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Rock Brook Restoration Project
The Farmington Valley and Northwest Chapters have joined forces in an effort to improve and restore prime brook trout habitat in Harwinton CT. Rock Brook is a major tributary to Lead Mine Brook and in turn the Naugautuck River and has been identified to hold native brook trout. Under the 'EBTJV' initiative, it is TUs' hope is that this habitat improvement project will help to keep this watershed viable to brook trout and improve the brook trout fishery in both of the downstream waters.
Below is the project description, watch in the coming months for an announcement asking for work crews
Re: Rock Brook Habitat Evaluation and Enhancement Habitat Status Rock Brook, Harwinton, begins at the outflow of the Cook’s Dam watershed just north of CT RT 4. The Department of Environmental Protection currently classifies this as Class A/AA water meaning it is Class A that is considered as a potential future drinking water source. Rock Brook in the area of Plymouth Road (+-1.4 miles from Cook’s Dam) flows within a channel averaging 12 feet in top of bank width and with and average depth of less than one foot. The moderate grade channel produces surface flow predominated by riffle-run. Substrate is composed of large boulder, small boulder, cobble with some course sand and sand-silt fines. The riparian in this area is comprised of mostly second growth woodland forest with a shrub understory. The width of the woody riparian area varies from several hundred feet to less than 10 feet. Riparian vegetation provides important stream bank stability and organic material to the brook. Rock Brook thru the property at 97 Plymouth Road contains two man made in-stream structures. One is a “rock wall” built the width of the streambed. This wall serves to obstruct fish emigration in this area of the brook, has caused stream bank erosion and has resulted in a buildup of sandy deposits immediately upstream. Upstream of the first wall there is a second wall, visually less obvious, consisting of mostly large boulders. This wall barrier has accumulated some large logs which have obstructed flows during peek rain and snow melt events causing the brook to divert thru adjacent woodlands and causing other streambank erosions. Resource Status Numerous surveys of Rock Brook fisheries resource have been conducted by the Connecticut Department of Environmental Protection Fisheries Division since the late 1980’s. Rock Brook in the area of Plymouth Road has been found to support brook trout (Salvelinus fontilalis), brown trout (Salmo trutta), blacknose dace (Rhinichthys atratulus) creek chub (Semotilus atromaculatus), longnose dace (Rhinichthys cataratae), white sucker (Catostomus commersoni), tessellated darter (Etheostoma olmstedi) and common shiner (Notropis cornutus). The trout and dace are commonly associated with Connecticut cold water woodland streams. Historically the most prevalent fish found in terms of numbers has been the blacknose dace. Sporadically warm water fish species such as yellow perch (Perca flavescens) have also been found in Rock Brook. Such occurrences are most likely the result of downstream emigration from warm water sources of Cook’s dam and Bull Pond rather than indicative of any self sustaining in-stream population. Brook trout is the Town of Harwinton’s only native trout specie. Populations of brook trout in Connecticut streams have been greatly reduced in over 70% of its watersheds with remaining populations becoming fragmented and isolated to watershed headwaters. In 15% of Connecticut streams brook trout have extirpated. Rock Brook is typical in showing substantially reduced populations of native trout. Currently there are some native wild brook trout remaining in Rock Brook. Enhancement Needs Although Rock Brook around Plymouth Road contains physical habitat conducive for mostly fry and yearling aged trout as well as minnow species, habitat is lacking for adult aged fish and specifically adult aged trout. Rock obstructions are causing a variety of problems harmful to the brook and harmful to trout. Elimination of obstructions, development of pool habitat and installation of instream cover is needed. Enhancemet Recommendations (1) Vortex rock weir. This structure type provides instream cover for fish, creates a self-scouring plunge pool immediately downstream and provides upstream grade control. The structure is suited for brooks and streams where rock and boulder material is available. Vortex rock weirs (diagramed in attachment B) are formed with large rocks placed in an upstream horse-shoe shape. Vortices are created by leaving gaps between the rocks; the gaps should be slightly larger than the largest bedload particle. The central point of the structure should be lower in elevation than the sides to allow a funneling of low stream flow and to allow for upstream fish migration. Weirs should be limited to intervals of 5 to 7 stream widths apart. Two rock weirs are recommended near the sites of the existing rock wall obstructions. (2) Boulder and rock placement. The primary goal of boulder placement is to provide overhead and lateral protective cover for fish (see Attachment C). Trout require such cover for resting and also feeding lies. Boulders also cause a breakup of uniform water currents and therefore dislodge and relocate fine sediments. The relocation of sediment fines improves the substrate suitability for aquatic insect life. Boulders can be placed individually or in clusters. Studies indicate clusters of three boulders provide better habitat cover than single boulders. Whether placed singly or in clusters, the boulders should be placed in or near the brook’s low flow channel (thalweg). Boulders should not obstruct more than 20% of the brook’s width at any given point. Large boulders of 3 to 4 feet in diameter, of angular shape, if available, are ideal for boulder placements. Even smaller boulders will provide some functionality. All boulders should be set in the stream be at a depth of 9 to 12 inches. There is no “rule-of –thumb” approach to selecting the number of boulders per length of stream. Machinery access for placement and availability of suitable material are the factors limiting the number of boulders. Boulder placements would be helpful if placed in the area between the current rock wall obstructions (and between the two proposed rock weirs). (3) Log stream banks. Dead tree trunks within a stream or near the streambed are used to stabilize visibly eroded areas of the historical streambed. Logs are usually manually placed using peaveys lengthwise along the streambed, bored with 2 , 3 or more holes and pinned with 4 to 5 foot lengths of rebar pipe pounded into the substrate. If there is sand or silt deposits in the area that material is scooped up and placed on the streambank side of the log to accelerate the building of new more permanent streambank that will support new vegetation growth. There are at least 2 logs in the upper rock wall obstruction that can be used for this purpose.
Primary fish passage obstructions
Click on the above photos to enlarge
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