Abstract

SANZ-PEREZ, Eugenio  and  MENENDEZ-PIDAL, Ignacio. Utility of Geomorphology, Archeology and History in Understanding the Fluvial Dynamics of the Rivers Duero and Tera in Numancia (Soria, Spain). Tecnol. cienc. agua [online]. 2016, vol.7, n.4, pp.5-23. ISSN 2007-2422.

Before the construction of the Cuerda del Pozo dam, the stretch of the River Duero being studied had not undergone significant morphological changes over the previous two or three centuries. This fact was deduced after consulting old maps, historic documents, aerial photographs and analyzing the geomorphology. In contrast, the River Tera has undergone constant changes, though the changes have taken place within the margins imposed by the edges of the river terrace, T, which is situated 7-9 m above the level of both rivers. In the River Duero, changes in the initial straight reach, flowing NNW-SSE, have been minimal. Then, in the downstream stretch flowing S-W, moderate changes have been noted including, above all, greater mobility during spate flows. Within this reach, the mobility of the riverbed of the Duero has perhaps been greater than in the vicinity of Garray, which represents a fixed point for both rivers. In this reach, and perhaps over this entire section, a trend has also been observed for the river Duero to be displaced towards the south in response to the general asymmetry of the valley: the terraces and floodplain of the left bank are much more developed. The construction of the Cuerda del Pozo reservoir (and the secondary Dombellas reservoir) has meant the virtual disappearance of high-frequency floods and a reduction in sediment input. This has been translated into a narrowing of the riverbed and, above all, in the establishment of the Duero as a single watercourse, which has settled the river in the more changeable southern band. There have been hardly any modifications over the last 80 years, with only a remote chance of the abandoned watercourses being occupied.

Keywords : Fluvial dynamics geomorphology; archeology; history; Duero and Tera rivers; Spain.

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