Channel Changes Over 12 Years on Grazed and Ungrazed Reaches of Wickiup Creek in Eastern Oregon

This article was downloaded by: [North Dakota State University]On: 17 October 2014, At: 14:52Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House,37-41 Mortimer Street, London W1T 3JH, UK

Physical GeographyPublication details, including instructions for authors and subscription information:http://www.tandfonline.com/loi/tphy20

Channel Changes Over 12 Years on Grazed andUngrazed Reaches of Wickiup Creek in Eastern OregonGregory N. Nagle a & Caty F. Clifton ba U.S. Forest Serviceb Umatilla National ForestPublished online: 15 May 2013.

To cite this article: Gregory N. Nagle & Caty F. Clifton (2003) Channel Changes Over 12 Years on Grazed and UngrazedReaches of Wickiup Creek in Eastern Oregon, Physical Geography, 24:1, 77-95

To link to this article: http://dx.doi.org/10.2747/0272-3646.24.1.77

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) containedin the publications on our platform. However, Taylor & Francis, our agents, and our licensors make norepresentations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of theContent. Any opinions and views expressed in this publication are the opinions and views of the authors, andare not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon andshould be independently verified with primary sources of information. Taylor and Francis shall not be liable forany losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoeveror howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use ofthe Content.

This article may be used for research, teaching, and private study purposes. Any substantial or systematicreproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in anyform to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions

http://www.tandfonline.com/loi/tphy20

http://dx.doi.org/10.2747/0272-3646.24.1.77

http://www.tandfonline.com/page/terms-and-conditions

http://www.tandfonline.com/page/terms-and-conditions

77

Physical Geography, 2003, 24, 1, pp. 77–95.Copyright © 2003 by V. H. Winston & Son, Inc. All rights reserved.

CHANNEL CHANGES OVER 12 YEARS ON GRAZED AND UNGRAZED REACHES OF WICKIUP CREEK IN EASTERN OREGON

Gregory N. Nagle*

U.S. Forest ServicePacific Northwest Research StationAquatic/Lands Interaction Program

3200 Jefferson WayCorvallis, Oregon 97331

Caty F. CliftonUmatilla National Forest2517 SW Hailey Avenue

Pendleton, Oregon 97801

Abstract: Stream channel cross sections were first compared in 1986 in grazed reaches and inside a 47-yr.-old grazing exclosure along Wickiup Creek in eastern Oregon. Signif-icant differences between grazed and ungrazed channels were found at that time. In 1998, we measured 49 cross sections placed at a similar spacing inside the exclosure and in three grazed reaches in order to examine changes over 12 yr. Although the grazed chan-nels were still significantly different than the ungrazed, in two out of three grazed reaches, the channels showed improvement in all parameters since 1985 although not all of these were statistically significant at the 90% level. Since 1990, the Wickiup riparian pasture has been managed more cautiously than many other streamside pastures in eastern Oregon and our results indicate that under careful grazing management, stream channels may show improvement from destructive past grazing without complete exclusion of livestock. As an alternative to the intensive method of measuring channel cross sections that was used in this study, we propose a rapid method of measuring stream channels that might be more useful in future studies of riparian grazing impacts. [Key words: riparian grazing, monitoring, exclosure, channel changes.]

INTRODUCTION

With the recent listings of many salmon stocks in the Interior Columbia Basin as threatened or endangered, livestock impacts on stream and riparian systems have become a critical concern. Livestock grazing of riparian areas in the western United States has been a contentious issue for several decades. Numerous lawsuits have been brought against federal agencies in an attempt to compel them to curb or eliminate livestock use in riparian areas on federal lands. In parts of four western states, the U.S. Forest Service and the Bureau of Land Management have been compelled by court orders to remove livestock from riparian areas due to their

*Please direct all correspondence to Gregory Nagle’s current address: Cornell University, Department of Natural Resources, Fernow Hall, Ithaca, NY 14853; e-mail: [email protected]

Dow

nloa

ded

by [

Nor

th D

akot

a St

ate

Uni

vers

ity]

at 1

4:52

17

Oct

ober

201

4

78 NAGLE AND CLIFTON

impacts on water quality, streamside vegetation, and changes in stream channel morphology that are detrimental to fisheries habitat.

Cattle exhibit a strong preference for riparian zones because of the availability of water, shade, thermal cover, and the quality and variety of forage (Kauffman and Krueger, 1984). Because of better moisture conditions, riparian meadows stay green and nutritious longer and become more palatable to cattle as the dry season progresses (Skovlin, 1984). In a grazing unit in eastern Oregon, the riparian zone comprising only 1.9% of the total land area accounted for 81% of the herbaceous cover used by livestock (Roath and Krueger, 1982). Data from riparian meadows along eight streams in eastern Oregon showed that cattle use was 5 to 30 times higher in riparian areas than on xeric uplands (Clary and Webster, 1989).

Excessive trampling and grazing of riparian plant species may weaken them, leaving them prone to washing out in floods. Heavy summer grazing of riparian wil-lows (Salix sp.) by cattle can decrease their vigor, sometimes resulting in death (Kindschy, 1989). When protective vegetation is lost, the stream can cut into allu-vial sediments. Platts et al. (1985) reported that floods badly damaged denuded channel banks in heavily grazed areas, while in areas protected from grazing, the vegetated banks actually aggraded by capturing sediment.

The degradation of riparian habitats in floodplains with deep alluvial soils is par-ticularly severe, where scouring and downcutting of the valley floor by streams can lead to a drop in the water table elevation. The desiccation of the valley bottoms often results in changes in plant community composition (Van Haveren and Jackson, 1986) as riparian and wet meadow species are replaced by species adapted to drier conditions (Cottam and Stewart, 1940; Dobyns, 1981; Jensen and Platts, 1989; Kovalchik and Chitwood, 1990). In streams with stable, rock sub-strates, degradation of riparian zones is generally not as severe, but may involve extensive lateral bankcutting and stream widening (Nagle, 1993).

