Evidencias anatómicas de avenidas torrenciales en diferentes especies arbóreas

La caracterización de la respuesta anatómica de árboles afectados por avenidas torrenciales, resulta determinante a la hora de definir indicadores útiles para el estudio de la frecuencia y magnitud del proceso utilizando técnicas dendrogeomorfológicas. Con este propósito, se han analizado 96 muestras provenientes de diferentes especies arbóreas (Pinus pinaster Ait., Quercus pyrenaica Willd., Alnus glutinosa L, Fraxinus angustifolia Vahl. y Populus sp.), de la madera afectada por la carga sólida transportada durante el evento torrencial que tuvo lugar en 1997 en el arroyo Cabrera (Navaluenga, Sierra del Valle, Gredos Oriental). En campo, la toma de muestras consistió en obtener cuñas de madera con una sierra de mano y testigos cilíndricos con barrena Pressler, de aquellos árboles localizados en los bancos de orilla que presentaban descortezados por impacto. En laboratorio se prepararon, a partir de los tejidos vegetales, láminas delgadas obtenidas en sección transversal y con espesores comprendidos entre 10-15 μm. Posteriormente, se procedió a la adquisición de imágenes microscópicas (300 ppp, x 50 aumentos) para el análisis de los diversos parámetros anatómicos cuantitativos y cualitativos mediante el software WinCELL (Regent Instrument). Los resultados obtenidos muestran un cambio claro en los parámetros anatómicos analizados, como respuesta al daño producido por el evento torrencial de 1997. Dependiendo de cada especie, los principales indicadores tuvieron que ver con: el lumen celular de las traqueidas de la madera temprana así como el porcentaje y grosor de la pared celular (en pino); tamaño de los vasos (en aliso, fresno y roble) y dimensiones de las células de madera temprana acompañantes a vasos (aliso y álamo). Por último, también se observó la existencia de falsos anillos (alisos), depósitos gomosos (alisos, robles y fresnos) y presencia de tejidos desestructurados. Estos parámetros se presentan como indicadores útiles para la datación eventos pretéritos en esta zona de estudio y sectores análogos

Civil Engineering Works versus Self-protection measures for the mitigation of floods economic risk. A case study from a new classification criterion for Cost-Benefit Analysis.

The application of classical cost-benefit analysis to flood risk mitigation measures can be improved by incorporating new comparative parameters, such as the risk-cost ratio, which is defined here for the first time. In addition, applying these analyses not only to the typical public structural measures (dams, dredging, flood storage reservoirs, transverse drainage works), but also to non-structural measures and self-protection (improving housing resistance to flooding, insurance policies), broadens the range of active risk management options. Last two categories are measures with lower initial investment (thus reducing costs) and visual and environmental impact, making them compatible with the EU Water Framework Directives and flood risk management. All these analyses of economic flood risk have been tested in a small Spanish village in the central Iberian Peninsula. For different flooding scenarios, new proposed RCR criterion allow us a rapid and effective quantification of the efficiency of each of the measures, allowing the ordered classification of the same; as well as the weighting of the results according to the particular needs of the decision makers (prioritizing well the reduction of damages, or the necessary economic investment). Thus, the RCR reveals itself as a powerful tool for flood risk management

Towards a classificatión of dendrogeomorphological evidences and their utility in flood hazard analysis

Se analizan los diferentes parámetros dendrogeomorfológicos válidos para la estimación de riesgo

Mejoras en la estimación de la frecuencia y magnitud de avenidas torrenciales mediante técnicas dendrogeomorfológicas

