||Determining Design Criteria for Land and Flow Characteristics that Produce Non-Erosive Sheet Flow
Lewis N. Lloyd
If a design engineer can show that a project site will produce sheet flow, then it significantly reduces the cost and complexity of stormwater control measures that must be built on site. The problem is that criteria for determining if sheet flow will cause adverse impacts to down slope properties, i.e. erosion and flooding, are not well defined in the VDOT Drainage Manual, resulting in uncertainty for projects claiming to implement sheet flow as a stormwater control measure. Research is needed to establish appropriate, well-defined, and implementable standards for knowing when it is appropriate to assume a site will result in sheet flow given a set of simple and easily established site conditions including; discharge rate, slope, land use, and soil type. This research can inform changes to guidance provided in the VDOT Drainage Manual and, ultimately, influence how future VDOT projects using sheet flow are implemented by the agency.