Taos A to Z Excerpt: Arroyo

Definition: “A steep-sided gully cut by running water in an arid or semi-arid region.” An arroyo is a nearly vertically walled, flat floored stream channel that forms in fine, cohesive, easily eroded material. Arroyos can cut as deeply as 65 feet into the valley floor, are often wider than 165 feet, and can be hundreds of miles long. Arroyos exist throughout the Western United States, but are most common in arid and semi-arid climates in the Southwest. They are found throughout New Mexico.

The rapid widening and deepening of arroyos have both changed the physical environment and been a costly nuisance in the West since settlement began in the mid-1800s. From 1870 to 1890, the number of livestock in New Mexico alone increased from 300,000 to 2,300,000. Valley floors, which were the most dependable forage areas for the animals, were quickly overgrazed. The fragile vegetation was consumed, and the soil was compacted and left extremely susceptible to erosion. To further exacerbate the soil conditions, both humans and livestock created trails along stream channels and nearby hillsides forming small ditches, leaving the land surface susceptible to arroyo formation. ~Aimee

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