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217 PORTLAND 14206900 Sylvan Creek

Prepared in cooperation with Clean Services BEAVERTON Organic Creek 99W sh Investigating the Sources, Transport, and Fate of A Organic in Fanno Creek, Oregon METZGER Summ er Cr N eek

The term organic matter refers to the remnants of all living TIGARD F a material. This can include fallen leaves, yard waste, nno 99W C re waste, downed timber, or the remains of any other ek and animal . Organic matter is abundant both on land Lake Oswego and in water. Investigating organic matter is necessary for 14206950 lati understanding the fate and transport of (a major Tua n constituent of organic matter). Organic matter is necessary for maintaining a healthy DURHAM River . It participates in a wide range of ecological 217 functions, such as supplying food to the microbes that are part EXPLANATION of the foundation of the food chain. Organic matter also plays USGS streamflow gaging station Study Area Watershed boundary OREGON a role in many other natural functions, including the binding and transport of some trace metals and controlling how light is 0 1 2 Miles absorbed in the water column. Organic matter in a stream can 0 1 2 Kilometers be found in many places, such as in the leaves that have fallen from a tree (termed “leaf litter”), in algae floating in the stream Figure 1. Location of Fanno Creek, Oregon. or attached to rocks, as part of the , or even suspended or dissolved in the water. Organic Matter and the Environment The U.S. Geological Survey (USGS), in cooperation with Clean Organic matter plays a vital role in the environment, Water Services, recently completed an investigation into the especially in the ecological health of a river system. It provides sources, transport, and fate of organic matter in the Fanno food for to eat. It supplies nutrients to the soil that Creek watershed. The information provided by this investigation need to grow. However, in some situations it can will help resource managers to implement strategies aimed at adversely affect the health of a river. When microbes break decreasing the excess supply of organic matter that contributes down organic matter in a stream, they use some of the to low dissolved-oxygen levels in Fanno Creek and downstream that is dissolved in the water. This decreased dissolved oxygen in the Tualatin River during summer. This fact sheet summarizes in the water can stress fish and other aquatic animals that the findings of the investigation. depend on oxygen to breathe. Some streams such as Fanno Creek in the Portland, Oregon, metropolitan area (fig. 1) are listed as impaired waterways

A. 30-day mean dissolved oxygen, no credit for supersaturation B. 7-day mean dissolved oxygen, no credit for supersaturation

12.0 EXPLANATION 12.0 Dissolved oxygen standard 10.0 10–90 percentile 25–75 percentile 10.0 8.0 Median

6.0 8.0 Dissolved oxygen standard Dissolved oxygen concentration (mg/L) 4.0 6.0

July 01 July 24 Oct. 01 Oct. 24 May 16 June 08 Aug. 16 Sept. 08 Nov. 16 Dec. 09 Dec. 31 Jan. 01 Jan. 17 Feb. 02 Feb. 18 Mar. 05 Mar. 21 Apr. 06 Apr. 22 May 08

Figure 2. Dissolved oxygen (DO) concentration in Fanno Creek between 2003 and 2014. The DO standard line indicates two of the minimum thresholds to protect fish at different times in their life: (A) 6.5 mg/L—30-day average of daily mean DO (minimum criterion for rearing and migration period of May 16 to December 31) and (B) 11 mg/L—7-day average daily mean DO (minimum criterion for spawning period of January 1 to May 15).

