Wednesday, July 13, 2016
Fish Passage is More Than Just Dams
We all drive across streams and rivers every day without much thought. Sometimes we look over the edge of a bridge to see the river running underneath. Sometimes, we don’t even know that a stream is running by underneath the road. Smaller streams tend to run through culverts, either round pipes or square cement boxes under the road. Unlike bridges, these culverts often constrict the stream and cause it to flow through a very narrow opening.
Narrow culverts and pipes do not make good passage for the fish and other wildlife that need to use streams and rivers as corridors. Fish need to move up and down stream to mate, eat and find refuge. Turtles, frogs and salamanders do too, as do mammals like river otters and raccoons. When they are forced to go up and over the road, small wildlife can be killed by traffic.
When the openings under roads are too narrow, flooding can happen and roads can wash out during storms. Many times road repairs are made and the culverts are replaced at the same size when they should in fact be bigger. Climate change is also causing larger storm events and more rain that swells streams and causes road flooding. Public works departments need to be aware of undersized culverts where they are causing harm to wildlife and public safety.
This summer, Save The Bay habitat interns are assisting staff with evaluating culverts and bridges in the Palmer and Kickemuit Rivers as part of our larger effort to study fish passage and habitat quality in these Upper Bay watersheds. We are on the lookout for areas where fish could get trapped or not be able to swim through a culvert. We are also helping to train new surveyors from the Rhode Island Department of Transportation and local conservation commissions.
So far, we have found a mix of different culverts from plastic pipes to cement boxes and stone bridges. None of these structures completely meet the standard of having dry passage or for the crossing to span both the stream and the river banks. In our car centered culture, it is sometimes a good learning experience to think of yourself as a fish or a turtle and to figure out how you would navigate your world with a human imprint.