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Hydraulic- hydromorphologic analysis as an aid for improving peak flow predictions
KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering, Hydraulic Engineering. (River Engineering)ORCID iD: 0000-0002-9202-3159
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Conventional hydrological compartmental models have been shown to exhibit a high degree of uncertainty for predictions of peak flows, such as the design floods for design of hydropower infrastructure. One reason for these uncertainties is that conventional models are parameterised using statistical methods based on how catchments have responded in the past. Because the rare occurrence of peak flows, these are underrepresented during the periods used for calibration. This implies that the model has to be extrapolated beyond the discharge intervals where it has been calibrated.

In this thesis, hydromechanical approaches are used to investigate the properties of stream networks, reflecting mechanisms including stage dependency, damming effects, interactions between tributaries (network effects) and the topography of the stream network. Further, it is investigated how these properties can be incorporated into the streamflow response functions of compartmental hydrological models.

The response of the stream network was shown to vary strongly with stage in a non-linear manner, an effect that is commonly not accounted for in model formulation. The non-linearity is particularly linked to the flooding of stream channels and interactions with the flow on flood-plains.

An evaluation of the significance of using physically based response functions on discharge predictions in a few sub-catchments in Southern Sweden show improvements (compared to a conventional model) in discharge predictions – particularly when modelling peak discharges.

An additional benefit of replacing statistical parameterisation methods with physical parameterisation methods is the possibility of hydrological modelling during non-stationary conditions, such as the ongoing climate change.

Place, publisher, year, edition, pages
Stockholm: KTH , 2010. , viii, 31 p.
Series
Trita-LWR. LIC, ISSN 1650-8629 ; 2051
Keyword [en]
Hydrological modelling, peak flow predictions, distributed routing, parameterisation, stage-dependency
National Category
Oceanography, Hydrology, Water Resources
Identifiers
URN: urn:nbn:se:kth:diva-25425ISBN: 978-91-7415-760-4 (print)OAI: oai:DiVA.org:kth-25425DiVA: diva2:358201
Presentation
2010-11-02, L43, Drottning Kristinas väg 30, KTH, Stockholm, 10:52 (English)
Opponent
Supervisors
Note
QC 20101022Available from: 2010-10-22 Created: 2010-10-21 Last updated: 2012-01-23Bibliographically approved
List of papers
1. Runoff modeling in flooded stream networks
Open this publication in new window or tab >>Runoff modeling in flooded stream networks
2007 (English)In: Proceedings of the International Symposium on Modern Technology of Dams – : the 4th EADC Symposium, Chengdu, China, October 12-18 2007., 2007, 441-450 p.Conference paper, Published paper (Other academic)
Abstract [en]

This paper outlines a procedure about how to create a compartment type of runoff model that is flexible for prediction of flows of different magnitudes. This methodology is expected to be most useful when applied to high flow situations, when predictions normally are conceived as extrapolations far outside calibration intervals. Focus is put on how to introduce response functions that include more detailed information regarding the river network geometry and the morphology of the channel cross-sections. The parametrisation formula is based on Manning’s equation for open channel flow and the geometrical data is derived from geographical information handled in a GIS software. These response functions can be expected to provide better extrapolations of the hydrograph for future extreme floods, especially for peak flows. This has implications for safety aspects of dams as well as for the economy of hydropower production.

Keyword
Peak flow modelling, response function, compartmental runoff model, river network geometry, hydromorphology, network routing model
National Category
Oceanography, Hydrology, Water Resources
Identifiers
urn:nbn:se:kth:diva-25301 (URN)
Note
QC 20101020Available from: 2010-10-20 Created: 2010-10-15 Last updated: 2015-09-03Bibliographically approved
2. Stage-dependent hydraulic and hydromorphologic properties in stream networks translated into response functions of compartmental models
Open this publication in new window or tab >>Stage-dependent hydraulic and hydromorphologic properties in stream networks translated into response functions of compartmental models
2012 (English)In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 420-421, 25-36 p.Article in journal (Refereed) Published
Abstract [en]

A distributed non-uniform routing model was constructed and applied to two stream networks in southern Sweden to investigate the effects of stage, topology and morphology on advective travel times within the stream networks.Using particle-tracking, we found markedly non-linear relationships between travel time distributions and discharge for both catchments under a range of hydraulic conditions, represented by discharges comprising percentiles between 30 and 99.9 extracted from the discharge data set for the two catchments in this study.The travel time distributions from the particle tracking were used to numerically parameterise the response function of a lumped hydrological model, which resulted in improvements, particularly in the prediction of high flows. A sensitivity analysis was performed on the routing procedure, particularly regarding the choice of Manning's friction coefficient and the choice of generic cross-sectional areas along the two stream networks showing that the uncertainty in routing parameters did not have a major effect on the final hydrograph. The new parameterisation performed better than the conventional model in every modelled case.A theoretical demonstration shows that correct descriptions of streamflow processes becomes more important with increased watershed scale, because the travel time within the stream network relative to the travel time on hillslopes increases with the watershed scale. The topology and topography of the stream network were shown to be the major factors influencing the network averaged travel time. These results demonstrate that physically based response functions (and model parameters) can be superior to compartmental model parameters that are based on numerical calibration and that are extrapolated to account for conditions during hydrological extremes.

Place, publisher, year, edition, pages
Elsevier, 2012
Keyword
Streamflow; Hydrological model; Distributed routing; Response function; Geomorphologic; Hydrodynamic
National Category
Oceanography, Hydrology, Water Resources
Identifiers
urn:nbn:se:kth:diva-58433 (URN)10.1016/j.jhydrol.2011.11.015 (DOI)000301082000003 ()2-s2.0-84856212851 (Scopus ID)
Funder
StandUp
Note

QC 20120402

Available from: 2012-01-05 Created: 2012-01-05 Last updated: 2017-12-08Bibliographically approved

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Åkesson, Anna

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