Urban Hydrology: Restoration and Monitoring of Johnson Creek in Portland, Oregon

[Intro Music: Scott Pemberton Trio, Little Bobby Cobalt]

[Segment #1: Introduction to Johnson Creek]

[Steven Sobieszczyk] Hello and welcome. This is the USGS Oregon Science Podcast for Tuesday, December 1, 2009. I’m Steven Sobieszczyk.

Today’s episode will have a much more local flair than previous podcasts. Our focus this month is the urban hydrology of Portland. Specifically, we’re examining the restoration efforts and streamflow monitoring in Johnson Creek watershed in Portland, Oregon. For those non-Portland area listeners, Johnson Creek is a tributary to the Willamette River in northwest Oregon. The USGS has a very long history with Johnson Creek, as we’ve had a presence in the watershed since as far back as 1941. With headwaters that start near the city of Gresham, Johnson Creek drains about 54 square miles as it flows westerly across the southeast Portland metropolitan area. If you live in the southeast, you’ve probably seen signs calling for the protection of the Johnson Creek watershed in the Woodstock and East Moreland neighborhoods. The stream, itself, is about 26 miles long and flows through a diverse landscape of varied development, including everything from forested, agricultural, rural, and highly developed urban lands.

Streamflow in the watershed is controlled by the underlying geology, landscape variability, and of course, human (or anthropogenic) activities. Modification of the landscape in the Johnson Creek watershed has altered parts of the watershed’s natural hydrology. However, even with over 60 years of streamflow monitoring, trends in streamflow commonly associated with urbanization are not present. This lack of change is likely due to the fact that most of the groundwork for development was present back when the monitoring started back in the 1940s.

Research for this episode coincides with a recent publication USGS Scientific Investigations Report, SIR 2009-5123: Hydrology of the Johnson Creek Basin, Oregon, by Karl Lee and Daniel Snyder. The investigation was part of a cooperative research project between the USGS and the cities of Portland, Gresham, and Milwaukie; the Clackamas County’s Water Environment Services; and Multnomah County. If you’re interested in reading the whole report, check out our links online. If you’d like a brief summary, stick around because in our next segment we’ll speak with lead author and USGS scientist Karl Lee.

If you live in the southeast Portland metropolitan area, and are listening, and have interest in getting involved in the monitoring or restoration efforts, check out the Johnson Creek Watershed Council website. They have some volunteer opportunities available. After all, understanding the hydrology of the basin involves more than just proper management of flooding and runoff, it includes riparian restoration efforts and continuous monitoring of streamflow and water quality. These are all important factors for maintaining the ecological health and sustainability of the stream.

Coming up after the break we’ll sit down with USGS scientist Karl Lee and discuss in more detail the specifics about the hydrology of Johnson Creek. Stick around.

[Midtro Music #1: Scott Pemberton Trio, Little Bobby Cobalt] 

[Segment #2: Interview with Karl Lee, USGS Hydrologist]

[Steven Sobieszczyk] Welcome back. As we alluded to earlier, for today’s episode we’re looking at urban stream hydrology. Specifically, we’re interested in the hydrology of the Johnson Creek watershed, here in southeast Portland (and the neighboring metropolitan area). For those of you who’ve ever jogged the Springwater Corridor or cruised SE 82^nd, you’ve no doubt crossed Johnson Creek. Likewise, if like me, you watch the nightly news during winter storms, you’ve probably seen coverage of flooding on Johnson Creek. To help walk us through why Johnson Creek seems to flood so often, what type of work is being done to restore its natural environment, and why the health of this creek is so important to us in Portland, I’m joined by USGS hydrologist Karl Lee. Thanks for joining me Karl. [Affirmative response] Before we get to the flood history of Johnson Creek, can you first describe the general hydrology of the basin?

[Karl Lee] Steve, we can divide basin up into 3 pieces. The part most of us see is the urban piece, that part in the cities of Gresham, Portland, and Milwaukie. And what many don't see, and what’s really important in the Johnson Creek Basin and that affects all us throughout the basin is the upland area - that hilly area to the south of the creek, and the agricultural areas out east towards Damascus. What’s important about the upland part is the slopes are steeper, the soils erode easily, and there are a lot of roads and ditches the direct water to the creek. Much of that relatively flat part of the basin (the urban part) has very porous soils, and a lot of water that hits these areas just soaks in and doesn't runoff into the creek. That's the scene in the winter time.

During the summer, Johnson Creek flows get real low, except for the lower several miles except from I-205 west towards the mouth of the creek where a lot of springs flow into Johnson Creek. The biggest ones of these have names: Crystal Springs and Errol Spring.

[Steven Sobieszczyk] How often dos Johnson Creek actually flood? It seems like every winter I see some news coverage of streets and homes flooded along Johnson Creek, itself?

[Karl Lee] I think Johnson Creek winds up in the news often because it is the largest creek in the Portland area, and at least part of the flow is in densely populated areas that are familiar to a lot of us.

