S. A. Kelly

Bio: S. A. Kelly is an academic researcher from Utah State University. The author has contributed to research in topics: Structural basin & Bluff. The author has an hindex of 6, co-authored 11 publications receiving 341 citations.

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

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 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 km2) Midwest river 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 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), September-December 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, and 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 of the North (RRB) basins. The reported streamflow increases in the MRB, IRB, and RRB are large (18 %–318 %), and should have important implications for channel adjustment and sediment and nutrient transport. Acknowledging both economic benefits and apparent detrimental impacts of artificial drainage on river flows, sediments, and nutrients, we question whether any other human activity has comparably altered critical zone activities, while remaining largely unregulated and undocumented. We argue that better documentation of existing and future drain tile and ditch installation is greatly needed.

High Resolution Monitoring of River Bluff Erosion Reveals Failure Mechanisms and Geomorphically Effective Flows

Abstract: Using a combination of Structure from Motion and time lapse photogrammetry, we document rapid river bluff erosion occurring in the Greater Blue Earth River (GBER) basin, a muddy tributary to the sediment-impaired Minnesota River in south central Minnesota. Our datasets elucidated dominant bluff failure mechanisms and rates of bluff retreat in a transient system responding to ongoing streamflow increases and glacial legacy impacts. Specifically, we document the importance of fluvial scour, freeze–thaw, as well as other drivers of bluff erosion. We find that even small flows, a mere 30% of the two-year recurrence interval flow, are capable of causing bluff erosion. During our study period (2014–2017), the most erosion was associated with two large flood events with 13- and 25-year return periods. However, based on the frequency of floods and magnitude of bluff face erosion associated with floods over the last 78 years, the 1.2-year return interval flood has likely accomplished the most cumulative erosion, and is thus more geomorphically effective than larger magnitude floods. Flows in the GBER basin are nonstationary, increasing across the full range of return intervals. We find that management implications differ considerably depending on whether the bluff erosion-runoff power law exponent, γ, is greater than, equal to, or less than 1. Previous research has recommended installation of water retention sites in tributaries to the Minnesota River in order to reduce flows and sediment loading from river bluffs. Our findings support the notion that water retention would be an effective practice to reduce sediment loading and highlight the importance of managing for both runoff frequency and magnitude.

Comment on “Climate and agricultural land use change impacts on streamflow in the upper midwestern United States,” by Satish C. Gupta et al.: COMMENT ON GUPTA ET AL. [2015]