In 1988, the General Accounting Office reported that only a small fraction of degraded western riparian areas have been restored (General Accounting Office, 1988). But over the last decade, there has been a growing recognition within federal agencies that many riparian areas are in poor condition largely due to past and cur-rent livestock use, and removing livestock from riparian zones can lead to dramatic improvements (Elmore and Beschta, 1987; Elmore and Kauffman, 1994; Belsky et al., 1999).

As an alternative to permanently halting riparian livestock use, many federal land managers believe that better management of livestock can also lead to significant improvement in riparian habitat. These approaches include reducing the number of cattle, reducing the season and length of use; and preventing access to sensitive riparian areas for a few years to allow for recovery of riparian vegetation, with con-trolled grazing following recovery (Elmore, 1992).

In eastern Oregon, hundreds of kilometers of streams on federal lands are managed with a goal of improving riparian areas but we lack standardized field protocols to monitor responses of riparian areas to these management practices. It is frequently difficult to determine what actually constitutes "recovery" since many streams have been severely altered since Euro-American settlement. Although it is clear that vegetation (Elmore, 1992) and many stream channel attributes

Dow

nloa

ded

by [

Nor

th D

akot

a St

ate

Uni

vers

ity]

at 1

4:52

17

Oct

ober

201

4

STREAM-CHANNEL CHANGES 79

(McDowell and Magilligan, 1997) may respond to elimination of livestock, little scientific research has been done on stream channel changes under different graz-ing management practices.

One of the more widely recognized riparian assessment methods used by federal personnel is the "green line" survey (Cagney, 1993). Percent coverage and compo-sition of perennial vegetation is estimated at the edge of the active channel. Since many heavily grazed streams have little or no edge vegetation, eliminating grazing or changing grazing practices often leads to impressive changes in vegetation cover, which is not a surprise given moist riparian conditions. The recovery of the forb and graminoid species is often pronounced but recovery of the woody species is less predictable due to browse by big game, beaver and other factors (Rasmussen, 1996).

Many studies of riparian grazing have focused on the responses of vegetation to the exclusion of grazing (i.e., Kauffman and Krueger, 1984; Schultz and Leininger, 1990; Case and Kauffman, 1997). However, Kondolf (1993) noted that the lush growth inside grazing exclosures may mask the fact that no significant improve-ments in channel form have occurred. It is generally assumed that a recovering stream in a meadow system should become narrower and deeper—that is, the width:depth ratio of the channel should decrease with time (Elmore and Beschta, 1987; Magilligan and McDowell, 1997). However, research to date on channel changes has shown mixed results. For a recent review of channel studies conducted in grazed and ungrazed stream reaches, see McDowell and Magilligan, (1997).

In a widely cited study that demonstrated statistically significant differences in channel morphology between grazed and ungrazed areas, Clifton (1989) measured 60 channel cross sections in 1986 along Wickiup Creek, Oregon, both inside an exclosure protected from livestock for 48 yr., and in five reaches up and down-stream of the exclosure. Results showed distinct differences in channel morphology between grazed and ungrazed reaches. Width, wetted perimeter, and channel form showed the largest differences between grazed and ungrazed reaches. Clifton (1989) surmised that these differences could largely be accounted for by the influ-ence of vegetation and livestock on channel morphology.

Only one other published study (Clary et al., 1996) has measured the channel characteristics on one stream over time under different management practices. Most studies have attempted to substitute space for time by examining grazed and ungrazed reaches along the same creek (McDowell and Magilligan, 1997). The pur-pose of this study was to resurvey Clifton's (1989) channel cross sections on Wickiup Creek and examine changes since 1986. There are few other locations where high quality channel cross sectional surveys could be repeated after such a length of time. As one of the oldest riparian livestock exclosures in eastern Oregon, Wickiup Creek offered a unique opportunity to compare channel differences over time between an exclosure and adjacent grazed areas. Research questions were: (1) What changes in channel morphology have occurred in the exclosure since 1986, and more important, (2) Have there been significant improvements in channels in the grazed reaches under management that is intended to foster riparian recovery.

Dow

nloa

ded

by [

Nor

th D

akot

a St

ate

Uni

vers

ity]

at 1

4:52

17

Oct

ober

201

4


STUDY AREA

Wickiup Creek is a second order tributary to the Silvies River in eastern Oregon entirely within the boundaries of the Malheur National Forest. It has a drainage area of 24 km2, characterized by forested slopes and narrow alluvial valleys. Average precipitation is 600 mm/yr. The study basin ranges in elevation from 1516 to 1975 m with an average elevation of 1650 m, and. is mostly forested (95%) with mixed stands of ponderosa pine (Pinus ponderosa), lodgepole pine (Pinus contorta), grand fir (Abies grandis), and douglas fir (Psuedotsuga menziesii). Downstream, the valley widens into open, sagebrush Artemisia spp. steppe. Streamside vegetation consists of annual and perennial herbaceous species, occasional clumps of willow (Salixspp.), and lodgepole dominated conifer stands. Seasonal livestock grazing and tim-ber harvest are the principal land use activities.

In 1938, a 2.8 ha fenced livestock exclosure was constructed along the middle portion of the creek (Fig. 1). Photos show that in 1932 (Fig. 2), the exclosure area was almost devoid of vegetation, with a channel incised to almost 2 m. By 1948 (Fig. 3), photos show that vegetative cover had increased dramatically. By 1956 (Fig. 4) the incised channel had narrowed, as vegetation captured sediment and raised the base level of the channel. In 1986 (Fig. 5), the channel was narrow and deep and banks were densely vegetated. The incised channel had narrowed as vegetation

Fig. 1. Location of Wickiup Creek and study reaches.

