Efectos de las fuentes cartográficas en los resultados de la modelación hidráulica de crecidas

[ES] En este trabajo se ha analizado el efecto de la cartografía en los resultados derivados de los modelos hidráulicos. Se han creado siete modelos de elevaciones del terreno (MDT) desarrollados a partir de tres fuentes cartográficas diferentes: un levantamiento por posicionamiento global GPS, un modelo digital de elevaciones a partir de datos altimétricos de alta resolución LiDAR (Light Detection And Ranging) y una cartografía vectorial de curvas de nivel. Los modelos cartográficos de partida han sido analizados y los resultados del modelo hidráulico se evaluaron en tres contextos diferentes: 1) los propios resultados del modelo: relación caudal-altura de la lámina de agua, 2) la sensibilidad relativa del modelo hidráulico a cambios en el parámetro de resistencia al flujo según el modelo cartográfico utilizado y 3) la delineación del área de inundación. Los cálculos hidráulicos se han basado en un modelo unidimensional (HEC-RAS). El trabajo demuestra la importancia de los modelos cartográficos, al obtener variaciones de 4.5 m en la determinación de la altura de la lámina de agua y de un 50% en la estimación del área inundada para las mismas condiciones de contorno.Este trabajo ha sido realizado en el ámbito del proyecto SPHERE (Systematic, Palaeoflood and Historical data for the improvEment of flood Risk Estimation), financiado por la Comisión Europea (contract number EVG1-CT-1999-00010), y del proyecto PALEOCAP financiado por la CICYT (REN2001-1633/RIES).Casas Planes, A.; Benito, G.; Thorndycraft, VR.; Rico, M. (2005). Efectos de las fuentes cartográficas en los resultados de la modelación hidráulica de crecidas. Ingeniería del agua. 12(4):309-320. https://doi.org/10.4995/ia.2005.2567309320124Ackermann, F. (1999). Airborne laser scanning - present status and future expectations.ISPRS Journal of Photogrammetry & Remote Sensing, 54, pp. 64-67.Baltsavias, E.P. (1999). "Airborne laser scanning: basic relations and formulas". ISPRS Journal of Photogrammetry & Remote Sensing, 54, pp. 199-214.Bates, P.B., Anderson, D.A, Price, D.A., Hardy, R.J., Smith, C.N. (1996). "Analysis and Development of Hydraulic Models for Floodplain Flows". En: Anderson, D.A, Walling, D.E. and Bates, P.B. eds. Floodplain Proceses, John Wiley & Sons Ltd.Bates, P.B., De Roo, A.P.J. (2000). "A simple raster-based model for flood inundation simulation". Journal of Hydrology, 236, pp.54-77.Bates, P.D., Marks, K.J., Horritt, M.S. (2003). "Optimal use of high-resolution topographic data in flood inundation models" Hydrological Processes, 17, pp. 537-557.Bonham-Carter, G.F. (1996). Geographic Information Systems for Geoscientists - Modelling with GIS. Pergamon, Oxford.Brasington, J., Rumsby, B.T., McVey, R.A. (2000). "Monitoring and modelling morphological change in a braided gravel-bed river using high-resolution GPS-based survey". Earth Surface Proceses and Landforms, 25, pp. 973-990.Burrough, P.A., McDonnell, R.A. (1998). Principals of Geographical Information Systems, Oxford University Press.Charlton, M.E, Large, A.R.G., Fuller, I.C. (2003). "Application of airborne LiDAR in River environments: The River Coquet, Northumberland, UK" Earth Surface Processes and Landforms, 28, pp. 299-306.Chow V.T., Maidment D.R, Mays L.W. (1988). Applied Hydrology, MacGraw-Hill, Inc., New York.Cobby, D.M., Mason, D.C. (1999). "Image processing of airborne scanning laser altimetry for improved river flood modeling". ISPRS Journal of Photogrammetry and Remote Sensing, 56, pp. 121-138.Cobby, D.M., Mason, D.C., Horritt, M.S., Bates, P.D. (2003). "Two-dimensional hydraulic flood modelling using a finite-element mesh decomposed according to vegetation and topographic features derived from airborne scanning