monitoring the channel process of a stream restoration project in an urbanizing watershed: a case...

RIVER RESEARCH AND APPLICATIONS

River. Res. Applic. 24: 169–182 (2008)

Published online in Wiley InterScience

MONITORING THE CHANNEL PROCESS OF A STREAM RESTORATIONPROJECT IN AN URBANIZING WATERSHED: A CASE STUDY

OF KELLEY CREEK, OREGON, USA

A. P. LEVELL and H. CHANG*

Department of Geography, Portland State University, 1721 SW Broadway, Portland, OR 97201, USA

(www.interscience.wiley.com) DOI: 10.1002/rra.1050

ABSTRACT

Pacific Northwest (PNW) streams in the United States were impacted by the 20th century development, when removal ofinstream structure and channelization degraded an aquatic habitat. The lower Kelley Creek in southeast Portland, USA waschannelized during the 1930’s Works Progress Administration (WPA) projects. Stream restoration reintroduced pool-rifflesequences and heterogeneous substrates to protect salmonids while mitigating impacts from flooding. We investigated whetherthe restored pool-riffle morphology changed substantially following effective discharge events. We examined channel forms forfour reaches representing three time periods—pre-development (two reference reaches), development and restoration. Weconducted thalweg profiles, cross-sections and pebble counts along the reaches to examine how channel geometry, residual pooldimensions and particle size distribution changed following effective discharge events. The effective discharge flows altered therestoration reach more substantially than the reference reaches. The restoration reach decreased in median particle size, and itscross-sectional geometry aggraded near its margins. However, the residual pool morphology remained in equilibrium.Richardson Creek’s reference reach degraded at the substrate level, while Kelley Creek’s reference reach remained inequilibrium. The restoration reach’s aggradation may have resulted from sedimentation along the nearby Johnson Creek.In contrast, Richardson Creek’s degradation occurred as upstream land use may have augmented flows. Stream channels withlow gradient pool-riffle morphologies are ideal for salmonid spawning and rearing and should be protected and restored withinurban corridors. The findings of our study suggest that the connectivity of streams and the dynamic fluvial geomorphology ofstream channels should be considered for stream restoration projects in humid temperate climates. Copyright # 2008 JohnWiley & Sons, Ltd.

key words: urban streams; restoration; channel; pool-riffle; morphology; pebble count; effective discharge; Pacific Northwest

Received 24 December 2006; Revised 26 May 2007; Accepted 27 June 2007

INTRODUCTION

Streams are dynamic in nature, and one of the most sensitive components of the landscape to disturbance. Human

activities, including dam construction, urban development and channelization, modify discharge rate and sediment

load (Graf, 2001; Gregory and Chin, 2002; Chin, 2006; Chang, 2007). Channelization increases the sediment

carrying capacity of a given discharge and induces streambed scour (Knighton 1998; Ward and Trimble, 2004).

Continued changes to the discharge and sediment load can force a stream into disequilibrium, altering the stream’s

morphology (Martin and Johnson, 1987). Peak flows in stream channels change the channel forms by scouring and

filling processes. The range of flows bound channel formation between the lower limits of competence and the

upper limits where the channel is out of its banks (Leopold et al., 1964). Channels in equilibrium have relatively

stable banks and bedforms; they neither aggrade nor degrade during discharges higher than the effective discharges

since the energy is dissipated once the flows top the banks (Ward and Trimble, 2004).

Restoring streams to their natural condition is a popular approach to mitigating stream degradation (Palmer and

Bernhardt, 2006). Stream naturalization steers an impacted stream towards a more natural state, diverging from the

human-modified or impacted channel (Frothingham et al., 2002). An understanding of a stream’s geomorphic

processes at the reach scale is essential to naturalize a site-specific project. This includes an appreciation for

*Correspondence to: H. Chang, Department of Geography, Portland State University, 1721 SW Broadway, Portland, OR 97201, USA.E-mail: [email protected]

Copyright # 2008 John Wiley & Sons, Ltd.