Dow

nloa

ded

by [

Nor

th D

akot

a St

ate

Uni

vers

ity]

at 1

4:52

17

Oct

ober

201

4


captured sediment and raised the base level of the channel. By 1998, a wetland had developed in the center of the exclosure where the stream flowed over a dense mat of sedges without a pronounced channel.

There are no historic photos of most of the grazed reaches so we assumed that the conditions of the riparian zone were similar to those inside the exclosure in

Fig. 2. Exclosure area in 1932 before cattle were removed.

Fig. 3. Same area in 1948.

Dow

nloa

ded

by [

Nor

th D

akot

a St

ate

Uni

vers

ity]

at 1

4:52

17

Oct

ober

201

4


1938. But by 1998 (Fig. 6), compared to many other grazed streams in eastern Oregon, grazed portions of Wickiup Creek appeared to be in good condition with a relatively narrow channel and high density of streamside vegetation, dominated by native sedges (Carex spp.). Portions of the grazed area of the creek show tram-pling and other impacts of grazing, although in many areas, grazing impacts were hardly evident next to the stream. Photos of the grazed reaches taken in 1986 showed much more trampling of the banks than was apparent after grazing in either 1998 or 1999.

The overall changes in Wickiup Creek are the responses of an abused riparian systems to gradual reductions in livestock impacts over a 60-yr. period. The 1000 ha Wickiup Creek pasture is part of the larger 5920 ha Flagtail grazing allotment. Until 1964, the Flagtail was part of a much larger allotment that was managed as a single pasture. Such large pastures were typical of grazing management before the mid-1960s, resulting in cattle concentrating in the areas close to the stream and under-utilizing upland forage. In 1964 the large allotment was broken into three smaller ones and in the early 1980s, this smaller Flagtail allotment was further divided into five pastures, one of which is the Wickiup riparian pasture.

The study reaches along Wickiup Creek are all within one 1000 ha riparian pas-ture, within the center of this is the 500 m long livestock exclosure. The total animal unit months (one AUM is the amount of forage consumed by one cow/calf pair in a

Fig. 4. Same area in 1956.

Dow

nloa

ded

by [

Nor

th D

akot

a St

ate

Uni

vers

ity]

at 1

4:52

17

Oct

ober

201

4


month) of grazing on the allotment since 1980 have remained the same, but break-ing up the allotment into smaller pastures reduced livestock concentrations and impacts on the riparian zone. These pastures were initially managed using a rest-rotation system, with grazing early in the spring for 1 yr., rested the second, and grazed later in the season the third year. The pasture is now managed on a deferred rotation system with grazing every year, but with varying start and finish dates.

Between 1907 and 1966, the season of use on the allotment was reduced from 6.5 mo. to 4 mo. and AUMs were reduced by 36%. Since 1966, the allocated AUMs in the entire Flagtail allotment have not decreased (Malheur National Forest, 1983). However, estimating the actual cattle usage of the Wickiup riparian pasture over the years is difficult since the number of cattle has varied from 138 to 359 head, though the total grazing was held at no more than 430 AUMs. From 1975 through 1981 there averaged 56 days of grazing. From 1982 through 1994, grazing averaged 21 days annually with 4 yr. of complete rest from grazing. From 1994 through 1998, there have been an average of 16 grazing days annually.

Fig. 5. Exclosure area in 1986.

Dow

nloa

ded

by [

Nor

th D

akot

a St

ate

Uni

vers

ity]

at 1

4:52

17

Oct

ober

201

4


In 1990, a new forest plan was implemented that emphasized protection of many important riparian areas on the Malheur National Forest, including Wickiup Creek. The new guidelines called for removal of livestock when utilization of ripar-ian sedges reached 45% along Wickiup Creek. In practice this often meant that cat-tle were removed as soon as they started to graze on riparian plants, regardless of whether the allocated grazing level of 430 AUMs was reached. Protection for the Wickiup riparian zone is stricter than for the other pastures in the allotment and likely accounts for its relatively good condition. Grazing is much heavier in smaller riparian areas on other pastures of the allotment, and widespread bank trampling is much more evident (Fig. 8).

METHOD

In September 1998, 49 channel cross sections were measured perpendicular to flow in four reaches, three grazed and one ungrazed (Fig. 1). Channel cross sections

Fig. 6. Grazed reach number 3 in 1998.

Fig. 7. Diagram of cross section survey.

Dow

nloa

ded

by [

Nor

th D

akot

a St

ate

Uni

vers

ity]

at 1

4:52

17

Oct

ober

201

4


were measured on straight stretches only, as in the 1986 survey. The method of measuring the cross sections is described in Harrelson et al. (1994). The cross sec-tion survey involves placing endpoints, stretching a tape and measuring elevations with a surveyors level (Fig. 7). All significant breaks in slope inside the channel are measured. Outside the channel, the active floodplain, bankfull elevations, banktop and stream terraces are measured.

Since the 1985 cross sections were not permanently marked, we could not remeasure at the exact locations. To sample as close to the 1985 cross sections as possible, we replicated the same spacing used in 1985. Reaches 2a (16 cross sec-tions), 2b (11 cross sections), and 3 (14 cross sections) were surveyed at 30 m inter-vals, while Reach 4 (8 cross sections) was surveyed at a varied spacing, duplicating the spacing of the 1985 survey (Table 1).

In the ungrazed exclosure Reach 2b, two adjacent cross sections had been eliminated in 1986 due to beaver damming that created a small pond. In 1998 we eliminated two cross sections in the same area and a cross section immediately upstream where a swale-like wetland complex had been created, probably from sediment aggradation in the former beaver complex downstream.

Variables describing channel morphology were determined from the channel cross section transects. The WinXSPro computer program (West Consultants, 1997) was used as a cross section analyzer to generate values for the variables describing channel morphology: width, cross sectional area, mean depth, wetted perimeter, width:depth ratio, and hydraulic radius.

