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approximately range from $ 5–20 USD/linear foot. Whilst minimal loss of vegetation is encountered through the implementation of the two stage drainage ditch contrary to alternate measures, vegetation preventing such channel widening to take place to form the adjacent benches will be destructed. Furthermore, the result of widening the ditch will be effected at the ditch top. Thus, proximate arable land above the ditch will be surrendered.
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Therefore, to restore and alleviate issues of water quality, given agriculture is the largest income generator of
Minnesota, the Nature Conservancy have begun to test a value analysis associated with the formation of two stage drainage systems in the region in the past decade. In 2010, a 7,000 linear
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finding that these deep and wide conventional ditches are highly susceptible to erosion and sedimentation, hindering the stability of the ditch, finding excessive levels of nitrogen and phosphorus in streams which culminate in eutrophication, in addition to increased flooding. Biske affirmed Hansen's
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The issue faced by
Minnesota's channel management systems concerns the implementation of traditional ditch systems that were used to straighten what were once headwaters streams, disrupting the fluvial processes of the hydrological system. In fact, more than 25,000 miles of these traditional drainage
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In acknowledgement of the above, the upfront costs associated with the formation of a two stage drainage ditch, particularly the benches adjacent to the water channel is likely higher than the cost incurred by more traditional maintenance approaches. Thus, since such initial investment is necessary,
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Ultimately, the constraints and associated costs of land loss necessary for ditch widening form a caveat. However, in order to maximise channel stability and ecological functionality to overcome the disadvantage, Ohio State
University studies suggest "the total width of the benches plus the existing
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or roadworks. Thus, the overall benefit of the two stage drainage ditch is the stability of the water channel and wider ecosystem, reduced rates of discharge during high flows and reduced sediment entering the water system, aiding in alleviating much of the environmental issues suffered in existing
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available and accessible at the bottom of the channel, thus, eliminating the cost associated with excavating and moving sediment to artificially manufacture the benches in a watershed with minimal natural bench formation. Secondly, a significant part of the water flow entering the channel comes in
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The two stage drainage ditch, with the introduction of the benches, creates a larger area on a cross-sectional basis than the existing, natural, trapezoidal channel. This is shown in the diagram below
Consequently, this has the effect of a reduced propensity to flooding in adjacent upland areas of
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From the daily results taken, testing for nitrate concentration in the channel, preliminary data demonstrated how, whilst there was insufficient data as at 2010 to report the full environmental benefits of the imposed two stage drainage ditch, there was a minimal reduction in daily nitrate levels
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Ultimately, as at the time the report was published, it was too soon to represent the nutrient attenuation benefits of the program. However, initial visual observations demonstrated habitat improvements and aquatic life improvements from the initial results of the nitrate reduction were already
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Whilst the upfront of two stage drainage ditch construction is expensive, the long term maintenance costs associated with the two stage drainage ditch are likely to be less than alternative management strategies and traditional ditch designs. This is because the benches built into the two stage
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The primary disadvantage associated with the two stage drainage ditch is the upfront cost of the earthwork necessary to increase the existing channel for the benches to be constructed. Construction costs for such earthwork are contingent upon the watershed size and depth of the ditch and
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management system requiring less frequent maintenance than a management design such as entrenchment. Ultimately, the long term reduction in costs acts to neutralise the high upfront cost required to construct the two stage drainage ditch opposed to alternative ditch designs.
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water channels. Concurrently, the two stage drainage ditch requires little to no maintenance due to it being a natural geomorphological management strategy that does not upset the equilibrium that a conventional strategy such as
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of land may already be currently used for other purposes or contains infrastructure and subsurface gas or sewer lines. Thus, the larger the channel is, the more soil, and thus, increased funds required to move the vegetation.
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which contains very little sediment so this flow picks up sediment once inside the ditch with minimal natural bench formation. Thus, for reasons of sedimentation and cost-saving in the form of land excavation and
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the landowner whom is implementing the two stage drainage ditch must do a cost-benefit analysis how the necessitation of the management system and the benefits of the project outweigh the associated costs.
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However, sustainable ditch design implementation, for example, a properly created two stage drainage ditch can alleviate such issues in a self-maintaining manner with minimal impact to the natural
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view that once such ditches are channelised and constructed, attempting to return the channels to their natural fluvial processes and meandering nature results in exacerbated erosion and
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would cause. Furthermore, much of the vegetation, except for the land needed to implement the adjacent grass benches (see disadvantage analysis below) and the natural shape and
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The optimal region to establish a two stage drainage ditch is where there are benches already naturally forming for binary reasons. Firstly, there is a supply of fine
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Evidently, referring to the diagram on the left, the existent channel needs to be extended by an additional 13 ft of land to create the floodplains (benches)
32:. Drainage ditches are typically formed around low-lying areas, roadsides or fields proximate to a water body or created to channel water from a more distant
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are formed within the land of the watershed of the water system, shown in the diagram to the right. By implementing benches either side of the
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of existing channels with minimal maintenance whilst allowing existent activities on the land proximate to the water body to continue such as
393:. The Nature Conservancy's investigation into the Minnesota region affirmed the above limitations of traditional drainage management above,
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In turn, the reduced level of contaminants (particularly from over-fertilised land) namely, nitrogen and phosphorus reduces the level of
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of the water channel remains largely unaltered during the formation of the two stage drainage ditch, thus, protecting the system's
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season and become a perpetuating financial burden to maintain if proactive drainage management systems are not properly exercised.