170 A. P. LEVELL AND H. CHANG

changes in channel form and sediment transport processes (Kondolf, 2000). Naturalization of damaged waterways

can succeed if the new channel can mimic an undisturbed, nearby reach. The characteristics of the reference reaches

can be used as templates for the new channel designs. Reference reaches are assumed to be similar in sediment

source, dynamic equilibrium, climate and geology and form and process (Niezgoda and Johnson, 2005).

Numerous studies designate pools and riffles as primary salmonid habitat components of low-gradient streams

(Wesche, 1985; Cherry and Beschta, 1989; Montgomery et al., 1995; Lunetta et al., 1997; Henshaw and Booth,

2000). A sinuous bed of heterogeneous substrate with properly spaced pool-riffle sequences and largewoody debris

(LWD) are key components to a dynamically functioning stream channel (Montgomery and Buffington, 1997;

Rinaldi and Johnson, 1997; Larson et al., 2001; Konrad et al., 2005). During low flow periods, the residual depth

will be the only available habitat for rearing salmonids (Lisle, 1987). Residual pool depth, however, does not detail

the three-dimensional morphology of a channel reach. The added dimension of residual pool volume further refined

the stream channel morphology analysis in the 1990s (Lisle and Hilton, 1992; Kaufmann et al., 1999; Larson et al.,

2001).

Johnson Creek is a tributary of the lower Willamette River that experienced rapid urban development during the

20th century. Like most Pacific Northwest (PNW) streams, salmonids historically populated this stream, which

provided an adequate habitat along its main stem and tributaries. The 13.7 km2 Kelley Creek is its largest tributary.

The 20th century development brought flood control modifications of channel morphology along Johnson Creek

and Kelley Creek. During the Great Depression of the 1930s, the Works Progress Administration (WPA) widened,

deepened and rock-lined 23 km of the creek to mitigate flooding. In July 2004, a 2.5-ha restoration project termed

the ‘Kelley Creek Confluence Project’ was implemented at the confluencewith Johnson Creek. The project restored

its pre-WPA historic meanders, re-graded the slope from greater than 2% to 0.8%, removed 21 956m3 of fill,

created 61m of backwater channels for salmonid rearing and spawning and added 1230m3of flood storage

(Figure 2, Bureau of Environmental Services (BES, 2004)). LWD, root wads and substrate cobbles and gravels were

strategically placed to enhance channel complexity (Johnson Creek Watershed Council, 2003).

The restoration of pool-riffle habitat is unsuccessful if the new channel cannot persist following an effective

discharge event. An effective discharge event is the event that, over long durations, transports the largest total

sediment load in a channel (Ward and Trimble, 2004). We examined whether the restored reach channel

morphology changed substantially following the effective discharge events. Addressing this question allowed us to

assess the dynamic processes of the morphology of the restored and unrestored reaches before and after effective

discharge events. If the restored reach responded similar to the unimpacted reach upstream and in Richardson

Creek, then the restored stream has been successful in withstanding the effective discharge storm events.

STUDY AREA

As shown in Figure 1, Kelley Creek and Richardson Creek are two low-order streams located in the

Willamette-Foothills ecoregion (Omernick, 1987; ODFW, 2000; Cole, 2003). Each watershed has forested

canyons, with excellent salmonid spawning grounds. The major difference between Kelley and Richardson Creeks

is the historic WPA confinement of lower Kelley Creek (Figure 2). Richardson Creek is unimpacted in its lower

reaches (Cole, 2003) and provides an acceptable reference site because of its low-gradient and unconfined valley

floor (Figure 2).

We examined four reaches representing channel morphology for three different time periods (Table I). The time

periods included the Pre-development Era (pre-1934), Development Era (1935–2003) and Restoration Era

(2004–present). The restoration reach at Kelley Creek (Reach 1), representing the Restoration Era, included 128m

of Kelley Creek’s restored pool-riffle morphology. The Pre-development Era represented more natural conditions

as found in lower Kelley Creek (Reach 2) and lower Richardson Creek (Reach 4) reference reaches. Reach 2 was

111m long and Kelley Creek’s unimpacted reach, upstream from Foster Road, contained low-gradient pool-riffle

morphology. Reach 4 began above the confluence with the Clackamas River and was 120m in length.