Fig. 8. Grazed and trampled riparian area outside Wickiup pasture in 1998.

Dow

nloa

ded

by [

Nor

th D

akot

a St

ate

Uni

vers

ity]

at 1

4:52

17

Oct

ober

201

4


The identification of "bankfull" stage is a critical parameter from which the other variables are calculated. In the 1986 cross sections, bankfull width was approxi-mated by "bank-top," which was the slope break at the top edge of the low flow channel where the water begins to spread out. Stream width in 1998 was also deter-mined by approximating this level, rather than the method of determining bankfull as described by Rosgen (1996). In Rosgen's method, bankfull is defined as the ele-vation where flooding begins—that is, at the point where water begins to flow onto a larger floodplain. Bankfull discharge is associated with a momentary maximum flow which on the average has a recurrence interval of 1.5 yr. (Rosgen, 1996).

The six variables from the 1986 and 1998 surveys were compared within reaches by using a two-tailed T test. A significance level of 90% (P = .1) was chosen. Vari-ables with a P value less than .1 were considered significantly different. These mor-phologic variables were also compared between the grazed and ungrazed reaches to determine if there were still significant differences in channels as there had been in 1986. The morphological data were first log transformed due to non normal dis-tribution in some of the variables and the Kruskal-Wallis Multiple-comparison Zvalue Test was used to compare the variables between reaches.

RESULTS

Channel Changes between 1986 and 1998

In grazed Reaches 3 and 4, all variables showed decreases between 1986 and 1998, indicating a change in channel form, although not all of these changes were statistically significant at the 90% level (Table 2). Reach 3 showed statistically sig-nificant changes (at the 90% level) in all parameters except the width:depth ratio. Width:depth ratio was borderline at a P value of .1. In Reach 4, width, area, and hydraulic radius showed statistically significant decreases. Reach 2A (Table 2) had a channel that widened slightly from 2 to 2.3 m and a width:depth ratio that increased from 9.4 to 10.9. This was not surprising because, for much of its length, the channel has been incised 2 m or more into its floodplain since 1938, when photos showed the initiation of a headcut at the lower end of this reach. Such a deeply incised channel is expected to be highly unstable for a long period as the banks continue to erode and a new channel and floodplain are established inside the gully. The trampling impacts of cattle on banks are likely much exacerbated in

Table 1. Summary of Reach Characteristics

ReachDistance

downstream (m) Description

2a 3,863–4,255Meadow, midbasin channel, intermittent to perennial flow. Deeply

incised at upstream end

2b 4,255–4,705Exclosure, perennial flow, channel runs through wet meadow with

swale like wetland developing in center

3 4,705–5,538 Forested/meadow reach, embedded large coarse wood, perennial flow

4 5,538–8,153 Meadow, perennial flow

Dow

nloa

ded

by [

Nor

th D

akot

a St

ate

Uni

vers

ity]

at 1

4:52

17

Oct

ober

201

4


such unstable conditions. During the 1998 grazing season, there were also much more cattle use observed in this reach compared to the downstream reaches.

The changes in Reach 2b, the ungrazed exclosure (Table 2), did not show clear trends in all variables since some variables increased while others decreased. There were statistically significant changes in the width:depth ratio, hydraulic radius, wet-ted perimeter and average depth. It was surprising to see an increase of width:depth from 2.6 to 4.6 although any values below 10 are considered optimal for a small channel such as this. This might be due to natural channel variability over a period of time or problems with the repeatability of cross sections.

Channel Differences between Grazed and Ungrazed Reaches

In 1998, as in 1986, the channel inside the exclosure was significantly different from those in the grazed reaches; width, mean depth, and width:depth being signif-icantly smaller inside the exclosure. These same variables also showed significant differences in 1986. This indicates that although the grazed channels have improved, they have not yet changed enough to match conditions within the exclo-sure, even with an increase in width:depth ratio inside the exclosure from 2.6 to 4.6.

DISCUSSION

Along Wickiup Creek, the grazed channels showed improvement in two of the three reaches, although changes were not statistically significant for all variables measured. Given the inherent variability in many channels, it might be difficult to demonstrate such statistically significant changes (McDowell and Magilligan, 1997). For instance, despite a decrease in average width:depth in Reach 3 from 18.14 to 11.5, the P value was only 0.1. It is also possible that riparian systems such as Wickiup's may take much longer to recover than might be assumed. Whether the measurement of more cross sections might have shown stronger statistical differ-ences is unknown. These data demonstrated that in both the 1986 and 1998 surveys, a few unusually wide, outlying cross sections could skew the means for an entire reach. This will likely be the case in many surveys with a limited number of cross sections. It also might illustrate some of the problems of using the cross sec-tion method to measure change in highly disturbed stream systems.

For many variables in three reaches, the coefficients of variation decreased between 1986 and 1998 (Table 2). Most variables for the exclosure showed decreases as did Reach 3, which also showed the largest decrease in the mean width;depth ratio. Variability increased in Reach 2A, a much more unstable chan-nel that also showed increases in width:depth ratio and stream width between 1986 and 1998.

Whether this decrease in variability actually indicates significant changes in the stability of the grazed channels is difficult to say since variability decreases were also seen in the exclosure. As noted above, these changes in the exclosure might be due to natural channel variability over time or problems with the repeatability of cross section measurements.

Dow

nloa

ded

by [

Nor

th D

akot

a St

ate

Uni

vers

ity]

at 1

4:52

17

Oct

ober

201

4


Tabl

e 2.

