MEANDER-WAVELENGTH / FLOW-DIMENSION RATIOS IN FREELY MEANDERING EXPERIMENTAL SANDY TURBIDITY CURRENTS

Flume studies are a prime means of research into the flow processes in and around sinuous submarine channels. Unfortunately, physical modeling of self-formed sinuous submarine channel initiation and development has proved to be extremely difficult; self-formed channels of sufficient scale and stability to sustain detailed measurements of flow-field characteristics have not as yet been achieved. A viable alternative approach for such experiments has been to design experiments with pre-formed channel morphologies in non-erodible substrates, but such experiments inadvertently raise issues of scaling relations between channel morphology and experimental turbidity flow characteristics.

This paper presents the results obtained from a physical model of erodible channels that have undergone sinuous turbidity currents, and aims to determine a quantitative relationship between submarine channel dimensions and meander wavelength by performing statistical analysis.

Sand-carrying (D50=160 Mu) turbidity currents were introduced at an angle into a straight channel that was pre-formed into an erodible substrate consisting of the same sand as suspended in the flow. Pre-existing and resulting channel and deposit dimensions were determined from digital elevation models (DEMs). These DEMs were generated in ArcGIS from contour plots derived from rectified photographs taken during drainage of the flume.

The results show sinuous deposition and erosion, which is interpreted as incipient sinuous channel formation. Analysis shows that a relationship exists between channel width and meander wavelength. The experimental meander wavelength scaling is compared with previous studies carried out on various subaerial and submarine channels. This comparison confirms that the observed incipient meandering obeys well-known geomorphological scaling relations.

This indicates that: 1) Characteristic meandering scales are comparable for experimental flows and natural prototypes over four orders of magnitude. 2) The ratio of meander-wavelength / flow-dimension is a fundamental scaling relation that should be taken into account in future flume studies. 3) Studies with freely-meandering, sand-carrying, experimental turbidity currents are achievable.