Connecting flood management and salmon habitat improvement


[Music playing] Faith: We’re here at Schweitzer Natural Area along Johnson Creek in a rehabilitated area that was done just a few years ago. You can still see some of little trees in front of us that were planted not so long ago and things. Janine, this site, we have a pretty wide flood plain area here. What were some of the things about flood control and habitat that were important for this site, as well as in the Portland area? Janine: Well, Johnson Creek floods very regularly and it’s been a problem in Portland for a number of years. And, we also have concerns about the salmon and returning salmon. So, this was a really good opportunity. We had enough space where we could create both aquatic habitat and have some flood management. So, we were able to open this area up, allow more flooding, some backwater areas that provide habitat, and really being able to achieve both goals of providing flood management, and increasing and improving aquatic habitat. Faith: So, instead of having them be separate, it really was the connection of the two that make this even that much more important and more beneficial in the long run too? Janine: Absolutely. Faith: Gardner, you know, what are some of the specifics in the design of this site and it’s got a lot of innovative techniques that were used here? Gardner: Yeah, well, this is, you know as are the challenges of designing for urban areas, we have to consider a whole new suite of things that affect urban channels. It’s very different than working in a natural system. So, one of those is the altered hydrology, we have higher peak flows and more frequent peak flows than we had historically. So, as Janine said, trying to control for that increased flooding, nuisance flooding that would occur here, the entire floodplain here was excavated down about five or six feet. And, every cubic yard of material that was put out of here is an extra cubic yard of flood storage the City has to decrease downstream flooding. We also looked at the new hydrology and the potential future hydrology as a means to design the channel. And so, the channel geometry, whether it be the cross section or the pattern in the landscape, was designed based on the current hydrology and the potential future hydrology. Faith: So, it had enough space in here to also get in some side channel habitat, which is very important for different species, not only the fish, but also other species that like standing water during certain time periods, or to get that refuge factor out too in this again, this channel that’s taking flows that it wouldn’t have had before. Higher than what it would’ve had prior to urbanization. Gardner: Exactly. Faith: The other interesting thing here, we don’t see any rock lined banks on the outside of the bends, which usually take a lot of the erosive flows. So, how are you able to avoid using that in this case? Gardner: Yeah, we didn’t want to end up with a channel like we had before that has the armored banks, that don’t have any ability for lateral adjustment. So, in this case, we used large logs to provide bank stability as well as habitat for fish. We also used what’s called an encapsulated soil lift, which is a fabric, piece of fabric that’s filled with soil to construct the banks. And so, those banks will provide interim stability until the vegetation that’s planted here grows up and can provide that long-term stability; and eventually, allow the stream to move around as streams do naturally. Faith: So, even though we have the Johnson Creek that still gets a lot of flooding, we’re able to include some of the more natural features that are beneficial both to the in-stream and the floodplain species. [Music playing]

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