Fingerprinting historical tributary contributions to floodplain sediment using bulk geochemistry

Kemper, John T.; Rathburn, Sara L.; Friedman, Jonathan M.; Nelson, J. M.; Mueller, Erich R.; Vincent, Kirk R.

doi:10.1016/j.catena.2022.106231

Cited by 9 publications

(3 citation statements)

References 88 publications

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“…Once the arroyo‐cutting event ended, the supply rate decreased, and floodplain shaving began to slowly remove excess sediment stored in the overbank, a process which continues today, evidenced by eroding banks being a factor of ∼3 times taller than laterally accreted floodplains (Figure 15). Sand Creek floods during the mid‐1950s to early 1960s also caused a period of elevated watershed sediment supply (Topping et al., 2018), but the supply was coarser and likely disproportionately deposited in the active channel rather than the floodplains (Kemper, Rathburn, et al., 2022). Sand Creek floods generated bed sediment waves that traveled through the study area, first causing an initial rapid phase of bed fining, followed by long‐term slower bed coarsening (Topping et al., 2018; Figure 15).…”

Section: Discussionmentioning

confidence: 99%

“…The Yampa River in Deerlodge Park evacuated 12 ± 11 MT/m (downstream)/year of sand during our study period, yet the river maintained the same geomorphic character and behavioral regime, reflective of a river in equilibrium accommodating minor watershed disturbances. The arroyo‐cutting event during the late nineteenth to early twentieth century (Kemper, Rathburn, et al., 2022, Kemper et al., 2023) and elevated stream flow during the twentieth‐century pluvial period (Woodhouse et al., 2006; Woodhouse & Pederson, 2018) caused a period of increased lateral instability and widespread overbank sedimentation on the pre‐1938 floodplain (Figure 15). Once the arroyo‐cutting event ended, the supply rate decreased, and floodplain shaving began to slowly remove excess sediment stored in the overbank, a process which continues today, evidenced by eroding banks being a factor of ∼3 times taller than laterally accreted floodplains (Figure 15).…”

Section: Discussionmentioning

confidence: 99%

“…At their confluence, the watersheds of the Little Snake River and upper Yampa River are approximately the same size, but approximately 75% of the total flow in Deerlodge Park comes from the upper Yampa River (Andrews, 1978; Topping et al., 2018). Most of the streamflow of the Little Snake River also arises in mountainous headwaters, but this tributary primarily flows through erodible badlands composed of fluvial and lacustrine sediments that are a significant source for fine sediment (Kemper, Rathburn, et al., 2022), as discussed below. We define fine sediment as any sediment grain size smaller than 2 mm.…”

Section: Hydrology Sediment Supply and Geomorphology Of The Study Areamentioning

confidence: 99%

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A Sediment Budget for a Sand Bed River Partitioned by Sand Fractions

Leonard,

Schmidt

2024

JGR Earth Surface

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Sediment budgets are widely used to measure reach‐scale sediment accumulation and evacuation. Such measurements, however, cannot determine when the disturbance is major and the measured sediment mass imbalance is reflective of a river adjusting to a new equilibrium state, as opposed to situations when the disturbance is minor, and the mass imbalance is reflective of a river adjusting within its existing behavioral regime. Sediment sorting among channels and floodplains can have a large effect on how a river responds to a disturbance. Fine sediment may accumulate in the floodplains while coarser sediment erodes from the channel bed. We demonstrate that if a sediment budget does not account for the different behavior and destination of grain sizes, the budget cannot reveal important channel adjustments. In this study, we evaluated how a sand bed river responded to increases in sediment supply by partitioning a sediment budget among silt/clay and five sand fractions. On average, 12 metric tons/meter (downstream)/year of sand was evacuated from the system, but sorting caused channel margins to behave differently from vegetated islands, revealing how a river can slightly narrow while in deficit. Floodplain shaving and bed coarsening evacuated sediment while channel geometry barely changed, consistent with a river adjusting to a minor disturbance within its behavioral regime. This study is an important reminder that sediment mass imbalance does not always lead to channel change. Mechanisms such as floodplain shaving and bed textural change help rivers absorb minor disturbances and resist channel change.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Hydrology Sediment Supply and Geomorphology Of The Study Areamentioning

confidence: 99%

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A Sediment Budget for a Sand Bed River Partitioned by Sand Fractions

Leonard,

Schmidt

2024

JGR Earth Surface

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Downstream decreases in water availability, tree height, canopy volume and growth rate in cottonwood forests along the Green River, southwestern USA

Thaxton,

Scott,

Kemper

et al. 2024

Ecohydrology

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Hydrologic stress is increasing in Fremont cottonwood (Populus fremontii) forests across the southwestern United States because of increased temperature and streamflow diversion. The spatial variability of this stress is large yet poorly understood. Along the Yampa and Green Rivers in Colorado and Utah, vapour pressure deficit and flow diversions increase downstream. To investigate effects of this gradient on cottonwoods, we measured the percent live canopy and height of randomly selected trees at three sites: Deerlodge Park on the Yampa River (DLP), Island Park on the upper Green (ILP) and Canyonlands National Park on the lower Green (CAN). From these same trees, we took increment cores to understand differences in tree growth in each forest over time. We then related tree metrics to local water availability, streamflow and climatic data. Cottonwoods at CAN were shorter and had lower percent live canopy and growth rate than similarly aged trees upstream. CAN trees that grew higher above the water surface also tended to have lower tree growth, height and live canopy percentage. Furthermore, the correlation between tree growth and maximum vapour pressure deficit showed a much stronger negative shift since 1990 at CAN than at the other sites. All of these differences suggest higher hydrologic stress at CAN, which we attribute to the combined effects of peak flow declines from Flaming Gorge Reservoir, flow diversion and the higher and increasing vapour pressure deficit at CAN. Further research on the variability of hydrologic stress on cottonwoods could help managers anticipate and mitigate the effects of drought stress in these iconic forests.

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Estimating catchment‐scale sediment storage in a large River Basin, Colorado River, USA

Kemper,

Knox,

Raffae

et al. 2024

River Research & Apps

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Catchment‐scale sediment storage is conceptualized as increasing in magnitude downstream, although reach‐scale controls may override this trend. We use empirical data from a literature review and two numerical models to quantitatively estimate sediment storage across the Colorado River Basin, USA. We use assumed alluvial thickness with floodplains delineated in the GFPLAIN model from 30 m digital elevation models. We use the SWAT+ model based on model‐estimated (i) groundwater storage and (ii) sediment storage. Existing studies indicate that sediment stored in floodplains and on low terraces is ~0.3–6 m thick. A first‐order approximation of volumetric storage capacity for natural floodplains is ~105 m3 per km. Sediment storage volumes of floodplains are ~108–1011 m3 over river lengths of 101–103 m. For the modeling estimates, we evaluated sediment storage by stream order and by elevation band within the Upper and Lower Colorado River Basins. Comparisons among the outputs cause us to place more confidence in the GFPLAIN and SWAT+ aquifer volume estimates. Each method includes substantial uncertainty and constitutes a first‐order approximation. Results suggest using 21 and 130 billion cubic meters as approximate lower and upper bounds for total sediment storage in the Upper Basin and 314 and 482 billion cubic meters as approximate lower and upper bounds for the Lower Basin. The largest proportion of sediment is stored in the montane and steppe zones in the Upper Basin and in the Sonoran zone in the Lower Basin.

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Fingerprinting historical tributary contributions to floodplain sediment using bulk geochemistry

Cited by 9 publications

References 88 publications

A Sediment Budget for a Sand Bed River Partitioned by Sand Fractions

A Sediment Budget for a Sand Bed River Partitioned by Sand Fractions

Downstream decreases in water availability, tree height, canopy volume and growth rate in cottonwood forests along the Green River, southwestern USA

Estimating catchment‐scale sediment storage in a large River Basin, Colorado River, USA

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