2.6	Watershed Conditions
2.7	Flow and Hydrology
	2.7.1	Gradient
	2.7.2	Flow
	2.7.3	Flooding
	2.7.4	Baseflows

2.6      Watershed Conditions

The following provides an overview of existing environmental conditions in Johnson Creek, and evaluates watershed health by summarizing and presenting data available on a series of key indicators. The importance and justification for the selection of the indicators is described in the Internal and IST Review Draft Framework for Integrated Management of Watershed and River Health (City of Portland 2002).

This baseline is not intended to be a comprehensive summary of existing information on Johnson Creek. A number of reports provide excellent overviews of the large amount of information on environmental conditions and restoration efforts within the watershed (e.g., JCCC1994; JCCC 1995; Meross 2000; BES 2001).

For the 2000-2001 ODFW Aquatic Habitat Inventory Project, Johnson Creek was segregated into 23 separate stream reaches. BES grouped these reaches into three main areas – lower, middle, and upper Johnson Creek in a subsequent modeling project. Lower Johnson Creek consists of reaches 1-7; Middle Johnson Creek consists of reaches 8-15; and upper Johnson Creek consists of reaches 16-23. Table 2 highlights the stream reaches and their location (see also Figure 4).

Table 2. ODFW Stream Reaches

Number	Boundary Location
1	Willamette River confluence to Hwy. 224 overpass
2	Hwy. 224 to Crystal Springs tributary junction
3	Crystal Springs tributary junction to Old Tacoma bridge crossing
4	Old Tacoma bridge crossing to Tideman-Johnson rail and footbridges
5	Tideman-Johnson rail and footbridges to Johnson Cr. Blvd. bridge crossing
6	Johnson Cr. Blvd. bridge crossing to SE Linwood Ave. bridge crossing
7	SE Linwood Ave. bridge crossing to SE 82nd Ave. bridge crossing
8	SE 82nd Ave. bridge crossing to I-205 bridges
9	I-205 bridges to SE 106th bridge crossing
10	SE 106th bridge crossing to SE 110th Drive bridge crossing
11	SE 110th Drive bridge crossing to Brookside restoration site
12	Brookside Restoration site to SE 132nd bridge crossing
13	SE 132nd bridge crossing to Kelley Cr. tributary junction
14	Kelley Cr. tributary junction to SE 190th bridge crossing
15	SE 190th bridge crossing to Main City Park in Gresham
16	Main City Park in Gresham to Palmblad Road bridge crossing
17	Palmblad Road bridge crossing to Sunshine Cr. (known to locals as “McDonald Creek”)
18	Sunshine Cr. or “McDonald Cr.” to U.S. Hwy 26
19	US Hwy 26 to SE Stone Road crossing
20	SE Stone Road crossing to first tributary junction east of SE Orient Dr.
21	First tributary junction east of SE Orient Dr. to second tributary junction east of SE Altman Road
22	Second tributary junction east of SE Altman Road to last marked tributary junction on USGS topo map
23	Last marked tributary junction on USGS topo map to where creek disappears into a culvert draining cornfields

The City of Portland ESA Program recently completed a summary of baseline environmental conditions in the Johnson Creek watershed. This document provides a brief narrative overview of existing conditions, and then evaluates a series of key indicators of watershed health by summarizing and presenting data available on each of the indicators (See Appendix A).  These data served as background information and were inputs into an Ecosystem Diagnosis and Treatment (EDT) model to assess protection and restoration opportunities in the Johnson Creek watershed (See Key Limiting Factors in Chapter 2.12).

2.7      Flow and Hydrology

2.7.1      Gradient

Johnson Creek is a low gradient stream that drops approximately 700 feet over its course. The average gradient along the mainstem is 0.5 percent.  The steeper upper section with a gradient of 0.8 percent begins in the headwaters and extends down to about 5.5 miles to Regner Road in Gresham. The middle section is extremely flat and takes on a slough-like character with an average gradient of 0.4 percent (McConnaha, 2002). Beginning about at SE 82^nd Avenue, Johnson Creek begins to cut its way down to the Willamette River with a correspondingly higher gradient than the middle section. 