U.S. Department of the Interior Fact Sheet 2015–3003 U.S. Geological Survey January 2015 Leaf Litter (Foliage) To estimate how much leafy material exists along Fanno Creek, USGS scientists used a combination of field measurements and remotely sensed data to calculate the foliage biomass, or the total dry weight of all leaf material (fig. 3). The annual leaf litter biomass was determined for two areas: (1) all foliage across the entire floodplain, and (2) only foliage overhanging the stream. Based on this analysis, an estimated 990 metric tons (t) of organic matter is produced annually above the Fanno Creek floodplain, with about 140 t present directly over the channel. The amount of leaf material that falls along the floodplain varies depending on the size and age of the trees, and the density of the tree canopy. Because forest-dominant reaches along Fanno Creek contain more mature deciduous trees with broader tree canopies than either wetland or urban- dominant reaches, they typically generate more leafy biomass in any given year. Sediment erosion was observed using metal stakes hammered into the streambanks and measured after high flow events. USGS research explored organic matter “above, around, and in” Fanno Creek. by the Oregon Department of Environmental Quality and require active management in order to improve dissolved- oxygen conditions and meet State standards. The standards vary seasonally and are based on whether fish are rearing or Organic Matter Transport with Fine Sediment spawning (fig. 2). For Fanno Creek, the primary sources of organic matter are terrestrial (land based), such as leaf litter USGS scientists also assessed the organic matter (and and , rather than aquatic, such as algae. So, how much carbon) contribution in the fine sediments along the floodplain terrestrial organic matter is available along the stream? To find and streambanks of Fanno Creek (fig. 4). Based on the carbon the answer, USGS scientists began by measuring the amount of content of samples collected from the streambanks and leaf litter, or foliage, available. measured rates of erosion and deposition, it was estimated that streambanks supplied between 50 and 120 t of organic matter annually during the study period. Generally, the organic matter stored in topsoil floodplain deposits was 2–5 times richer Organic matter in Fanno Creek comes mostly in carbon than that sampled directly from the subsoil of the from terrestrial sources, such as leaf litter. streambanks. Comparatively, the streambanks supplied less organic matter to Fanno Creek than that measured from the foliage above.

Figure 3. Three-dimensional (3-D) view of tree canopy as represented by remotely sensed data (light detection and ranging [lidar]) near Durham City Park, Oregon. Lidar from Fusion software available at http://forsys.cfr.washington.edu/ fusion/fusionlatest.html.)

Deposition plates (30 x 30 centimeters) along the floodplain were routinely buried by sediment during high flow events. 50 Using cutting-edge instream water-quality instruments (optical EXPLANATION fluorescence sensors) and laboratory analyses (fluorescence Organic matter spectroscopy and isotope chemistry), investigators estimated Maximum estimate 25 Minimum estimate the amount and characteristics of dissolved, particulate, and in the stream. Each year, about 320 t of organic carbon floats or flows through Fanno Creek, with 0 about 70 percent of organic carbon dissolved in the water. The concentration of the varies throughout the year, but generally amounts to at least 3–4 milligrams per -25 liter (mg/L) during most of the year. The instream and laboratory Organic matter, in tonnes Organic matter, analyses confirm previous findings that the carbon in the stream predominantly originates from terrestrial organic matter, such as -50 from leaf litter or other surface-soil runoff.

Downstream Upstream -75 Water sample being collected by Figure 4. Organic matter contribution from fine sediments along USGS personnel from Fanno Creek. Fanno Creek. Positive values indicate overall deposition or storage; negative values indicate erosion or export. Net deposition is greatest along the middle sections of Fanno Creek where wetlands have been restored

Organic Matter as Instream Carbon In addition to estimating organic matter contributions from above and along Fanno Creek, USGS scientists also assessed the instream movement and characteristics of organic matter.

Mapping Erosion and Deposition Based on geomorphic maps of the floodplain (fig. 5), USGS scientists have identified where sediment is being eroded and deposited along Fanno Creek. The maps are useful resources for those who plan and restore wetlands or riparian areas. Approximately 70 percent of the creek’s banks appeared highly erodible and resulted in 550–3,300 t of sediment being exported from Fanno Creek during the year-long study.

Ponded water A. Features B. Erosion C. Deposition on floodplain

No deposition on high-elevation floodplain Low-bench in active channel “Other” hillslope or Ponds on high- Channel blocked storm drain erosion elevation floodplain by large retain organic material and runoff No erosion at Reinforced bank reinforced by riprap banks Deposition on Feature low-elevation Bank floodplain Bar Culvert Dam/Blockage Floodplain Erosion Deposition Low bench Fluvial Fluvial Reinforced Mass wasting Mass wasting Secondary water NA NA None/Minimal None/Minimal Mass wasting AAXXXX_figValle y01 wall Mass wasting Wetted channel Other Other deposit below at a cut bank a cut bank Base maps modified from Oregon Department of and Mineral 0 50 100 Meters Industries digital data, 1-meter resolution. UTM Zone 10, NAD83 0 250 500 Feet Figure 5. Examples of (A) channel features, (B) erosion areas, and (C) deposition areas mapped by USGS scientists near Fanno Creek Park in Tigard, Oregon. Organic Matter Transport Following the First Storm of Autumn