Cha

nnel

Cha

nges

bet

wee

n 19

86 a

nd 1

998

in W

icki

up C

reek

(in

Met

ers)

with

Coe

ffici

ents

of V

aria

tion

(CV

)

CV

Rea

ch 2

A g

raze

dR

each

2B

exc

losu

reR

each

3 g

raze

dR

each

4 g

raze

d

Year

sam

pled

P va

lue

Year

sam

pled

P va

lue

Year

sam

pled

P va

lue

Year

sam

pled

P va

lue

1986

1998

1986

1998

1986

1998

1986

1998

Wid

th2.

00(2

0%)

2.34

(35%

).1

81.

21(6

5%)

1.45

(22%

).3

23.

34(5

2%)

2.08

(28%

).0

23.

27(2

6%)

2.45

(36%

).0

8

Ave

rage

dep

th0.

24(3

3%)

0.24

(33%

).8

70.

40(3

2%)

0.32

(25%

).0

60.

21(3

8%)

0.20

(35%

).6

10.

25(2

8%)

0.24

(45%

).8

Wet

ted

peri

met

er2.

23(2

0%)

2.76

(30%

).0

41.

70(3

7%)

2.30

(17%

).0

093.

41(4

9%)

2.36

(29%

).0

43.

40(2

5%)

2.90

(24%

).2

Are

a m

20.

47(2

9%)

0.56

(51%

).3

0.42

(38%

)0.

46(3

9%)

.41

0.67

(38%

)0.

41(2

5%)

.01

0.80

(22%

)0.

53(2

0%)

.003

Wid

th to

dep

th r

atio

9.39

(46%

)10

.9(4

4%)

.38

2.61

(53%

)4.

60(2

5%)

<.0

0118

.14

(75%

)11

.5(4

4%)

.113

.48

(67%

)12

.57

(60%

).8

Hyd

raul

ic ra

dius

0.21

(28%

)0.

19(2

6%)

.34

0.25

(20%

)0.

21(2

3%)

.07

0.20

(35%

)0.

16(3

1%)

.08

0.24

(25%

)0.

2(2

0%)

.09

Dow

nloa

ded

by [

Nor

th D

akot

a St

ate

Uni

vers

ity]

at 1

4:52

17

Oct

ober

201

4


All of these results should be viewed with some caution since the comparison of channel variables between 1986 and 1998 hinged on the determination of the bankfull/banktop points. We chose these points to approximate the approach used in 1986 as closely as possible but there could still be problems because of a lack of repeatability in this measurement. As described below, there are often discrepan-cies between studies in how the banktop/bankfull parameter has been determined.

The present good conditions along Wickiup Creek are not typical of many more heavily grazed riparian areas on the forest. We suggest that these changes in the Wickiup riparian pasture are mostly due to being managed more carefully than other pastures in the grazing allotment. Channel improvements in the Wickiup riparian area reflect the potential for success of the most cautious grazing manage-ment approaches which are being used on federal grazing lands. In eastern Oregon this has meant limiting the impacts of livestock on riparian areas by controlling the season or intensity of use. Although it has been suggested that the rest-rotation and deferred rotation grazing management used on Wickiup Creek can lead to moder-ate levels of riparian improvements (Elmore, 1992; Elmore and Kauffman, 1994), we know of no other studies besides ours that have quantified improvements in channel conditions under such management.

One negative aspect of the rest-rotation and deferred rotation grazing which has been used in Wickiup Creek is that shrub and tree species may be impacted more than in some other grazing systems (Elmore and Kauffman, 1994). In comparison with the grazed reaches, there is much more willow (Salix sp.) present in the exclo-sure, although the local range manager reported that after cattle exclusion willow had increased in the exclosure and then declined sharply for as yet unknown rea-sons. This decrease could be due to herbivory from big game and beaver, or increased soil saturation.

Other Possible Factors Driving Channel Changes

Without access to streamflow and climate data it is difficult to tease out how these variables might have influenced changes on Wickiup Creek. No streamflow data are available for Wickiup Creek for any years since 1938. The closest rainfall monitoring station is 30 km distant at a lower elevation with precipitation averaging about 60% of that on Wickiup Creek. Data from this station is also incomplete for 5 of the years between 1987 and 1998 and for many of the years prior to 1987.

Bank and gully erosion from upstream may expain the early recovery of them. Exclosure between 1938 and 1986. A photo from 1938 showed a gully nick point 200 m upstream of the exclosure which migrated to incise the creek to a depth of about 2 m along a 300 m length. This gully has stabilized with no active nick points and is now feeding less sediment into the stream that might be deposited in the grazed reaches.

The amount of fine sediment moving through a drainage, available for capture in riparian areas, may be a key determinant of a stream's capacity for recovery. It may appear ironic that in some seriously degraded streams, sediment may be of benefit if its capture by riparian vegetation can raise the base levels of the channels and

Dow

nloa

ded

by [

Nor

th D

akot

a St

ate

Uni

vers

ity]

at 1

4:52

17

Oct

ober

201

4


restore floodplain morphology by rebuilding stream banks and narrowing the chan-nels (Winegar, 1977; Jensen and Platts, 1989).

There might not be enough sediment moving off the uplands to rebuild channels and restore floodplain functions to pre-degradation states for many decades or longer in Wickiup Creek. Surface erosion often delivers far less sediment to chan-nels than has often been assumed. Even in heavily logged areas in eastern Oregon's Blue Mountains, erosion from roaded and clearcut slopes amounted to less than one ton km2/yr. (Gill, 1995) and much of the sediment in steams in this region may be from erosion inside the channel. Abusive grazing may result in severe hillside sheet and rill erosion. But because cattle concentrate in streamside riparian zones, these small areas have often suffered the most severe degradation (Kauffman and Krueger, 1984; Elmore and Beschta, 1987; Armour et al., 1991) and eroded, tram-pled streambanks may also be the largest direct sediment contributors.

