This post is first in a series about innovation at UDOT. Many in the transportation community and the general public are familiar with UDOT’s method of building bridges off-site and then moving them into place. Other important innovations garner less attention. Check back for future posts on other innovations at UDOT.
When roads cross streams, culverts need to accommodate fish.
Research on how successfully fish pass through culverts has resulted knowledge about how to accommodate small non-game native Utah species.
Connectivity between waterways is important to many fish species in Utah, explains Drew Cushing, Utah Department of Wild Life Resources Sport Fish Coordinator. Culverts can increase stream velocity and prevent fish from spawning, finding food, and escaping temperature extremes from season to season.
The wildlife and transportation community has had a good understanding of how to make culverts passable to large fish. However, less has been known about how to accommodate small fish. UDOT sponsored research in two phases has resulted in a better understanding of how to make sure small native Utah fish can move freely so important fish populations can be maintained.
The first phase of research was conducted by Lindsay D. Esplin, EIT and Dr. Rollin Hotchkiss of BYU. In a lab setting, Esplin and Hotchkiss tested how different types of substrate affected fish passage rates. Their findings indicate that placing small rocks, approximately the size of the fish, reduced stream velocity and created places for the fish to pause before continuing to swim. During the experiment, fish were observed stopping, foraging and swimming up and down the rock-lined artificial water way inside the lab.
The second phase of research was conducted in the field near Salina, Utah. Researchers Suzanne Monk, EIT and Hotchkiss conducted fish passage tests by measuring fish population densities at three sites along Salina Creek. All sites had different characteristics including a rock lined culvert, a bare box culvert and a stream section without a culvert. The rock-lined culvert and the stream both contained rocks that were close to the same size as the small fish.
While small fish were able pass through all locations, fish passed through the rock lined culvert more successfully than the bare box culvert. While more research is needed, the field test seemed to clearly confirm that placing small rocks approximately the size of fish inside a culvert allows the fish to pass successfully.
The results of the lab and field test will inform the way UDOT builds new and retrofits in-use culverts.
Next week: Pre-cast panels help speed-up freeway repair.