Using Organic Matter to Increase Stability of Simulated Streambeds in Stream Simulation Culverts
Abstract
Fish barriers in the Pacific Northwest have led to large reductions in fish population. The stream simulation design process was developed by the State of Washington in 1999 to address the widespread barriers caused by road crossings by creating more natural streambeds inside crossings. This is challenging because the designs must meet performance criteria and balance ecosystem factors (i.e. sediment transport, low-flow channels) that promote fish passage. Each design is so it is advantageous to maximize the lifespan of the simulated streambed to prevent flattening or wash out, but little guidance exists in this area. Many options for increasing the resilience of simulated streambeds exist and this research investigated the use of organic materials with simulated streambeds in a laboratory flume. The specific channel features evaluated were 1.) deformable grade controls, and 2.) meandering bars with logs. Both features involved different diameters, lengths, and distribution of woody material placed at various angles relative to flow, and the latter added root wads between meandering bars. Streambeds were subjected to ten, twenty-five, and fifty-year flood frequency events and the change in streambed elevation was used to quantify channel stability. Streambed elevations were captured in a novel way using high-resolution (~1mm) EinScan-H, handheld 3D-scanner, providing millions of data points per trial. Twenty-six configurations were tested with variable amount, size, and length of wood material relative to a uniform streambed (no organic material). This research showed that deformable grade controls perpendicular to the flow are efficient channel stabilizers under a wide range of flow events, and that meander bars augmented with organic materials can also provide some stabilization. The results suggest that incorporating either, or both, of these features into simulated streambeds can increase the lifespan of designs and are particularly suited to maintaining a small low-flow channel for fish passage.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFMEP52C0775F