Improving Design Guidance for In-Stream Structures Used in Stream Restoration

Vane-type in-stream structures and step pool storm conveyance (SPSC) are more ecologically friendly alternatives to traditional stream channel stabilization and stormwater conveyance techniques. Vane-type structures have been widely accepted as elements of stream restoration projects and are regularly implemented in streams throughout the United States. However, these structures commonly experience partial or total failures of function or stability, often due either to improper installation or misapplication. This study undertook a thorough review of the available design guidance for the single-arm vane, j-hook vane, cross vane, and w-weir, which revealed that the existing guidance is composed of non-standardized recommendations largely based on practitioner experience and rules of thumb. Existing guidance was synthesized with current structure research and practitioner surveys to create factsheets for each of the four structures and the SPSC, with the intent of improving structure application and offering concise general guidance. This study also endeavored to improve the design of the SPSC by determining the most accurate of several common prediction methods for Manning's roughness coefficient n, used in SPSC design velocity calculations. This was done by using Rhodamine WT dye tracer experiments to determine n values during storm flows in two SPSC structures in Annapolis, MD, which were then compared to predicted n values. Values of Manning's n determined in the SPSCs at low flows (0.28-12) often exceeded the predicted n values (-0.17-3.9) by several orders of magnitude. Though the applicability of these results is limited, an increase in design n to 0.1-0.2 is still recommended.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Biological Systems Engineering

Department dc:contributor.department

Biological Systems Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2019

Author dc:creator

• Hickman, Elizabeth L.

Chair dc:contributor.committeechair

• Wynn-Thompson, Theresa

Committee members dc:contributor.committeemember

• Hession, W. Cully
• Strom, Kyle Brent

• in-stream structure
• rock vane
• rock weir
• step pool storm conveyance (SPSC)
• stream restoration

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

vt_gsexam:18999

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/88534