Reframing the Ditch

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Virginia Tech

Reframing the Ditch explores the application of native canopy using green street tools as a method to move beyond minimums and improve biological diversity of stormwater conveyances in a way that is consistent with visual landscape preference theory. Small stream water quality impairment is an issue found in 83% of stream headwaters in the Eastern United States. The Clean Water Act (1972), which regulates pollutant discharge into U.S. surface waters, mandates that municipalities create an implementation plan to improve water quality of their impaired streams. Water quality impairment is often exacerbated when headwater streams flow through urban areas. Urban areas are concentrations of human activity and as such bring concentrations of impermeable surfaces and stormwater runoff. As development increases, dedicated space for stormwater changes. Natural flow patterns that interacted with stratified layers of native vegetation often become constrained to ditches and pipes with little or no vegetation within the conveyance corridor. Reframing the Ditch creates an approach to help municipalities improve water quality of headwater streams by addressing water quality in ditches before water reaches the stream.

The objective of urban conveyance systems is to move stormwater runoff into waterways as quickly as possible. When we design these conveyances to simply minimize stormwater interference, we ignore the potential contribution this land has for our public urban systems. This project looks for an intermediary between minimums and maximums. Maximums, also known as restoration, allows for messy, dynamic systems that are not hydrologically or visually appropriate in most urban environments.

This thesis reveals ditches as complex landscapes that require high preforming vegetation, which ultimately limits the number of native species suitable for such harsh environments. Additionally, the more impermeable an environment is and the farther a ditch is from the top of the watershed, the more stormwater runoff there is, and the more space is required to process water and improve water quality. Cost, lack of available vegetation and lack of space may limit the application of this design in most circumstances. However, there are appropriate landscapes where this design methodology can provide valuable insight for landscape implementation plans aimed at improving water quality, while also providing public space, enriching neighborhood aesthetics and highlighting the function of our urban drainage systems.

Water quality, green streets, landscape preference, biodiversity, native vegetation, stormwater conveyances, urban ditches, trees for stormwater management