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    High stage events and stream bank erosion on small grazed pasture stream reaches in the rathbun lake watershed, southern IOWA, USA
    (Health & Environment Assoc, 2019) Tüfekçioğlu, Mustafa; Isenhart, Thomas M.; Schultz, Richard C.
    Stream bank erosion in agricultural landscapes is a major pathway for non-point source sediment and phosphorus loading of receiving waters. Previous studies have shown direct and indirect effects of land use on stream bank erosion, and identified high erosion rates within riparian pastures. One potential impact of agricultural land-use on stream bank erosion is the alteration of stream stage characteristics, including an increase in frequency of high-stage events over short periods of time (forming flash hydrographs). The objective of this study was to assess the relationship between the number of high stream stages and corresponding stream bank soil erosion. The study was conducted in six grazed pasture stream reaches within the Rathbun Lake Watershed, a reservoir on the Chariton River located within the Southern Iowa Drift Plain. The erosion pin method was utilized to measure the change in stream bank erosion in response to differences in the number of high stream-stage events, which were monitored by pressure transducers. The measured seasonal bank erosion rates were correlated with the different stream stages data to assess their impact on stream bank erosion. Based on the different model assumptions, there were generally strong linear relationships between high stage and bank erosion. Approximately 75% of the variability in stream bank erosion rates was directly linked to the number of high stages/erosive stream flow depths. Conservation practices that reduce these erosion rates will be those that increase soil-water infiltration, reduce the frequency of high stream flow events and increase bank stability through perennial vegetation cover or reducing disturbance within the riparian zone.
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    The relationship between erosion and precipitation and the effects of different riparian practices on soil and total-p losses via streambank erosion in Small streams in Iowa, USA
    (Multidisciplinary Digital Publishing Institute (MDPI), 2024) Tüfekçioğlu, Mustafa; Zaimes, George N.; Kahriman, Aydın; Schultz, Richard C.
    Streambank erosion in agricultural landscapes contributes high amounts of sediment and total-P to surface water, resulting in the degradation of stream habitats and reduction in ecological services. Moreover, the implication of future climate change on bank erosion is also a growing concern. Streambank erosion rates from riparian forest buffers (RFo), grass filters (GFi), row-crops (RCr) and pastures, including fenced pastures (FPa), rotationally grazed pastures (RPa), intensive rotationally grazed pastures (IPa), and continuously grazed pastures (CPa), in three landform regions of Iowa, were measured over seven years. Bank erosion pins were measured seasonally (spring, summer and fall) in the first five years (2002–2006) and yearly for two more years (2007–2008). It was found that summer and spring seasons are the important ones since the relationships between erosion and precipitation were significantly “strong” in almost all the riparian practices, and precipitation was found to be the main factor driving streambank erosion. Streambank mean soil losses and soil total-P losses from RFo (23.3 tons km?1 yr?1 and 9.8 kg km?1 yr?1, respectively), GFi (31.1 and 9.9) and FPa (44.0 and 23.7) practices were all significantly lower than the grazing pasture practices, including RPa (142.3 and 58), CPa (255 and 105.1), IPa (234.6 and 122.7) and RCr fields (352.9 and 118.9). Also, RPa had significantly lower total-P loss than CPa, IPa and RCr practices (RFo, GFi, FPa < RPa < CPa, IPa, RCr). RCr practices had the highest streambank soil losses among all other riparian practices (RFo, GFi, FPa < RPa < IPa, CPa < RCr). The study showed that riparian conservation practices (RFo, GFi and FPa) showcased significant benefits in mitigating streambank soil loss and associated soil total-P load to streams. However, their effectiveness is highly sensitive to changing climatic conditions and the extent of spatiotemporal variations.
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    Riparian grazing impacts on streambank erosion and phosphorus loss via surface runoff
    (Wiley, 2013) Tüfekçioğlu, Mustafa; Schultz, Richard C.; Zaimes, George N.
    Surface runoff is one of the major pathways of sediment and phosphorus (P) transport to surface waters. Rainfall simulations were conducted on nine grazed pasture sites with different stocking rates in three different Iowa (United States) regions. The purpose of the simulations was to determine the impacts of cattle grazing on the amounts of sediment and P in surface runoff within a 15-m wide strip on both sides of the stream from different source areas (SAs). These riparian SAs included stream-side loafing areas, cattle streambank access paths to the stream, and the other vegetated areas adjacent to the streambanks. The runoff samples collected during the simulations were analyzed for suspended sediment (SS) and total phosphorus (TP). Soil bulk density and antecedent soil moisture samples were collected around the rainfall simulation plots to identify differences in compaction, infiltration, and surface runoff among the SAs. SS and TP losses from access paths and loafing areas within the 15-m wide strips accounted for up to 72 and 55% of the total losses, respectively, even though they accounted for only 2.7% of the total area within the 15-m wide strips. This suggests that access paths and loafing areas require special attention to mitigate the impacts of cattle on stream water pollution. Significant correlations were found between stocking rates and both SS and TP losses suggesting that low stocking rates can reduce sediment and P export to streams from the SAs.
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    Riparian land-use ımpacts on stream bank and gully erosion in agricultural watersheds: what we have learned
    (MDPI, 2019) Zaimes, George N.; Tüfekçioğlu, Mustafa; Schultz, Richard C.
