the remnants of Tropical Depression Number 2 dropped perhaps 50 or more inches of rain across Coahuila Province, Mexico, which flowed steadily through the Rio Grande basin, requiring a series of planned flood control actions to mitigate the possibility of severe river flooding across the Lower and Middle Rio Grande Valley. Severe flooding in Monterrey, Nuevo Leon, Mxico from June 30th through July 2nd, from an estimated 30 inches of rain in this area was a portent of future impacts on the Rio Grande during the weeks to come, lasting for much of July and the first third of August.

Major flooding continued for nearly a month at Rio Grande City - and by proxy, southwest Hidalgo County - continuing through August 3rd! Flood conditions (50 feet or higher) continued a few days beyond, with levels dropping below flood stage on August 10th at Rio Grande City and just a little bit later in southwest Hidalgo County. In total, the river was likely in flood at points downstream in southwest Hidalgo County, from the morning of July 9th through at least August 10th - more than month.

A number of small communities along the Rio Grande west of the Lower Rio Grande Valley Flood Control System were impacted by the sprawling river into early August, while releases remained at 60,000 cubic feet per second at Falcon International Reservoir until July 29th. These communities included locations in southwest Hidalgo County. The system of levees and floodways (spillways) downstream of Penitas (where improved levees begin along the river itself) largely worked as designed, containing and diverting water along the river and associated floodways extending through southern and eastern Hidalgo County into extreme northern Cameron and extreme southern Willacy County. However, additional water damage occurred to properties built inside the levees and floodways. Voluntary and mandatory evacuations were ordered for a number of threatened communities; as of this writing, no fatalities had been reported directly from the high waters. There were dozens of water rescues on the river through the period, many of them trans migrants attempting to cross from Mexico into Texas.

On August 3rd, President Obama declared most counties in the Rio Grande Valley a Major Disaster, eligible for federal funding to assist with the longer term recovery. Deep South Texas Counties included Cameron and Hidalgo. Property and Crop damages from the flood may ultimately total well over $50 million when all assessments are completed. As of the end of July, property damage estimates in Hidalgo County had reached $22 million. Crops planted in flood zones were destroyed by the long duration of nutrient rich waters. Note: final damage cost estimated are provided in the July Storm Data report.

View location on OpenStreetMap → (26.1129, -97.9355)

Source: NOAA Storm Events Database, event_id 247573. Narrative written by the NWS forecast office that issued the report.