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Final Report for the TSD work in Mower County
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... The Nature Conservancy provided funding for the ditch construction and modifications. Most of the research data were collected as part of the final project report [6] to the state of Minnesota. ...
... Sediment deposition within the rock filter itself was small. More details of the rock side inlet design and the experimental procedures are given by Krider et al. [6]. ...
... Selecting the locations for interception trenches in the field is not easy, and additional work is needed before the use of rock seepage trenches can be recommended. More information on the rock trench design can be obtained in Krider et al. [6]. ...
... The Nature Conservancy provided funding for the ditch construction and modifications. Most of the research data were collected as part of the final project report [6] to the state of Minnesota. ...
... Sediment deposition within the rock filter itself was small. More details of the rock side inlet design and the experimental procedures are given by Krider et al. [6]. ...
... Selecting the locations for interception trenches in the field is not easy, and additional work is needed before the use of rock seepage trenches can be recommended. More information on the rock trench design can be obtained in Krider et al. [6]. ...
... Objectives within this paper were to characterize improvements in the riparian and instream habitat and the fish community response. The geomorphic assessment of the channel and bank stability, nitrogen removal, and cost effectiveness are discussed elsewhere (Krider et al. 2014(Krider et al. , 2017. Some cross section and longitudinal profile results from Krider et al. (2017) are included in this paper to describe geomorphic changes in width and depth variability which are important for understanding fish habitat quality. ...
... This site also had landowners who were supportive of the project. With funding and assistance from The Nature Conservancy and the Mower County Soil and Water Conservation District, 1.89 km of the MDD was converted to the twostage design in October 2009 (Krider et al. 2014). This design also included other features to increase stability and improve water quality, including a seepage trench, rock inlet, and linear bench treatment systems (Krider et al. 2014(Krider et al. , 2017. ...
... With funding and assistance from The Nature Conservancy and the Mower County Soil and Water Conservation District, 1.89 km of the MDD was converted to the twostage design in October 2009 (Krider et al. 2014). This design also included other features to increase stability and improve water quality, including a seepage trench, rock inlet, and linear bench treatment systems (Krider et al. 2014(Krider et al. , 2017. Bankfull channel dimensions were calculated based on regional curves previously developed by Magner and Brooks (2007) for south-central Minnesota. ...
Water quality and stream habitat in agricultural watersheds are under greater scrutiny as hydrologic pathways are altered to increase crop production. Ditches have been traditionally constructed to remove water from agricultural lands. Little attention has been placed on alternative ditch designs that are more stable and provide greater habitat diversity for wildlife and aquatic species. In 2009, 1.89 km of a conventional drainage ditch in Mower County, Minnesota, was converted to a two‐stage ditch (TSD) with small, adjacent floodplains to mimic a natural system. Cross section surveys, conducted pre‐ and post‐construction, generally indicate a stable channel with minor adjustments over time. Vegetation surveys showed differences in species composition and biomass between the slopes and the benches, with changes ongoing. Longitudinal surveys demonstrated a 12‐fold increase in depth variability. Fish habitat quality improved with well‐sorted gravel riffles and deeper pool habitat. The biological response to improved habitat quality was investigated using a Fish Index of Biological Integrity (FIBI). Our results show higher FIBI scores post‐construction with scores more similar to natural streams. In summary, the TSD demonstrated improvements in riparian and instream habitat quality and fish communities, which showed greater fish species richness, higher percentages of gravel spawning fish, and better FIBI scores. This type of management tool could benefit ditches in other regions where gradient and geology allow. Research Impact Statement: Two‐stage ditch construction improved riparian and instream habitat conditions for wildlife and fish communities, thus a tool for watershed managers.
... Without maintenance, channelized ditches often naturally evolve into a two-stage channel type (D'Ambrosio et al., 2015). Two-stage drainage ditches are designed to mimic the stable conditions found in natural low-order streams (Ward et al., 2004;USDA-NRCS, 2007;Krider et al., 2014) (Figure 1). They are usually constructed to replace conventional ditches and are most beneficial at sites where present conventional drainage ditches are unstable (Kramer, 2011). ...
... In addition, the design has outer banks with a more gradual sideslope (Figure 1). This feature, combined with the bench construction, makes the twostage ditch wider than the conventional design and can support larger flow capacities (Krider et al., 2014;Kramer, 2011). With less erosion and sediment JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION deposition, this design reduces ditch cleanout costs associated with sediment imbalance (Ward et al., 2004;Powell et al., 2007;Peterson et al., 2010). ...
... This resulted in places where the channel was scoured down to clay material (pools) and other places where larger sand and gravel sized particles accumulated and were well sorted (riffles). Given its lack of need for maintenance since construction, the design is not likely to require maintenance and clean-out often associated with the conventional design, making it an economically viable option in many cases (Krider et al., 2014). Increased stability can be attributed to the two-stage design with a narrow, low-flow channel, and floodplain benches that support a larger amount of plant biomass (Powell and Bouchard, 2010). ...
