arroyar

A technical verb describing what heavy rain does to bare ground: cutting channels and gullies (arroyadas) as it runs off, or, more generally, forming small streams (arroyos). It belongs to geology and land-management vocabulary rather than everyday conversation.

• La lluvia torrencial arroyó la ladera del cerro. — The torrential rain cut gullies into the hillside.
• El agua arroyó el camino de tierra tras la tormenta. — The water carved channels into the dirt road after the storm.
• Sin vegetación, el terreno se arroya con facilidad. — Without vegetation, the ground erodes into gullies easily.

Confusing arroyar with arrollar — they're pronounced similarly in some accents but unrelated: arroyar is about rain eroding the land into channels, arrollar is about running something over or overwhelming it.