On September 30, the remnants of Hurricane Polo brought heavy rain to the U.S. Southwest, causing road flooding and prompting resident evacuations.
In New Mexico, evacuation orders were issued for several small communities amid concerns that a dam could fail.
Just as important as the amount of rain were the already-saturated ground and waterways.
3-Line Summary
1. Polo’s remnants worsened flooding damage in the Southwest
2. Roads and areas around dams in New Mexico were flooded
3. Wet ground carries rainwater away more quickly
Road Flooding and Dam-Failure Concerns in New Mexico
According to reports on September 30, the remnants of Polo, which had weakened in northwestern Mexico, passed through the U.S. Southwest and brought heavy rain to New Mexico and Arizona. The New Mexico Department of Transportation reported flooded roads and highway debris across the state. In southern New Mexico, some drivers were trapped inside their vehicles until the water receded.
The most urgent situation was around McCloud Dam in Doña Ana County, New Mexico. After heavy rain raised the possibility that the dam could fail, the National Weather Service issued a flash-flood emergency warning, and county authorities ordered nearby residents to evacuate. Residents of small communities along the Rio Grande, including Rincon, Salem, and Garfield, were instructed to move to higher ground.
FOX Weather reported that three flash-flood emergency warnings were issued for Doña Ana County after dam operators reported that a failure could be imminent. There were also reports in Rincon that water had overtopped a levee. However, county authorities said evacuation orders were lifted in some areas after conditions improved.
Paths of Water That Suddenly Swell Even in the Desert
The flooding also highlights the characteristics of the areas where the rain fell. NPR reported that the Southwest was already saturated from rain that had continued since Monday night. When the ground can no longer absorb as much water, subsequent rainfall flows rapidly across the surface rather than seeping into the ground.
Arroyos, which are normally dry waterways, can turn into torrents during heavy rain. In Arizona, a person who had been on top of a flooded vehicle was rescued by helicopter, and in Zion National Park in Utah, three people stranded in a canyon after a flash flood were rescued. In northern Phoenix, a truck was swept away by a waterway, but the driver escaped.
CBS News reported that more than 60 flash floods were reported across the Southwest from September 29 through the night of September 30, and that hourly rainfall in some areas reached 4 inches. The key point in forecasts at the time was that the risk of heavy rain would continue as Polo’s remnants combined with other weather systems even after Polo dissipated. What stands out in this case is that, more than the storm’s name, the already waterlogged ground and normally dry waterways increased the risk of flooding within a short period.
References
Tags #CaliforniaFlooding #USFlooding #Polo #HurricanePolo #FlashFlood #NewMexicoFlooding #DamFailureConcerns #USSouthwest #HeavyRainFlooding #RoadFlooding #ClimateDisaster #ArizonaFlooding