Arroyo

The cave is inaccessible during a flash flood because the arroyo turns into a raging river.

Arroyo is just another name for a wash.

Arroyo is just another word for a wash.

Near-synonyms: wadi, nahal

Across the field were the tents, and beyond them the brown cottonfields that stretched out of sight to the brown arroyo foothills and then the snow-capped Sierras in the morning air.