Abstract

DOFFO, Nelso C et al. Estimación de crecidas extraordinarias en el arroyo Tegua (Córdoba), a partir de evidencias geomorfológicas, sedimentológicas y modelación hidráulica. Rev. Asoc. Geol. Argent. [online]. 2014, vol.71, n.1, pp.48-55. ISSN 0004-4822.

The Tegua stream drains a 160,000 ha basin in the center-west of Córdoba. Its is born in Comechingones ranges (Pampeanas ranges) and develops its middle and lower basin in the Pampean plain. The regional climate is temperate subhumid (AAR = 800-930 mm). Despite the long history of damages to infrastructure and productive land, there are no gauging records, which makes difficult the assessment of historical floods, therefore, geomorphological-sedimentological techniques and hydraulic modeling are useful methodology for estimating extraordinary floods. It is proposed to recognize geomorphologicalsedimentological flood evidences, to determine stream sections for the hydraulic modeling, and to estimate peak flows and their relation to flood disasters. To estimate the discharge, the program HEC-RAS 4.0 was used. A 700 m long channel segment was chosen in the middle basin, with a subrectilinear pattern, steady section, and a slope of 0.0025. Sedimentary and non-sedimentary evidences of flooding were found and 17 cross sections were surveyed. Two values roughness of Manning "n" roughness coefficient were calculated, one for the channel bed (0,0204), and the other for the banks (0,06), according to tables. Flow rates of 55, 115, 140 and 200 m3/s were determined; their flood sheets are consistent with the surveyed evidence. The incision of the channel in cemented sediments has significantly stabilized the channel, making possible its hydraulic modeling. A highest flood with serious consequences (2007) was related to the non-sedimentary evidence and to an estimated stream flow of 200 m³/s.

Keywords : Floods; Morphological-sedimentological evidence; Subcritical flow; Numerical modeling; Córdoba.

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