The Deva arrives from the Picos country — limestone fed, clear, responsive to the dramatic altitude range between source and the lowlands. Some reaches run limestone gorge similar to the Cares, other sections open into partly-confined pool-riffle on pale limestone cobble. The upper Deva is characterized by step-pool and slots through Picos limestone; the canyon is dramatic and restricting in flood. The middle river opens slightly, allowing pool-riffle sequences to develop on durable limestone. The Deva's character is of a river that belongs to the Picos geography — powerful, clear, responding quickly to high-altitude rainfall. The pools are well-formed and deep, cut into pale limestone that shows its age and durability. Lower reaches flatten as the river approaches the sea at Llanes. The limestone bedrock throughout provides secure wading once you understand the algae patterns and the slope; the confined upper sections demand respect in high water.

Wading: Wet limestone bedrock in the upper gorge and La Hermida

Still carries one of the clearest practical reo identities in Asturias. Coto structure and angling culture support this.