Nagle and Ritchie (1999) used residual nuclear bomb-derived 137Cs as a sediment tracer to quantify source areas of channel bottom sediment within three tributaries of the Umatilla and upper Grande Ronde basins in northeastern Oregon. Land use in each stream was dominated by agriculture, logging, or grazing. A sim-ple mixing model was used to estimate the relative portion of channel bottom sed-iment derived from the surface horizon and channel banks. Calculations from the 137Cs tracer indicated that channel banks accounted for 56%, 74%, and 93% of the of the bottom sediment in the three study drainages.

Although little empirical research has yet been done on the possible role of bea-ver, there is a widespread belief among many watershed scientists in Oregon that beaver can play a critical role in furthering stream recovery. A primary impact of beaver dams and their associated wetlands might be the capture of fine sediment (Butler and Malanson, 1995) in sediment starved streams. Even if beaver dams wash out, vegetation often stabilizes much of the sediment deposited upstream of dams. In one of the only studies to examine the impacts of beaver on channel morphology, Fouty (2003) used channel cross sections to document the tremendous impacts bea-ver dams had on the capture of sediment along Price Creek, in southwest Montana. There have been beaver present in one short section in the Wickiup exclosure at various times since 1938 although a lack of riparian willow has likely limited their impacts and duration of occupancy. It is difficult to say what specific impacts beaver might have had on the recovery in the exclosure. During the 1998 survey, three cross sections were eliminated inside the exclosure due to beaver ponding, as were two cross sections in the same area in 1986. There are no beaver present in the other reaches, probably due to a paucity of mature willow necessary for beaver to persist in this area.

Methodological Considerations for Future Channel Monitoring Studies

It is not yet clear what monitoring methods are most appropriate for assessing highly variable channel responses to restoration efforts. We need methods that can allow us to cover large areas, are repeatable, and can produce statistically valid results.

Dow

nloa

ded

by [

Nor

th D

akot

a St

ate

Uni

vers

ity]

at 1

4:52

17

Oct

ober

201

4


Thus far, reports of channel responses to grazing exclusion have been mixed. Magilligan and McDowell (1997) noted the statistical difficulties inherent in the use of parametric tests such as analysis of variance and differences of means in channel studies. Instead, they used exploratory data analysis to graphically displayed differ-ences in four eastern Oregon creeks between grazed areas and exclosures greater than 14 yr. old. The channels within the exclosures had bankfull widths 10% to 20% narrower than grazed areas and the percent of channel area occupied by pools was 8% to 15% higher. However, not all of the channel properties showed adjust-ment and they noted that 14 yr. might not be enough time for recovery.

Lancaster et al. (1998) reported no changes in channel morphology after 10 yr. of grazing exclusion in a stream in northern California. Kondolf (1993) reported no differences in channel width within and outside a 24-year-old grazing exclosure in the Sierra Nevada. Medina and Martin (1988) also reported no difference in width:depth ratios within and outside an 8-year-old exclosure in Mew Mexico. Both Medina and Martin (1988) and Kondolf (1993) speculated that the lack of channel improvement might be due to continuing unstable conditions in the water-sheds which were still grazed, while the exclosures occupied only a small portion of the stream length. Kondolf (1993) also suggested that despite the increase in plant cover along the banks, the lack of channel narrowing and bank building might be due to a paucity of clastic sediments (mud, sand, and gravel) since most sedi-ments passed through as dissolved loads. In the only published study using repeat surveys to examine channel differences over time, Clary et al. (1996) reported that although there was no statistically significant difference in width:depth ratios between grazed reaches and an exclosure, the exclosure still showed a decreasing trend over a 6-yr. monitoring period while outside the exclosure under moderate to heavy grazing, the width:depth ratio actually increased.

The variation reported in channel responses is likely due to different stream conditions but perhaps also to the varying approaches for measuring channel attributes. It is not clear in some studies how parameters such as stream width and width:depth ratios were determined, and whether straight or meandering stream sections were measured. Harrelson et al. (1994) mention that cross sections should be put in on straight stretches between two meander bends. It is not apparent from the literature whether this approach was followed by other researchers. Kondolf (1993) measured cross sections on a specific spacing and made no mention of avoiding meanders in placing them. In contrast, Clifton's (1989) cross sections were only on straight parts of the channel. Another source of confusion appears to be the parameters used to determine the width:depth ratio. It is not apparent how stream width was determined in many studies. The National Resources Conservation Ser-vice (1995) suggests that the width:depth ratio be determined by the average wetted width divided by the water depth at mean summer flow. In contrast. Rosgen (1996) uses bankfull width and depth, with bankfull defined as the discharge associated with a recurrence interval of about 1.5 yr. The determination of this bankfull level is notoriously difficult even for experienced hydrologists.

The problems that some researchers had in demonstrating significant differences might be due to inherently high variability in stream channels but the small number of cross sections in studies such as Kondolf's (1993; 7 in the exclosure and 8 in the

Dow

nloa

ded

by [

Nor

th D

akot

a St

ate

Uni

vers

ity]

at 1

4:52

17

Oct

ober

201

4


grazed reach) may have masked differences between grazed and ungrazed reaches. Although we had more cross sections to compare in the grazed reaches of Wickiup Creek than have been reported in other studies (Medina and Martin, 1988; Kondolf, 1993), it is not known how many cross sections would adequately compare changes in such variable systems over time.

Intensively measured channel cross sections such as we used in this study are useful for closely monitoring small areas but they are time consuming and difficult to use in covering long stretches of stream. If many sites are to be monitored over time, a simpler, more easily replicable approach is necessary. Other studies have reported the use of low flow width and depth (McDowell and Magilligan, 1997), unlike bank-full width which is somewhat subjective, these are specific measurements that can be made quickly. Robison and Beschta (1989) suggest using wetted width and thalweg depth (the deepest part of the channel) to estimate stream cross sectional area, mea-surements which can be done by one person with a measuring rod. By measuring wetted width and thalweg depth at 1 to 2 m intervals along a stream, many cross sec-tional area measurements can be made, thus improving statistical power, better account for stream variability, and allowing coverage of more stream length. Robison and Beschta's study (1989) of 334 cross sections in 9 stream reaches indicated no sta-tistical difference in cross sectional area using this quick method compared to meth-ods using fewer, more detailed transects. In places subject to summer thunderstorms, occasional high flows may throw off low flow measurements.

