160-1 Nested, Spatially Distributed Annual River Channel Sediment Budgets Pinpoint Sediment Sources and Identify Downstream Sediment Transport Pathways

Session: Advances in Fluvial Processes and Sediment Transport, Part I

Presenting Author:

Authors:

Abstract:

Traditional watershed-scale sediment budgets sum sediment sources such as bank erosion (BE) and headwater tributary inputs (HI) and subtract sediment sinks (floodplain deposition, FD) to compute watershed sediment yield (Qs).  This approach, however, does not identify the contributions of individual sources (HI and BE) to the output (Qs), because unknown fractions of sources are stored on floodplains.   We overcome this limitation by dividing the channel network of the White Clay Creek, PA, into 140 nested reaches, each with its own sediment budget.  The nested framework partitions sediment between transport and storage as it moves downstream, quantifying the contribution from individual sources to the watershed sediment yield.   We use gaging station data to specify HI (with drainage basin scaling for unmeasured tributaries) and Qs.  Published sediment fingerprinting divides HI into upland hillslope (HS) (76%) and tributary river corridor (BE) (24%) contributions. BE is estimated from empirical functions, while FD is obtained from measured floodplain accretion rates and modeled floodplain inundation.  The watershed-integrated budget defines the magnitudes of sources and sinks, but does not define source contributions to the outlet flux:  BE is 1.35 +/- 0.05 times the computed output, while corresponding values for FD and HS are 0.89 +/- 0.04 and 0.54 +/- 0.02.  The computed Qs (11710 Mg/yr) is within the uncertainty (9300-43000 Mg/yr) of the measured output, so the budget balances.   Reach-scale budgets identify local sediment hotspots, while routing computations indicate that BE supplies 76 +/- 5% of the watershed sediment yield, with HS contributing 24 +/- 3%.  Legacy sediments comprise 34 +/- 6% of the output Qs.  These results can improve sediment management decision-making.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-5667

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