Andrew J. Manning

By A. J. Manning, J. V. Baugh, R. L. Soulsby, J. R. Spearman and R. J. S. Whitehouse

Part of the book: Sediment Transport

By Andrew J. Manning, Jeremy R. Spearman, Richard J.S. Whitehouse, Emma L. Pidduck, John V. Baugh and Kate L. Spencer

Part of the book: Sediment Transport

By Alfred Sunday Alademomi, Andrew J. Manning, Victor J. Abbott and Richard J.S. Whitehouse

The Lagos Lagoon system and its adjacent tidal basins exhibit dynamics that are significantly different on both spatial and temporal scales. As urbanisation and human activities around the lagoon have intensified, the volume of sediment deposited into the basin is increasing on a daily basis. Changes on the lagoon bed over a 6-year time scale using repeated bathymetric data (2008, 2014) are presented, and the related data acquisition technique is explained. Data reduction is followed by analysis of the lagoon water bed dynamics using abstracted profile lines from the bathymetric data within a GIS environment. The results of the significant accretion and erosion within the lagoon system were analyzed spatially to quantify the volume of sediment gain or loss on the lagoon bed. The findings partly show that over 6 years, an average height of 0.16 m was gained by the lagoon. This amount translates into an annual accretion rate of 0.026 m. These findings enhance the prospect of verifying in the long term whether the Lagos Lagoon is gradually disappearing. To the best of the author’s knowledge, this research reveals for the first time the complex evolutionary changes (channel movement, accretion, erosion, infill and movement of shoal) on the Lagos Lagoon bed.

Part of the book: Lagoon Environments Around the World

By Maurizio Brocchini, Matteo Postacchini, Lorenzo Melito, Eleonora Perugini, Andrew J. Manning, Joseph P. Smith and Joseph Calantoni

Microtidal river mouths are dynamic environments that evolve as a consequence of many forcing actions. Under the hydrodynamic viewpoint, river currents, sea waves and tides strongly interact, and their interplay determines specific sediment transport and morphological patterns. Beyond literature evidence, information comes from field observations made at the Misa River study site, a microtidal river along the Adriatic Sea (Italy), object of a long-going monitoring. The river runs for 48 km in a watershed of 383 km2, providing a discharge of about 400 m3/s for return periods of 100 years. The overall hydrodynamics, sediment transport and morphological evolution at the estuary are analyzed with particular attention to specific issues like: the generation of vortical flows at the river mouth, the influence of various wave modes (infragravity to tidal) propagating upriver, the role of sediment flocculation, the generation and evolution of bed features (river-mouth bars and longitudinal nearshore bars). Numerical simulations are also used to clarify specific mechanisms of interest.

Part of the book: River Deltas Research

By Claire Chassagne, Zeinab Safar, Zhirui Deng, Qing He and Andrew J. Manning

Modelling the flocculation of particles in a natural environment like an estuary is a challenging task owing to the complex particle-particle and particle-hydrodynamic interactions involved. In this chapter a summary is given of recent laboratory and in-situ studies regarding flocculation. A flocculation model is presented and the way to implement it in an existing sediment transport model is discussed. The model ought to be parametrized, which can be done by performing laboratory experiments which are reviewed. It is found, both from laboratory and in-situ studies, that flocculation between mineral sediment and organic matter is the dominant form of flocculation in estuarine systems. Mineral sediment in the water column is < 20 μm in size and its settling velocity is in the range [0–0.5] mm/s. Flocs can then be categorized in two types: flocs of size [20–200] μm and flocs of size > 200 μm. The origin of these two types is discussed. The two types of flocs are found at different positions in the water column and both have settling velocities in the range [0.5–10] mm/s.

Part of the book: Sediment Transport

By Bernhard Vowinckel, Kunpeng Zhao, Leiping Ye, Andrew J. Manning, Tian-Jian Hsu, Eckart Meiburg and Bofeng Bai

Due to climate change, sea level rise and anthropogenic development, coastal communities have been facing increasing threats from flooding, land loss, and deterioration of water quality, to name just a few. Most of these pressing problems are directly or indirectly associated with the transport of cohesive fine-grained sediments that form porous aggregates of particles, called flocs. Through their complex structures, flocs are vehicles for the transport of organic carbon, nutrients, and contaminants. Most coastal/estuarine models neglect the flocculation process, which poses a considerable limitation of their predictive capability. We describe a set of experimental and numerical tools that represent the state-of-the-art and can, if combined properly, yield answers to many of the aforementioned issues. In particular, we cover floc measurement techniques and strategies for grain-resolving simulations that can be used as an accurate and efficient means to generate highly-resolved data under idealized conditions. These data feed into continuum models in terms of population balance equations to describe the temporal evolution of flocs. The combined approach allows for a comprehensive investigation across the scales of individual particles, turbulence and the bottom boundary layer to gain a better understanding of the fundamental dynamics of flocculation and their impact on fine-grained sediment transport.

Part of the book: Sediment Transport

By Andrew J. Manning, Leiping Ye, Tian-Jian Hsu, James Holyoke and Jorge A. Penaloza-Giraldo

In recent decades, oil spill contamination has tended to occur more commonly in deltaic and estuarial systems. The management of oil spillages has been a major challenge in the surrounding deltas due to the highly sensitivity nature of deltaic ecosystems. Many deltas have an abundance of clay minerals that can flocculate, and these play an important role in determining the transport of spilled oil contamination and its eventual fate, particularly given that suspended sediment and microbial activities are often prevalent and diverse in natural environments. The primary work presented here focuses on laboratory experimental studies that help develop improved parameterizations of flocculation processes for oil-sediment-biogeochemical modeling. Oil-mineral flocs (OMA) have been successfully created from a series of laboratory flocculation experiments. A floc video instrument LabSFLOC-2 has been adopted for the first time to study the settling dynamics of OMAs. Experimental results reveal OMAs can easily form in any oil, cohesive sediment, and seawater mixtures. However, Kaolin and Bentonite forms dramatically different OMA structures, which leads to their variable characteristics. In the Bentonite clay cases, the oil flocs tend to be much larger and with higher densities than those in Kaolin clay cases, resulting in significant variability of flocs settling velocities.

Part of the book: River Deltas Research

By Xiao Yu, Sivaramakrishnan Balachandar, Jarrell Smith and Andrew J. Manning

Two-phase computational fluid dynamics - discrete element method (CFD-DEM) framework has gained attention in cohesive sediment transport due to its capability of resolving particle-particle interactions and capturing the time evolution of individual flocs and hence the flocculation dynamics of cohesive sediment in turbulent flows. For cohesive sediments of size smaller than the Kolmogorov length scale, the point-particle approach is commonly used, in which the flow around particles is not fully resolved, and the hydrodynamic force on particles is parameterized by the drag law. The accuracy of floc dynamics, aggregation, breakup, and reshaping therefore strongly depends on force parameterization of individual point-particles that make up the floc. In this chapter, we review recent advances in the state-of-art two-phase CFD-DEM model approach on cohesive sediment transport and make recommendation for future research.

Part of the book: Sediment Transport Research [Working title]