Para prevenir el riesgo de inundación, en el análisis científico de la peligrosidad asociada a las avenidas fluviales, clásicamente se han empleado métodos hidrológico-hidráulicos y, en menor medida, histórico-paleohidrológicos y geológico-geomorfológicos. Sin embargo, estas técnicas plantean enormes incertidumbres científicas por la disponibilidad de los datos de partida, su validez espacio-temporal, y su representatividad estadística. La Dendrogeomorfología es un conjunto de técnicas que, aprovechando fuentes de información registradas en las raíces, troncos y ramas de los árboles y arbustos ubicados en determinadas posiciones geomorfológicas (bancos de orilla, barras longitudinales, llanura de inundación, etc.), permite completar (e incluso suplir) el registro sistemático y paleohidrológico de avenidas torrenciales que han acontecido en esa corriente. En este artículo se propone investigar, se muestran los resultados-tipo y se discute sobre la aplicación y limitaciones de las fuentes de datos y los métodos científicos derivados del análisis dendrogeomorfológico. Para llevarlo a cabo, se sugiere una combinación de métodos de adquisición de datos en campo, estudios de laboratorio y análisis de datos en gabinete, con un plan de trabajo que contempla doce tareas o actividades: 1, caracterización geomorfológica; 2, caracterización florística; 3, muestreo de ejemplares: 4, adquisición de datos topográficos detallados; 5, preparación de las muestras; 6, conteo y medida de los anillos de crecimiento; 7, estudio anatómico e histológico; 8, sincronización de las series; 9, detección y datación de eventos; 10, modelación hidráulica de tramos; 11, análisis estadístico de caudales de avenida; y 12, cartografía de las áreas de peligrosidad por avenidas torrenciales y mapas de riesgo. - In order to prevent flood risks, scientific fluvial flood hazard analysis has been carried out traditionally with hydrologic and hydraulic methods, and secondarily, using palaeohydrological-historical and geological-geomorphological methods. Nonetheless, these techniques pose countless uncertainties due to the availability of the data, their spatio-temporal validity and their statistical representativeness. Dendrogeomorphology is a set of techniques that takes advantage of sources of information registered in roots, trunks and branches of trees or treelike bushes placed in certain geomorphological locations (such as banks, longitudinal bars, flood prone areas, etc.), that may be useful to complete the systematic registry or paleohydrologic data of torrential floods that have occurred in a certain stream. The aim of this paper is to research the usefulness and limitations of the data sources and methodologies derived from the dendrogeomorphological analysis. For accomplishing this objective a combination of methods is proposed, from data acquisition methods in field, laboratory studies, to data analysis. The schedule comprises twelve tasks: 1, geomorphologic characterization; 2, floristic characterization; 3, species sampling: 4, acquisition of detailed topographic data; 5, sample arrangement; 6, growth ring count and measurement; 7, hystologic and anatomic study; 8, series synchronization; 9, event detection and dating; 10, hydraulic reach modelling; 11, flow data statistical analysis; y 12, hazard and flood prone areas cartography and risk mapping

Wood anatomy of debris-flood scars in broadleaved tree species of central Spain

Valor de las características de la anatomía de la madera en la cordillera central ibérica en relación con las avalanchas de alta montañ

Can the discharge of a hyperconcentrated flow be estimated from paleoflood evidence?