In mid-October 2012, the first autumn storm swept across through microbial activity, reinforcing the conclusion that the Fanno Creek watershed. This first rain disturbed fine easy-to-mobilize sediment and decomposing organic matter particulate materials that had been accumulating during spring had accumulated in the streambed during the dry summer and summer along the streambed and washed some materials months. Downstream in the Tualatin River, this storm into the stream from nearby storm systems and soils (fig. 6). plume containing decomposing organic matter resulted in Real-time water-quality monitoring equipment recorded the a measurable and significant decrease in dissolved oxygen, event (fig. 7). Due to the mobilization of this accumulated a condition that tends to occur with the first autumn storms material, a large part of the annual supply of organic matter in most years and is a potential water-quality concern for was transported during this storm, despite the fact that bigger resource managers. storms occurred later in the year. Not only was the proportion

A. First storm of autumn: Fanno Creek /s) 3 of the organic matter greater during this first storm, but the 250 30 transported material also was characteristically different than 200 25 150 20 other storms. The organic matter showed more 15 100 10 5 50

5 organic carbon Autumn flush 0 0 Dissolved and total 4 Summer B. Effects of first storm of autumn: Tualatin River (mg/L) and discharge (m 3 14 8.0

Turbidity (FNU) Turbidity 12 7.5 2 10 7.0 8 6.5 6.0 1 6 5.5 4 0 5.0 Principal component 2 2 4.5 0 -1 4.0 12 13 14 15 16 17 18 Dissolved oxygen (mg/L) -2 October 2012 -5 -4 -3 -2 -1 0 1 2 3 4 EXPLANATION Principal component 1 Turbidity Total organic carbon Discharge Dissolved organic carbon Dissolved oxygen Figure 6. Statistical analysis of water-quality samples collected Figure 7. First autumn storm readings for Fanno Creek and from Fanno Creek. The two sample periods (summer low flow downstream in the Tualatin River. (A) Turbidity, total organic and the first autumn storm) were characteristically different from carbon, discharge, and dissolved organic carbon patterns in Fanno other samples collected. Creek in October 2012. Arrow indicates the beginning of the storm. (B) Dissolved oxygen and turbidity in the Tualatin River. The effects of the storm plume show up downstream about 1.5 days later.

Implications for Watershed Management Fanno Creek flows through a heavily urbanized part of the Portland, Oregon area.As such, the watershed has many interested stakeholders, including municipalities, counties, utility providers, conservation groups, and private citizens. The health and safety of the creek has implications to more than just the aquatic life in the stream, but also to people who live and play along the creek. Therefore, it is useful to understand the critical water-quality issues in Fanno Creek and provide the maps, data, and insights necessary to assist resource managers to make decisions regarding management and restoration activities to maintain and enhance the stream environment.

Full Results of the Study Goldman, J.H., Rounds, S.A., Keith, M.K., and Sobieszczyk, Steven, 2014, Investigating organic matter in Fanno Creek, Oregon, part 3 The results of the Fanno Creek study have been published in the of 3—Identifying and quantifying sources of organic matter to an Journal of Hydrology as a series of three articles. Figures presented urban stream: Journal of Hydrology, v. 519D, p. 3028–3041, http:// in this fact sheet were modified from these articles. dx.doi.org/10.1016/j.jhydrol.2014.07.033.

Sobieszczyk, Steven, Keith, M.K., Rounds, S.A., and Goldman, J.H., Authors: Steven Sobieszczyk, Mackenzie K. Keith, Jami H. Goldman, and 2014, Investigating organic matter in Fanno Creek, Oregon, part 1 Stewart A. Rounds of 3—Estimating annual foliar biomass for a deciduous dominant For information contact: urban riparian corridor: Journal of Hydrology, v. 519D, p. 3001– 3009, http://dx.doi.org/10.1016/j.jhydrol.2014.06.054. Director, Oregon Water Science Center U.S. Geological Survey Keith, M.K., Sobieszczyk, Steven, Goldman, J.H., and Rounds, S.A., 2130 SW 5th Ave., Portland, OR 97201 2014, Investigating organic matter in Fanno Creek, Oregon, part http://or.water.usgs.gov/ 2 of 3—Sources, sinks, and transport of organic matter with fine ISSN 2327-6932 (online) sediment: Journal of Hydrology, v. 519D, p. 3010–3027, http:// http://dx.doi.org/10.3133/fs20153003 Publishing support provided by the dx.doi.org/10.1016/j.jhydrol.2014.07.027. U.S. Geological Survey, Tacoma Publishing Service Center