laser altimetry" Hydrological Processes, 17, pp. 1979-2000.Fix R.E., Burt T.P. (1995). "Global Positioning System: an effective way to map a small catchment". Earth Surface Proceses and Landforms, 20, pp. 817-827.French, J.R. (2003) "Airborne LiDAR in support of geomorphological and hydraulic modelling", Earth Surface Processes and Landforms, 28, pp. 321-335.Gomes Pereira, L.M., Wicherson, R.J. (1999). "Suitability of laser data for deriving geographical information: a case study in the context of management of fluvial zones". ISPRS Journal of Photogrammetry and Remote Sensing, 54 (2-3), pp. 105-114.Hardy, R.J., Bates, P.D., Anderson, M.G. (1999). "The importance of spatial resolution in hydraulic models for floodplain environments". Journal of Hydrology, 216, pp. 124-136.Horritt, M.S. (2000). "Development of physically based meshes for two-dimensional models of meandering channel flow". International Journal for numerical methods in engineering, 47, pp. 2019-2037.Horritt, M.S., Bates, P.D. (2001a). "Predicting floodplain inundation: rasted-based modelling versus the finite-element approach". Hydrological Processes, 15 (5), pp. 825-842.Horritt, M.S., Bates, P.D. (2001b). "Effects of spatial resolution on a raster based model of flood flow". Journal of Hydrology, 253, pp. 239-249.Hydrologic Engineering Center (1998a). HEC-RAS, River Analysis System User's Manual, Version 3.1, Davis, California.Hydrologic Engineering Center (1998b). HEC-RAS Hydraulic Reference Manual, Davis, California.Hydrologic Engineering Center (2002). HEC-GeoRAS: An extensión for support of HEC-RAS using Arcview User's Manual, Versión 3.1, Davis, California.Keim, R.F., Skaugset, A.E., Bateman, D.S. (1999). "Digital terrain modeling of small stream channels with a total-station theodolite". Advances in water resources, 23, pp. 41-48Lane S.N., Chandler J.H., Richards K.S. (1994). Developments in monitoring and terrain modelling small-scale river bed topography, Earth Surface Proceses and Landforms, 19, pp. 349-368.Marks, K., Bates, P. (2000). "Integration of high resolution topographic data with floodplain flow models". Hydrological Processes, 14, pp. 2109-2122.Martín Vide, J.P. (2002). Ingeniería de ríos. Ediciones UPC, Barcelona.Navitronic Systems AS (1993). Navisound 50 Operators Manual, Denmark.Nicholas, A.P., Walling, D.E. (1997). "Modelling flood hydraulics and overbank deposition on river flood-plains". Earth Surface Processes and Landforms, 22 (1), pp. 59-77.Omer, C.R., Nelson, E.J., Zundel, A.K. (2003). "Impact of varied data resolution on Hydraulic Modeling and Floodplain Delineation". Journal of the American Water Resources Association, 39(2), pp. 467-475.Raber, G., Jensen, J.R., Schill, J.R., Schuckman, K. (2003). "Creation of digital terrain models using an adaptive LiDAR vegetation point removal process" Photogrammetric Engineering and Remote Sensing, vol. 68, 12, pp. 1307-1315.Ruiz, A.; González, X.; Herms, I. & Bastianelli, L. (2002). "Flood Risk Mapping Based on Airborne Laser Scanner Data: case of the Llobregat River". En: Proceedings of the Int. Conference on Flood Estimation, 6-8 March 2002, Bern, Switzerland.Tate, E.C. (1999). Floodplain mapping using HEC-RAS and ArcView GIS, Center for Research in Water Resources, University of Texas at Austin.Wehr, A., Lohr, U. (1999). "Airborne laser scanning-an introduction and overview" ISPRS Journal of Photogrammetry & Remote Sensing, 54, pp. 68-82.Werner, M.G.F. (2001). Impact of grid size in GIS based flood extent mapping using a 1D flow model. Phys.Chem.Earth (B), Vol. 26, No 7-8, pp.517-522.Wilson, M.D., Atkinson, P.M. (2003). "A comparison of remotely sensed elevation data sets for flood inundation modeling". Proceedings of the 7th International Conference on Geocomputation. University of Southampton, U.K

