It hit its peak '... well above the 30,000 cfs max.'

U.S. Army - Thursday 7th December, 2017
it-hit-its-peak--well-above-the-30000-cfs-max
 

GUAYNABO, Puerto Rico -- Rio Yauco is a normally-modest stream on Puerto Rico's southwest coast. It flows roughly 21 kilometers from Lago Lucchetti to Mar Caribe. Its name derives from coayuco, meaning 'yucca plantation.' It is bordered by and funnels rainfall from hills and mountains to the north, east and west.

Yauco Pueblo is a small community about six kilometers from the coast. Over the last 22 years, the U.S. Geological Survey Rio Yauco monitoring station just upstream has recorded median flows during the September to December timeframe ranging from four to 60 cubic feet per second, with the flows overwhelmingly registering in the mid- to high-20s.

On September 20, 2017, as Hurricane Maria made landfall 103 kilometers away at Yabucoa on the island's southeast corner, the monitoring station hit its peak.

'The flow was well above the 30,000 cfs max the equipment can measure,' said Jorge Tous, a hydraulic engineer from the Jacksonville District, working on the Maria response.

For perspective, one cubic foot is about the size of a basketball. People living next to the Yauco, familiar with seeing 20 basketballs per second rolling down the gulley next to their village now saw and heard 30,000 of them roaring through the narrow ravine every second.

Each of the Cumberland, Tombigbee, Illinois and Sacramento rivers typically has a lower average flow.

The next day, the station once again measured more than its 30,000 cfs maximum. Over the next month, the station measured four additional excessive flows of 1,000, 1,500 (twice) and 3,000 cfs.

On a hot, humid late-November morning, Wilmel Varela stands before media cameras being interviewed under a blazing sun about the flood risk reduction project under construction within earshot of the pueblo. He is there because the Rio Yauco jumped its bank, washed out a banana plantation and took a shorter path of least resistance to the coast.

It cut a swath through the banana farm, levelled a baseball park, flooded Highway 127 at the main entrance to town, and rendered Highway 2, which connects Yauco with large cities like Ponce and Mayaguez, impassable. The only way in or out was over the mountains, a daylong trip. The flood destroyed farmland and restricted the movement of police, medical assistance and emergency response vehicles. It impacted the availability of food, water, fuel, generators and everything else that comprises a normal life.

Constructing the remedy was not an easy task.

'When we got here, none of the materials needed to do this project were available locally,' said Varela, the resident engineer for the USACE Antilles Office. 'We spent three days looking all across the island trying to find them.'

Valera said awarding the emergency project within days had multiple and far-reaching benefits.

'It's providing good solutions and economic opportunities,' he said. 'It's been good for small business. We have 20 jobs here. The supervisors are local.'

Varela said the plan to build an effective levee was developed onsite. They constructed a temporary 15-foot high levee to contain the now slow-flowing Rio Yauco. Behind that, excavators, bulldozers, virbratory soil compactors and pumps work in harmony to prepare the soil and place 6,000 cubic meters of 12- to 18-inch rock that will form the backbone of the new 400-foot levee.

As is typical with Hurricane Maria responders, Varela says the impacts of the construction project extend beyond the physical structure.

'We have a good partnership with the land owner,' on whose property the construction is taking place,' he said. The benefits are more far-reaching.

'This levee will protect hundreds of people downstream,' Valera said.