2.7.2      Flow 

Land uses, piping of flow, and the addition of impervious surfaces highly impact flow patterns in the watershed. A 1984 study of the effects of development and resultant impervious surfaces on peak flows in Johnson Creek (Clement, 1984) concluded that for a storm of a given size the peak flow under 1980’s conditions was 30 percent greater than under 1940’s conditions. However, peak flow frequency at the Sycamore streamflow gauge (River Mile 10.2) shows no discernable upward trend over the last 60 years (ODFW Stream Reach 13).

General hydrologic patterns in Johnson Creek are driven by patterns of rainfall and groundwater inflow. High flows normally occur in December, January, and February in response to abundant rainfall and high amounts of runoff as soils become saturated through the rainy season. Summer low flows in July, August and September reflect minimal groundwater contributions to streamflow throughout the watershed (Figure 5, below).

Figure 5.  Monthly Average Flow by Decade

Figure 5: Average monthly flow for the period of record at the Sycamore flow gauge (1940-2000). There does not appear to be any obvious pattern of increasing high flows over time in the decadal averages. This is consistent with Clark (1999), who found increasing “flashiness”, but no significant increase in peak flows.

During the 1995 and 1996 Water Years the USGS has reported that Johnson Creek at Sycamore (station 14211500), had one of the lowest percent-base-flow components of streamflow (47 to 52 percent) compared to more than 50 other streamflow gaging stations throughout the Willamette basin. This was thought to be attributable to rapid runoff from urban areas of the basin and lack of infiltration of precipitation into the groundwater system due to extensive impervious land cover (USGS, 2002).

There is also evidence of adverse impacts from excessive peak flows. The Sycamore gage provides the longest period of record with which to evaluate changes in flow over time due to human activities. Statistical evaluation of flow since 1940 indicates some increase in the flashiness of peak flows over the period of record (Clark 1999). Since much of the intensive rural and urban development upstream of the Sycamore gage occurred after the gage was installed, the gage data provides some indication that increased flashiness may be related to increased development. However, the range of variables (including soil type, slope, other geological factors, and watershed characteristics and conditions) makes it impossible to establish a direct cause and effect relationship. Significant impacts on peak flows in Johnson Creek also appear to be affected by alterations in the stream channel and floodplain that change the way floods flow through Johnson Creek (Portland ESA, 2002).

2.7.3      Flooding

The flow of Johnson Creek is primarily precipitation fed with peak flows typically in December through February and low flow in late summer and early fall. The U.S. Geological Survey (USGS) operates four gaging stations throughout the Johnson Creek watershed. In addition, the Oregon Department of Water Resources Department operates a gaging station in Crystal Springs Creek. A summary of these gaging stations is listed in Table 3.

Table 3. USGS Gaging Stations within the Johnson Creek Drainage Basin

USGS Gage Number/Location	River Mile	Drainage Area (mi.2)	Period of Record	Extremes for Period of Record *
14211400 Johnson Cr. at Regner Road (Gresham)	16.3	17.8	February 1998 to current year	Max.: 629 ft3/s Feb. 27,28, 1999; gage=8.58 ft. Min.: 0.26 ft3/s Sep. 27,28, 2000
14211499 Kelley Cr. at SE 159th Dr. (Portland)	At mouth	4.69	March 2000 to current year	Max.: 81 ft3/s May 10, 2000, Mar. 27, gage=4.34 ft. Min.: 0.03 ft3/s Sep. 27, 2000
14211500 Johnson Cr. at Sycamore, (Portland), Oregon	10.2	26.5	July 1940 to current year	Max.: 2,620 ft3/s Dec. 22, 1964; gage=14.68 ft. and 2,350 ft3/s Feb. 7, 1996; gage= 14.28 ft. Min.: 0.08 ft3/s Aug. 21, 1966
14211546 Crystal Springs Creek at Clatsop St. (Portland)	At mouth	???	Periodic measurements during late 1980’s and 1998-2000	Average flows approx. 10-14 cfs prior to 1997 and 17-20 cfs 1997-1998. Higher flows thought to be caused by higher than normal precipitation and subsequent elevated groundwater discharges (Adolfson, 2001).
14211550 Johnson Cr. at Milwaukie, Oregon	0.7	51.8	April 1989 to current year	Max.: 2,170 ft3/s Feb. 8, 1996; gage=30.27 ft. Min.: 10 ft3/s July 1, and 3-5, 1994

* Does not include peak flows recorded during January 2003.