La crue catastrophique de 1617 en Catalogne (nord-est de l'Espagne) et son contexte climatique

[EN] This paper presents a reconstruction of the catastrophic floods of AD 1617 in Catalonia (northeast Spain). Compilation of archival data sources shows that heavy rainfall occurred from 2 to 6 November 1617 and that the resultant flooding caused severe damage throughout the region, including the destruction of at least 389 houses, 22 bridges and 17 water mills. Discharges of 2700–4500 m3 s−1 and ≤2000 m3 s−1 were estimated from dated palaeostage indicators for the Ter and Segre rivers, respectively, whilst 4680 m3 s−1 was calculated for the Llobregat River flood in a previous study (Thorndycraft et al., 2005). The magnitude of the 1617 floods of the Llobregat and Ter rivers exceeded the largest events of the instrumental data series (2300 and 2350 m3 s−1, respectively). The 1617 floods are also compared to the longer-term palaeoflood record, which shows that the largest floods in the region were associated with colder phases of climatic variability.[FR] Cet article présente une analyse de la crue catastrophique de 1617 en Catalogne (nord-est de l'Espagne). Les sources documentaires montrent que de fortes intensités de pluie ont eu lieu du 2 au 6 novembre 1617 et ont provoqué de graves dommages dans toute la région, avec la destruction d'au moins 389 maisons, 22 ponts et 17 moulins. La modélisation hydraulique a permis de calculer les débits associés aux crues extrêmes de trois bassins (Ter, Segre et Llobregat) à partir des traces laissées par les sédiments de crue, avec respectivement 2700–4500 m3 s−1 et une valeur inférieure à 2000 m3 s−1 pour les deux premiers bassins, et 4680 m3 s−1 pour le troisième d'après l'estimation faite par Thorndycraft et al. (2005). L'intensité de la crue de 1617 sur le Llobregat et le Ter a largement dépassé la plus forte crue enregistrée par le réseau hydrométrique actuel (respectivement 2300 et 2500 m3 s−1). L'événement de 1617 a été resitué dans la chronique pluri-séculaire des paléo-crues, qui montre que les crues les plus fortes ont été associées à des périodes climatiques froides.Peer reviewe

A Late Holocene palaeoflood record from slackwater flood deposits of the Llobregat river, NE Spain

11 páginas, 7 figuras, 3 tablas.-- El PDF del artículo es su versión post-print.The palaeofloods of the Llobregat River are the first to be reconstructed for any Spanish Mediterranean river basin. In total, 56 individual slackwater flood units were identified in eight valley side alcoves located along two study reaches, Pont de Vilomara and Monistrol de Montserrat. The majority of the deposits are fine sands or very fine sandy silts, with a variety of sedimentary structures identified, namely parallel laminations, climbing ripples (both in-phase and in-drift) and current ripples. The estimation of the palaeoflood discharges associated with these deposits, using the HEC-RAS onedimensional hydraulic model, has provided long-term data regarding flood magnitude within the catchment. Palaeofloods at Pont de Vilomara, radiocarbon dated to 2640 ± 55 BP and 2580 ± 75 BP, have minimum estimated discharges of 3700-4300 m3s-1. The largest palaeoflood at Monistrol de Montserrat, dated to 305 ± 50 BP, has an estimated minimum discharge of 4700 m3s-1. The results indicate that the instrumental discharge series is of insufficient length to have witnessed the largest magnitude flood events within the Llobregat catchment and that the use of palaeoflood hydrology is a valuable means of improving the flood record of Mediterranean catchments.The research was carried out as part of the SPHERE Project (Systematic, Palaeoflood and Historical data for the improvEment of flood Risk Estimation), funded by the European Commission (contract number EVG1-CT-1999-00010).Peer reviewe

