Natural and managed rivers throughout the world display a wide range of hydrographs that vary in shape from steep and flashy to gradual and consistent, thus influencing the volume, timing, and quality of water available for aquatic ecosystems.  Although hydrograph shape is an inherent feature of river systems, relatively few investigations have focused on the influence of flow variability on channel grain sizes and bedload transport, and many uncertainties remain.  Accurate predictions of bedload transport and mobile channel grain size distributions that take into account flow variability are needed to determine how climate change, flow regulation, and precipitation environments (e.g. snow vs. rain dominated) will influence aquatic habitat diversity and river restoration success.

We explored the effects of hydrograph shape on sediment transport volume and grain size distribution in a wadable gravel-bedded stream in California, USA.  We tracked the movement of tagged particles and collected bedload samples through a series of small and moderate storm events across two dry years.  We will provide an overview of the results, including details on the sizes and travel distances of mobilized tagged grains, changes to bedload size distributions during storm event hydrographs, and changes to overall channel morphology.  We will use this data to inform potential modifications to predictive sediment transport equations.  We will then discuss the implications of the research for future studies and broadly for management of sediment and flows in regulated rivers.