CONCLUSION

We compared stream channel cross section measurements taken in 1986 and 1998 in one ungrazed and three grazed reaches of Wickiup Creek in eastern Oregon. Grazed channels were still significantly different from the channel inside a 60-year-old ungrazed exclosure. In 1998, the channel characterisitics: mean width, mean depth, and width:depth ratio remained significantly smaller inside the exclo-sure.

In two grazed reaches, the channel showed improvement in all parameters although not all of these were statistically significant at the 90% level. Summer grazing in the Wickiup riparian pasture is managed more carefully than is still typ-ical for many streams on federal lands in eastern Oregon, and the degree of channel improvement reported in this study on grazed areas may not be found elsewhere. Nonetheless our results indicate the potential success of changes in grazing prac-tices that have become more common on federal lands.

The intensive channel cross section method used in this study to compare grazed and ungrazed stream reaches, presents problems with statistical analysis and repeatability. The rapid method of taking multiple channel cross sectional area measurements by using the thalweg (the deepest part of the channel) depth and wetted width (Robison and Beschta, 1989) shows much promise for future riparian monitoring work.

Acknowledgments: Primary funding was provided by the Aquatic/Lands Interaction Program of the U.S. Forest Service, Pacific Northwest Research Station, Corvallis, Oregon. Kathryn Ronnenberg pro-vided invaluable help with the graphics. We are grateful for help with the fieldwork and analysis of the

Dow

nloa

ded

by [

Nor

th D

akot

a St

ate

Uni

vers

ity]

at 1

4:52

17

Oct

ober

201

4


data from Pat McDowell, Emily Schubert, Zig Napkora, Jim Still, Robin Harris, Jeff Way, and Suzanne Fouty. Conversations with Boone Kauffman and Bob Beschta were invaluable, as were the editing com-ments by Nick Otting, Dana Lytgen, and Kate Dwire.

REFERENCES

Armour, C. L., Duff, D. A., and Elmore, W. (1991) The effects of livestock grazing on riparian and stream ecosystems. Fisheries, Vol. 19, 7–11.

Belsky, A. J., Matzke, A., and Uselman, S. (1999) Survey of livestock influences on stream and riparian ecosystems in the western United States. Journal of Soil and Water Conservation, Vol. 54, 419–431.

Butler, D. R. and Malanson, G. P. (1995). Sedimentation rates and patterns in beaver ponds in a mountain environment. Geomorphology, Vol. 13, 255–269.

Cagney, J. (1993) Greenline Riparian-Wetland Monitoring. Denver, CO: U.S. Dept of the Interior, Bureau of Land Management. Technical Reference 1737-8.

Case, R. L. and Kauffman, J. B. (1997) Wild Ungulate influences on the recovery of willows, black cottonwood and thin-leaf alder following cessation of cattle graz-ing in northeastern Oregon. Northwest Science, Vol. 71, 115–124.

Clary, W. B., Shaw, N. L., Dudleyk, J. G., Saab, V. A., Kinney, J. W., and Smithman, L. C. (1996) Response of a Depleted Sagebrush Steppe Riparian System to Graz-ing Control and Woody Plantings. Boise, ID: U.S.D.A. Forest Service. Research Paper INT-RP-492.

Clary, W. P. and Webster, B. F. (1989) Managing Grazing of Riparian Areas in the Intermountain Region. USDA Forest Service. Boise, ID: Intermountain Research Station. General Technical Report INT-263.

Clifton, C. F. (1989) Effects of vegetation and land use on channel morphology. In R. E. Gresswell, B. A. Barton, and J. L. Kershner, eds., Practical Approaches to Riparian Resource Management. Billings, MT: U.S. Government Printing Office, U.S. Bureau of Land Management, 121–129.

Cottam, W. P. and Stewart, G. (1940) Plant succession as a result of grazing and of meadow dessication by erosion since settlement in 1862. Journal of Forestry, Vol. 38, 613–626.

Dobyns, H. F. (1981) From Fire to Flood: Historic Human Destruction of Sonoran Desert Riverine Oases. Soccoro, NM: Ballena.

Elmore, W. (1992) Riparian responses to grazing practices. In R. J. Naiman, ed., Watershed Management: Balancing Sustainability and Environmental Change. New York, NY: Springer Verlag, 442–457.

Elmore, W. and Kauffman, J. B. (1994) Riparian and watershed systems: Degradation and restoration. In M. Vavra, W. A. Laylock, and R. D. Pieper, eds., Ecological Implications of Livestock Herbivory. Denver, CO: Society for Range Management, 212–231.

Elmore, W. and Beschta, R. L. (1987) Riparian areas: Perceptions in management. Rangelands, Vol. 9, 260–265.

Fouty, S. C. (2003) Current and Historic Stream Channel Response to Changes in Cattle and Elk Grazing Pressure and Beaver Activity. Unpublished doctoral dis-sertation, University of Oregon, Department of Geography.

Dow

nloa

ded

by [

Nor

th D

akot

a St

ate

Uni

vers

ity]

at 1

4:52

17

Oct

ober

201

4


General Accounting Office. (1988) Public Rangelands: Some Riparian Areas Restored but Widespread Improvement Will Be Slow. Washington, DC: GAO-RCED-88-105.

