Linking Channel Dynamics to Deposits: How Does Process Understanding Change With the Scale of Observation?

Abstract

Linking stratigraphic and sedimentological attributes of depositional landforms to process dynamics is challenging due to the limited spatial and temporal scales over which measurements may be made relative to the scales that the landforms develop. Here we present process-oriented studies of river and submarine channel levee development, and of floodplain evolution conducted using vastly different scales of observation. Levee development studies were conducted in a laboratory basin on experimental channels a few centimeters deep, while the floodplain studies were conducted using globally available satellite imagery spanning decades. In the laboratory, very high spatial and temporal resolution measurements of jet and density current hydrodynamics and sediment transport were made and linked to patterns of deposition. While these process-based experiments are vastly simplified, relative to natural systems, they provided fundamental insights into the conditions necessary for levee formation at the distal ends of rivers and submarine channels. These insights have served to elucidate how balances in lateral sediment transport and jet dynamics govern deltaic channel formation and provided validation datasets for state of the art morphodynamic models. In submarine systems, the dynamics of density, flow spreading, and entrainment of ambient water critically constrain depositional patterns and highlight fundamental difference between submarine and terrestrial systems despite common channel morphologies. Using multi-temporal satellite imagery we measured of river planform change and floodplain development on rivers systems across the globe. These measurements allow us to use natural systems as experimental realizations from a broad range of settings. This large-scale study of floodplain systems does not provide direct measurements of hydrodynamic and morphodynamics controls, but does provide the opportunity to relate variations in the rate of planform change to other measurable attributes of river systems such as: size, discharge, drainage area, slope, sediment supply and character, climate, and vegetation. These coupled measurements help to isolate the dominant watershed-scale controls on floodplain development and motivate hypotheses on the dominant controls on river mobility. This type of study also has the potential to provide empirical parameterizations for system scale modeling of sedimentology and earth system dynamics.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015