Sunday, July 20, 2014

Flooded Arroyo

Weather: Rain most nights.

What’s blooming in the area: Hybrid roses, yellow potentilla, silver lace vine, trumpet creeper, datura, bouncing Bess, purple garden phlox, alfalfa, sweet pea, yellow yarrow.

Beyond the walls and fences: Tamarix, velvetweed, scarlet bee blossom, blue trumpets, purple mat flower, pink and white bindweed, Queen Anne's lace, goat’s head, horseweed, wild lettuce, Hopi tea, plains paper flowers, tahoka daisy, strap leaf and golden hairy asters.

In my yard, looking east: Maltese cross, large-flowered soapwort, Jupiter’s beard, hollyhocks, winecup mallow, sidalcea, pink evening primrose.

Looking south: Betty Prior, Fairy and miniature roses.

Looking west: Elephant garlic, Johnson’s Blue geranium, catmint, ladybells, sea lavender, Mönch daisy, purple coneflower.

Looking north: Coral beard tongue, butterfly milkweed, golden spur columbine, Mexican hat, black-eyed Susan, chocolate flower, blanket flower, coreopsis, anthemis.

In the open, along the drive: Dorothy Perkins rose, fernbush, buddleia, larkspur, white yarrow.

Bedding plants: Snapdragon, sweet alyssum, blue salvia, moss rose, French marigold.

Animal sightings: Geckos, small birds, bees, hawk moth, grasshoppers, small black ants.

Weekly update: The headline in this week’s Rio Grande Sun is "Heavy Rain Causes Flooding." Ardee Napolitano says we had five inches Monday night and another .6 inches Tuesday.

And I slept through it. Almost. I did wake several times, but each time it was a steady, soaking rain, not the hard rain one associates with flash flood warnings.

When I went to the post office Wednesday, I saw the usual signs. Standing water on the shoulder, sand washed across the road from uphill dirt drives.

The one thing that was odd was the bridge over Arroyo Seco on State Road 399 by the Black Mesa Golf Club. Instead of sand along the shoulders of the road, it was only on the bridge.

When I went back this morning to look, it was obvious a great deal of water had passed, and some must have washed over the top of the bridge. I saw sand collected on the tops of the bridge supports.

Much of the vegetation on the upriver side was laying down. Anything with any elevation was smeared with dirt.

Beyond the arroyo bank, the ground was still wet from where water had collected.

Bridges act as ad hoc flood control structures. No matter how wide their banks, they narrow and limit the amount of water through a channel. Thus, the protect the banks on the downstream side.

No matter how narrow their supports, they impede the flow. Water back ups, but does not rush forward until it breaches the top. This must be what happened this week.

What, I wonder, is where the water came from. All the flooding reported by the Española newspaper was in areas near the Río Grande below bluffs where the pavement collected water, then dumped it in nearby yards.

Arroyo Seco flows from the southeast. It merges three intermittent creeks that flow north through those hills to the east of 84/285 north of Pojoaque. Each of those has two branches. There’s also one short tributary coming from the north.

They merge with another arroyo coming from the east into a northwest tracking sand bed.

Soon after, the arroyo goes under the road before the La Puebla exit, parallels 84/285 for a short distance then continues to flow east of the badlands for about a mile before breaking through to flow across SR 399.

When I drove to Santa Fé Thursday, there was no sign of extra water at the 84/285 bridge. The arroyo must have collected its extra load in the distance between bridges, with runoff from the badlands and, possibly, a concentration of rain. We’ve all seen odd patterns of rainfall.

The Española town flooding had human origins. This seems to have been nature unregulated, with a manmade structure preventing serious flooding downstream.

Notes: Rio Grande Sun, 17 July 2014.

Photographs: All taken this morning, 20 July 2014. The last shows the vertical cut made by the water well up the side.

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