Our Process
- Completed a review of technologies for hellbender habitats
- Analyzed five potential solutions with the use of the following decision matrix
- Decided on a design of a combination of boulder clusters and flagstone cover rocks
- Sized the structures to be stable during bankfull velocities
- Design the position and orientation of the structures to be resistant to sedimentation
potential Design solutions
Boot-shaped Nest Boxes
Hydrodynamic Nest Boxes
Boulder Clusters
Flagstone Cover Rocks
Design Decision
After evaluating the potential solutions against the criteria we decided to use a combination of Boulder Clusters and Flagstone Cover Rocks for our design.
habitat structure Sizing calculations
Rosgen Geomorphic Channel Design Figure 11-43
The diameter of each boulder was calculated using the Rosgen equation and graph shown above. This equation calculates the minimum diameter (x) in meters that each boulder can have to withstand the bankfull shear stress (y) in kilograms per square meter.
- The minimum diameter of each boulder was calculated to be 1.185 m or 3.887 ft using a shear stress of 24.266 kg/m2.
Flagstone Rock Sizing
The formula below from the National Engineering Handbook was used to calculate an equivalent weight for the flagstone rocks.
The equivalent weight of the flagstone rocks was calculated to be 3804.7 pounds, or nearly two tons.
- Each footer rock weighs approximately 495 pounds.
Economic ANalysis
Deliverables
- Provide a set of AutoCAD (Civil3D) drawings detailing our designed hellbender habitat structures in the stream
- Hope to oversee the proper installation of the structures at the site, but this depends on the timeline of the ongoing stream restoration project at the site