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In eastern Nebraska, stream straightening and dredging efforts since the 1890s have disturbed the natural equilibrium of stream channels and have led to streambed adjustment by degradation and subsequent channel widening. This report describes a study to evaluate the effect these disturbances have had on stream channels in eastern Nebraska. Two set...
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... These authors also briefly summarized all the previous studies on this salt basin area. In the new millennium, Rus et al. (2003) studied channel widening and its impact on Salt Creek Basin saline wetlands. They noted that streambed degradation is accelerating the drainage of saline wetlands along Little Salt Creek and suggested installing grade control structures to prevent channel widening from affecting the wetlands. ...
Nebraska’s eastern saline wetlands are globally unique and highly vulnerable inland salt marsh ecosystems. This research aims to evaluate the status of the saline wetlands in eastern Nebraska to discover the conditions of saline wetland hydrology, hydrophytes, and hydraulic soil. The research adopts machine learning and Google Earth Engine to classify Sentinel-2 imagery for water and vegetation classification and the National Agriculture Imagery Program imagery for salinity conditions. Six machine learning models are applied in water, soil, and vegetation detection in the study area. The optimal model (linear kernel SVM) generates an overall accuracy of 99.95% for water classification. For saline vegetation classification, the optimal model is the gradient tree boost with an overall accuracy of 94.07%. The overall accuracy values of saline soil classification using the optimal model (linear kernel SVM) varied among different years. The results of this study show the possibility of an observation approach for continuously monitoring Nebraska’s eastern saline wetlands. The water classification results show that the saline wetlands in this area all have a similar temporal water cover pattern within each year. For saline vegetation, the peak season in this area is between June and July. The years 2019 (19.00%) and 2018 (17.69%) had higher saline vegetation cover rates than 2017 (10.54%). The saline soil classification shows that the saline soil area is highly variable in response to changes in the water and vegetation conditions. The research findings provide solid scientific evidence for conservation decision-making in these saline wetland areas.
... In 1906, the lake was renamed Capitol Beach. To accommodate the residential and commercial developments there, saline wetlands and associated streams at Capitol Beach were further ditched, drained, and filled (Murphy 1992;Rus et al. 2003). Construction of Interstate 80 northwest of Capitol Beach resulted in the continued filling of saline wetlands. ...
Current Species Status: The Salt Creek tiger beetle (Cicindela [Ellipsoptera] nevadica lincolniana) was listed as a federally endangered subspecies on November 7, 2005 (70 FR 58335, October 6, 2005). On May 6, 2014 (79 FR 26013), we published a revised final rule designating approximately 449 hectares (1,110 acres) of critical habitat for the Salt Creek tiger beetle in Lancaster and Saunders Counties in Nebraska. The Salt Creek tiger beetle has a recovery priority number of 6C, which means it is a subspecies that faces a high level of threat, including conflict with development activities; a priority number of 6C also indicates it has a low potential for recovery. The Salt Creek tiger beetle has one of the most restricted ranges of any insect in the United States and is currently limited to segments of Little Salt Creek and adjacent remnant saline wetlands in northern Lancaster County, Nebraska. Habitat Requirements and Limiting Factors: The Salt Creek tiger beetle requires open, barren saline mud flats and mud banks of streams with saline seeps for constructing larval burrows, moving to and from dispersal corridors, foraging, and maintaining thermoregulation (ability of an organism to regulate its body temperature using internal and external mechanisms). The primary threat to this species is loss and degradation of saline wetland and stream habitats due to commercial, residential, and agricultural development. Construction of levees, reservoirs, and additional channelization of Salt Creek resulted in the degradation and loss of saline wetlands and seeps and entrenchment of its associated tributaries (i.e., Rock, Little Salt, Oak, and Haines Branch Creeks). Contamination, artificial lights, invasive plants, floods, and drought can also have a negative impact on this insect. The Salt Creek tiger beetle is currently found on only one stream segment (Little Salt Creek), which makes it subject to high extinction risk should a catastrophic event occur.