Water quality and stream habitat in agricultural watersheds are under greater scrutiny as hydro-logic pathways are altered to increase crop production. Agricultural drainage ditches function to remove water quickly from farmed landscapes. Conventional ditch designs lack the form and function of natural stream systems and tend to be unstable and provide inadequate habitat. In October of 2009, 1.89 km of a conventional drainage ditch in Mower County, Minnesota, was converted to an alternative system with a two-stage channel to investigate the improvements in water quality, stability, and habitat. Longitudinal surveys show a 12-fold increase in the pool-riffle formation. Cross-sectional surveys show an average increase in bankfull width of approximately 10% and may be associated to an increased frequency in large storm events. The average increase in bankfull depth was estimated as 18% but is largely influenced by pool formation. Rosgen Stability Analyses show the channel to be highly stable and the banks at a low risk of erosion. The average bankfull recurrence interval was estimated to be approximately 0.30 years. Overall, the two-stage ditch design demonstrates an increase in fluvial stability, creating a more consistent sediment budget, and increasing the frequency of important instream habitat features, making this best management practice a viable option for addressing issues of erosion, sediment imbalance, and poor habitat in agricultural drainage systems. (KEY TERMS: fluvial processes; best management practices; physical stability; drainage ditches; erosion; instream habitat.)
... Powell et al. 2007a; Jayakaran et al. 2010). The potential for reduced velocities at high flow due to increased momentum transfer through the cross-section (Myers 1978; Knight and Hamed 1984) and increased vegetation on the banks and benches is also beneficial for reducing bank erosion and suspended load in these channels (Krider et al. 2014; Wang et al. 2014). At the other end of the flow spectrum, low water flows tend to have a higher stage when benches are incorporated as they narrow the width of the bottom of the ditch. ...
Alternative management approaches for agricultural streams based on hydrogeomorphological principles such as a two-stage channel are promising, but need to be further tested in contexts other than the Midwestern United States. In Quebec (Canada), the presence of many deep drain outlets may limit their applicability. The objectives of this research are to (1) assess the feasibility of implementing the two-stage channel design in Quebec; (2) determine how alternative management approaches compare with traditional management from an economical point of view, and (3) evaluate the impact of modifying the drain outlet design using small horseshoe wetlands to accommodate hydrogeomorphological adjustments of the channel. A combination of case studies and numerical modelling (HEC-RAS, Hydrologic Engineering Center’s River Analysis System) was used for three study sites located in the Montérégie region (QC). Based on regional hydraulic geometry curves, additional space on each bank required for a two-stage channel ranged between 1.3 and 2.8 m for a width equal to 3 times the inset channel. Hydraulic modelling confirms previous findings of improved drainage capacity at high flow, (up to a 54% increase). Cost analysis reveals that two-stage and over-widened channels are 3 to 4 times more expensive to implement when compared to traditional trapezoidal clean-out dredging operations, mainly due to spoil removal and transportation. However, self-formed channels are less expensive since they only require additional riparian land. A crop yield analysis in the near-stream zone at three sites which are frequently flooded revealed markedly lower productivity in zones within the flooding space. The horseshoe wetland design for drain outlets could also be maintained at low cost, and would promote more heterogeneity than the traditional trapezoidal ditches. Using alternative agricultural stream management approaches based on hydrogeomorphological concepts would be feasible in the Quebec context without compromising the overall productivity of this key economic sector.Des méthodes de gestion alternatives des cours d’eau agricoles basées sur des principes d’hydrogéomorphologie, comme les chenaux à deux niveaux, sont prometteuses mais requièrent d’être testées dans des contextes différents de ceux des états du Midwest américain. Au Québec (Canada), la présence de drains profonds pourrait limiter leur applicabilité. Les objectifs de cette recherche sont (1) d’évaluer la faisabilité d’implanter les chenaux à deux niveaux au Québec; (2) de comparer le coût de méthodes de gestion alternatives et traditionnelle et (3) de déterminer l’impact d’une modification des sorties de drain à l’aide de zones humides réduites permettant des ajustements hydrogéomorphologiques du chenal. Une combinaison d’études de cas et de modélisation numérique (HEC-RAS, Hydrologic Engineering Center’s River Analysis System) est utilisée pour trois sites d’étude en Montérégie (QC). Selon des courbes régionales de géométrie hydraulique, l’espace additionnel requis pour des chenaux à deux niveaux se situe en moyenne entre 1,3 et 2,8 m pour un chenal ayant 3 fois la largeur du chenal mineur. La modélisation confirme les résultats antérieurs sur l’amélioration de la capacité de drainage (jusqu’à 54%). L’analyse économique révèle que les chenaux à deux niveaux et sur-élargis sont 3 à 4 fois plus coûteux que le dragage traditionnel des chenaux trapézoïdaux, en grande partie en raison du coût d’enlèvement des déblais. Les chenaux auto-formés sont toutefois moins chers puisqu’ils ne nécessitent qu’un peu plus d’espace. Une analyse de la productivité à trois sites fréquemment inondés révèle des rendements nettement plus faibles dans l’espace d’inondabilité. Les sorties de drain aménagées dans des milieux humides réduits diminueraient aussi les coûts d’entretien, tout en procurant une meilleure hétérogénéité que dans les chenaux trapézoïdaux. Ces mesures alternatives de gestion des cours d’eau agricoles basées sur des concepts hydrogéomorphologiques pourraient être employées au Québec sans compromettre la productivité de ce secteur économique névralgique.