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Traditional drainage ditches and systems such as the 'Conventional Ditch' to the right have been beset by issues of perpetuating
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by improving the interaction of sediment/soil and water on the adjacent benches above the water body that function similar to
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that hampers soil quality and erosion and subsequent sedimentation into the water channel. The result of this is improved
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In acknowledgement of such environmental issues, the primary purpose of the two stage drainage ditch is to more effectively
371:, it is more beneficial to impose a two stage drainage ditch in a location where benches are already naturally forming.
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compared other ditch designs. Hence, the two stage ditch design will less likely fill up over time, resulting in a
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s, the two stage drainage ditch is better equipped in managing the speed and filtration of nutrient flow and other
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Comparison of land requirements for the
Existing Channel with the introduction of the Two Stage Drainage Ditch
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291:"Over a mile long reach adds up to over 1.5 acre of land needed for the two stage drainage ditch design".
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taking place in the water. The limited level of eutrophication within the water decreases the level of
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from the surrounding land into the water body, thus, resolving such environmental issues (see below).
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and substantially reduces ongoing maintenance costs, contrary to other drainage management systems.
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equilibrium of the wider ecosystem of the particular water body. Converse to traditional drainage
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proximate to the water body. Consequently, these issues exacerbate until the water channel becomes
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and instability problems caused by an inability of the existing channel to manage large volumes of
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feet two stage drainage ditch known as the 'Adams Birr' was implemented (see
Figures to right).
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beginning to take place, as the process of eutrophication in the water channel began to slow.
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drainage ditch create an inset channel that is largely self-flushing and has a more effective
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Further, the two stage drainage ditch approach also improves water quality through nutrient
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of data would further demonstrate the positive impact the two stage drainage ditch has on
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Photograph of a Two Stage
Drainage Ditch as part of the Indiana Watershed Initiative
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Inadequate drainage ditches and water management systems accelerate processes of
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during peak flows. Consequently, this erosion of the surrounding land caused by
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inset channel be 3-5 times the inset channel width that will form over time".
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in aquatic life and hampering the agricultural functionality of the ditches.
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Reduced
Flooding, Soil Saturation, Erosion & Improved Growing Conditions
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intake, measured against the total daily precipitation intake. A longer
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that create anoxic conditions in the water system. This elicits in a
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drainage performance and thus, growing conditions in the root zone
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Biske, Richard (September 30, 2010). "2-Stage
Drainage Ditch".
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Cross
Sectional Diagram of Adams Birr implemented in Minnesota
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Advantages and Disadvantages of the Two Stage Drainage Ditch
40:. The two stage drainage ditch is classified as a 'surface'
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Cross Sectional Diagram of a 'Conventional' Drainage Ditch
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Higher Upfront Cost than Alternative Management Strategies
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of the channel, thereby improving the water stability and
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Cross Sectional Diagram of a Two Stage Drainage Ditch
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elicits in issues of deteriorating water quality and
586:"Considerations for Implementing Two Stage Channels"
115:, bank and channel widening, and the degradation of
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555:Laboratory of Water and Drinking Water Research
551:"Effects of eutrophication in drainage ditches"
385:ditch lines exist along agricultural fields in
142:Benefits that resolve such Environmental Issues
28:is a depression in the land created to channel
344:Scaled Diagram of the Two Stage Drainage Ditch
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624:Agricultural Ditches - Ohio State University
593:Agricultural Ditches - Ohio State University
549:Janse &Van Puijenbroek (27 March 1988).
522:"Hydrological Restoration (Two Stage Ditch)"
495:"Two-Stage Channels | Agricultural Drainage"
179:Ecosystem Response - Reduced Eutrophication
123:and require extensive, costly maintenance.
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413:The Solution: Two Stage Drainage Ditch
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246:the watershed, and thus, less
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567:10.1016/S0269-7491(98)80082-1
466:Indiana watershed initiative
320:sediment transport capacity
283:Vegetation and Acreage Loss
42:sustainable drainage system
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617:"Building Better Ditches"
36:for the purpose of plant
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72:The Environmental Issues
391:Upper Mississippi River
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78:water contamination
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165:entrenchment
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136:contaminants
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34:water source
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561:: 547–552.
189:floodplains
117:arable land
46:floodplains
24:A drainage
504:2019-05-12
471:2019-05-12
449:References
252:subsurface
227:Advantages
160:irrigation
121:impassable
50:water body
38:irrigation
387:Minnesota
672:Drainage
666:Category
359:sediment
208:duckweed
193:wetlands
428:nitrate
297:acreage
173:ecology
169:meander
156:farming
101:erosion
86:drought
84:during
629:13 May
598:13 May
534:12 May
132:ditche
620:(PDF)
589:(PDF)
525:(PDF)
295:This
82:soils
30:water
26:ditch
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Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
