by Ben Day, senior environmental specialist
The Tennessee Department of Environment and Conservation, jointly with the Nashville and Memphis U.S. Army Corps of Engineers districts, approved the use of the Stream Quantification Tool for the assessment of the quality of streams in the state. The SQT assesses and ranks various metrics within five different stream function categories to quantify the difference between degraded and restored stream conditions.
For example, two metrics used to assess the functional category of “Geomorphology,” or the shape of a stream channel, are “pool spacing ratio” and “pool depth ratio.” In this case, we would test the diversity of the stream bed channel by measuring the length and depth of pools of water relative to the measurement of other features in the stream bed.
Typically, to be utilized by environmental consultants proficient in natural channel design techniques, the TN SQT will assess the existing conditions of streams proposed to be impacted by development. It will also establish the “functional lift,” or resource improvement, associated with stream restoration projects used as compensatory mitigation for aquatic resource losses associated with impacts permitted under TDEC’s Aquatic Resources Alteration Permit program. The intent in development and adoption of the TN SQT was to provide an assessment methodology that will provide clear expectations to the public and a consistent and more efficient review that is rooted in sound science, is compliant with all applicable laws, and can provide accurate data for consistent regulatory review across the state.
The SQT was originally developed for use in North Carolina, and other states throughout the country have now adopted use of the tool. In order to make the SQT applicable to Tennessee, TDEC is in the process of finalizing a statewide assessment of reference stream segments that will provide representative conditions for high function streams within each region of the state. This data will be used to provide a target functional level for restoration projects. Typically, a project will not be able to provide significant lift (improvement) to each metric and the user will need to focus on site specific, reasonably achievable restoration metrics. The tool can help to guide more effective restoration, as it will identify areas where restoration will provide the most benefit.
TDEC has published a series of user manuals, spreadsheets and reference information that have been developed to assist the public and regulatory agencies in assessing streams. These tools, as well as more detail regarding the approval and implementation of the program, are available on TDEC’s website. For a deeper dive into the background and measurement methods of the tool, check out TDEC’s data collection and analysis manual and its spreadsheet user manual. If you think your project may require assessments of the site’s stream conditions, contact us at Tioga today.