Abstract. The longitudinal profiles of bedrock channels are a major component of the relief structure of mountainous drainage basins and therefore limit the elevation of peaks and ridges. Further, bedrock channels communicate tectonic and climatic signals across the landscape, thus dictating, to first order, the dynamic response of mountainous landscapes to external forcings. We review and explore the stream-power erosion model in an effort to (1) elucidate its consequences in terms of large-scale topographic (fluvial) relief and its sensitivity to tectonic and climatic forcing, (2) derive a relationship for system response time to tectonic perturbations, (3) determine the sensitivity of model behavior to various model parameters, and (4) integrate the above to suggest useful guidelines for further study of bedrock channel systems and for future refinement of the streampower erosion law. Dimensional analysis reveals that the dynamic behavior of the stream-power erosion model is governed by a single nondimensional group that we term the uplift-erosion number, greatly reducing the number of variables that need to be considered in the sensitivity analysis. The degree of nonlinearity in the relationship between stream incision rate and channel gradient (slope exponent n) emerges as a fundamental unknown. The physics of the active erosion processes directly influence this nonlinearity, which is shown to dictate the relationship between the uplift-erosion number, the equilibrium stream channel gradient, and the total fluvial relief of mountain ranges. Similar[y, the predicted response time to changes in rock uplift rate is shown to depend on climate, rock strength, and the magnitude of tectonic perturbation, with the slope exponent n controlling the degree of dependence on these various factors. For typical drainage basin geometries the response time is relatively insensitive to the size of the system. Work on the physics of bedrock erosion processes, their sensitivity to extreme floods, their transient responses to sudden changes in climate or uplift rate, and the scaling of local rock erosion studies to reach-scale modeling studies are most sorely needed.

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Resumen. El ratio LE (logarítmico exponencial) es una herramienta geomorfológica para ajustar perfiles longitudinales fluviales aplicando una ecuación. Los resultados permiten evaluar y cuantificar anomalías o rupturas (knickpoints) con diferentes orígenes. Para este caso, se analizaron 33 pequeñas cuencas de un sector de la costa septentrional del Mar de Alborán (Málaga-Granada, España), que se compararon entre sí utilizando ratio LE y otros modelos (Hack, Shulits y Green). En todos los casos se obtuvo mediante ratio LE una correlación lineal de R 2 ≥0,95 (p<0,05) entre perfil real y modelo. Sus desviaciones permitieron identificar anomalías o rupturas de carácter geológico con consecuencias morfológicas: fallas, cabalgamientos, buzamientos y diferencias en contactos litológicos. Se observó asimismo elevada significación entre reducciones de la pendiente fluvial y niveles de aplanamientos regionales, así como niveles escalonados a distintas alturas en las aceleraciones de tramos finales (desembocadura) de perfiles de ríos que atraviesan áreas de acantilados. Palabras clave: Perfiles longitudinales de ríos; anomalías geomorfológicas; ratio LE; causas estructurales; erosión hídrica; knickpoints.[en] Analisys of longitudinal river profiles for the detection of geomorphological anomalies. Application to a sector of the northern coast of Alborán Sea (Spain) Abstract. The LE ratio (exponential logarithmic) is a useful geomorphological tool to adjust longitudinal fluvial profiles using an equation. The obtained results allow assessing and quantifying anomalies as well as ruptures (knickpoints) An. geogr. Univ. Complut. 38(1) 2018: 161-194 coast of the Alboran Sea (Málaga-Granada, Spain) were analyzed by applying the LE ratio and other tested indexes (Hack, Shulitsand Green). In all cases, we obtained by means of a LE ratio a linear correlation coefficient about R 2 ≥0.95 (p<0.01) between the real profile and the evaluated model. Regarding this, several knickpoints were consequences of geological causes: faults, overthrusts, and dips, and differences in lithologic contacts. Moreover, high correlations were found between a decrease of profile inclinations and regional flattening surfaces. Finally, we observed different heights of stepped levels as a consequence of the acceleration of the fluvial stream profile through the steeps. Keywords: Longitudinal fluvial profiles; geomorphological anomalies; ratio LE; structural causes; water erosion; knickpoints.[fr] Analyse des profils longitudinaux des rivières pour la détection des anomalies géomorphologiques. Application à un secteur de la côte nord de la mer d'Alboran (Espagne) Résumé. Le ratio LE (logarithmique exponentielle) est un outil géomorphologique pour ajuster les profils longitudinaux des rivières en utilisant une équation. Les résultats permettent d'évaluer et de quantifier les défauts ou ruptures (knickpoints) de différentes origines. Dans ce cas, 33 petits bassins fluviaux dans un secteur de la côte septentrional de la mer d'Alboran (Malaga-Grenade, Espagn...