Abstract: This comment cautions against dismissing agricultural practices as a significant cause of hydrologic change in Midwestern agricultural landscapes. In a recent paper, Gupta et al. [2015] considered the important issue of quantifying the relative contributions of climate and land use/land cover (LULC) change on the observed hydrologic changes in Midwestern agricultural landscapes. They reached the conclusion that ‘‘higher streamflows for most watersheds in the Upper Midwest are mainly due to increased precipitation’’ (p. 5315), implying that LULC changes exerted minimal effect on the hydrologic response of agricultural landscapes. Undoubtedly, both climate and land use change are affecting the hydrology of Midwestern agricultural landscapes in complex ways that are not easy to unravel. Higher temperatures have led to earlier snowmelt and a longer growing season [Walsh et al., 2014]. Changes in precipitation have been reported in total volumes and in the intensity, duration, and frequency of extreme storms [see, e.g., Groisman et al., 2012]. Progressive conversion of wetlands to cultivated land and replacement of small grains with corn and soybean [see, e.g., Foufoula-Georgiou et al., 2015, Figure 2; Lark et al., 2015] are altering evapotranspiration and water cycle dynamics. Even though the specifics of the expansion and intensification of subsurface agricultural tile drainage have been poorly documented (e.g., as described by Sugg [2007]), Gupta et al.’s dismissal of agricultural tile drainage as a significant contributor to changes in hydrologic response is not supported by rigorous analyses and is thus counterproductive [see also Schilling, 2016; Schottler et al., 2016]. Subsurface tile drainage in low-relief landscapes and poorly drained soils of the agricultural Midwest is installed to increase row-crop production by allowing an earlier planting season and providing favorable soil moisture conditions for crop growth. The flushing of snowmelt and spring rainfall through tiles accelerates the drainage of saturated soils within the root zone and promotes drier soil conditions that benefit farm equipment operation. After planting that typically occurs in April and May, the unsaturated vadose zone augmented by tiles provides favorable conditions for crop growth. Tile drains are most active during March through June before crops have matured, and this contribution of tile discharge to streamflow can be significant especially in smaller watersheds. A recent study concluded that tile discharge accounted for 55% of the annual watershed discharge in a 389 ha subwatershed in Ohio [Williams et al., 2015]. During the mid to late summer, increased root uptake and interception by crops prevent tile drainage except in response to large rainfall events. Given the benefits of earlier planting times and enhanced crop growth, the continued installation and expansion of drain tiles calls for careful consideration of their spatial and temporal effects on hydrology. The critical questions that need to be answered are (1) to what extent and how exactly has climate and LULC change affected the hydrologic response of intensively managed agricultural landscapes; (2) what frequencies and what time scales of the hydrologic response have been most affected; (3) when during the year is each of the causes of change dominant; and finally, (4) what are the environmental, ecological, and This article is a comment on Gupta et al. [2015], doi:10.1002/2015WR017323. Key Points: Subsurface tile drainage alters water cycle dynamics Quantifying the nature of subannual hydrologic change and its cascade to sediment and nutrient transport is essential for management Correspondence to: E. Foufoula-Georgiou, efi@umn.edu Citation: Foufoula-Georgiou, E., P. Belmont, P. Wilcock, K. Gran, J. C. Finlay, P. Kumar, J. A. Czuba, J. Schwenk, and Z. Takbiri (2016), Comment on ‘‘Climate and agricultural land use change impacts on streamflow in the upper midwestern United States’’ by Satish C. Gupta et al., Water Resour. Res., 52, 7536–7539, doi:10.1002/ 2015WR018494. Received 11 DEC 2015 Accepted 18 AUG 2016 Accepted article online 6 SEP 2016 Published online 24 SEP 2016 VC 2016. American Geophysical Union. All Rights Reserved. FOUFOULA-GEORGIOU ET AL. COMMENT ON GUPTA ET AL. 7536 Water Resources Research PUBLICATIONS

River Hydrology, Morphology, and Dynamics in an Intensively Managed, Transient Landscape

Abstract: River Hydrology, Morphology, and Dynamics in an Intensively Managed, Transient Landscape

Anthropogenic transformation of the terrestrial biosphere

Abstract: Human populations and their use of land have transformed most of the terrestrial biosphere into anthropogenic biomes (anthromes), causing a variety of novel ecological patterns and processes to emerge. To assess whether human populations and their use of land have directly altered the terrestrial biosphere sufficiently to indicate that the Earth system has entered a new geological epoch, spatially explicit global estimates of human populations and their use of land were analysed across the Holocene for their potential to induce irreversible novel transformation of the terrestrial biosphere. Human alteration of the terrestrial biosphere has been significant for more than 8000 years. However, only in the past century has the majority of the terrestrial biosphere been transformed into intensively used anthromes with predominantly novel anthropogenic ecological processes. At present, even were human populations to decline substantially or use of land become far more efficient, the current global extent, duration, type and intensity of human transformation of ecosystems have already irreversibly altered the terrestrial biosphere at levels sufficient to leave an unambiguous geological record differing substantially from that of the Holocene or any prior epoch. It remains to be seen whether the anthropogenic biosphere will be sustained and continue to evolve.