... The location at which a stream is perennial is an estimate because it depends on variables such as the elevation of the water table and the elevation of the streambed, both of which change over time. The water table fluctuates in response to groundwater recharge and extraction (Young et al., 2014) and the elevation of the streambed changes in response to erosion and aggradation (Chen et al., 1999;Rus et al., 2003). Erosion is common in many streams in eastern Nebraska (Joeckel et al., 2007;Chen et al., 1999;Rus et al., 2003) including Wahoo Creek, Rock Creek, and Salt Creek in Saunders County (Chen et al., 1999). ...
... The water table fluctuates in response to groundwater recharge and extraction (Young et al., 2014) and the elevation of the streambed changes in response to erosion and aggradation (Chen et al., 1999;Rus et al., 2003). Erosion is common in many streams in eastern Nebraska (Joeckel et al., 2007;Chen et al., 1999;Rus et al., 2003) including Wahoo Creek, Rock Creek, and Salt Creek in Saunders County (Chen et al., 1999). ...
... Incision commonly results in knickpoints until increasing stream power eventually causes the knickpoint to collapse in an upstream migration process. Knickpoints typically continue to migrate upstream and may also proceed up tributaries (Rus et al., 2003), as documented in several modified alluvial streams in Iowa, Nebraska, and Tennessee (Daniels, 1960;Simon, 1989;Rus et al., 2003). In areas of highly erodible material such as loess, knickpoints form quickly in reaction to major disturbances such as channelization (Daniels, 1960;Thomas et al., 2004). ...
... Incision commonly results in knickpoints until increasing stream power eventually causes the knickpoint to collapse in an upstream migration process. Knickpoints typically continue to migrate upstream and may also proceed up tributaries (Rus et al., 2003), as documented in several modified alluvial streams in Iowa, Nebraska, and Tennessee (Daniels, 1960;Simon, 1989;Rus et al., 2003). In areas of highly erodible material such as loess, knickpoints form quickly in reaction to major disturbances such as channelization (Daniels, 1960;Thomas et al., 2004). ...
... In areas of highly erodible material such as loess, knickpoints form quickly in reaction to major disturbances such as channelization (Daniels, 1960;Thomas et al., 2004). Conversely, if bedrock is present in the streambed, the exposed formation will act as a more permanent knickpoint that slows the degradation process and reduces upstream channel grade (Miller, 1991;Rus et al., 2003). Due to limited data collected upstream of the Dutchman Creek confluence, it is difficult to conclude whether the degradation process has slowed upstream of the knickpoint in the upper Cache River. ...
Over the past century, channelization, agricultural tiling, and land use changes have resulted in significant stream channel degradation of the Cache River in southern Illinois. With the increasing interest in restoration of the watershed's bottomland forests and swamps, we sought to characterize geomorphic change over the past 110 years to inform restoration and management. A previously surveyed stretch of river was resurveyed in the fall of 2011, following a record flood in the spring of that year. Results suggest that the slope of the channel in this section of the river has increased 345% between 1903 and 1972 (p < 0.01), but has not changed significantly since (p = 0.12). Within that same time period, bank heights increased between 1 and 7 m and bed elevation decreased between 1 and 5 m. Changes in resurveyed cross sections appear to be primarily due to recent flood scour. It appears as though early 20th Century stream channel modifications had immediate effects on the geomorphology of the channel; however, channel geometry is now at or near equilibrium. This case study of the Cache River watershed demonstrates how and why successful restoration will require integration of geomorphic processes of the system.
... These streams isolate the causes of down cutting because (1) the study area is underlain predominantly by erodable loess, (2) stream adjustment to base-level lowering is rapid, (3) most determinants of base-level lowering are identifiable in both time and space, and (4) independent variables such as slope and land use can be controlled statistically. The study area possesses an extensive historical record of streambed elevations in the form of hundreds of bridge cross sections along fifteen Missouri River tributaries (U.S. Army Corps of Engineers 1987, 1991Rus, Dietsch, and Simon 2003). The Nebraska reach of the Missouri River basin thus serves as an experimental site in which to test temporal models of stream incision and to develop a spatial model of stream incision at watershed scales. ...
... Because of the loess mantle on the uplands, the region is described as highly erodable by the Soil Conservation Service (1981). Alluvial soils and stream beds and banks consist primarily of loess-derived silt, silty-clay loam, and loamy silt (Rus, Dietsch, and Simon 2003). ...