A reach with intact WPA lining represented the Development Era (Reach 3). Reach 3 was upstream from the

restoration beginning at SE 159th and was 80m in length.

The Kelley Creek watershed is a 1194 ha rural subwatershed of Johnson Creek, in southeast Portland, Oregon.

The Kelley Creek watershed is 44% agriculture, 43% forest, with the remaining land use consisting of industry,

Copyright # 2008 John Wiley & Sons, Ltd. River. Res. Applic. 24: 169–182 (2008)

DOI: 10.1002/rra

Figure 1. Location map of Kelley Creek and Richardson Creek. Note the reach locations. This figure is available in colour online atwww.interscience.wiley.com/journal/rra

URBAN STREAM RESTORATION 171

residential, wetlands, or opens space. It is a perennial 2nd order stream, with five 1st order tributaries at the

subwatershed scale. The stream receives most of its runoff during winter months, with less intense peak flows

during summer storm events. Annual precipitation averages 1020mm, most of which falls as rain (Bureau of

Environmental Services (BES, 2004)).

The lower riparian soils are primarily silt loams. Silt loams and other well-drained soils allow water to infiltrate

rather than runoff (Ward and Trimble, 2004). The upper watershed consists of a relatively poorly drained loams

Cascade Silt Loams (Adolfson Associates, Inc., 2000). The geology of the lower watershed consists primarily of

Pleistocene and Pliocene sedimentary lacustrine and fluvial deposits (Walker and Macleod, 1991). The lower

Kelley Creek channel is underlain by sedimentary lithology, influenced by the 100 year old Johnson Creek

floodplain. Flood deposits and sedimentary lithology augments channel erosion and bank failure, adding to the

sediment load (Kaufmann and Hughes, 2006).


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Figure 2. Study reaches (a) Restored lower Kelley Creek reach (Reach 1), (b) unimpacted reference reach at Kelley Creek (Reach 2), (c)impacted reach at Kelley Creek (Reach 3) and (d) unimpacted reference reach at Richardson Creek (Reach 4). This figure is available in colour

online at www.interscience.wiley.com/journal/rra


The Richardson Creek watershed is a 1096 ha subwatershed of the Clackamas River basin. The watershed land

use consists of rural, rural residential and forest. Forests and shrubs cover 47%, agricultural land 34%, urban

development in the upper reaches 12% and open spaces 8% (Ecotrust, 2003). Low-gradient pool-riffle channels in a

‘U-shaped’ floodplain (Figure 3) are surrounded with steep hillslopes. Channel gradient ranges from 1% to 5%.

LWD loading is high at 39 pieces/75m. Aquatic macroinvertebrate communities are abundant. Mayflies, caddis

flies and stoneflies dominate the taxonomy (Cole, 2003). Steelhead trout and Coho salmon are present in this

reference reach (Ecotrust, 2003).

The soils in the riparian corridor consist primarily of haploxeroll and silty loams. The haploxeroll soils are found

in the canyon walls bounding lower Richardson’s channel. These soils are well drained, and subsurface flow is the

primary hydrologic conveyance. The silty loam soils of the floodplain are highly erodible, with poor drainage

(Gerig, 1985). The lowest portion of the reference reach is underlain with Holocene alluvial deposits. This alluvial

fan unit is composed of sand, gravel and silt covering the Clackamas River floodplain. Talus and scree line the

hillslopes. Upstream from the alluvial deposits lay Pliocene and Miocene tuffaceous sedimentary rocks and tuff

(Walker and Macleod, 1991).

Table I. Geomorphic characteristics of study reaches

Geomorphic Feature Reach 1 Reach 2 Reach 3 Reach 4

Reach length (m) 128 111 80 120Slope (%) 1.4 2 1.9 2.2Bankfull width (m) 7.0 5.9 5 4.7Bankfull depth (m) 0.56 0.43 0.4 0.35Hydraulic radius 236 264 300 153


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Figure 3. Representative cross-section sites and pebble count locations. This figure is available in colour online at www.interscience.wiley.com/journal/rra


METHODS

We measured particle size distribution, cross-sectional geometries and residual pool dimensions to investigate

whether the restoration reach resembled the unimpacted reference reaches following effective discharge events.

