River morphodynamics with creation/consumption of grain size stratigraphy 1: laboratory experiments

Abstract

Rivers with poorly-sorted bed sediment create their own stratigraphy as they deposit sediment. Prediction of the subsequent river degradation into its own deposit requires knowledge of the spatial structure of the grain size variation of the deposit. The ultimate goal of the present work is the development, testing and verification against experimental data of a numerical model of morphodynamics that can store stratigraphy into memory as it is created by aggradation, and can subsequently consume this stratigraphy if and when the river later degrades into the deposit. Such a morphodynamic model is tested using a surface-based bedload transport relation known to be applicable to the experiments considered here. Part 1 of a two-part paper addressing this issue describes the laboratory experiments and uses the experimental results performed at mobile-bed equilibrium to evaluate a bedload transport relation. In the companion paper, this bedload transport relation is installed into a morphodynamic model that specifically includes the creation/consumption of stratigraphy. The model is then tested against the experimental data.

Keywords:

• Bedload
• hiding function
• laboratory flume
• mobile-bed equilibrium
• sediment mixture
• stratigraphy

Acknowledgements

This research was funded in part by the National Center for Earth-surface Dynamics, a Science and Technology Center of the US National Science Foundation (EAR-0203296). Special thanks are due to Andrew Waratuke, Marc Killon and Tim Prunkard, who helped greatly with a pump that frequently broke down.