The central stretch of Calders river valley, from the ruined castle of Calders to Colònia Jorba, is a succession of sunken and curled meanders. In the inner side of one meander, which is also the right or northern riverbank, there is the plain of Rubió that picks its name from the farmhouse. Opposite, on the left, southern, or external bank of the meander, the Calders river has cut through the steep slope displaying a 300-meter long by 20-50 meters wide flat surface of hard marine sandstone: the Calders river rocky esplanade in Rubió. Rarely such large surface of rock remains uncovered!
The Calders river rocky esplanade in Rubió orientates from northeast to southwest according to the direction of the river that usually flows along its northern or inner border. Water springs from several points on the slope on the southern bank -the external of the meander bank that floods dig out. This water remains on the rocky esplanade as a very shallow, temporary wetland before reaching the river (photos 2 and 3). The pristine, almost still water of this wetland provides a suitable environment to the aquatic or waterside species that can’t tolerate pollution.
The rocky esplanade of the Calders river in Rubió is a similar geomorphology to that of the Llosa pool on the Guardiola stream on sandstone rock as well, and to those in Antius (Súria) and in the Pont Vell in Manresa from the Cardener river but made of limestone.
[photos Florenci Vallès and Jordi Badia]