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Two Stage Drainage Ditch
A drainage ditch is a depression in the land created to channel water. 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 water source for the purpose of plant irrigation. The two stage drainage ditch is classified as a 'surface' sustainable drainage system, contrary to a sub-surface system. The two stage drainage ditch is a modification of the land whereby grass benches which serve as floodplains 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 water body, the energy of surface runoff dissipates, sustaining fluvial processes of the channel, thereby improving the water stability and water quality of existing channel.

The Environmental Issues
Inadequate drainage ditches and water management systems accelerate processes of water contamination, excessively desiccate soils during drought season and become a perpetuating financial burden to maintain if proactive drainage management systems are not properly exercised.

Traditional drainage ditches and systems such as the 'Conventional Ditch' to the right have been beset by issues of perpetuating erosion and instability problems caused by an inability of the existing channel to manage large volumes of water discharge during peak flows. Consequently, this erosion of the surrounding land caused by surface runoff elicits in issues of deteriorating water quality and sedimentation, bank and channel widening, and the degradation of arable land proximate to the water body. Consequently, these issues exacerbate until the water channel becomes impassable and require extensive, costly maintenance. 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 geomorphological equilibrium of the wider ecosystem of the particular water body. Converse to traditional drainage ditche s, the two stage drainage ditch is better equipped in managing the speed and filtration of nutrient flow and other contaminants from the surrounding land into the water body, thus, resolving such environmental issues (see below).

Benefits that resolve such Environmental Issues
In acknowledgement of such environmental issues, the primary purpose of the two stage drainage ditch is to more effectively transport sediment and other contaminants using natural fluvial processes of existing channels with minimal maintenance whilst allowing existent activities on the land proximate to the water body to continue such as farming, irrigation 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 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 entrenchment 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 meander of the water channel remains largely unaltered during the formation of the two stage drainage ditch, thus, protecting the system's ecology and substantially reduces ongoing maintenance costs, contrary to other drainage management systems.

Ecosystem Response - Reduced Eutrophication
Further, the two stage drainage ditch approach also improves water quality through nutrient assimilation by improving the interaction of sediment/soil and water on the adjacent benches above the water body that function similar to floodplains or wetlands. Consequently, sediment and other contaminants are lodged along these linear benches, limiting the leakage effect of such sediment from the surrounding watershed into the water channel itself.

In turn, the reduced level of contaminants (particularly from over-fertilised land) namely, nitrogen and phosphorus reduces the level of eutrophication taking place in the water. The limited level of eutrophication within the water decreases the level of algal blooms and growth of duckweed that create anoxic conditions in the water system. This elicits in a loss of biodiversity in aquatic life and hampering the agricultural functionality of the ditches.