A long-term flood discharge record derived from slackwater flood deposits of the Llobregat River, NE Spain

16 páginas, 7 figuras, 4 tablas.-- El PDF del artículo es su versión post-print.Slackwater palaeoflood deposits were identified along two bedrock gorge study reaches of the Llobregat River, at Pont de Vilomara and Monistrol de Montserrat. The compiled palaeoflood record consists of two principal flood series: (a) a relatively complete record of low to high magnitude flood events from the last ca. 100 years and (b) evidence of the largest palaeoflood events that have occurred over the last ca. 2700 years. The longer term extreme palaeoflood record indicates that the discharge of the 1971 flood, the largest on record, was exceeded on at least eight occasions, with two periods of high magnitude flooding identified: (a) the Late Bronze Age (2500–2700 years ago) and (b) the Little Ice Age (AD 1500–1700). At Pont de Vilomara, palaeodischarge estimates of 3700–4300 m3/s compare to a discharge of 2300 m3/s for the 1971 event. Downstream at Monistrol, an estimate of 4680 m3/s for flood deposits dated as AD 1516–1642, and believed to be those of the AD 1617 flood, compared to 2500 m3/s for the 1971 flood.The research was carried out as part of the SPHERE Project (Systematic, Palaeoflood and Historical data for the improvEment of flood Risk Estimation), funded by the European Commission (contract number EVG1-CT-1999-00010). The research was also supported by the Spanish Committee for Science and Technology (CICYT) through grant no. REN-2001-1633.Peer reviewe

The topographic data source of digital terrain models as a key element in the accuracy of hydraulic flood modelling

The effects of the topographic data source and resolution on the hydraulic modelling of floods were analysed. Seven digital terrain models (DTMs) were generated from three different altimetric sources: a global positioning system (GPS) survey and bathymetry; high-resolution laser altimetry data LiDAR (light detection and ranging); and vectorial cartography (1:5000). Hydraulic results were obtained, using the HEC-RAS one-dimensional model, for all seven DTMs. The importance of the DTM's accuracy on the hydraulic modelling results was analysed within three different hydraulic contexts: (1) the discharge and water surface elevation results from the hydraulic model; (2) the delineation of the flooded area; and (3) the relative sensitivity of the hydraulic model to changes in the Manning's n roughness coefficient. The contour-based DTM was the least accurate with a root mean square error (RMSE) of 4·5 m in the determination of the water level and a variation of up to 50 per cent in the estimation of the inundated area of the floodplain. The GPS-based DTM produced more realistic water surface elevation results and variations of up to 8 per cent in terms of the flooded area. The laser-based model's RMSE for water level was 0·3 m, with the flooded area varying by less than 1 per cent. The LiDAR data also showed the greatest sensitivity to changes in the Manning's roughness coefficient. An analysis of the effect of mesh resolution indicated an influence on the delineation of the flooded area with variations of up to 7·3 per cent. In addition to determining the accuracy of the hydraulic modelling results produced from each DTM, an analysis of the time-cost ratio of each topographic data source illustrates that airborne laser scanning is a cost-effective means of developing a DTM of sufficient accuracy, especially over large areas.Funded by: European Commision; Grant Number: EVG1-CT-1999-00010. -- CICYT; Grant Number: REN2001-1633/RIESPeer reviewe