Stream channel surveys conformed to Harrelson et al. (1994), Kaufmann et al. (1999) and Kershner et al. (2004)

protocols. Reach lengths were 20 times the bankfull channel width to ensure the inclusion of bankfull

channel-forming forms and processes (Harrelson et al., 1994; Montgomery et al., 1995).

Thalweg profiles were surveyed during low flow periods of October 2005 and May 2006 to measure changes in

bed forms that result in the formation of pools in streams. Thalweg profile surveys lead to the compilation of

residual pool volumes. A metric stadia rod was positioned in the deepest part (thalweg) of the channel at each

station interval. The depth included the water depth until the stadia rod touched the streambed armor, including fine

sediment along the bottom. Wetted width was noted at every five stations. Wetted widths were included in the

residual pool volume equation.

Residual pool depth (Dr) was quantified by subtracting the depth at the downstream riffle crest (tail-outs) (drc)

from the deepest pool depth (dp), while incorporating the mean reach slope (Equation 1) (Lisle, 1987). The mean

reach slope was acquired using a clinometer along each cross-section. The residual pool depth equation included

the thalweg depth, standard deviation of mean thalweg depth, the thalweg station interval length (i.e. distance

between the two thalweg stations) and mean reach slope.

Dr ¼ dp � drc (1)

where Dr is the residual pool depth, dp is the pool depth and drc the riffle crest depth.

Pools were measured for wetted width, depth and length for a residual pool volume analysis. Wetted width is the

horizontal distance of the water surface across a channel. The residual pool volume equation was applied to each

reach and analysed through an algorithm acquired from Kaufmann (personal communication, 2006). This formula

assumes a triangular cross-section shape; therefore the residual wetted width is the residual pool depth multiplied

by wetted width and divided by average thalweg depth (Equation 2).

Wr¼ ½ðWÞ � ðDr=DÞ� (2)


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where Wr is the residual wetted width, W the wetted width, Dr the residual pool depth and D the average thalweg

depth.

We compared median particle sizes (D50) before and after effective discharge events by determining the fluvial

process impacting the substrate size distribution, or whether the streambed is in aggradation, degradation or

equilibrium. Particle size distribution was determined according to Wolman (1954), Kondolf and Wolman (1993)

and Harrelson et al. (1994). We counted at least 100 particles on a representative cross-section within each reach

along a riffle (Figure 3). A representative cross-section is one that has consistent distributions of bed material

analogous to the entire reach (Harrelson et al., 1994). An Al-Sci Gravel-o-meter field sieve allows only the

intermediate axis of each pebble to pass through the sieve.

A cross-sectional analysis examined the mean and total geometric change. The width increments were selected

based on fluvial features within the reach. Rebar stakes marked the endpoints of each cross-section to locate the

following events. The cross-sections were coded among the reaches as follows (R¼ reach, reach number,

X¼ cross-section and cross-section number, or R#X#). The mean and sum of cross-sectional depths and areas were

calculated for each year’s survey. For geometric changes within the channel analysis, the cross-sections were

divided into four quartile segments. The quartiles were separated as left bank, near left bank (NLB), near right bank

and right bank (RB).

RESULTS

Three 2-year recurrence interval effective discharge events occurred on December 30, 2005, January 11, 2006, and

January 17, 2006 at lower Kelley Creek (Figure 4). The peak discharge amounts were 6.3m3s�1, 6.7m3s�1 and

6.2m3s�1, respectively. These events were adequate to evaluate the channel’s competence to withstand an effective

discharge flow event.

Particle size distribution

At the restoration reach (Reach 1), after the effective discharge events, a bar of fine sediment appeared below the

right bankfull lines, increasing the fine sediment accumulation. The median particle size (D50) in May 2006 was

substantially finer than the one surveyed in October 2005 (38–19mm) (Table II, Figure 5). The larger substrate on

the centre bar of the channel withstood the effective discharge events (D84), but fines accumulated near the channel

margins.