... B. Daniels and Jordan 1966), channel widening (Lohnes 1997;Bravard, Kondolf, and Piegay 1999), channel evolution (Hadish et al. 1994;Simon and Rinaldi 2000), channel stabilization (Lohnes 1997), and the effect of human alterations to stream channels (Ruhe and Daniels 1965;U.S. Army Corps of Engineers 1991;Simon 1994;Schneiders 1996;Simon and Rinaldi 2000). Causes of historic incision include (1) nineteenthcentury land clearing and poor soil conservation practices (Simon and Rinaldi 2000), (2) channelization completed primarily in the early twentieth century (Simon andRinaldi 2000, 2006;Rus, Dietsch, and 1991;Schneiders 1996;National Research Council 2002;Rus, Dietsch, and Simon 2003). The net result is a severely eroded landscape in which streams have degraded by as much as eight meters over the past hundred years (U.S. Army Corps of Engineers 1991; Rus, Dietsch, and Simon 2003). ...
Stream channel incision is severe in the loess-dominated region of western Iowa and eastern Nebraska, with recent incision related to sediment capture by reservoirs on the Missouri River. This study confirms that the temporal pattern of incision follows the rate law proposed by Graf (1977) with half-lives ranging from two to nine years and stream channels throughout the affected watersheds approaching a new dynamic equilibrium in one to three decades. The resulting spatial pattern of incision on tributaries is demonstrated to follow a simple rule of base-level lowering at the outlet multiplied by a flow-length ratio (R = 0.71). This rule is used to estimate depth of channel incision along all tributary streams of the Nebraska reach of the Missouri River and confirms that Missouri River degradation, along with other local disturbances such as channelization, is an important cause of tributary stream incision in the study area. Using the flow-length ratio rule, a spatial model of stream channel incision is developed that accounts for influences of channelization, grade controls, the erodability of geologic materials, and time.
... A short Nebraska Game and Parks Commission (NGPC) publication written for the general public entitled Nebraska Salt Marshes: Last of the Least (Farrar and Gersib 1991) provides a brief history of the region related to the salt basins and a very basic overview of the ecology, hydrology, and geology of the wetlands. Finally, a report by Rus et al. (2003) described streambed adjustments and channel widening in eastern Nebraska, and discusses installation of a number of grade-control structures to prevent channel incision into the Salt Creek Basin saline wetlands near Lincoln. ...
Many endangered or threatened ecosystems depend on ground water for their survival. Nebraska’s saline wetlands, home to a number of endangered species, are ecosystems whose development, sustenance, and survival depend on saline ground water discharge at the surface. This study demonstrates that the saline conditions present within the eastern Nebraska saline wetlands result from the upwelling of saline ground water from within the underlying Dakota Aquifer and deeper underlying formations of Pennsylvanian age. Over thousands to tens of thousands of years, saline ground water has migrated over regional scale flowpaths from recharge zones in the west to the present-day discharge zones along the saline streams of Rock, Little Salt, and Salt creeks in Lancaster and Saunders counties. An endangered endemic species of tiger beetle living within the wetlands has evolved under a unique set of hydrologic conditions, is intolerant to recent anthropogenic changes in hydrology and salinity, and is therefore on the brink of extinction. As a result, the fragility of such systems demands an even greater understanding of the interrelationships among geology, hydrology, water chemistry, and biology than in less imperiled systems where adaptation is more likely.
Results further indicate that when dealing with ground water discharge–dependent ecosystems, and particularly those dependent on dissolved constituents as well as the water, wetland management must be expanded outside of the immediate surface location of the visible ecosystem to include areas where recharge and lateral water movement might play a vital role in wetland hydrologic and chemical mixing dynamics.
... The Pfankuch (1975) system of channel-stability evaluation that is included in Rosgen (1996) is of questionable utility because its numerical scheme is more subjective (different parameter weighting), limited to coarsegrained systems, and contains some questionable ranking schemes (i.e., more stable values for deep, narrow channels). In addition, analysis of historical or time-series aerial photographs, gaging station records (i.e., Blench, 1973;Simon and Hupp, 1992;Jacobson, 1995;Rus et al., 2003), historical surveys (i.e., Daniels, 1960;Parker and Andres, 1976;Rinaldi and Simon, 1998;Simon and Rinaldi, 2000)) and dendro-chronologic evidence of recent bank-failure frequency and deposition rates (i.e., Simon and Hupp, 1992) may aid in identifying the scale of the problem and not just the local symptom. Once the scale of the instability has been determined, the second, or analytic level of investigation is conducted. ...
