Application of an Instrumented Tracer in an Abrasion Mill for Rock Abrasion Studies

One of research fields in studying dynamics of gravel-bed rivers is the interaction between sediment particles in motion and incision rates in rock-bottom river reaches. This natural phenomenon of rock abrasion was studied in a laboratory in a Dubree-type abrasion (tumbling) mill with the diameter of 711 mm, using different mixtures of fluvial sediments as abrasive media. A set of rock plates of different lithologies was fixed to the inside mill wall to evaluate rock abrasion by moving sediment particles. The dynamics of the abrasion process of the rock plates was studied by a spherical instrumented tracer with the diameter of 99 mm. This paper describes our solution to the problem of recognizing and differentiating between impacts of the instrumented tracer with different bodies: sediment particles, rock plates, soft lining of the mill and steel side plates of the mill. For this purpose, the signal analysis of measured 3D accelerations of the instrumented tracer gave sufficient information to recognize the tribological surrounding and sufficiently describe the intensity of the abrasion process (number and amplitudes of contact forces). An effective and computationally inexpensive algorithm for automatic impact recognition and evaluation was developed, based on time domain analysis. Furthermore, the frequency domain analysis gave a method for discriminating different signals. Both mentioned methods allow us to classify all recorded signals into groups based on similarity of measurement conditions

Hydraulics are a first order control on CO2 efflux from fluvial systems

Evasion of carbon dioxide (CO2) from fluvial systems is now recognized as a significant component of the global carbon cycle. However the magnitude of, and controls on, this flux remain uncertain and improved understanding of both are required to refine global estimates of fluvial CO2 efflux. CO2 efflux data show no pattern with latitude suggesting that catchment biological productivity is not a primary control and that an alternative explanation for inter-site variability is required. It has been suggested that increased flow velocity and turbulence enhance CO2 efflux, but this is not confirmed. Here, using contemporaneous measurements of efflux (range: 0.07 – 107 µmol CO2 m-2 s-1), flow hydraulics (mean velocity range: 0.03 – 1.39 m s-1) and pCO2 (range: 174 – 10712 µatm) at six sites, we find that flow intensity is a primary control on efflux across two climatically different locations (where pH is not a limiting factor) and that the relationship is refined by incorporating the partial pressure of CO2 (pCO2) of the water. A remaining challenge is how to upscale from point to reach or river basin level. Remote imaging or river surface may be worth exploring if subjectivity in interpreting surface state can be overcome

Land subsidence over oilfields in the Yellow River Delta

Subsidence in river deltas is a complex process that has both natural and human causes. Increasing human activities like aquaculture and petroleum extraction are affecting the Yellow River delta, and one consequence is subsidence. The purpose of this study is to measure the surface displacements in the Yellow River delta region and to investigate the corresponding subsidence source. In this paper, the Stanford Method for Persistent Scatterers (StaMPS) package was employed to process Envisat ASAR images collected between 2007 and 2010. Consistent results between two descending tracks show subsidence with a mean rate up to 30 mm/yr in the radar line of sight direction in Gudao Town (oilfield), Gudong oilfield and Xianhe Town of the delta, each of which is within the delta, and also show that subsidence is not uniform across the delta. Field investigation shows a connection between areas of non-uniform subsidence and of petroleum extraction. In a 9 km2 area of the Gudao Oilfield, a poroelastic disk reservoir model is used to model the InSAR derived displacements. In general, good fits between InSAR observations and modeled displacements are seen. The subsidence observed in the vicinity of the oilfield is thus suggested to be caused by fluid extraction

Segmentation of topographic change by geomorphic units to assess physical habitat transitions in a restored river

River restoration schemes that utilise natural processes need to be monitored post-implementation to inform adaptive management, to assess their success at delivering sustained ecological improvements and to contribute to the design of other schemes. All three of these monitoring objectives require an understanding of the geomorphic mechanisms that cause channel adjustment and how they shape the mosaic of geomorphic units that make up physical habitat. In the last decade repeat, high-resolution topographic surveys of river restoration schemes have become commonplace through the application of a range of geomatics technologies including echo-sounders, laser scanners and Structure from Motion photogrammetry. Such datasets offer opportunities to map geomorphic change and geomorphic unit evolution to quantitatively analyse the relative roles of different processes in generating physical habitat. Here, we present results from an investigation into the morphodynamics of the Whit Beck river restoration scheme, implemented by the West Cumbria Rivers Trust, UK. We use repeat Digital Elevation Models (DEMs) to quantify patterns of erosion and deposition using the Geomorphic Change Detection (GCD) toolbox and to map geomorphic units, using the Geomorphic Unit Tool (GUT). The segmentation of maps of erosion and deposition with maps of geomorphic units quantifies physical habitat transitions. The resulting analysis indicates the different mechanisms of adjustment that generate physical habitat throughout the restoration scheme and how they are linked to different initial conditions

Spatiotemporal modeling of hydrological return levels: A quantile regression approach

Extreme river flows can lead to inundation of floodplains, with consequent impacts for society, the environment and the economy. Extreme flows are inherently diffcult to model being infrequent, irregularly spaced and affected by non-stationary climatic controls. To identify patterns in extreme flows a quantile regression approach can be used. This paper introduces a new framework for spatio-temporal quantile regression modelling, where the regression model is built as an additive model that includes smooth functions of time and space, as well as space-time interaction effects. The model exploits the exibility that P-splines offer and can be easily extended to incorporate potential covariates. We propose to estimate model parameters using a penalized least squares regression approach as an alternative to linear programming methods, classically used in quantile parameter estimation. The model is illustrated on a data set of flows in rivers across Scotland

Application of an instrumented tracer in an abrasion mill for rock abrasion studies

One of research fields in studying dynamics of gravel-bed rivers is the interaction between sediment particles in motion and incision rates in rock-bottom river reaches. This natural phenomenon of rock abrasion was studied in a laboratory in a Dubree-type abrasion (tumbling) mill with the diameter of 711 mm, using different mixtures of fluvial sediments as abrasive media. A set of rock plates of different lithologies was fixed to the inside mill wall to evaluate rock abrasion by moving sediment particles. The dynamics of the abrasion process of the rock plates was studied by a spherical instrumented tracer with the diameter of 99 mm. This paper describes our solution to the problem of recognizing and differentiating between impacts of the instrumented tracer with different bodies: sediment particles, rock plates, soft lining of the mill and steel side plates of the mill. For this purpose, the signal analysis of measured 3D accelerations of the instrumented tracer gave sufficient information to recognize the tribological surrounding and sufficiently describe the intensity of the abrasion process (number and amplitudes of contact forces). An effective and computationally inexpensive algorithm for automatic impact recognition and evaluation was developed, based on time domain analysis. Furthermore, the frequency domain analysis gave a method for discriminating different signals. Both mentioned methods allow us to classify all recorded signals into groups based on similarity of measurement conditions

‘InfraRivChange’: A Web Application to Monitor River Migration at Sites of Critical Bridge Infrastructure in the Philippines

No abstract available