At the reference reaches, however, different patterns were observed. Particle size distribution along the

unimpacted reach at Kelley Creek (Reach 2) did not change substantially. The median particle size (D50) remained

Figure 4. Effective discharge event at restoration reach (December 2005). This figure is available in colour online at www.interscience.wiley.com/journal/rra


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Table II. Particle size and residual pool characteristics for the restoration reach (Reach 1), unimpacted reference reaches atKelley Creek (Reach 2) and at Richardson Creek (Reach 4) before and after effective discharge events

Parameter Reach 1 Reach 2 Reach 4

Fall Spring Fall Spring Fall Spring

D50 (mm) 38 19 54 54 38 54D16 (mm) 19 12 25 27 19 27AREASUM (m2) 18.9 17.1 12 16.9 5.5 10.3RP100 (100m) 13.3 12.7 11.6 16.4 4.2 7.9VOLSUM (m3) 46.4 48.4 29.2 30.1 11 24.2RPV100 (100m2) 32.8 36.8 28.2 29.2 8.8 18.5SSS (%) 35 46 38 27 8 22

D50, median particle size;D16, particle size is 16%finer; AREASUM, the total residual pool area for Reach 1; RP100, the pool area divided by thereach length� 100; VolSUM, the total residual pool volume per reach; RPV100, the residual pool volume divided by the reach length (L)� 100;SSS, soft suspended solid.


constant at 54mm, but the D16 slightly increased from 25mm to 27mm. At the unimpacted reach at Richardson

Creek (Reach 4), coarse sediments increased substantially following the events (Table II). The D50 increased from

38mm to 54mm, and the D16 increased from 19mm to 27mm.

Residual pools

At the restoration reach, the thalweg depth remained relatively constant within the bankfull channel. Residual

pools sustained their area and volume following the effective discharge events (Table II, Figure 6). Table II displays

a slight reduction in RP100 and an increase in RPV100 for Reach 1. The total residual pool area (AREASUM) and

the pool area divided by the reach length multiplied by 100 (RP100) decreased slightly. In contrast, the total

residual pool volumes (VolSUM) and the residual pool volume divided by the reach length multiplied by 100

(RPV100) increased (Table II).

Figure 5. Seasonal cumulative particle size distribution for Reach 1. This figure is available in colour online at www.interscience.wiley.com/journal/rra


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Figure 6. Seasonal change in residual pool volumes (RPVs) for Reach 1. The RPV difference appears unsubstantial, yet the spring RPVs areslightly larger. This figure is available in colour online at www.interscience.wiley.com/journal/rra


The unimpacted reach at Kelley Creek (Reach 2), however, showed slight increases in the residual pool area

(12! 16.9) and volume (29.2! 30.1) following the effective discharge events. At Reach 4, there was a major

change (approximately 100% increases) in the residual pool area and volume (Table II).

Cross-sectional geometry

Cross-section transects surveys showed a small but evident profile change following effective discharge events at

the restoration reach. Channel geometry at the cross-section profile changed slightly following the effective

discharge events. An accumulation of fine sediment along the channel margins aggraded the cross-sectional profile

at R1X1 (Figure 7). Upstream from R1X1, R1X2 (Figure 7) also aggraded near its channel margins. R1X2 scoured

in the centre of the channel in the spring of 2006 (Figure 7).

The quartile analysis examined two-dimensional geometric change within a cross-section (Paige and Hickin,

2000). R1X1 had a loss of cross-sectional area (mean width times depth) at its right and left banks (Table III). This

is the area where the sediment bar accumulated below bankfull depth along both banks. Within the right side of the

centre of the channel (NRB), the cross-section (NRB (A)) degraded following the events. In R1X2 the left side

(LB and LB (A)) accumulated over ½ a meter of fine sediment. This aggradation contrasted with NRB degrading by

1/10 of a meter (Table III).

The unimpacted reference reach at Kelley Creek (Reach 2) decreased in cross-sectional geometry along the RB

and increased in the channel centre following the events (R2X1, Figure 8). Slight degradation occurred on the RB

(Table III). The channel of the unimpacted reference reach at Richardson Creek (Reach 4) was in a different

position in the spring survey than the fall. Its cross-sectional morphology changed positions (e.g. the RB rebar

became entrenched in the channel and was missing). The cross-section could not be replicated because of the

missing rebar and channel change.

