FERC - ENVIRONMENTAL STUDIES & DAM REMOVAL

Coosa River Bypass HDSS Survey 2021, AL

Coosa River Bypass HDSS Survey 2021, AL

Trutta utilized the High Definition Stream Survey (HDSS) in 2021 to evaluate a 12-mile section of the Coosa River to support Alabama Power Company’s FERC relicensing requirements for hydropower operations. We used longitudinal HDSS and cross-sectional data collection to analyze stream features. HDSS StreamView videos offered a baseline for river conditions, aiding in the easy identification of problematic areas. A comparison with Trutta’s previous surveys from 2014 and 2018 revealed positive trends, including improvements in bank condition, water depth, and channel substrate in response to initiation of environmental flows.

Contour Generation to Support Calculation of Exposed Snail Habitat: Coosa River, Alabama

For large dam operators, assessing the impacts of management actions on all of the competing uses for water can be a complex task. For the Alabama Power Company (APC), understanding the impact of a reservoir drawdown on potential habitat of endangered mussel species was one such problem. Bathymetry data was collected utilizing a sonar-based kayak-mounted depth profile system integrated with RTK-GPS to calculate surface areas exposed by reservoir drawdowns for defined contour intervals in the 6-mile Coosa River reach. Collected hydrographic data and overbank elevations from the National Elevation Dataset were imported into ArcGIS and merged into a unified geodatabase. Channel elevations were characterized in areas not represented in the survey by importing the data into HEC-RAS and interpolating missing cross-sections. The cross-sectional data was then exported into HEC-RAS and interpolated cross-sections were modeled at 10 m intervals. Interpolated cross-sections were incorporated with the survey data in an elevation geodatabase, and utilizing geospatial kriging techniques, an elevation surface was generated. This surface was utilized to generate contours for specific elevation ranges to support calculation of endangered snail habitat.

High-Definition Stream Survey of the Caney Fork River, TN

Cold water releases from the Center Hill Dam support a high-quality trout fishery in the lower portion of the Caney Fork River, TN. The trout fishery and recreational paddling opportunities (kayaks and canoes) draw people from all over the region and greatly benefit the local economy. The US Army Corps of Engineers (USACE) manages the flow releases from Center Hill Dam to support power production, flood control, and the trout fishery. The USACE plans to upgrade its generation capacity at Center Hill Dam, and as a result, will change the current amount and duration of the generation flows coming out of the dam. The Cumberland Chapter of TU, Tennessee Wildlife Resources Agency (TWRA), and Tennessee Department of Environment and Conservation (TDEC) are concerned about the potential negative effects of the flow changes and are interested in ways to improve water quality, trout habitat and fishing success for anglers. We used the HDSS approach to gather continuous, geo-referenced data on 27 miles of the Caney Fork River corridor from the Center Hill Dam downstream to the confluence with the Cumberland River. We captured data on both river banks and depth, water quality, habitat type and bottom characteristics of the river channel. Concurrent to our HDSS data collection, TWRA conducted their electrofishing trout sampling and we outfitted their sampling boat with GPS and video to document the exact locations of fish captures during the survey. The HDSS data documented habitat availability while the TWRA data documented trout habitat use. The information was then used to determine the location and extent of trout habitat, areas susceptible to streambank erosion, areas suitable for instream habitat enhancement, and areas most suitable for wade or boat fishing. The results provided TU, TWRA and TDEC with complete documentation of river corridor conditions, information on the trout population, prioritized locations for trout enhancement projects, and fishing maps to improve angler success. This project highlights the strength of the HDSS approach to efficiently gather a wide range of river corridor information to support both management applications and recreational angler needs. Along with the report, the field data and results from the Caney Fork River HDSS project were provided in digital format.

Tallapoosa River High Definition Stream Survey: Tallapoosa River, AL

The High Definition Stream Survey (HDSS) was effectively employed to gather comprehensive data on the Tallapoosa River, covering a 44-mile stretch below Harris Dam. The survey included information on stream bottom, water depth, riverbank conditions and channel cross-section bathymetry, offering valuable insights for river management, restoration, and habitat improvement projects. Specifically, the Alabama Power Company was able to use the data as part of a relicensing study for the R.L. Harris Hydroelectric Project. The recorded HDSS video serves as a baseline for monitoring changes over time. It also enables easy comparison and identification of problem areas, aiding decision-makers who may not have the means to physically inspect the river.

Dam Removal Monitoring: Big Canoe Creek, Alabama

Goodwin’s Mill Dam was removed from the Big Canoe Creek in order to eliminate a barrier to fish and mussel movement. Given the high cost of dam removal and subsequent stream restoration, it is important to monitor stream conditions to assure that improved habitat conditions have resulted from the dam removal actions. One problem when attempting to document changes resulting from dam removal using traditional transect surveys is that the changes to the stream can occur over a broad area up and downstream from the removal site. This makes determining the placement and number of transects extremely subjective. More transects over a wider area will likely document changes more effectively, but this come with a high cost to the annual monitoring budget. To solve this problem, we used the High Definition Stream Survey method. In only 2 1/2 hours, this technique allowed us to quickly collect 1-meter resolution data of both stream banks and the stream bottom for over 3 miles of stream centered on the dam site. The geovideo surveying method was used to delineate pool-riffle-run sequencing, substrate type and embeddedness, depth, bank full depth, bank angle and height, bank erosion potential, and riparian diversity. This information will help show trends in sediment movement, stream geometry, and habitat conditions by comparing the results of annual surveys and to document (hopefully) improving conditions resulting from the dam removal effort.

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