Quantification of uncertain bed roughness under design conditions
and propagation to the design water levels, a case study for the river
Rhine

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Warmink, J.J. and Booij, M.J. and Hulscher, S.J.M.H. and Klis, H. van der (2010) Quantification of uncertain bed roughness under design conditions
and propagation to the design water levels, a case study for the river
Rhine.
In: Proceedings of the 10 International Symposium on Stochastic Hydraulics (Water 2010). Infoagua, pp. 1-8.

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Abstract:Hydrodynamic river models are applied to design and evaluate measures for purposes such
as safety against flooding. The modeling of river processes involves numerous uncertainties, resulting in
uncertain model results. Knowledge of the type and magnitude of these uncertainties is crucial for a meaningful
interpretation of the model results. The aim of this study is to quantify the uncertainty due to the
hydraulic roughness predictor for the river bed in the main channel and assess its effect on the uncertainty
in the modelled water levels under design discharge conditions. This uncertainty in the main channel
roughness predictor consists of the uncertainty between different roughness predictors and the uncertainty
within each roughness predictor. To assess the uncertainty between the selected roughness predictors, we
compared five roughness predictors that computed the hydraulic resistance of the river bed in the Dutch
river Rhine, based on measurements of bed forms characteristics and water levels for different discharges.
The propagation of this uncertainty to the water levels is carried out using a two dimensional hydrodynamic
river model with dimensions similar to the river Rhine in The Netherlands. It is shown that different
roughness predictors result in significantly different roughness values for the same measurements of bed
form and flow characteristics.
To determine the uncertainty between the different roughness predictors under design conditions, the
Generalized Extreme Value distribution is used to extrapolate the predicted roughness values for each
roughness predictor to design conditions. The uncertainty between and within the roughness predictors
are combined to show that with 95% confidence the Nikuradse roughness for the main channel of the river
Rhine under design conditions lies between 0.32 m to 1.03 m. The uncertain roughness results in a large
uncertainty range in the design water levels of 71 cm.
Item Type:Book Section
Faculty:
Engineering Technology (CTW)
Research Group:
Link to this item:http://purl.utwente.nl/publications/78717
Conference URL:http://www.infoagua.net/eventos/234/10th-international-symposium-on-stochastic-hydraulics-and-5th-international-conference-on-water-resources-and-environment-research.aspx
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