Breaching in fine sands and the generation of sustained turbidity currents in submarine canyons
Version of Record online: 11 JUL 2003
Volume 50, Issue 4, pages 625–637, August 2003
How to Cite
Mastbergen, D. R. and Van Den Berg, J. H. (2003), Breaching in fine sands and the generation of sustained turbidity currents in submarine canyons. Sedimentology, 50: 625–637. doi: 10.1046/j.1365-3091.2003.00554.x
- Issue online: 11 JUL 2003
- Version of Record online: 11 JUL 2003
- Manuscript received 11 April 2002; revision accepted 5 December 2002.
- massive sands;
- slope failure;
- submarine canyon;
- turbidity current
Abstract Natural, moderately loosely packed sands can only erode from the surface of the bed after an increase in pore volume. Because of this shear dilatancy, negative pore pressures are generated in the bed. In cases of low permeability, these negative pressures are released relatively slowly, which retards the maximum rate of erosion. This effect is incorporated in a new, analytically derived, pick-up function that can explain the observation of gradual retrogressive failure of very steep subaqueous slopes, sometimes more than 5 m high, in fine non-cohesive sands. This process, termed ‘breaching’ in the field of sediment dredging, may produce large failures in sand bars or river banks. The analytical function that describes the breaching process in fine sand is incorporated in a one-dimensional, steady-state numerical model of turbidity currents describing the spatial development of flow. This model is applied to simulate a large ‘flushing’ event in Scripps Submarine Canyon, Pacific coast of California. Breach retrogradation and the successive evolution in time of the resulting turbidity current in the canyon are predicted in a sequence of discrete steps. Predicted velocities are compared with values measured during a flushing event. Implications for the interpretation of deep-water massive sands are discussed.