Seeing the floodwaters bank-to-bank on the floodway going through Mercedes is a visual remainder of the wide swath left behind by hurricanes.
Even when a big storm doesn’t hit your region directly, its network of rain and tropical moisture leaves a wide footprint that can extend for hundreds of miles. Hurricane Alex of late June 2010 was one of those storms, coming ashore less than 100 miles south of Brownsville and then rumbling through northeast Mexico.
The heavy rains over Mexico would feed rivers and streams flowing into the Rio Grande, putting the floodways to the test. Brownsville is lucky. The city sits east of the floodways and dams that divert and control floodwaters. The volume of excess waters that inevitably flow downstream is greatly diminished by the time it reaches Brownsville – thanks mainly to the floodways and the Arroyo Colorado.
A city like Laredo is not so fortunate. The river running through Laredo absorbs the swollen waterways flowing in from Mexico after a hurricanes has rumbled through. There are no arroyos or floodways to save Laredo, so hence, the visuals of last week of the Rio Grande lapping up to the city’s international bridges.
Falcon Lake will absorb some of the great volumes of water, but Roma and Rio Grande City still have to sweat it out downstream from the big lake because of Mexican rivers flowing into the Rio Grande south of Falcon. Once the swollen river hits Mission, there’s Anzalduas Dam, two floodways and the Arroyo Colorado ready to divert the excess waters to its ultimate destination, the Laguna Madre.
The Rio Grande Valley’s main floodway comes out of Anzalduas, heading east and south of McAllen, Pharr-San Juan-Alamo and Weslaco before meeting up with the Arroyo Colorado south of Mercedes. This is a critical juncture in the Valley’s floodway system – and where a catastrophic failure occurred during 1967″s Hurricane Beulah.
Beulah, a category 4 storm that made a direct Valley hit, dumping over 15 inches in much of the region. The region’s floodway system was far inferior to what exists today, and could not remotely handle the awesome volume of river water heading east toward the heart of the Valley. A perilous decision had to be made. Divert much of the floodwaters to the floodway and risk inundating much of the region – or let more of it go down the arroyo.
The powers-that-be of the day, (and debate still rages on who they really were), opted for the arroyo. This would mean that Harlingen – to its bitter lament – became the Valley’s unintended floodwater reservoir in the aftermath of Beulah.
We can hope to avoid such a momentous decision in the current era with the tens of millions of dollars spent on floodway improvements since the crisis of 1967. Still, there are no floodway improvements that can shield considerable pockets of Valley residential developments from too much rain.
We see it every time when big rains hit here. The TV people will wade into flooded neighborhoods with their chic boots. The residents will cry out for government help and say it always floods when it rains in buckets. In many cases, these are areas where it has historically flooded going way back, with county governments inadequately funded to invest the several millions needed to provide additional drainage.
There are precious few guarantees, really, when it rains 15-to-20 inches over an area in a day or two. The canals are cleared, the floodways are at the ready, and you hope for the best. Driving over the floodway at Mercedes – water bank-to-bank – you hope the system holds up and will be up to the test when a bigger one inevitably hits.
- R. Daniel Cavazos