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| Titel |
Sensitivity Analysis of a process based erosion model using FAST |
| VerfasserIn |
Petra Gabelmann, Jan Wienhöfer, Erwin Zehe |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250103162
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| Publikation (Nr.) |
 EGU/EGU2015-2560.pdf |
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| Zusammenfassung |
| Erosion, sediment redistribution and related particulate transport are severe problems in
agro-ecosystems with highly erodible loess soils. They are controlled by various factors, for
example rainfall intensity, topography, initial wetness conditions, spatial patterns of soil
hydraulic parameters, land use and tillage practice. The interplay between those
factors is not well understood. A number of models were developed to indicate those
complex interactions and to estimate the amount of sediment which will be removed,
transported and accumulated. In order to make use of physical-based models to
provide insight on the physical system under study it is necessary to understand the
interactions of parameters and processes in the model domain. Sensitivity analyses give
insight in the relative importance of model parameters, which in addition is useful for
judging where the greatest efforts have to be spent in acquiring or calibrating input
parameters.
The objective of this study was to determine the sensitivity of the erosion-related
parameters in the CATFLOW model. We analysed simulations from the Weiherbach
catchment, where good matches of observed hydrological response and erosion
dynamics had been obtained in earlier studies. The Weiherbach catchment is located in
an intensively cultivated loess region in southwest Germany and due to the hilly
landscape and the highly erodible loess soils, erosion is a severe environmental
problem.
CATFLOW is a process-based hydrology and erosion model that can operate on
catchment and hillslope scales. Soil water dynamics are described by the Richards equation
including effective approaches for preferential flow. Evapotranspiration is simulated using an
approach based on the Penman-Monteith equation. The model simulates overland
flow using the diffusion wave equation. Soil detachment is related to the attacking
forces of rainfall and overland flow, and the erosion resistance of the soil. Sediment
transport capacity and sediment deposition are related to overland flow velocity
using the equation of Engelund and Hansen and the sinking velocity of grain sizes,
respectively.
The sensitivity analysis was performed based on virtual hillslopes similar to those in the
Weiherbach catchment. We applied the FAST-method (Fourier Amplitude Sensitivity
Test), which provides a global sensitivity analysis with comparably few model runs.
We varied model parameters in predefined and, for the Weiherbach catchment,
physically meaningful parameter ranges. Those parameters included rainfall intensity,
surface roughness, hillslope geometry, land use, erosion resistance, and soil hydraulic
parameters.
The results of this study allow guiding further modelling efforts in the Weiherbach
catchment with respect to data collection and model modification. |
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