A large-scale floodplain delineation algorithm is applied to identify potentially inundated areas at the basin scale. The model, which mainly uses a digital elevation model (DEM) and design flood peak discharge at the outlet as input data, is implemented within a geographic information system (GIS). It implements a preliminary GIS-based terrain analysis framework for estimating the stream network, surface flow direction and drainage grids, while the core algorithm implements an automated fluvial cross-section extraction for discharge and flow height estimation. The delineation is then implemented by filtering the floodplain cells as those cells whose elevation is lower than the corresponding channel flow height. The proposed 'hydrogeomorphic floodplain', obtained on the Tiber River basin (approx. 17 000 km ) avec la reconnaissance topographique à 90 m de résolution mondiale par le radar de la navette spatiale de la NASA (SRTM) est comparée aux cartes officielles des inondations de l'Autorité du bassin du fleuve Tibre. L'étude de cas présentée montre la possibilité d'utiliser un algorithme de SIG automatisé et les données de télédétection largement disponibles pour l'identification préalable de l'empreinte des plaines inondables à l'échelle mondiale.
This paper discusses various methods for calculating the minimum instream flows for the protection of aquatic life for the purpose of illustrating its increasing complexity. These procedures are the Montana method (Tennant, 1976); the wetted perimeter method (Collings, 1974; Cochnauer, 1976) and the IFIM method (Instream Flow Incremental Methodology; Bovee, 1982). An analysis is then made of some regionalisation criteria based on these methods, from which useful suggestions can be drawn for the development of a procedure to be applied to basins. A method is thus proposed for calculating the recommended flows for protecting the aquatic environment based on simple hydrological variables, such as Q7 10, which can be estimated for a basin on the basis of area A and a Base Flow Index (BFI) which summarises its hydrogeological characteristics. This approach can be used when the field data necessary for more complex methods is not available. These require the defining of the environmental suitability of a watercourse for certain designated reference fish species, according to the flow and the morphology of the channel. The positive results of this approach were verified by Leonard (1990) and this methodology was applied to the Tiber river basin.
Two single input stochastic models of the type proposed by Box & Jenkins were applied to sediment yield data from an experimental basin in the USA. The models were fitted to a calibration set of eight events and then applied to predict and simulate sediment yield for four sets of events. The results so obtained supported the adaptability of these models to real time forecasting schemes and provided some information about the dependency of sediment yield on rainfall and runoff rates.
Relationsentre précipitations, débits liquides et débits solides par 1'intermédiaire de modèles stochastiques RESUME Deux modèles stochastiques du type proposé par Box & Jenkins, avec une seule variable en entrée (les précipitations ou le débit liquide) ont été appliqués dans l'étude du transport solide d'après les observations effectuées sur un bassin expérimental des Etats Unis. L'ajustement des modèles répose sur huit séries de données et l'application a été vérifiée sur quatre séries différentes de données. I1 en résulte que ces modèles sont recommandés pour l'utilisation des schémas prévisionnels "en temps réel" et ils donnent aussi des informations sur la relation de dépendance du transport solide par rapport aux précipitations et aux débits liquides.
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