Modeling of near-bank flow velocities during flow events as basis for developing bank erosion equations

River morphodynamics and sediment transportBank erosion and protectio

Structural Measures to Optimize Sediment Management Downstream a Chain of Reservoirs at the Danube River

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchive

Numerical Study of Morphodynamics and Ecological Parameters Following Alternative Groyne Layouts at the Danube River

Sediment Transport and Morphodynamic

Integrative Bedload Measurement Systems in Austria - Development and Evaluation of Bedload Transport Measurement Techniques and Optimization of Calculations

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchive

Numerical modeling of sediment transport in the Danube River: uniform vs. non-uniform formulation

River morphodynamics and sediment transportRiver morphology and morphodynamic

Numerical Analysis of the Effects of Engineering Measures on the Sediment Transport and Morphodynamics on the Lower Danube

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchive

Grundlegende Prozesse betreffend Hydraulik, Sedimenttransport und Flussmorphologie an der Donau

Im Rahmen des Pilotprojektes Bad Deutsch-Altenburg wurde vor, während und nach der gleichzeitigen Umsetzung mehrerer Maßnahmen (Buhnenumbau, Granulometrische Sohlverbesserung GSV, Uferrückbau und Gewässervernetzung) ein umfassendes Monitoringprogramm durchgeführt. Ziel war es, neben der Ist-Zustandserfassung, Begleitung und Dokumentation der Bauphase und der Erfassung der Entwicklung nach Bau auch die zugrunde liegenden Prozesse hinsichtlich Hydraulik, Sedimenttransport und Flussmorphologie zu analysieren. Erstmals wurde dabei die zeitliche Schwankung der Sohlschubspannung direkt gemessen. Die auftretenden Sohlschubspannungen folgten dabei in Abhängigkeit von der Turbulenzintensität einer Log-Normal- oder einer Normalverteilung. Diese Schwankungen sind mit ein Grund, weshalb schon bei Niederwasser ein nennenswerter Geschiebetransport gemessen wurde. Der effektive Durchfluss des Geschiebetransportes liegt dabei im Bereich von 2000 und 2200 m3/s. 50% Prozent des Geschiebes wird bei Durchflüssen bis 2300 m3/s transportiert, mit Jahresfrachten von 306.000 bis 594.000 t für die Jahre 2006 bis 2014. Bei Betrachtung des Transportverhaltens einzelner Tracersteine in 3 Größenklassen durchwanderten 74% der Steine die 3 km lange Strecke in einem Jahr, mit Geschwindigkeiten von 6,2 bis 10,6 m/d. Kleine Steine bewegten sich häufiger und weiter als mittlere und große, welche ein ähnliches Transportverhalten aufwiesen. Die erstmalig an der Donau beschriebenen Kiesdünen erreichten im Vergleich wesentlich höhere Geschwindigkeiten mit 2,5 bis 9 m/h. Ein Abgleich mit Fangkorbmessungen zeigte, dass Kiesdünen, wenn sie auftreten, den überwiegenden Teil des Geschiebetransportprozesses bestimmen.In the scope of the Pilotproject Bad Deutsch-Altenburg a comprehensive monitoring program was conducted, prior, during and after the implementation of several measures (groyne reconstruction, granulometric bed improvementGBI, river bank restoration and side arm reconnection). Beside the documentation of the current status, during the construction works and after the implementation of the measures, description and analyses of the underlying processes concerning hydrodynamics, sediment transport and morphology were a main objective. For the first time the instantaneous bed shear stress was measured directly in a gravel bed river. The probability distributions of the occurring bed shear stress, showed a dependency on the turbulence intensity, either following a log-normal or a normal distribution. Those fluctuations seem to be one of the reasons for a notable bed load transport, measured during low flow conditions in the Danube. The effective discharge lies in a discharge range from 2000 to 2200 m3/s, with 50% of the bed load being transported at discharges up to 2300 m3/s and an annual bed load transport between 306,000 and 594,000 tons for the years 2006 to 2014. Regarding the transport behaviour of single tracer stones 74% passed the 3 km long reach within one year, with a virtual velocity between 6,2 and 10,6 m/d. Small stones moved more frequent and farther, compared to the medium and big stones, who showed a comparable transport behaviour. In comparison gravel dunes moving with 2,59 m/h have a substantially higher velocity, and tend to dominate the bed load transport process when occurring.(VLID)136346

In situ measurements of fine sediment infiltration (FSI) in gravel-bed rivers with a hydropeaking flow regime

The overpresence of fine sediment and fine sediment infiltration (FSI) in the aquatic environment of rivers are of increasing importance due to their limiting effects on habitat quality and use. The habitats of both macroinvertebrates and fish, especially spawning sites, can be negatively affected. More recently, hydropeaking has been mentioned as a driving factor in fine sediment dynamics and FSI in gravel-bed rivers. The primary aim of the present study was to quantify FSI in the vertical stratigraphy of alpine rivers with hydropeaking flow regimes in order to identify possible differences in FSI between the permanently wetted area (during base and peak flows) and the so-called dewatering areas, which are only inundated during peak flows. Moreover, we assessed whether the discharge ratio between base and peak flow is able to explain the magnitude of FSI. To address these aims, freeze-core samples were taken in eight different alpine river catchments. The results showed significant differences in the vertical stratification of FSI between the permanently wetted area during base flow and the dewatering sites. Surface clogging occurred only in the dewatering areas, with decreasing percentages of fine sediments associated with increasing core depths. In contrast, permanently wetted areas contained little or no fine sediment concentrations on the surface of the river bed. Furthermore, no statistical relationship was observed between the magnitude of hydropeaking and the sampled FSI rate. A repeated survey of FSI in the gravel matrix revealed the importance of de-clogging caused by flooding and the importance of FSI in the aquatic environment, especially in the initial stages of riparian vegetation establishment

River Bed Degradation and Morphological Development Before and After River Restoration Measures at the Danube River East of Vienna

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchive