Landscape evolution, valley excavation, and terrace development following abrupt postglacial base-level fall

Gran, Karen B.; Finnegan, N. J.; Johnson, Andrea L.; Belmont, Patrick; Wittkop, Chad; Rittenour, Tammy M.

doi:10.1130/b30772.1

Cited by 89 publications

(131 citation statements)

References 64 publications

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“…For example, in the Le Sueur River, south central Minnesota, tall river bluffs contribute the greatest proportion (57%) of fine sediment (Belmont et al, 5 2011;Day et al, 2013). While bluffs have contributed to high sediment loads in the Le Sueur River since long before agricultural impacts, the total contribution of sediment from bluffs today is well above the Holocene average due to systematic increases in streamflows over the last 70 years (Belmont et al, 2011;Gran et al, 2013). This story is not unique to south-central Minnesota, as many basins across the Midwestern corn belt and around the world are experiencing greater runoff, higher sediment and nutrient loads, and accelerated loss of habitat than in the historical past (Blann et al, 2009).…”

Section: Whether Humans Climate or Both Have Caused Streamflow Changmentioning

confidence: 99%

Human amplified changes in precipitation-runoff patterns in large river basins of the Midwestern United States

Kelly¹,

Takbiri²,

Belmont³

et al. 2016

Preprint

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Abstract. Complete transformations of land cover from prairie, wetlands, and hardwood forests to homogenous row crop agriculture scattered with urban centers are thought to have caused profound changes in hydrology in the Upper Midwestern US since the 1800s. Continued intensification of land use and drainage practices combined with increased precipitation have 10 caused many Midwest watersheds to exhibit higher streamflows today than in the historical past. While changes in crop type and farming practices have been well documented over the past few decades, changes in artificial surface (ditch) and subsurface (tile) drainage systems have not. This makes it difficult to quantitatively disentangle the effects of climate change and artificial drainage intensification on the observed hydrologic change, often spurring controversial interpretations with significant implications for management actions. In this study, we investigate four large (23,000-69,000 km 2 ) Midwest river 15 basins that span climate and land use gradients to understand how climate and agricultural drainage have influenced basin hydrology over the last 79 years. We use daily, monthly, and annual flow metrics to document streamflow changes and discuss those changes in the context of climate and land use change. While we detect similar timing of precipitation and streamflow changes in each basin, overall the magnitude and significance of precipitation changes are much less than we detect for streamflows. Of the basins containing greater than 20% area drained by tile and ditches, we observe 2 to 4 fold 20 increases in low flows and 1.5 to 3 fold increases in high and extreme flows. Monthly precipitation has increased slightly for some months in each basin, mostly in fall and winter months (August -March), but total monthly streamflow has increased in all months for the Minnesota River Basin (MRB), every month but April for the Red River Basin (RRB), SeptemberDecember and March in the Illinois River Basin (IRB), and no months in the Chippewa River basin (CRB). Using a water budget, we determined that the soil moisture/groundwater storage term for the intensively drained and cultivated MRB, IRB, 25and RRB, has decreased by about 200%, 100%, and 30%, respectively while increased by roughly 30% in the largely forested CRB since 1975. We argue that agricultural land use change, through wetland removal and artificial drainage installation, has decreased watershed storage and amplified the streamflow response to precipitation increases in the Midwest. Highly managed basins with large reservoirs and urban centers, such as the Illinois River basin (IRB), may be able to buffer some of these impacts better than largely unregulated systems such as the Minnesota River (MRB) and Red River 30

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Section: Whether Humans Climate or Both Have Caused Streamflow Changmentioning

confidence: 99%

Human amplified changes in precipitation-runoff patterns in large river basins of the Midwestern United States

Kelly¹,

Takbiri²,

Belmont³

et al. 2016

Preprint

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“…These experiments tested how different overland flow rates affect erosion and permanent gully growth on a series of permanent gullies initiated through base level fall, a common feature of post-glacial landscapes in the Upper Midwest, USA Gran et al, 2013;Lenhart et al, 2013). We represented a range of natural permanent gullies using two different substrates.…”

Section: Methodsmentioning

confidence: 99%

Impacts of changing hydrology on permanent gully growth: experimental results

Day

Gran

Paola

2018

Hydrol. Earth Syst. Sci.

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Abstract. Permanent gullies grow through head cut propagation in response to overland flow coupled with incision and widening in the channel bottom leading to hillslope failures. Altered hydrology can impact the rate at which permanent gullies grow by changing head cut propagation, channel incision, and channel widening rates. Using a set of small physical experiments, we tested how changing overland flow rates and flow volumes alter the total volume of erosion and resulting gully morphology. Permanent gullies were modeled as both detachment-limited and transport-limited systems, using two different substrates with varying cohesion. In both cases, the erosion rate varied linearly with water discharge, such that the volume of sediment eroded was a function not of flow rate, but of total water volume. This implies that efforts to reduce peak flow rates alone without addressing flow volumes entering gully systems may not reduce erosion. The documented response in these experiments is not typical when compared to larger preexisting channels where higher flow rates result in greater erosion through nonlinear relationships between water discharge and sediment discharge. Permanent gullies do not respond like preexisting channels because channel slope remains a free parameter and can adjust relatively quickly in response to changing flows.

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“…The limited landscape relief in the USRB likely contributes to lower rates of post-settlement alluvial deposition than in CCW ) and a fluvial suspended load dominated by near-channel sources rather than agricultural fields (Neal and Anders, 2015). In the MRV, the legacy of drainage of Lake Agassiz strongly controls landscape relief and ongoing erosion and sediment transport that is focused near the entrenched Minnesota River and its tributaries (Gran et al, 2013).…”

Section: Evolution Of the Modern Czmentioning

confidence: 99%

Critical Zone Structure in the Glaciated Interior Lowlands, Usa: A Conceptual Model From the Intensively Managed Landscape Critical Zone Observatory

Anders¹,

Bettis

Grimley

et al. 2018

Geological Society of America Abstracts With Programs

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The concept of a critical zone (CZ) supporting terrestrial life has fostered groundbreaking interdisciplinary science addressing complex interactions among water, soil, rock, air, and life near Earth's surface. Pioneering work has focused on the CZ in areas with residual soils and steady-state or erosional topography. CZ evolution in these areas is conceptualized as progressive weathering of local bedrock (e.g., in the flow-through reactor model). However, this model is not applicable to areas in which weathering profiles form in transported materials including the formerly glaciated portion of the Central Lowland of North America. We present a new conceptual model of CZ evolution in landscapes impacted by continental glaciation based on investigations at three study sites in the Intensively Managed Landscapes Critical Zone Observatory (IML-CZO) The IML-CZO is devoted to the study of CZ processes in a region characterized by thick surficial deposits resulting from multiple continental glaciations, with bedrock at depths of up to 150 m. Here the physical (glacial ice, loess, developing soil profiles) and biological (microbes, tundra, forest, prairie) components of the CZ vary significantly in time. Moreover, the spatial relationships between mineral components of the CZ record a history of glacial-interglacial cycles and landscape evolution. We present cross-sections from IML-CZO sites to provide specific examples of how environmental change is recorded by the structure of the mineral components of the CZ. We build on these examples to create an idealized model of CZ evolution through a glacial cycle that represents the IML-CZO sites and other areas of low relief that have experienced continental glaciation. In addition, we identify two main characteristics of CZ structure which should be included in a conceptual model of CZ development in the IML-CZO and similar settings: (1) mineral components have diverse origins and transport trajectories Anders et al. CZ Structure at IML-CZO including alteration in past CZs, and, (2) variability in climate, ecosystems, and hydrology during glacial-interglacial cycles profoundly influence the CZ composition, creating a legacy retained in its structure. This legacy is important because the current physical CZ structure influences the occurrence and rates of CZ processes, as well as future CZ responses to land use and climate change.

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Landscape evolution, valley excavation, and terrace development following abrupt postglacial base-level fall

Cited by 89 publications

References 64 publications

Human amplified changes in precipitation-runoff patterns in large river basins of the Midwestern United States

Human amplified changes in precipitation-runoff patterns in large river basins of the Midwestern United States

Impacts of changing hydrology on permanent gully growth: experimental results

Critical Zone Structure in the Glaciated Interior Lowlands, Usa: A Conceptual Model From the Intensively Managed Landscape Critical Zone Observatory

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