What we call a flood depends a lot on where you sit. Yes, the river rises every year, some years more than others, some years higher than others…if homes, businesses, and roads are in the way of the rising creek, we have a problem. We've been measuring how high and how much water flows since the 1940's and we don’t see a trend toward higher annual peak flows. For Johnson Creek, what makes a flood happen is a lot of rain over a short period of time, and sometimes it’s accompanied by melting snow. The stream channel is only so big, can only handle so much water, and if the water is greater than that, it spills out onto the flat areas - like the area out by I-205.

[Steven Sobieszczyk] For urban areas like southeast Portland, where there is a lot of concrete and impervious surfaces, how is storm runoff normally managed?

[Karl Lee] In this urban area, we can do our best to manage runoff by mimicking the natural function of the creek. This means we keep the tree and plant cover in the upland area (that intercept rain that would otherwise shoot straight out to the creek). We provide, where we can for a meandering stream channel with logs and big rocks (this slows the flow, traps sediment, and again, lets water soak in). We provide for floodplain areas so when the water gets up and over the banks it has a place to go. In the areas away from the creek, we let the rain soak in, and in time (like the next week or the next month) the water will seep back slowly into the ground and wind up seeping back into the creek when we really need it. Some of the rainwater winds up in the sewer system, which isn't helpful for the creek, and can overtax treatment plants.

[Steven Sobieszczyk] While researching for this interview I kept seeing literature on restoration efforts in the basin. Can you describe some of these efforts, such as what’s been done and where?

[Karl Lee] Yes, there have been many many restoration projects in the Johnson Creek basin, from very small projects to the very large ones. Generally, the restoration projects are aimed at restoring the natural function to the creek, like I just talked about. For example, tree planting along tributaries captures rainwater and provides shade. Large-scale stream-channel reshaping, such as those you see out along the Springwater trail between Milwaukie and Portland, and again between Portland and Gresham, these are big projects that provide backwater areas, places for the stream to go during high flow. Over time, and with enough of these projects, we’re going to be slowing the floodwaters down (increasing that time from a few hours to a few days) this may reduce the flooding we see on TV. These changes will be monitored in the streamflow data the USGS collects. In addition to slowing down the flow, sort of providing the 'brakes' on how fast rainwater gets into the creek, restored areas provide habitat for wildlife and for people. Its amazing to me to see these big projects, these plantings go on (trees are growing), and even more amazing seeing the wildlife move into these areas.

[Steven Sobieszczyk] Prior to the show we were discussing some interesting aspects of Johnson Creek, such as the importance of stream temperature. What controls the stream temperature in Johnson Creek? And why is temperature important?

[Karl Lee] Stream temperature during the time of year when we (and the fish) notice most is when the weather is warm, and streamflow is pretty low. What keeps the flows going during the summer time is primarily groundwater that’s flowing into the stream from springs and other seeps. That groundwater is very cool – it’s in the 50s. This groundwater is coming from water that’s been seeping into the ground over the winter. Fish do better in cool water because cool water has more oxygen in it than warm water. We have a lot of native fish populations in Johnson Creek to protect. We can do our best to keep these spring-fed creeks cool by providing shading and avoiding large open ponds that can really warm up on a warm day.

[Steven Sobieszczyk] Is this type of groundwater recharge in the lower basin common, or is it unique to Johnson Creek?

[Karl Lee] Well, this is sort of unique to the Johnson Creek basin, I think. We get about half of the increase in streamflow from…lets say out by I-205 to the mouth of the creek…about half that increase in flow is from these springs. So if those springs weren’t there, those flows would be even lower than it is.

[Steven Sobieszczyk] Well, I that’s all questions I have for today. Thanks for sitting in for an interview, Karl. [Affirmative response] We are all but done with today’s show, but first we have some general housekeeping to take care of. First, we wanted to give a USGS Oregon Science Podcast shout out to the Scott Pemberton Trio for their generosity and support by supplying our sweet new theme music. Thank you, Norman. It’s nice having good music to bumper our episodes, rather than that free public domain stuff you find online. Next, we’d like to wish our former Science Center director Dennis Lynch best of luck as he leaves his leadership role here to pursue a new leadership appointment in southern Oregon. And lastly, we’d like to do our monthly pandering, and ask during this season of giving and thanks, give the gift of the USGS Oregon Science Podcast.

For links to topics discussed, check out the show transcripts on our Website at: or.usgs.gov/podcasts. As always, if you have any questions or comments about the USGS Oregon Science Podcast, email us at oregonpodcast@usgs.gov. We do, in fact, read every email. Thank you for listening. If you want to hear more about other research the USGS is doing around the country, please check out the other USGS podcasts at usgs.gov/podcasts.

Until next time, I’m Steven Sobieszczyk.

This podcast is a product of the U.S. Geological Survey, Department of the Interior.

[Outro Music: Scott Pemberton Trio, Little Bobby Cobalt]