The long-term average streamflow at the Sycamore gaging station is 54 cubic feet per second (cfs) (USGS and McConnaha, 2002). Maximum flows usually are recorded in December or January. Minimum flows occur usually in August or September. Bankfull discharges at the Sycamore gage are around 867 cfs and occur about 3 times each year. Flood stage is reached at a flow of around 1,080-cfs, which occurs on average about 1.8 times each year.  Major floods correspond to flows of 1,650 cfs, which has occurred about once every 3-4 years. The streamflow gage at Milport Road (Milwaukie) and its associated drainage area is almost twice as large as the drainage area of the Sycamore gage. Yet, the total annual runoff at the Milwaukie gage is only about 45 percent higher than runoff at the Sycamore gage. This supports the conclusion that the upper watershed (located upstream of the Sycamore gage) is contributing a much greater stream flow than is proportionate to its size (Portland ESA, 2000).

Flooding events primarily affect four areas within Portland: 1) Tideman-Johnson Park at SE 45^th; 2) the area west of SE 82^nd; 3) the Lents area, and 4) lower Powell Butte. Due to its low gradient most flooding takes place in the middle section of the creek where floodwaters tend to spread out (McConnaha 2002). Lents is by far the largest area affected, flooding approximately 10-20 acres on average once every other year. Designated as a Flood Risk area by the City of Portland, this area has stricter development codes. Based on past history, the Lents area faces a high risk each winter that Johnson Creek will overflow its banks and flood nearby community roads and properties. Since 1941, there have been 37 out-of-bank flood events, 28 of which have resulted in property damage. Twenty-one of these events were considered “nuisance events” (a 10-year flood or less) (Lents Technical Memorandum, Portland BES, 2002). Frequently flooded areas in Lents include: 1) along Johnson Creek from 117^th to 101^st; 2) Foster Road between 111^th and 101^st; 3) Springwater Trail from 111^th to Foster Road; and 4) Beggar’s Tick Marsh associated marshlands.

Several of the largest flooding events in gaged history for Johnson Creek occurred during the 1990s (Portland ESA, 2000). Since 1978, 156 flood insurance claims have been paid, totaling approximately $2,015,300 (FEMA estimate 1997). Areas of inundation for the February 1994 and 1996, and November 1996 flood events have been mapped and identified (Portland Bureau of Planning, 2001). It is important to note that mapped flooded areas can range in accuracy depending on the data and methodology used. See map of 1996 flood inundation areas in Figure 6.

While most of the watershed and its tributaries are fed primarily by precipitation (average annual varies from 40 inches near the mouth to over 70 inches in the upper watershed), and surface water, some areas are controlled primarily by groundwater processes. Crystal Springs is the largest springs in the Portland Basin, with a total discharge of more than 5,000 gallons per minute (McFarland and Morgan, USGS, 1996). Crystal Springs Creek flooded during the summer of 1997 due to high ground water levels. It was the first recorded flooding and was attributed to three consecutive record precipitation years (Portland ESA, 2000). Holgate Lake, formed by the local water table, is located near the intersection of Holgate Boulevard and Southeast 136^th Ave.  The lake is located on private property. Elevated water levels in this area have caused flooding in the surrounding area, including damage to residences south and west of the lake. The latest episode of flooding occurred in the spring of 1999.

2.7.4      Baseflows

Flow monitoring in Johnson Creek indicates that low flow conditions in Johnson Creek may adversely impact aquatic life. ODFW has set minimum flow targets to protect salmonids in Johnson Creek (Meross 2000). Flows in the middle and upper watershed frequently do not meet those minimum flows, particularly in spring and summer months. Below Crystal Springs, which provides consistent and abundant groundwater flows, minimum instream flows are typically met. 

Johnson Creek suffers from a lack of base flows during the late spring/early summer through early fall season. Some of the tributaries dry up during the summer periods and the velocity and volume of base flows in the main stem of Johnson Creek become minimal. A lack of minimum stream flows can contribute to reduced habitat and degraded conditions in terms of properly functioning conditions for aquatic species. Springs and groundwater are significant assets to many watersheds including Johnson Creek, providing maintenance of summer time flows, cool clear water, and refuge areas for many aquatic species. Springs are major contributors to the Crystal Springs Creek and Errol Creek tributaries, and springs also contribute significantly to base flows in Johnson Creek within Reach 5 (near Tideman Johnson Park), and Minthorn Spring to Reach 1.

