Modellierung und Prognose der Erosion feiner Sedimente

Predicting erosion of fine, cohesive sediments is an important task within sustainable management of water-bodies. This is above all due to the fact, that these sediments tend to bind pollutants which are re-suspended in the case of erosion. The given work deals with this subject in two parts, being the identification of a suited mathematical model on the one hand and the demonstration of its abilities predicting erosion during a reservoir depletion within a case study on the other hand. Existing mathematical models describing erosion of fine sediments were developed differing four cases of erosion, namely floc- or mass erosion and depth-limited or depth-unlimited erosion respectively. Based on a theoretical analysis of such models, a new erosion model is proposed which aims at unifying prediction of these cases. Within laboratory experiments eroding deposited kaolinite in an annular flume, not only the validity of the new model but also the increasing quality in modelling measured erosion processes compared with other models is proven. The new model describes the rate of erosion of sediments as a function of bottom shear stress as well as density and shear resistance of the sediment deposition. As the new model is a product of two non-dimensional numbers, its empirical parameter – the characteristic erosion velocity – gets a physically plausible meaning, which is not the case in most other models. Further experiments, increasing the bottom shear stress linearly with time as a simulation of typical erosion events, show a dependency between the characteristic erosion velocity and the time-rate-of-change of the driving stress. Just as this, an influence of the vertical gradient of shear resistance to the erosion process is shown. To take account of these parameters, an extension of the new erosion model is proposed. In the case study, erosion of fine sediments during a reservoir depletion is simulated using four different erosion models. Vertical density profiles of sediment deposition as well as critical shear stresses of the sediment surface are quantified based upon in situ measurements, whereas multiple sediment- and model parameters are varied within their band-width found in a literature review. Results of this sensitivity study show, that mean sediment concentrations simulated with the new model are in close agreement with measurements carried out during depletion. Furthermore, sensitivity of the simulation results to empirical parameters using the new erosion model is small compared to the other models investigated. Based on the given results, it is stated that the new erosion model is an important step towards a reliable prediction of erosion of fine sediments. However, future research programs are necessary to improve understanding of erosion processes and experimental conditions for related investigations in the laboratory as well as in situ.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2005

Author dc:creator

• Schweim, Christoph

Contributors dc:contributor

• Köngeter, Jürgen

• info:eu-repo/classification/ddc/550
• Aquatisches Sediment
• Erosion
• Prognose
• Mathematisches Modell
• Geowissenschaften
• Sedimenttransport
• kohäsive Sedimente
• Erosionsmodell
• Erosionsmessung
• Gewässergüte

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-121566%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:59819