Image-based surface reconstruction in geomorphometry - merits, limits and developments

Abstract: . Photogrammetry and geosciences have been closely linked since the late 19th century due to the acquisition of high-quality 3-D data sets of the environment, but it has so far been restricted to a limited range of remote sensing specialists because of the considerable cost of metric systems for the acquisition and treatment of airborne imagery. Today, a wide range of commercial and open-source software tools enable the generation of 3-D and 4-D models of complex geomorphological features by geoscientists and other non-experts users. In addition, very recent rapid developments in unmanned aerial vehicle (UAV) technology allow for the flexible generation of high-quality aerial surveying and ortho-photography at a relatively low cost. The increasing computing capabilities during the last decade, together with the development of high-performance digital sensors and the important software innovations developed by computer-based vision and visual perception research fields, have extended the rigorous processing of stereoscopic image data to a 3-D point cloud generation from a series of non-calibrated images. Structure-from-motion (SfM) workflows are based upon algorithms for efficient and automatic orientation of large image sets without further data acquisition information, examples including robust feature detectors like the scale-invariant feature transform for 2-D imagery. Nevertheless, the importance of carrying out well-established fieldwork strategies, using proper camera settings, ground control points and ground truth for understanding the different sources of errors, still needs to be adapted in the common scientific practice. This review intends not only to summarise the current state of the art on using SfM workflows in geomorphometry but also to give an overview of terms and fields of application. Furthermore, this article aims to quantify already achieved accuracies and used scales, using different strategies in order to evaluate possible stagnations of current developments and to identify key future challenges. It is our belief that some lessons learned from former articles, scientific reports and book chapters concerning the identification of common errors or "bad practices" and some other valuable information may help in guiding the future use of SfM photogrammetry in geosciences.

Connectivity as an emergent property of geomorphic systems

Abstract: Connectivity describes the efficiency of material transfer between geomorphic system components such as hillslopes and rivers or longitudinal segments within a river network. Representations of geomorphic systems as networks should recognize that the compartments, links, and nodes exhibit connectivity at differing scales. The historical underpinnings of connectivity in geomorphology involve management of geomorphic systems and observations linking surface processes to landform dynamics. Current work in geomorphic connectivity emphasizes hydrological, sediment, or landscape connectivity. Signatures of connectivity can be detected using diverse indicators that vary from contemporary processes to stratigraphic records or a spatial metric such as sediment yield that encompasses geomorphic processes operate over time and space. One approach to measuring connectivity is to determine the fundamental temporal and spatial scales for the phenomenon of interest and to make measurements at a sufficiently large multiple of the fundamental scales to capture reliably a representative sample. Another approach seeks to characterize how connectivity varies with scale, by applying the same metric over a wide range of scales or using statistical measures that characterize the frequency distributions of connectivity across scales. Identifying and measuring connectivity is useful in basic and applied geomorphic research and we explore the implications of connectivity for river management. Common themes and ideas that merit further research include; increased understanding of the importance of capturing landscape heterogeneity and connectivity patterns; the potential to use graph and network theory metrics in analyzing connectivity; the need to understand which metrics best represent the physical system and its connectivity pathways, and to apply these metrics to the validation of numerical models; and the need to recognize the importance of low levels of connectivity in some situations. We emphasize the value in evaluating boundaries between components of geomorphic systems as transition zones and examining the fluxes across them to understand landscape functioning.

Dendritic connectivity controls biodiversity patterns in experimental metacommunities

Abstract: Biological communities often occur in spatially structured habitats where connectivity directly affects dispersal and metacommunity processes. Recent theoretical work suggests that dispersal constrained by the connectivity of specific habitat structures, such as dendrites like river networks, can explain observed features of biodiversity, but direct evidence is still lacking. We experimentally show that connectivity per se shapes diversity patterns in microcosm metacommunities at different levels. Local dispersal in isotropic lattice landscapes homogenizes local species richness and leads to pronounced spatial persistence. On the contrary, dispersal along dendritic landscapes leads to higher variability in local diversity and among-community composition. Although headwaters exhibit relatively lower species richness, they are crucial for the maintenance of regional biodiversity. Our results establish that spatially constrained dendritic connectivity is a key factor for community composition and population persistence.