Little past Rudagüera, in Torrelavega, the Besaya River flows into the valley until it reaches its mouth in the Ria of San Martín near Suances, flowing into the Bay of Biscay
In the region around Rudagüera, in Torrelavega, the Besaya River enters a valley and eventually reaches the sea, flowing into the Ria of San Martín before emptying into the Bay of Biscay