Gill, R. E. (1995) Sediment Delivery to Headwater Stream Channels Following Road Construction and Timber Harvest in the Blue Mountains, Oregon. Unpublished masters thesis, Oregon State University, Corvallis, OR.

Harrelson, C. C., Rawlins, C. L., and Potyondy, J. P. (1994) Stream Channel Refer-ence Sites: An Illustrated Guide to Field Technique. Ft. Collins, CO: USDA, Forest Service, General Technical Report RM-245.

Jensen, S. E. and Platts, W. S. (1989) Restoration of degraded riverine/riparian hab-itat in the Great Basin and Snake River region. In J. A. Kusler and M. E. Kentula, eds., Wetland Creation and Restoration: The Status of the Science (Vol. 1). Corvallis, OR: U.S. Environmental Protection Agency, 77–117.

Kauffman, J. B. and Krueger, W. C. (1984) Livestock impacts on riparian ecosystems and streamside management implications: A review. Journal of Range Manage-ment, Vol. 37, 430–438.

Kindschy, R. H. (1989) Regrowth of willow following simulated beaver cutting. Wildlife Society Bulletin, Vol. 17, 290–294.

Kondolf, G. M. (1993) Lag in stream channel adjustment to livestock exclosure, White Mountains, California. Restoration Ecology, Vol. 1, 226–230.

Kovalchik, B. L. and Chitwood, L. A. (1990) Use of geomorphology in the classifi-cation of riparian plant associations in mountainous landscapes of central Oregon, USA. Forest Ecology and Management, Vol. 33/34, 405–418.

Lancaster, D. L., Vance, L., Tate, K. W., and Lile, D. (1998) The Cedar Creek Resto-ration project and the limits of cross-section monitoring as an indicator of change. In D. F. Potts, ed., Proceedings, AWRA Specialty Conference: Rangeland Management and Water Resources. Herndon, VA: American Water Resources Association, 136.

Magilligan, F. J. and McDowell, P. F. (1997) Stream channel adjustments following elimination of cattle grazing. Journal of the American Water Resources Associa-tion, Vol. 33, 867–878.

Malheur National Forest. (1983) Environmental Assessment Report: Flagtail Allot-ment Management Plan. John Day, OR: Author.

McDowell, P. F. and Magilligan, F. J. (1997) Response of stream channels to removal of cattle grazing disturbance: overview of western U.S. exclosure studies. In S. S. Y. Wang, E. J. Langendoen, and F. D. Shields, Jr., eds., Proceedings of Conference on Management of Landscapes Disturbed by Channel Incision. Oxford, MS: Uni-versity of Mississippi, 469–475.

Medina, A. L. and Martin, S. C. (1988) Stream channel and vegetation changes in sections of McKnight Creek, New Mexico. Great Basin Naturalist, Vol. 48, 373–381.

Nagle, G. N. (1993) The Rehabilitation of Degraded Riparian Areas in the Northern Great Basin. Unpublished masters thesis, Cornell University, Ithaca, NY.

Nagle, G. N. and Ritchie, J. (1999) The use of tracers to study sediment sources in three streams in northeastern Oregon. Physical Geography, Vol. 20, 348–366.

Dow

nloa

ded

by [

Nor

th D

akot

a St

ate

Uni

vers

ity]

at 1

4:52

17

Oct

ober

201

4


Natural Resources Conservation Service. (1995) Riparian Appraisal and Aquatic Habitat Evaluation. Boise, ID: Author, Range Technical Note No. ID-67.

Platts, W. S., Gebhardt, K. A., and Jackson, W. L. (1985) The effects of large storm events on basin-range riparian stream habitats. In Riparian Ecosystems and Their Management: Reconciling Conflicting Uses. First North American Riparian Con-ference April 16–18, 1985, Tucson, AZ. Fort Collins, CO: USDA Forest Service General Technical Report RM-120, 30–34.

Rasmussen, C. G. (1996) Results of a Riparian Survey Method Used in Eastern Oregon. Unpublished masters thesis, Oregon State University, Corvallis, OR.

Roath, L. R. and Krueger, W. C. (1982) Cattle grazing and behavior on a forested range. Journal of Range Management, Vol. 35, 332–338.

Robison, E. G. and Beschta, R. L. (1989) Estimating stream cross sectional area from wetted width and thalweg depth. Physical Geography, Vol. 10, 190–194.

Rosgen, D. (1996) Applied River Morphology. Pagosa Springs, CO: Wildland Hydrology.

Schultz, T. T. and Leninger, W. C. (1990) Differences in riparian vegetation structure between grazed areas and exclosures. Journal of Range Management, Vol. 43, 295–299.

Skovlin, J. M. (1984) Impacts of grazing on wetlands and riparian habitats: A review of our knowledge. In Committee on Developing Strategies for Rangeland Man-agement, ed., Developing Strategies for Rangeland Management. Natural Resources Council, National Academy of Sciences. Boulder, CO: Westview, 1001–1103.

Van Haveren, B. P. and Jackson, W. L. (1986) Concepts in stream riparian rehabili-tation. Transactions of the 51st North American Wildlife and Natural Resources Conference, Vol. 51, 280–289.

West Consultants. (1997) WinXSPro. Version 1.31. Ft. Collins, CO: Author, Pre-pared for USDA Forest Service, Rocky Mountain Research Station.

Winegar, H. H. (1977) Camp Creek channel fencing-plant, wildlife, soils, and water response. Rangeman's Journal, Vol. 4, 10–12.

Dow

nloa

ded

by [

Nor

th D

akot

a St

ate

Uni

vers

ity]

at 1

4:52

17

Oct

ober

201

4

Channel Changes Over 12 Years on Grazed and Ungrazed Reaches of Wickiup Creek in Eastern Oregon

Documents

Transcript of Channel Changes Over 12 Years on Grazed and Ungrazed Reaches of Wickiup Creek in Eastern Oregon