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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Modelling long-term runoff from upland catchments

Cheesman, Joanne E. January 1998 (has links)
The aim of the research contained in this thesis was to develop a model of long-term upland catchment runoff that can be used for ungauged catchments. This is a problem due to the complex spatial and temporal nature of runoff and the main contributing processes, precipitation (P) and evapotranspiration (Et). It is also a problem due to the lack of suitable data on which to base and test models of these processes, particularly in remote upland areas such as the north-west of England, the study area of this research. Long-term runoff is important since it represents the maximum rate at which water is available for human use and management, for assessment of water resource yield and for prediction of extreme events that are particularly important in respect to climate change. Methods currently in use by water companies in the UK, such as North West Water Limited (NWW), are inadequate since they fail to account for the spatial and temporal nature of runoff. New more reliable methods are therefore required which will equip water managers with flexible and responsive runoff modelling tools based upon routinely available data and that are sensitive to the complex physical nature of the processes involved. A physically based distributed runoff model was developed using GIS technology and spatial data to interpolate and extrapolate available point-based hydrometeorological data. The strategy required the development of models to derive areal representations of P and Et. For the P modelling several interpolation techniques and artificial neural network models were investigated. The results were evaluated against an independent data set. The results showed that a geostatistical interpolation technique, detrended Kriging, which uses pointbased precipitation and spatial elevation data provided the most accurate estimates when compared to other methods. The models of Et involved extrapolation of point-based Et values derived from the Penman-Monteith formula (Monteith, 1965), using spatial land cover data. A point-based temperature function model (Wright and Harding, 1993) that reduces the Penman estimates of Et for upland sites was spatially implemented using spatial temperature and elevation data. No independent data were available for model evaluation but first estimates of errors were gained through comparison of errors of runoff and precipitation estimates. Overall it was found that the most accurate E, model results were derived when the temperature function model was not implemented. Evidence of whether or not a lumped or heterogeneous land cover representation provided the more accurate results was unclear. Error evaluation and sensitivity analysis of the modelled runoff was carried out using measured runoff records and the results were compared to those produced using the North West Water model. It was found that the GIS-based model provided improved estimates of long-term average annual runoff for upland catchments. The largest component of the errors of the GIS-based method were associated with the Et estimates. This was principally a result of poor quality and limited availability of data for the study area. The research highlights many wider issues related to the use of GIS and spatial data for hydrological modelling.
12

Verklausungsgefahr der Elbe: Risikoanalyse einer Verklausung (eines Aufstaus) der Elbe infolge verschiedener Szenarien von Sturz- und Rutschprozessen in der Sächsischen Schweiz

Graf, Kaspar, Salz, Maren 25 August 2016 (has links)
Im Elbtal zwischen tschechischer Grenze und Pirna wurden auf einer Strecke von rund 30 km entlang der teilweise steil aufragenden Felsanschnitte mögliche Sturz-, Rutsch- und Murgangszenarien beurteilt. Daraus wurden die Auswirkungen für die Elbufer und den gesamten Flussquerschnitt unter Einbeziehung von nummerischen Modellierungen abgeleitet. Für die Berechnung und Modellierung wurden das Modell RAMMS und das Debris Flow Modul verwendet. Für Sturz-, Rutsch- und Murgangprozesse werden die »verklausungsrelevanten« Szenarien als äußerst unwahrscheinlich erachtet. Die generelle Gebirgsstabilität ist als gut einzuschätzen. Erstmalig wurden große Sturz-, Rutsch- und Murgangszenarien in einer sehr detaillierten Herangehensweise bearbeitet. Die Ergebnisse bilden eine fundierte Basis für weitere Betrachtungen. Redaktionsschluss: 28.02.2015

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