Natural risks, river floods and climate change

9 páginas, 10 figuras.[EN]: Flood response to Global Warming is one of the major uncertainties on the latest IPCC (Trenberth et al., 2007). The lack of long instrumental records makes difficult to provide robust links between extreme events and climate variability. In this paper, we describe the methodological procedures used on scientific research for reconstructing past floods in the context of variability. Evidences from past floods based on sedimentary and geomorphic records (palaeofloods) show a higher frequency of floods during the initial and final stages of cold periods (e.g. Little Ice Age 1550-1850 A.D.). During the instrumental period (1910 to the present), Iberian Atlantic rivers show a decrease on frequency for ordinary flood events, and in Mediterranean rivers data point out to an increase in the hydrological variability with higher frequency of flash floods.[ES]: Entre las principales incertidumbres del Informe del Panel Intergubernamental sobre Cambio Climático (IPCC) (Trenberth et al., 2007) se encuentra la predicción de crecidas extremas en respuesta al Calentamiento Global. La falta de registros instrumentales dificulta en gran medida la posibilidad de diagnosticar la magnitud y frecuencia con la que ocurrirán los eventos extremos en relación con la variabilidad climática. Las evidencias de crecidas pasadas basadas en indicadores geológicos (sedimentarios y geomorfológicos) permiten ampliar los registros de eventos extremos (paleocrecidas) a los últimos milenios, y comprender su respuesta en relación al clima. En este trabajo se pretende describir el procedimiento metodológico utilizado en la literatura científica para la reconstrucción de eventos extremos obtenidos del pasado reciente basado en el estudio de procesos geológicos externos. Los registros sedimentariosobtenidos en diferentes ríos peninsulares muestran que las paleocrecidas son más frecuentes durante los estadios iniciales y finales de periodos fríos (e.g. Pequeña Edad del Hielo 1550-1850 A.D.). En el periodo instrumental (1910 hasta la actualidad), los ríos Atlánticos de la Península Ibérica han experimentado una disminución de la frecuencia de las crecidas ordinarias, y, en las cuencas Mediterráneas los datos existentes apuntan al aumento en la irregularidad hidrológica y la generación de crecidas relámpago.Este trabajo constituye una contribución del Proyecto CGL2008-06474-C02-01/BTE “Riesgo de Inundaciones en ríos Mediterráneos en respuesta a la variabilidad climática y cambios ambientales” financiado por el Ministerio de Ciencia y Tecnología. La redacción del mismo se realizó durante una estancia de G. Benito en el U.S. Geological Survey (Portland, Oregon) dentro del Programa de Movilidad de Profesores (Programa Salvador de Madariaga) financiada por el Ministerio de Educación (Ref.: PR2008-0154)Peer reviewe

Caesium-137 dating applied to slackwater flood deposits of the Llobregat River, NE Spain

14 páginas, 6 figuras, 1 tabla.-- El PDF del artículo es su versión post-print.During a palaeoflood study of the Llobregat River (NE Spain), analysis of 137Cs was carried out on slackwater flood deposits to obtain an improved flood chronology for the most recent flood sediments. At the Monistrol study reach, 137Cs was measured in flood deposits preserved in valley side rock alcoves, with a range of 137Cs concentrations of 2.80–10.06 mBq/g measured. The 137Cs was associated with sediment mobilised from the upstream catchment by erosion and transported to the alcoves during floods. The onset of measured caesium activity in the sedimentary profiles permitted the deposits to be divided between those from floods that occurred before the mid-1950s and those from events after this period. Combining the information derived from the slackwater flood stratigraphy, the minimum discharge estimates associated with the flood deposits, 137Cs analysis and the instrumental peak discharge series, it was possible to identify the particular flood events responsible for the majority of the slackwater flood units. At Vilomara, however, 137Cs activity was measured in palaeoflood deposits dated to the Late Bronze Age and located at an elevation not reached by the floodwaters of the largest modern events. The data from this site indicated that the 137Cs was not associated with sediments transported by floods but was rainfall-derived, the rainwater reaching the deposits through fissures in the rock. To ensure the successful application of caesium dating to slackwater flood deposits preserved within rock alcoves, or caves, some general guidelines are proposed. The technique is best applied: (1) when there is a sedimentary profile of greater than 1 m depth; (2) when the profile is sampled away from zones affected by direct percolation or springwater entering the alcove; and (3) where there are various levels of contrasting textures within the profile.The research was funded by the European Commission through the project “Systematic, palaeoflood and historical data for the improvement of flood risk estimation—SPHERE” (contract number EVG1-CT-1999-00010).Peer reviewe