MAGNITUD Y FRECUENCIA DE SUCESOS HIDROMORFOLÓGICOS DEL BAJO SEGURA ANTERIORES A SU ENCAUZAMIENTO

Abstract

In this century, before the canalization works, the Lower Segura had a narrow channel with a semi-stable meandenng planform, protected by embankments, but it was vulnerable to the overflows, which control locally its geometry and affect to the flood-plain. In the short-term, the morphological adjustments of this fluvial system are mainly dominated by the occurrence of extreme hydrological events, causing overall changes and canying out large sediment discharges. Small adjustments into the channel belong to moderate discharges which. on the other hand, reflect the features of modified regime. This work shows the different hydrological events produced in the Lower Segura along the period 1963-86. Four classes are established according to their geomorphological effectiveness: 1) overbank flows, 2) bankfull conditions, 3) moderate discharges, and 4) low flows. After defining the discharge thresholds for each class, a frequency and probability analysis is taken, relating the observed values with the obtained by theoretical probability distributions (e.g. Gumbel extreme value type 1 (EVI)).