Many flood events involving water and sediments have been characterized using classic hydraulics principles, assuming the existence of critical flow and many other simplifications. In this paper, hyperconcentrated flow discharge was evaluated by using paleoflood reconstructions (based on paleostage indicators [PSI]) combined with a detailed hydraulic analysis of the critical flow assumption. The exact location where this condition occurred was established by iteratively determining the corresponding cross section, so that specific energy is at a minimum. In addition, all of the factors and parameters involved in the process were assessed, especially those related to the momentum equation, existing shear stresses in the wetted perimeter, and nonhydrostatic and hydrostatic pressure distributions. The superelevation of the hyperconcentrated flow, due to the flow elevation curvature, was also estimated and calibrated with the PSI. The estimated peak discharge was established once the iterative process was unable to improve the fit between the simulated depth and the depth observed from the PSI. The methodological approach proposed here can be applied to other higher-gradient mountainous torrents with a similar geomorphic configuration to the one studied in this paper. Likewise, results have been derived with fewer uncertainties than those obtained from standard hydraulic approaches, whose simplifying assumptions have not been considered. © 2011 by the American Geophysical Union.This work was funded by the Spanish Ministry of Science and Innovation within the framework of the CICYT Dendro-Avenidas project (CGL2007-62063) and the MAS Dendro-Avenidas project (CGL2010-19274). We are especially grateful to Robert D. Jarrett, Vern Manville, and one anonymous reviewer for their comments and helpful suggestions on previous versions of this manuscript.Bodoque, J.; Eguibar Galán, MÁ.; Diez-Herrero, A.; Gutierrez-Perez, I.; Ruiz-Villanueva, V. (2011). Can the discharge of a hyperconcentrated flow be estimated from paleoflood evidence?. Water Resources Research. 47(W12535). doi:10.1029/2011WR010380S47W12535Alcoverro, J., Corominas, J., & Gómez, M. (1999). The Barranco de Arás flood of 7 August 1996 (Biescas, Central Pyrenees, Spain). Engineering Geology, 51(4), 237-255. doi:10.1016/s0013-7952(98)00076-3Alexandrov, Y., Laronne, J. B., & Reid, I. (2007). Intra-event and inter-seasonal behaviour of suspended sediment in flash floods of the semi-arid northern Negev, Israel. Geomorphology, 85(1-2), 85-97. doi:10.1016/j.geomorph.2006.03.013BAAS, J. H., & BEST, J. L. (2008). The dynamics of turbulent, transitional and laminar clay-laden flow over a fixed current ripple. Sedimentology, 55(3), 635-666. doi:10.1111/j.1365-3091.2007.00916.xBallesteros, J. A., Bodoque, J. M., Díez-Herrero, A., Sanchez-Silva, M., & Stoffel, M. (2011). Calibration of floodplain roughness and estimation of flood discharge based on tree-ring evidence and hydraulic modelling. Journal of Hydrology, 403(1-2), 103-115. doi:10.1016/j.jhydrol.2011.03.045Bathurst, J. C. (1985). Flow Resistance Estimation in Mountain Rivers. Journal of Hydraulic Engineering, 111(4), 625-643. doi:10.1061/(asce)0733-9429(1985)111:4(625)BERZI, D., & JENKINS, J. T. (2008). A theoretical analysis of free-surface flows of saturated granular–liquid mixtures. Journal of Fluid Mechanics, 608, 393-410. doi:10.1017/s0022112008002401Biron, P. M., Lane, S. N., Roy, A. G., Bradbrook, K. F., & Richards, K. S. (1998). Sensitivity of bed shear stress estimated from vertical velocity profiles: the problem of sampling resolution. Earth Surface Processes and Landforms, 23(2), 133-139. doi:10.1002/(sici)1096-9837(199802)23:23.0.co;2-nBisantino, T., Fischer, P., & Gentile, F. (2009). Rheological characteristics of debris-flow material in South-Gargano watersheds. Natural Hazards, 54(2), 209-223. doi:10.1007/s11069-009-9462-4Bousmar, D., & Zech, Y. (1999). Momentum Transfer for Practical Flow Computation in Compound Channels. Journal of Hydraulic Engineering, 125(7), 696-706. doi:10.1061/(asce)0733-9429(1999)125:7(696)Costa, J. E. (1984). Physical