The difference in quartile geometric change between the analyses in Reach 2 differs from the restoration reach

(Reach 1, Table III). The dominant channel geometry change in the restoration reach was at the margins, while the

unimpacted reach at Kelley Creek was more substantial in the channel centre (e.g. NRB and NLB). The sum of the

NLB and near left bank area (NLB (A)) for the unimpacted reaches at Kelley Creek changed between 0.3 and 0.2 of

a meter. In contrast, a change along the RB was between 0.02 and 0.1 of a meter (Table III).

DISCUSSION

Channel morphology is the fundamental endpoint in modelling hydraulics in stream rehabilitation. Stream

morphology controls terrestrial vegetation and fauna, macroinvertebrates and fish (Schweizer et al., 2007).

Effective discharge events can significantly alter channel morphology parameters at the substrate, cross-section and

longitudinal profile scales (Olsen et al., 1997; Gomez et al., 2001; Ward and Trimble, 2004). In our study, the


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Figure 7. Cross-sectional change following effective discharge events along restoration reach at (a) R1X1 and (b) R1X2. This figure is availablein colour online at www.interscience.wiley.com/journal/rra


restoration reach (Reach 1) did not change substantially in residual pool dimensions, but did change in particle size

distribution and cross-sectional geometry, particularly in riffles or bars. Fining of particle sizes (D50 declined from

38mm to 19mm) in the restoration reach suggests that streams are in an aggradation state (Gomez et al., 2001). An

aggrading stream negatively impacts the salmonid habitat by reducing riffle-pool sequences and infiltrating its

spawning bars with fine sediment (Lisle, 1982; Kaufmann and Hughes, 2006). The fact that Kelley Creek’s

Table III. Quartile cross-sectional changes for the restoration reach (Reach 1¼R1X1, R1X2, R1X3) and the reference reach(Reach 2¼R2X1) (in meters)

LB LB (A) NLB NLB (A) NRB NRB (A) RB RB (A)

R1X1Sum �0.190 �0.018 0.000 0.000 �0.040 0.011 �0.470 �0.119Mean �0.048 �0.005 0.000 0.000 �0.010 0.003 �0.118 �0.030

R1X2Sum �0.510 �0.155 0.140 0.070 0.170 0.056 �0.050 �0.004Mean �0.102 �0.031 0.028 0.014 0.043 0.014 �0.010 �0.001

R1X3Sum �0.090 �0.030 0.220 0.113 0.460 0.349 0.010 0.001Mean �0.018 �0.006 0.044 0.023 0.077 �0.008 0.002 0.032

R2X1Sum �0.2 �0.025 �0.36 �0.201 �0.07 �0.103 0.12 �0.019Mean �.0333 �0.004 �0.072 �0.018 �0.014 �0.005 0.024 0.0076

LB left bank; NLB, near left bank; NRB, near right bank; RB, right bank; and (A), area. The quartiles were analysed for sum and mean of bothchange in elevation and area. Negative numbers denote in a decrease in geometry from fall 2005 surveys.


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Figure 8. Seasonal comparisons of cross-sectional change at the unimpacted reach at Kelley Creek (R2X1, Reach 2). Note the cross-sectionview faces downstream, therefore the left side is left bank and the right side is right bank. This figure is available in colour online at

www.interscience.wiley.com/journal/rra


restoration reach fined more substantially following the effective discharge flows suggests the restored parameters

(e.g. pools and riffles, LWD) did not adequately adjust to natural fluvial processes.

Cross-sections are the most directly affected components of channel forms and processes by flashy discharges

and sediment supplies (Henshaw and Booth, 2000). Lisle (1986) discovered that 25% of bars were scoured or filled

following a single flood event in northwestern California. Champoux et al. (2003) noted that sediment bar

development in a Wisconsin stream channel indicated instability. In their study, as stream channels became

unstable, bars developed in the channel and LWD accumulated along the banks following years of storm events. In

our study, the sediment bar caused aggradation in cross-sectional geometry (or loss decreased geometry). This

could reflect low shear stress during effective discharge events (e.g. fill over scour). However, the depositional state

of lower Kelley Creek may enhance build up the riffles over time.

