EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Understanding the impacts of hydrograph transience on sediment transport

Colin Phillips1, Eric Lajeunesse2, Kimberly Hill3, and Chris Paola4
Colin Phillips et al.
  • 1Northwestern University, McCormick School of Engineering, Civil and Environmental Engineering, evanston, United States of America (
  • 2Institut de Physique du Globe de Paris
  • 3Civil, Environmental, and Geo- Engineering, University of Minnesota
  • 4Earth & Environmental Sciences, University of Minnesota

Sediment transport is an inherently challenging process to predict due to a variety of granular and hydrodynamic phenomena. These challenges are only enhanced in natural systems where the forcing of the hydrograph and the availability of sediment is decidedly unsteady. Here we show through several field and laboratory experiments comprised of sediment flux and tracer displacement under unsteady hydrographs that their dynamics can be understood through the application of an integrated forcing metric (impulse), where the impulse represents the integrated excess transport capacity of a flood or a sequence of floods. When viewed through this framework we show that the cumulative bed load flux and tracer displacement from the particle flight length scale up to multi annual timescales are linearly related with the impulse parameter despite highly unsteady forcing. By considering the integrated forcing and sediment flux the transience of the hydrograph can be recast into a simple linear relation with parallels to long term landscape evolution models, where the details of the hydrograph are approximated as a characteristic flood stress times an intermittency factor. Through the use of an impulse metric we gain new insights that are obscured when only considering the instantaneous fluxes.

How to cite: Phillips, C., Lajeunesse, E., Hill, K., and Paola, C.: Understanding the impacts of hydrograph transience on sediment transport, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12903,, 2020


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displays version 1 – uploaded on 02 May 2020
  • CC1: Question, Thomas Pähtz, 04 May 2020

    Is my following understanding of your findings on slide 3 correct:

    It seems to me that the linear relationship between Q_*b and T_*b can be reinterpreted as a linear relationship between the sediment transport rate averaged over the duration of the flood (i.e., times of above-critical shear stress) and the 1.5th power of the excess shear stress averaged over the duration of the flood. If true, this would essentially mean that this linear relation is a Meyer-Peter & Müller - like relationship generalized from steady to unsteady conditions.

    Thomas Pähtz

    • AC1: Reply to CC1, Colin Phillips, 04 May 2020

      Yes that interpretation is correct. For these experiments it needn't be precisely an MPM style relation, however it must include the basic components within MPM (excess shear stress to a 1.5 power or a similar combination). At really short timescales the relation tends to break down or for the particular rising or falling limbs of the experiments, however when the entire 'flood' is considered the transport follows an MPM-like transport relation.