Geomorphology of Debris Flows. Developments and Applications of Geomorphology, 268-317. doi:10.1007/978-3-642-69759-3_9COUSSOT, P., & MEUNIER, M. (1996). Recognition, classification and mechanical description of debris flows. Earth-Science Reviews, 40(3-4), 209-227. doi:10.1016/0012-8252(95)00065-8Coussot, P., Laigle, D., Arattano, M., Deganutti, A., & Marchi, L. (1998). Direct Determination of Rheological Characteristics of Debris Flow. Journal of Hydraulic Engineering, 124(8), 865-868. doi:10.1061/(asce)0733-9429(1998)124:8(865)Desilets, S. L. E., Ferré, T. P. A., & Ekwurzel, B. (2008). Flash flood dynamics and composition in a semiarid mountain watershed. Water Resources Research, 44(12). doi:10.1029/2007wr006159Dietrich, W. E., & Whiting, P. (1989). Boundary shear stress and sediment transport in river meanders of sand and gravel. River Meandering, 1-50. doi:10.1029/wm012p0001Ervine, D. A., Willetts, B. B., Sellin, R. H. J., & Lorena, M. (1993). Factors Affecting Conveyance in Meandering Compound Flows. Journal of Hydraulic Engineering, 119(12), 1383-1399. doi:10.1061/(asce)0733-9429(1993)119:12(1383)Gaume, E., Livet, M., Desbordes, M., & Villeneuve, J.-P. (2004). Hydrological analysis of the river Aude, France, flash flood on 12 and 13 November 1999. Journal of Hydrology, 286(1-4), 135-154. doi:10.1016/j.jhydrol.2003.09.015Grant, G. E. (1997). Critical flow constrains flow hydraulics in mobile-bed streams: A new hypothesis. Water Resources Research, 33(2), 349-358. doi:10.1029/96wr03134Hessel, R. (2006). Consequences of hyperconcentrated flow for process-based soil erosion modelling on the Chinese Loess Plateau. Earth Surface Processes and Landforms, 31(9), 1100-1114. doi:10.1002/esp.1307House, P. K., & Baker, V. R. (2001). Paleohydrology of flash floods in small desert watersheds in western Arizona. Water Resources Research, 37(6), 1825-1839. doi:10.1029/2000wr900408House, P. K., & Pearthree, P. A. (1995). A geomorphologic and hydrologic evaluation of an extraordinary flood discharge estimate: Bronco Creek, Arizona. Water Resources Research, 31(12), 3059-3073. doi:10.1029/95wr02428Hungr, O. (s. f.). Classification and terminology. Springer Praxis Books, 9-23. doi:10.1007/3-540-27129-5_2Iverson, R. M. (1997). The physics of debris flows. Reviews of Geophysics, 35(3), 245-296. doi:10.1029/97rg00426Iverson , R. M. 2003 The debris-flow rheology myth, paper presented at debris-flow hazards mitigation: mechanics, prediction, and assessment 303 314 Millpress Rotterdam, Davos, SwitzerlandIverson, R. M., Logan, M., LaHusen, R. G., & Berti, M. (2010). The perfect debris flow? Aggregated results from 28 large-scale experiments. Journal of Geophysical Research, 115(F3). doi:10.1029/2009jf001514Jarrett, R. D. (1987). Closure to « Hydraulics of High‐Gradient Streams » by Robert D. Jarrett (November, 1984). Journal of Hydraulic Engineering, 113(7), 927-929. doi:10.1061/(asce)0733-9429(1987)113:7(927)Jarrett, R. D., & Tomlinson, E. M. (2000). Regional interdisciplinary paleoflood approach to assess extreme flood potential. Water Resources Research, 36(10), 2957-2984. doi:10.1029/2000wr900098Lavigne, F., & Suwa, H. (2004). Contrasts between debris flows, hyperconcentrated flows and stream flows at a channel of Mount Semeru, East Java, Indonesia. Geomorphology, 61(1-2), 41-58. doi:10.1016/j.geomorph.2003.11.005McCoy, S. W., Kean, J. W., Coe, J. A., Staley, D. M., Wasklewicz, T. A., & Tucker, G. E. (2010). Evolution of a natural debris flow: In situ measurements of flow dynamics, video imagery, and terrestrial laser scanning. Geology, 38(8), 735-738. doi:10.1130/g30928.1Pierson , T. C. 2005 Distinguishing between debris flows and floods from field evidence Small Watersheds U.S. Geological Survey 2004 3142Pierson, T. C. (s. f.). Hyperconcentrated flow — transitional process between water flow and debris flow. Springer Praxis Books, 159-202. doi:10.1007/3-540-27129-5_8Pierson, T. C., & Costa, J. E. (1987). A rheologic classification of subaerial sediment-water flows. Reviews in Engineering Geology, 