The cross-sections examined in our study illustrated the within channel variations of aggradation and

degradation. Complex processes can be masked when one overlooks within channel variations (Paige and Hickin,

2000). The degradation of cross-section R1X2 could have occurred because the effective discharge events entrained

the D84, while depositing fine sediments on the margins. Aggradation causes riffles to extend, residual pools to

deteriorate and sediment to become finer (Madej, 1999).

Gravel bar restoration augments available salmonid spawning habitat. Cover and egg incubation habitat is

provided by the interstitial zones in gravel bars (Schweizer et al., 2007). The bars, however, will only develop if

there is a net deposition of gravelly sediment in the watershed. Gravel bar development following effective

discharge events can rapidly augment available fish habitat (Pitlick and Van Steeter, 1998). In contrast, fine

sediment bars will offset successful salmonid habitat restoration by degrading the biological quality of spawning

bars, filling the substrate interstices inhabited by macroinvertebrates (Pitlick and Van Steeter, 1998; Schweizer

et al., 2007). Siltation of interstitial gravels influences the exchange between surface and ground water zones

(Schweizer et al., 2007).

In our study, upstream land use increased accumulation of fine sediment budgets in the restoration reach

following effective discharge events, consequently altering its cross-sectional geometry and median particle size

and available salmonid habitat. Impervious surfaces along the impacted reach upstream (Reach 3) of the

Development Era flushed fine sediment into the restoration reach, causing unnatural fluvial adjustment. Land use

modification also alters the riparian vegetation by reducing soil infiltration capacity and permeability that increases

surface runoff and sediment yield to a stream (Martin and Johnson, 1987). The fine sediment bars at the restoration

reach essentially developed from the lack of a riparian buffer. A riparian buffer filters fine sediments before entering

the channel (Kaufmann and Hughes, 2006). The impacted reach upstream of the Development Era (Reach 3) had

excessive riparian clearing that induces sediment and hydrologic change downstream at the restoration reach.

In Richardson Creek (Reach 4) the upstream development may have induced coarsening following the effective

discharge events. Richardson Creek’s higher gradient and shear stress than Kelley Creek may explain the increasing

median particle size (38–54mm) following the events. This reach is attempting to naturally adjust to its hydraulic


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radius, including its higher gradient. The gradient has the most control over stream morphology features since it

adjusts slower than the other morphologic parameters (Allan, 1995).

Wood and Armitage (1997) stated that two major sources contributing to sedimentation are instream sources and

non-channel sources. Instream fine sediment sources are influenced by discharge and streambed stability. Extensive

shear stress on stream banks will cause accelerated erosion and instream sedimentation. The restoration reach does

not appear to be impacted by accelerated bank erosion, but this may occur in the future if the impacted reach

continues to have poor riparian functions. Recreational and residential land use near the impacted reference reach

of the Development Era includes bare soil exposure, a principal source of non-channel fine sediment.

LESSONS LEARNED

Our findings suggest a need for a holistic watershed analysis in stream restoration. Awatershed analysis addresses

which watershed components are in need of restoration. Using a systemic approach, watershed analysis describes

the biophysical processes, spatial distribution, linkages and development history in the watershed (Bohn and

Kershner, 2002). Past and current relationships among stream channels, landforms, biological systems and land

management activities are analysed for future management decisions. If effective, the watershed analysis will direct

land management to be consistent with the dominant habitat forming process of the watershed (Bohn and Kershner,

2002). Limitations from past projects developed from small-scale projects with little consideration of drainage

basin linkages (Dollar, 2004). The Kelly Creek Restoration Project did not deviate from such conventional

restoration projects. Hydrologic connectivity, which refers to the water-mediated transfer of energy, matter and/or

organisms within or between elements of the hydrologic cycle, was not fully considered in the restoration project.

Connectivity is a fundamental concept in both landscape ecology and metapopulation biology (Pringle, 2003).

