Jesús Horacio

Geomorphology and river restoration: dam removal monitoring in Gipuzkoa

espanolSe presenta la metodologia disenada para el seguimiento geomorfologico del derribo de azudes, asi como los resultados obtenidos hasta el momento en dos casos concretos: las presas de Mendaraz (rio Urumea) e Inturia (rio Leitzaran) en Gipuzkoa. Se han realizado secciones transversales, abundantes mediciones de procesos sobre testigos, analisis de los nuevos depositos generados y muestreos granulometricos y morfometricos. En el caso de Mendaraz se han registrado rapidas movilizaciones de sedimentos e importantes cambios geomorfologicos aguas arriba y abajo del obstaculo. Este proceso de recuperacion de la dinamica fluvial natural y de regularizacion del cauce fue favorecido y acelerado por la crecida extraordinaria de noviembre de 2011. Ademas de sus beneficios para el estado ecologico, se ha constatado que el derribo de presas es una medida eficaz para la restauracion de la dinamica geomorfologica en cauces fluviales. El seguimiento geomorfologico es una labor fundamental para cuantificar y valorar la dinamica generada a raiz del derribo de la presa y toda su evolucion posterior. EnglishA methodology for dam removal monitoring and the results of two case studies is presented: Mendaraz dam (Urumea River) and Inturia dam (Leitzaran River), both located in Gipuzkoa. This monitoring is conducted by river survey cross-sections, measurements of processes and granulometrical analysis. Fast sediment erosion and sedimentation together with geomorphological adjustments were detected after dam removal. In Mendaraz an extraordinary flood favored these processes. The recovery of fluvial dynamics shows benefits not only from the ecological point of view but also for the restoration of natural river dynamics. Geomorphological monitoring is a key tool to quantify and assess river evolution and dynamics after dam removal.

Geomorphic classification of rivers: a new methodology applied in an Atlantic Region (Galicia, NW Iberian Peninsula)

The classification of rivers based on geomorphological criteria played, in the past, a secondary role for management decision making, although in the last years they have experienced a shift from the scientific field to that of the technical. Currently, managers require the most simplified form of classifications in order to use them in plans and planning projects, management and restoration. On the one hand, this means that classifications should be directed toward simplifying the diversity of fluvial environments in a number of manageable types, and on the other hand, to apply to each geomorphic type a management model. In this study, we have developed a method of “Geomorphic Classification of Rivers” according to specific stream power variables and median grain size. The new method is dynamic (ability to readjust and gain robustness with the incorporation of new data) and predictive. We obtained six types directly from the method, although we added a seventh type (bedrock rivers) for its special singularity. Each geomorphic type presents concrete values of specific stream power and median grain size, which additionally involves a hydraulic geometry adjusted to terms of balance. The change from a geomorphic type to another would reflect a geomorphologic imbalance in the form of greater power and sediment size. Our results have been compared with six commonly used classifications (e.g., Rosgen Classification System or River Styles Framework). “Geomorphic Classification of Rivers” stands as a flexible tool that allows the development of a “personalized” geomorphic classification for rivers of the same geomorphological province. Through the temporary revision of various sites that act as control points, we can learn, should the case arise, the intensity and geomorphic change of the site. “Geomorphic Classification of Rivers” acts as an alert system for any geomorphologic disturbance. Its simple application and interpretation facilitate the implementation in the administrative environment, or its attachment to other commonly used classifications.