1-12. doi:10.1130/reg7-p1Pierson, T. C., & Scott, K. M. (1985). Downstream Dilution of a Lahar: Transition From Debris Flow to Hyperconcentrated Streamflow. Water Resources Research, 21(10), 1511-1524. doi:10.1029/wr021i010p01511Rico, M., Benito, G., & Barnolas, A. (2001). Combined palaeoflood and rainfall–runoff assessment of mountain floods (Spanish Pyrenees). Journal of Hydrology, 245(1-4), 59-72. doi:10.1016/s0022-1694(01)00339-0Roca, M., Martín-Vide, J. P., & Moreta, P. J. M. (2009). Modelling a torrential event in a river confluence. Journal of Hydrology, 364(3-4), 207-215. doi:10.1016/j.jhydrol.2008.10.020Ruiz-Villanueva, V., Bodoque, J. M., Díez-Herrero, A., & Calvo, C. (2011). Triggering threshold precipitation and soil hydrological characteristics of shallow landslides in granitic landscapes. Geomorphology, 133(3-4), 178-189. doi:10.1016/j.geomorph.2011.05.018Shiono, K., & Knight, D. W. (1991). Turbulent open-channel flows with variable depth across the channel. Journal of Fluid Mechanics, 222(-1), 617. doi:10.1017/s0022112091001246Shu, A., & Fei, X. (2008). Sediment transport capacity of hyperconcentrated flow. Science in China Series G: Physics, Mechanics and Astronomy, 51(8), 961-975. doi:10.1007/s11433-008-0108-4Siviglia, A., & Cantelli, A. (2005). Effect of bottom curvature on mudflow dynamics: Theory and experiments. Water Resources Research, 41(11). doi:10.1029/2005wr004475Sleiti, A. K., & Kapat, J. S. (2008). Effect of Coriolis and centrifugal forces on turbulence and transport at high rotation and density ratios in a rib-roughened channel. International Journal of Thermal Sciences, 47(5), 609-619. doi:10.1016/j.ijthermalsci.2007.06.008SMITH, G. A. (1986). Coarse-grained nonmarine volcaniclastic sediment: Terminology and depositional process. Geological Society of America Bulletin, 97(1), 1. doi:10.1130/0016-7606(1986)972.0.co;2Sohn, Y. K., Rhee, C. W., & Kim, B. C. (1999). Debris Flow and Hyperconcentrated Flood‐Flow Deposits in an Alluvial Fan, Northwestern Part of the Cretaceous Yongdong Basin, Central Korea. The Journal of Geology, 107(1), 111-132. doi:10.1086/314334Sosio, R., & Crosta, G. B. (2009). Rheology of concentrated granular suspensions and possible implications for debris flow modeling. Water Resources Research, 45(3). doi:10.1029/2008wr006920Svendsen, J., Stollhofen, H., Krapf, C. B. ., & Stanistreet, I. G. (2003). Mass and hyperconcentrated flow deposits record dune damming and catastrophic breakthrough of ephemeral rivers, Skeleton Coast Erg, Namibia. Sedimentary Geology, 160(1-3), 7-31. doi:10.1016/s0037-0738(02)00334-2Tinkler, K. J. (1997). Critical flow in rockbed streams with estimated values for Manning’s n. Geomorphology, 20(1-2), 147-164. doi:10.1016/s0169-555x(97)00011-1Trieste , D. J. R. D. Jarrett 1987 Roughness coefficients of large floodsVan Maren, D. S., Winterwerp, J. C., Wu, B. S., & Zhou, J. J. (2009). Modelling hyperconcentrated flow in the Yellow River. Earth Surface Processes and Landforms, 34(4), 596-612. doi:10.1002/esp.1760Wan, Z., Wang, Z., & Julien, P. Y. (1994). Hyperconcentrated Flow. Journal of Hydraulic Engineering, 120(10), 1234-1234. doi:10.1061/(asce)0733-9429(1994)120:10(1234)Winterwerp, J. C. (2001). Stratification effects by cohesive and noncohesive sediment. Journal of Geophysical Research: Oceans, 106(C10), 22559-22574. doi:10.1029/2000jc000435Jiongxin, X. (1999). Erosion caused by hyperconcentrated flow on the Loess Plateau of China. CATENA, 36(1-2), 1-19. doi:10.1016/s0341-8162(99)00009-

Tapping into the Campus Power Structure: The Duty of Black Student Leaders in Predominantly White Universities

As young student leaders, the knowledge gained through experience, discipline, reading, and a clear vision can be helpful in developing strategies to produce a more positive campus climate

Advanced methodologies for the dendrogeomorphic analysis of past floods and related risks

This communication presents an overview of their first results and innovate methodologies, focused in their possibilities and limitations for the reconstruction of recent floods and paleofloods over the World