Effective watershed management works to establish ecosystem connectivity to mitigate these losses. A new

paradigm is needed for waterway management in connecting ecosystems and naturalizing streams to their

pre-impacted conditions.

Successful urban stream restoration projects should include local geomorphology. Palmer et al. (2005) found

numerous channel modification projects focused on aesthetics and may not be effective for local geomorphic

conditions. Stream restoration will seldom produce complete ‘restoration’ of fluvial systems (Dollar, 2004). Most

studies question the acceptable rate and sustainability of change (Wade et al., 2002; Dollar, 2004; Palmer et al.,

2005). Site-specific objectives for PNW stream restoration typically focus on salmonid habitat restoration

(Montgomery et al., 1995; Larson et al., 2001; Booth et al., 2004) without consideration of local geomorphology.

As studied in the Kelly Creek restoration project, successful urban stream restoration should consider local

watershed geomorphology (e.g. sediment supply, gradient and flow) and its relationship to salmonid habitat in a

constrained environment.

Our study suggests a need for continuous monitoring and evaluation of channel geomorphic change immediately

after restoration, as this is the period of most rapid change (Kondolf andMicheli, 1995). Since aggradation changes

the bed load transport of the fluvial system (Lisle, 1982), it is critical to monitor fluvial adjustments following

events. A channel falls out of dynamic equilibrium as it aggrades. Channels became wider in response to

aggradation. In addition to the biological communities, aggradation could affect the adjacent land use properties. A

lack of acceptable measurements for monitoring stream restoration, however, has hindered many post-project

evaluations (Kondolf and Micheli, 1995). Biological post-project evaluations are well documented (Gore et al.,

1997; Keim et al., 2002), but monitoring post-project channel morphology receives less attention (Kondolf and

Micheli, 1995). Funding is currently lacking possibly because channel morphology is not covered under the

Endangered Species Act (ESA). To improve salmonid habit and other threatened aquatic vertebrates, a well-defined

channel morphology monitoring protocol needs to be included prior to evaluations.

CONCLUSIONS

The Kelley Creek Confluence Project immediately rehabilitated natural channel form to lower Kelley Creek. It also

restored potential salmonid habitat to the Johnson Creek watershed. Its residual pool habitat can be utilized by


DOI: 10.1002/rra


rearing salmonids and other aquatic species during low flow. The restoration reach appeared to be more stable than

the impacted reach. However, its channel processes are not as stable as its antecedent condition, as represented by

the unimpacted reference reaches of the Pre-development Era. The fining of the D50 could indicate a sedimentation

problem in the watershed. The majority of aggradation occurred at the channel margins, unlike the unimpacted

reference reaches. This reflects increased sedimentation near the restored channel. Upstream land use activities,

sedimentation from Johnson Creek floodplain and instream disruptions could increase aggradation.

Assessing Kelley Creek reaches as connected process-based channels is fundamental to successful stream

restoration. A successful stream restoration project must be able to persevere through annual storm events.

Process-based changes in fluvial systems need to be monitored long-term to determine successful instream

restoration parameters. The major concern with lower Kelley Creek is the fragmentation of its reaches. Linking the

restoration reach (Reach 1) with the unimpacted reach (Reach 2) of the Pre-development Era requires community

participation to mitigate effects from the impacted reach (Reach 3) of the Development Era. The sedimentation

problem should be addressed through patient riparian planting and additional restoration such as the removal of all

the WPA lining and realign the impacted reach. Once the connectivity among stream reaches within a drainage

basin increases, restoration becomes effective, which eventually leads to ecological connectivity of the drainage

basin.

ACKNOWLEDGEMENTS

This research was supported by an equipment grant from the Department of Geography at Portland State

University, USA. Philip Kaufmann of U.S. Environmental Protection Agency kindly provided us for an algorithm

for residual pool volume calculation. We thank Maggie Skendarian, Chad Smith, and Greg Savage of the City of

Portland and the U.S. Army Corps of Engineers Portland District Aerial Photography Library for sharing channel

imagery data. Thanks also go to Aaron Borisenko, Mike Mulvey, and Doug Drake of the Oregon Department of

Environment Quality for helping field survey protocol and techniques.

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