The Portland ESA Program assessed baseline conditions for flow and hydrology indicators in Johnson Creek (see Table 4). These indicators and their assessed base line condition compared to properly functioning conditions were incorporated into an Ecosystem Diagnosis & Treatment (EDT) Model. See Watershed Problems and Opportunities in Chapter 2 for discussion of this model and results of selected indicator attributes and their protection and restoration values. Additional baseline data graphs from the Portland ESA program are provided in Appendix E.

Table 4. Flow and Hydrology Indicators within the Johnson Creek Watershed

Indicator	Baseline Condition	Key Function	Key Process or(Source)	Effect	Notes
Hydrograph	Not Properly Functioning	A stream’s hydrograph characterizes the frequency, magnitude, and duration of flow. The hydrograph plays a key role in stream formation processes and characteristics.	An altered hydrograph can result from climate change and human development activities including a loss of vegetation in a watershed and increased impervious surfaces.	Altered hydrographs can result in stream scour and bank erosion. Altered hydrographs are also characteristic of changes in the magnitude, frequency, and duration of both peak and base flows.	Peak Flow: Statistical evaluation of flow since 1940 indicates that Johnson Creek has become “flashier” over time. While increases in absolute peak flows are not evident, the amount of rainfall needed to produce a peak flow had decreased over time (Clark, 1999). Base Flow: Low flow conditions in Johnson Creek may adversely impact salmonids: Flows in the middle and upper watershed frequently do not meet minimum flows, particularly in spring and summer months.
Impervious Surfaces	At Risk	The amount of effective impervious surface within a watershed has been generally shown to be negatively correlated with overall watershed health.  Impervious surface reduces opportunities for stormwater infiltration. Collects pollutants.	Impervious surfaces include roads, buildings, parking lots, and other compacted surfaces that result from urbanization.	Impervious surfaces reduce groundwater recharge resulting in low summer flows. Increased stormwater runoff erodes banks and incises channels. Polluted runoff impairs aquatic organisms and reduces species richness and diversity.  Water flows through system faster.	The City of Portland is in the process of obtaining estimates of impervious surfaces in the upper watershed. In the middle and lower watershed, smaller tributaries are at or above threshold values of 10-15 percent effective impervious area. The mainstem may have relatively low values when compared to other urban streams because of low levels of imperviousness in the upper watershed and diversion (CSO) of impervious areas in the most densely urbanized sections.
Hydrologic Sources	Not Properly Functioning	Springs, seeps, wetlands, floodplains supply water to streams. Provide cold water sources. Forests and uncompacted soils hold water and maintain streamflows.	Groundwater baseflow Springs, seeps in terraces and banks Off-channel wetlands Forests, intact topsoil	Loss of hydrologic sources results in low summer flows, higher stream temperatures, and water quality problems. Fish barriers	Thirty-eight percent of the former drainage network of the watershed has been artificially routed or diverted (piped, sumped, or diverted to the CSO), although only 8 percent of this flow has been piped away. Crystal Springs provides consistent and abundant inflows of groundwater, supplementing insufficient baseflows in the lower mainstem. Changes in groundwater dynamics through the rest of the watershed are unknown.
Floodplain Presence and Connectivity	Not Properly Functioning	Floodplains allow interaction with the stream channel, lateral channel movement, storage of floodwaters providing attenuation, and reduction in downstream flooding.  Provide room for dynamic channel movement and water storage areas, and off-channel wetlands. Floodplains also provide habitat connectivity, refugia, sediment transport and storage, organic inputs and nutrient cycling.	Floodplains develop from an interaction of geology, hydrology, climate, and geomorphic processes.	The lack of floodplains and connectivity concentrates water into the main channel, increasing scour and degrading instream habitat.  Water flushes through system faster.	Due to channel alterations, the historical floodplain of Johnson Creek is minimally accessible or inaccessible through much of its length.

Source: Portland ESA Program and modified by Adolfson.