Over the past 10 years the Rosgen classification system and its associated methods of “natural channel design” have become synonymous to some with the term “stream restoration” and the science of fluvial geomorphology. Since the mid 1990s, this classification approach has become widely adopted by governmental agencies, particularly those funding restoration projects. The purposes of this article are to present a critical review, highlight inconsistencies and identify technical problems of Rosgen’s “natural channel design” approach to stream restoration. This paper’s primary thesis is that alluvial streams are open systems that adjust to altered inputs of energy and materials, and that a form-based system largely ignores this critical component. Problems with the use of the classification are encountered with identifying bankfull dimensions, particularly in incising channels and with the mixing of bed and bank sediment into a single population. Its use for engineering design and restoration may be flawed by ignoring some processes governed by force and resistance, and the imbalance between sediment supply and transporting power in unstable systems. An example of how C5 channels composed of different bank sediments adjust differently and to different equilibrium morphologies in response to an identical disturbance is shown. This contradicts the fundamental underpinning of “natural channel design” and the “reference-reach approach.” The Rosgen classification is probably best applied as a communication tool to describe channel form but, in combination with “natural channel design” techniques, are not diagnostic of how to mitigate channel instability or predict equilibrium morphologies. For this, physically based, mechanistic approaches that rely on quantifying the driving and resisting forces that control active processes and ultimate channel morphology are better suited as the physics of erosion, transport, and deposition are the same regardless of the hydro-physiographic province or stream type because of the uniformity of physical laws.
... As mentioned above, in eastern Nebraska, streambed adjustment has led to deeply incised channels. Rus et al. (2003) did a survey of 151 stream sites in eastern Nebraska. They found that many of the sites had degraded channel beds that were primarily caused by channel straightening (channel straightening results in a net increase in the stream bed slope and increased sediment carrying capacity of the stream) that dates back to as early as the 1890s. ...
... To reduce flooding the Little Nemaha River and its tributaries were dredged, straightened and cleared of vegetation starting in the early 1900's. This disturbance is regarded as the main cause of present channel instabilities throughout the basin (Rus 2003). In the upper reaches of the basin, Muddy Creek was straightened between 1947 and 1953. ...
... In the upper reaches of the basin, Muddy Creek was straightened between 1947 and 1953. Knickpoints from channel straightening migrated upstream and most effects on streambeds had already occurred (Rus 2003). In our study area, knickpoints are still evident, working up the 1 st order portions of the streams (D.E. ...
... Eisenhauer, personal communication, 2003). A recent USGS study (Rus 2003) indicated that in the Little Nemaha River Basin, streambed degradation since settlement averaged 1.9 meters for 21 bridge locations throughout the basin. ...
We assessed the effect of beaver dams on channel gradation of an incised stream in an agricultural area of eastern Nebraska. A topographic survey was conducted of a reach of Little Muddy Creek where beaver are known to have been building dams for twelve years. Results indicate that over this time period the thalweg elevation has aggraded an average of 0.65 m by trapping 1730 t of sediment in the pools behind dams. Beaver may provide a feasible solution to channel degradation problems in this region.
... To reduce flooding the Little Nemaha River and its tributaries were dredged, straightened and cleared of vegetation starting in the early 1900's. This disturbance is regarded as the main cause of present channel incision throughout the basin (Rus 2003). In the upper reaches of the basin, Muddy Creek was straightened between 1947 and 1953. ...
... In the upper reaches of the basin, Muddy Creek was straightened between 1947 and 1953. Knickpoints from channel straightening migrated upstream and most effects on streambeds have already occurred (Rus 2003). In our study area, knickpoints are still evident, working up the 1 st order portions of the streams. ...
... In our study area, knickpoints are still evident, working up the 1 st order portions of the streams. It is estimated that in the Little Nemaha River Basin, streambed degradation since settlement averaged 1.9 meters for 21 bridge locations throughout the basin (Rus 2003). ...
