The Caudal merges from significant tributaries to arrive into the Nalón system. The upper reaches show mixed lithology — slate, quartzite, sandstone — in step-pool confines. The descent is steep and response to rainfall pronounced. The middle Caudal opens into pool-riffle sequences on cobble. The river carries the blended character of multiple tributary systems, and that diversity shows in the water — sometimes amber with slate, sometimes clearer with limestone influence, depending on which tributary has most recently delivered spate flow. The wading demands attention throughout.

Wading: Slippery embedded cobble and anthropogenic debris