River bank erosion and lateral accretion linked to hydrograph recession
and flood duration in a mountainous snowmelt-dominated system
Abstract
Changes in the magnitude and frequency of river flows have potential to
alter sediment dynamics and morphology of rivers globally, but the
direction of these changes remains uncertain. A lack of data across
spatial and temporal scales limits understanding of river flow regimes
and how changes in these regimes interact with river bank erosion and
floodplain deposition. Linking characteristics of the flow regime to
changes in bank erosion and floodplain deposition is necessary to
understand how rivers will adjust to changes in hydrology from societal
pressures and climatic change, particularly in snowmelt-dominated
systems. We present a lidar dataset, intensive field surveys, aerial
imagery and hydrologic analysis spanning 60 years, and spatial analysis
to quantify bank erosion, lateral accretion, floodplain overbank
deposition, and a floodplain fine sediment budget in an 11-km long study
segment of the meandering gravel bed East River, Colorado, USA. Stepwise
regression analysis of channel morphometry in nine study reaches and
snowmelt-dominated annual hydrologic indices in this mountainous system
suggest that sinuosity, channel width, recession slope, and flow
duration are linked to lateral erosion and accretion. The duration of
flow exceeding baseflow and the slope of the annual recession limb
explain 59% and 91% of the variability in lateral accretion and
erosion, respectively. This strong correlation between the rate of
change in river flows, which occurs over days to weeks, and erosion
suggests a high sensitivity of sedimentation along rivers in response to
a shifting climate in snowmelt-dominated systems, which constitute the
majority of rivers above 40° latitude.