Cooks Creek Watershed Culvert Study – 2012

Funding: Trout Unlimited Embrace-A-Stream Grant, $4,250
Chapter Matching Funds: $3,781
Consultant: Princeton Hydro
Project Partner: Cooks Creek Watershed Association

In December, 2012 the chapter’s culvert survey of the Cooks Creek Watershed was completed. The survey was the first watershed-scale culvert survey to be done in Pennsylvania. With the information gathered by the survey the chapter can begin the process of reconnected those stream reaches in the watershed now blocked by culverts that impede fish passage.

Stream connectivity is important for trout in a number of ways: access to thermal refuge, spawning habitat, and eliminating genetic isolation of populations. However, poor design of culverts and bridges can negatively affect stream connectivity. Culverts can act as barriers to fish passage as follows: the culvert can be perched above the stream bed so fish have to jump large heights, high current velocities in culverts make it impossible for fish to move through, the water depth within the culvert can be too shallow, and they may not provide resting areas for fish that are migrating upstream.

To begin the survey process, project consultant Princeton Hydro utilized publicly available geographic data layers to identify approximately 100 potential road-stream crossings. (see adjacent map) Building from existing culvert assessment resources, the culvert survey protocol developed by the Vermont Agency of Natural Resources was adapted for use in the Cooks Creek watershed. Chapter members and Cooks Creek Watershed Association members were then trained by Princeton Hydro in how to survey culverts to identify those that are blocking fish passage. In the summer and fall of 2011 members of both organizations then surveyed 97 culverts throughout the watershed.

After obtaining the volunteers’ field data, which included data sheets and photos, Princeton Hydro reviewed the data and began the iterative process of demoting culverts that were not barriers to fish passage (e.g. were not perched and had adequate flow depth). Princeton Hydro identified approximately 20 stream crossing retrofit sites and conducted follow-up site visits to confirm volunteers’ findings, collect additional information, and identify any site constraints. The number of priority crossings was further pared down to eleven (11) crossings through subsequent prioritization based on:
1. public or private ownership of the road;
2. length of stream that would be reconnected;
3. presence of trout;
4. subwatershed size;
5. proximity to the main stem of Cooks Creek;
6. local geology;
7. local land cover; and,
8. past water quality monitoring.

Private ownership (i.e. a private driveway) was considered reason for lower priority because private landowners may not be supportive and public grants may be difficult to obtain for work on private property. The length of stream to be reconnected was measured as the distance to the next upstream and downstream barriers. Presence of trout was based on BCTU members’ local knowledge, volunteer observations and existing sampling records from Pennsylvania Fish and Boat Commission. Crossings with drainage areas that are less than 0.25 square miles were deemed lower priority because they are less likely to support trout due to inadequate perennial flow. As one of the implicit goals of the project was to reconnect currently isolated tributaries to Cooks Creek; first barriers off of the main stem were given higher priority than barriers farther removed from the mainstem with one exception: where native brook trout were present. Local drainages underlain by carbonate bedrock yield better water quality and more moderate water temperatures; as such, barriers in those drainages were given higher priority. Similarly, local drainages with greater forest land cover yield better water quality and more moderate water temperatures; barriers in those drainages were given higher priority. Finally, volunteers from BCTU and CCWA who conducted long-term water quality monitoring identified those barriers situated in subwatersheds with relatively higher water quality.

Of the 11 crossings that were identified as potentially appropriate for a retrofit effort, it became apparent that many potential target crossings were situated consecutively. As such, removing consecutive culverts created an opportunity to maximize the length of stream reconnected. As a basic means of comparison, the length of stream per barrier removed was calculated for each group of consecutive barriers, which helped identify a pair of crossings with the highest priority: sites 19 and 20. Narrative summaries and retrofit cost estimates for these culverts can be viewed HERE. Conceptual retrofit designs can be viewed HERE.

The final culverts identified as the best candidates for retrofit are both on the same tributary located in the area of the watershed with underlying limestone geology. (see adjacent map) If both culverts are retrofitted, 1.5 miles of high quality, cold water tributary would be reconnected to the mainstem of Cooks Creek. The chapter will now begin to investigate sources of funding to implement the retrofits.

Join Us/Membership | Support Us