Estimacions hidrològiques i de moviment de sediment a la riuada del 7 d'Agost de 1996 a la conca del Barranco de Arás (Pirineu aragonès)

During 7 August 1996 a summer thunderstorm with rainfall intensity up to 500 mm h-1 occurred over the 18 km2 Arás drainage basin, a mountainons torrent tributary of the Gállego river in central Pyrenees. The resultant flood peak was of the order of 500 m3 S-1, a thousandyear ietum penod discharge for the area. As a consequence, the campground located on the alluvial fan at the torrent outlet was flooded with seven-hundred people inside, causing eighty-six people death and many injured, damage on properties and great social impact. Two physical factors can be identified as main responsible for this high magnitude and low frequency event: i) the low permeability of the soil due to high moisture content caused by an unusual rainy season, which resulted in large excess of quick surface runoff and ii) in-channel high steep slopes up to 20%, which causetl flood waves at estimated velocities of 7 m S-l. The most active storm-cell was located in the headwaters Betés subbasin, which represents 20% of the catchment area but contributed 60% of the peak discharge. Specific maximum discharge in the Betés basin reached 85 m3 S-1 km-2. Mobilisation of sediment from stream bed and footslopes was also extremely high. The competence of the torrent was enough to entrain rocks up to 10 m size in some reaches, under shear stress of 10000 Pa. A minimum of 100,000 tm of coarse and fine sediment was exported out of the Arás basin, part of it stored in a series of check-dams located in the lower reaches of the torrent, part eroded from bed and banks in the drainage net. Estimated bedload transport rate at the peak discharge has been estimated around 300 kg m-1 S-1, tliree orders off magnitude higher than those recorded in mountainous torrents in the Catalan Coastal Ranges during floods

Aplicación de modelos de transporte de sedimento en un río permamente con granulometría dispersa

[Resumen] Este trabajo analiza el funcionamiento de diversos modelos de transporte de sedimento en un río permanente con lecho de arena y gravas (Arbúcies, Cordilleras Costero Catalanas). El grado de correlación entre las predicciones de los modelos y las tasas de transporte de sedimento obtenidas en el campo varía considerablemente. El mejor ajuste lo presentan las ecuaciones de ACKERS & WHITE (1973) y ENGELUND & HANSEN (1967), reflejo de su diseño original para ríos de granulometría dispersa y movimiento de dunas en el lecho respectivamente. Los modelos desarrollados por Brownlie (1981) y van Rijn (1984) muestran un funcionamiento más deficiente, a causa del desajuste entre los datos de campo y algunas condiciones de aplicación de los modelos. La discrepancia entre valores estimados y observados pone de relieve la complejidad de los procesos hidráulicos y sedimentológicos en ríos permanentes, relacionados tanto con la migración de formas durante caudales bajos como con la destrucción durante crecidas de sectores del lecho con acorazamiento de gravas.[Abstract] Bed-material load sampled under a wide range of hydraulic conditions in a perennial and poorly sorted sandy gravel-bed river (Arbúcies, Catalan Coastal Ranges), is used to test the performance of four well-know bed-material formulae. The degree of agreement between observed and predicted values varies greatly. The best agreement with measured values was obtained using the ACKERS and WHITE (1973) and ENGELUND & HANSEN (1967) models, a reflection of its original design for poorly sorted sediment and streambed formed into dunes. Contrastingly, the wide range of hydraulic conditions from which the data was obtained and the poor sorting of the bed sediment affected the performance of the van Rijn (1984) and Brownlie (1981) equations and, thus, deserves further study

Balanç hidroquímic d'una conca mediterrània en estat seminatural: el cas de la riera d'Arbúcies

A study of hydrochemical characteristics of the Arbúcies river (a seminatural mediterranean basin) has been undertaken during 1991. Mean solute yield for each on has been determined using the correlation curves between discharge and concentration, and the flow duration curve. The hydrochemical budget of the Arbúcies drainage basin shows that the basin is a net source for all the elements. The cationic denudation rate obtained in this granitic basin is 5.24 keq/ha/year. This high rate is due to the intensive chemical weathering of the granodionte, that delivers an important amount of cations which will release to be transported. The results demostrate clearly the strength of lithological control on stream loads, particulary on the dissolved component.Es presenta un balanç hidroquímic de la riera d'Arbúcies, una conca rnediterrania semi-natural, després del primer any de monitorització. La producció anual de material dissolt per a cadascun dels ions, s'ha determinat utilitzant les corbes de correlació entre fluxe i concentració, i la taula de freqüència de cabals. El balanç químic de la riera d'Arbúcies mostra que tots els elements presenten un balanç positiu, fet que demostra que l'exportació neta positiva ha de provenir de fonts internes al sistema. La taxa de de denudació catiònica obtinguda és de 5,24 keq/ha/any, en constrast amb les taxes inferiors obtingudes en conques sobre pisarres i filites. Això és degut a la intensa meteorització química de la granodiorita, que allibera gran quantitat de cations i els deixa en situació de ser transportats. Aquest fet és conseqüència de les elevades temperatures i I'alta disponibilitat hídrica al llarg de l'any en aquesta conca. Des d'un punt de vista geomorfològic es demostra la importancia fonamental del control litològic en la càrrega de sediment dels rius, particularment sobre la part en dissoluci

Mercat elèctric i competitivitat

A escala europea, la crisi econòmica i financera actual ha posat en relleu la importància de l'economia real i d'una indústria forta. Tal com reconeix la mateixa Comissió Europea en les seves diferents comunicacions, la interacció de la indústria amb la resta de l'entramat econòmic europeu va molt més enllà del mateix procés productiu. Les activitats industrials s'integren en cadenes de valor cada vegada més riques i complexes, en les quals conflueixen grans empreses, amb presència global en els mercats, i petites i mitjanes empreses de tots els sectors i països

Transport interchanges effects on their surroundings in Tunja (Colombia) and cordoba (Spain): A comparative approach

ABSTRACT: This article proposes a methodology to study the urban implications of transport interchanges. The methodology was evaluated through the study of commercial establishments and urban quality in the surroundings of two transport interchanges. The case studies are a bus station in Colombia and a combined high-speed rail and bus station in Spain. The article draws two types of conclusions; firstly, that the comparative methodology proposed is effective in determining the influence of transport interchanges and secondly that it provides specific conclusions about the activities in the station's surrounding area. The article demonstrates that the surroundings of the transport interchanges have greater commercial activity than similar areas of the city. It also concludes that the different income levels of HSR and bus users provoke a variety and quantity of commercial activities within each type of station. Furthermore, it concludes that the perceived quality of the interchange surroundings is deeply influenced by its level of integration within the urban plan, despite the negative side effects related to transport

Norte de Jalisco. Una Región "remota" de Occidente

Este modesto libro trata de ser una aportación al conocimiento del Norte de Jalisco, región casi ignorada a nivel nacional- e incluso regional- pero que encierra en potencia recursos naturales y humanos, con los cuales se puede lograr en el futuro un mayor desarrollo. Las dificultades que el medio físico ofrece para lograr un mayor y rápido avance socioeconómico, no pueden servir de justificantes para perpetuar ese atraso general y esa estructura regional, pues sus habitantes tienen el mismo derecho al progreso que cualquier otro grupo, de no importar cuál rumbo del espacio nacional