Riverbed Dynamics

 

Traditional geomorphological techniques for analysing small-scale sediment structure are typically constrained to 1D or 2D approaches, such as coring, photography etc. Even where more advanced techniques are available (e.g. laser displacement scanning), these tend to be restricted to imaging the surface of the sediment bed in a manner preclusive of true 3D analysis of volumetric space and the sub-surface particle characteristics and packing arrangements. Using Magnetic Resonance Imaging (MRI) overcomes these limitations, providing researchers with a technique with which to provide novel 3D spatio-temporal data on the internal structure of opaque porous media and the related fluid exchange and chemical reactions occurring within.

Sediment samples have been removed from a 9m long flume 0.3m wide, located in the University of Glasgow’s department of Civil Engineering.

(A) Coarse framework material (d50=17mm). (B) Water-worked framework and fine feed (d50=2.4mm) material in flume. (C) MR Image of sealed upper layers of bed shown in B. (D) MR Image through silted bed water-worked with finer feed (d50=0.5mm). Image resolution is 300mm resolution in the x, y and z directions. Individual slice dimensions are x=79mm by y=76mm.

Such in-situ MRI data can be used as input for computer models. Below is a link showing how kaolin particles carried in the surface flow, are deposited in the sub-surface (click link to see movie).