    Stream bank and gully erosion are major sources of nonpoint source pollutants, especially in landscapes dominated by agriculture. Implementation of upland conservation practices in landscapes dominated by agriculture reduces upland sediment transport more than water runoff, leading to excessive stream bank and gully erosion. This review focus on ten different studies conducted in streams in Iowa that investigated riparian land-use impacts on stream banks, gullies, and other riparian sediment sources (cattle loafing areas and cattle stream access points). The riparian land-uses investigated were riparian forest buffers; grass filters; continuous, rotational, and intensive rotational pastures; pastures with cattle fenced out of the stream; and row-cropped fields. Results of these studies indicate that maintaining perennial deep-rooted vegetation in riparian areas and excluding cattle from the stream channel stabilizes stream banks and gullies. Cattle loafing areas and cattle stream access points appear to also be important sediment sources. Re-establishing perennial riparian vegetation is a sustainable and cost-effective conservation practice because it reduces sediment in streams while maintaining the majority of the watershed in agricultural production. The limited available funds for the implementation of holistic watershed conservation practices suggest using targeted approaches, at the watershed scale, to improve conservation practice effectiveness.
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    Riparian land-use, stream morphology and streambank erosion within grazed pastures in southern lowa, USA: A catchment-wide perspective
    (MDPI, 2020) Tüfekçioğlu, Mustafa; Schultz, Richard C.; Isenhart, Thomas M.; Kovar, John L.; Russell, James R
    Factors influencing streambank erosion at the field/reach scale include both watershed andriparian land-uses, stream hydrology and channel morphology at the catchment scale. This studyassesses the relationship of riparian land-uses, stream morphologic characteristics and catchmentscale variables to streambank erosion within grazed riparian pastures in the Southern Iowa DriftPlain. Thirteen cooperating beef cow–calf farms and their catchments ranging from 2.5 to 12.9 km2in the Rathbun Lake watershed in South Central Iowa (USA) were chosen to conduct this study.Results suggest that the integration of stream morphologic characteristics and riparian land-uses atboth the reach and catchment scale are necessary to explain the current level of streambank erosionmeasured at the reach scale. Larger catchment size or catchments with more total channel lengthwere found to experience more bank erosion at the reach scale. A significant positive relationshipbetween percent sand-and-silt in the bank soil and bank erosion rates implies that bank soils with lesscohesiveness are more erodible. Catchment-scale assessments of the thirteen watersheds showedthat within the 50 m corridor on both sides of the stream, 46 to 61% of riparian area was devoted toagricultural use and only 6 to 11% was in ungrazed perennial vegetation, much of it enrolled in theUSDA Conservation Reserve Program. Overall, this and previous Rathbun watershed studies haveshown that intensive agricultural use of riparian areas over such extents of time and scale could bedirectly (in field scale) and/or indirectly (watershed scale) related to excessive amounts of streambankerosion (ranging from 8.6 to 38.3 cm/yr) to receiving streams and lakes leading to their impairmentand reduction in ecological services. Exclusion of cattle grazing in the riparian areas along bufferedstream lengths (2.1% of the total watershed area) of the Rathbun watershed would reduce this impact.This approach could also be applicable to other similar watersheds with extensive land-use undergrazed management.
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    Understanding stream bank erosion and deposition in Iowa, USA: A seven year study along streams in different regions with different riparian land-uses
    (Academic Press Inc, 2021) Zaimes, George Nick; Tamparopoulos, Alexios E.; Tüfekçioğlu, Mustafa; Schultz, Richard C.
    Agricultural activities such as row-cropping and grazing, have accelerated stream bank erosion. Accelerated stream bank erosion increases nonpoint source pollutants in aquatic ecosystems, significantly degrading them. Mitigating stream bank erosion is a priority worldwide, especially in agricultural watersheds. The objective of this study was to analyze the impacts of riparian land-use management on stream bank erosion and deposition, along with analyzing its temporal and spatial patterns. The study was conducted in three regions of Iowa (central, northeast and southeast) along 30 stream reaches adjacent to seven different riparian land-uses. The riparian land-uses were riparian forest buffers, grass filters, pastures with the cattle excluded from the stream, intensive rotational grazing, rotational grazing, continuous grazing and row crop fields. Seasonal erosion and deposition data (Spring, Summer and Autumn) were collected along these reaches for 5 years and yearly for the following two years. To analyze the data, conventional statistical methods (ANOVA and Tukey's test) along with innovative techniques (percentile plots, cumulative erosion curves and bubble charts) were utilized. Based on the analysis, of this extensive in time (seven years) and large in size (1500 pins measured 17 times in three regions) field dataset, major results were obtained in regard to stream bank erosion in Iowa, USA. Stream banks exhibited high year-to-year variation in erosion and deposition showcasing the need for long-term datasets to better understand stream bank erosion and deposition. Seasonal erosion, also had high variability with Spring recording the most erosion followed by Summer and Autumn. Certain seasons exhibited high stream bank erosion indicating that managers need to focus on these seasons, to reduce erosion effectively. In addition, seasonal measurements can highlight depositional events that might be masked with annual measurements. Riparian land-uses significantly impacted stream bank erosion. Riparian forest buffers and grass filters significantly mitigated stream bank erosion while traditional agricultural practices like continuous grazing and row-crop agriculture had accelerated stream bank erosion. Finally, the percentile plots, cumulative erosion curves and bubble charts captured some stream bank responses that would have been unnoticed using conventional statistical methods, allowing decision makers, stakeholders and the general public, to support and approve measures to mitigate this environmental problem. Nature-based solutions utilizing riparian perennial vegetation can sustainably mitigate stream bank erosion.