Flash Flood — Hidalgo, Texas

2020-07-26 · near Retampego, Hidalgo, Texas

Event narrative

Torrential rains associated with both the eastern and southern eyewall (late evening of July 25th) and persistent southeast to northwest feeder bands that followed (after midnight through late afternoon of July 26th) created widespread flash and areal flooding across many portions of populated Hidalgo County as then-Tropical Storm Hanna slowly moved from Hidalgo County into Starr County, Texas, and eventually into northern Mexico on July 26th. Heaviest rainfall directly associated with Hanna and the feeder bands fell in the Mission-South McAllen-Pharr region, where measured and estimated rainfall of 10 to 15 inches produced 18 inches to 4 feet of water depth and required a number of water rescues during the prolonged period of flooding. A few specific reports included:

*Numerous water rescues in the City of Mission (pre-dawn hours, July 26)

*Numerous streets with up to 2 feet of water depth in Weslaco (8 AM July 26 report)

*Canal overtopping banks and flooding roads in South McAllen on S. 23rd Street (830 AM July 26th)

*3 feet of water, rising, in Mission (830 AM report)

*Water entering homes in southeast Edinburg, estimated just after sunrise July 26

An unknown number of properties were damaged by floodwaters, but dozens if not hundreds of vehicles had varying levels of floodwater inside them. In total, there were at least 200 persons and several dozen pets rescued/evacuated by State of Texas rescue teams from Texas Task Force 1 and the Texas Parks and Wildlife Department, to name two.

Public and individual assistance dollar damages, as well as insured damages, from flood waters was calculated using NCEI's total dollar damage estimate (divided among the affected counties by local storm data experts). Total property damage from flood waters for Cameron County was $9.968 million. In addition, an initial public assistance value was available - subject to further updates - and was estimated to be $7.99 million. Please note that a second round of flooding rain on July 27th exacerbated the ongoing conditions but that value is folded into this episode for brevity. Crop damage due to the flooding was estimated to be 27.1 million, heavily weighted by damage to cotton but also some damage to other dryland crops.

Final public, individual assistance, and insured damage was likely to range somewhere from $200 to $500 million when all data are counted later in 2020 and beyond.

Wider weather episode

Hurricane Hanna, the 2020 Atlantic season's first Hurricane, made landfall along the unpopulated Padre Island National Seashore on the mid-Kenedy County coastline as a Category 1 storm at around 5 PM Central Time Saturday, July 25th, carrying sustained 90 mph winds with gusts over 100 mph in a small portion of the inner eye wall. The hurricane spun slowly but steadily into southern Kenedy and northern Hidalgo County through just after midnight on the 26th, then through Starr County as a Tropical Storm before moving into Tamaulipas before daybreak and eventually near Monterrey, Nuevo Leon, by noon before dissipating during the evening of the 26th. Following the passage of the inner eye wall, broad feeder bands of torrential rains and gusty tropical storm force winds continued through the mid to late morning hours of July 26th, slowly migrating from east to west across the populated Rio Grande Valley.

Other than storm surge flooding, which peaked just north of Baffin Bay on the Kleberg and Nueces County coast near Corpus Christi, Hanna's memory for the Rio Grande Valley will be flooding rainfall, power outages, and an array of damage to poorly constructed buildings, from minor roof damage to complete demolition. Between 8 and 15 inches of rain fell from Port Mansfield to Harlingen, and along Interstate Highway 2 out through Mission and Sullivan City. The combination of high rainfall, locally high rainfall rates, and poor drainage left between 18 inches and four feet of water depth in many areas, most commonly from western Cameron through southeastern Hidalgo County, as well as a separate pocket in the Mission/La Joya/Sullivan City area. The rainfall wiped out 95% of the region's cotton crop; the combination of crop loss and production loss was more than one third of a billion dollars alone ($366 million)...most of which was in the Rio Grande Valley region.

At the peak of the storm, 250 thousand electric customers were without power, including all of Willacy County. Though storm surge was cut short by strong westerly flow across Cameron County, radiating swells did produce a notable surge of 3 feet or greater (estimated) from near Port Mansfield through Kenedy County. When the damage and economic loss is counted to infrastructure and agriculture combined, it is likely that Hanna cost at least one billion dollars across the Rio Grande Valley and the Deep S. Texas ranch country.

View location on OpenStreetMap → (26.1006, -97.8674)

Source: NOAA Storm Events Database, event_id 914463. Narrative written by the NWS forecast office that issued the report.