SELBY CREEK STREAM HABITAT RESTORATION AND RIPARIAN REVEGETATION PROJECT: GEOMORPHIC ANALYSIS AND REVIEW

Transcription

1 SELBY CREEK STREAM HABITAT RESTORATION AND RIPARIAN REVEGETATION PROJECT: GEOMORPHIC ANALYSIS AND REVIEW Submitted to Bioengineering Institute P.O. Box 1554 Laytonville, CA By Matthew O Connor, PhD, PG #6847 P.O. Box 794, Healdsburg, California May 25, 2007

2 TABLE OF CONTENTS Introduction... 1 Study Area and Geomorphic Setting... 1 Watershed Characteristics... 1 Alluvial Fan Characteristics and Current Conditions... 2 Influence of Restoration Objectives on Geomorphic Processes... 3 Field Investigation... 4 Field Methods... 5 Results... 5 Hydraulic Analysis and Bed Load Transport Rates... 6 Bankfull Flow Estimates... 6 Bed Load Transport Rate Estimates... 8 Potential Project Impacts on Geomorphic Processes... 9 Conclusions and Recommendations References Cited APPENDIX... 13

3 Selby Creek Restoration Plan Geomorphic Review 1 Introduction This geomorphic review of the restoration design plan for Selby Creek in the northern Napa River watershed provides an evaluation of the likely effectiveness of the restoration plan, taking into consideration watershed and reach fluvial geomorphology. Specific issues of potential concern include flood potential and channel stability. This analysis provides an overall evaluation of restoration plan objectives and techniques, and identifies proposed restoration plan elements that might be inappropriate for the reach. Elements of the geomorphic review process included review of the restoration plan, field observations pertaining to fluvial geomorphology and reach/site prescriptions, analysis of hydraulics and sediment transport based on independent field surveys conducted for this review, discussion of potential design issues and monitoring objectives with representatives of Bioengineering Institute (the restoration plan designer and contractor), and development of recommendations. The focus of this geomorphic review was modified somewhat from the original scope of work. Observations of field conditions at the outset of the review indicated that potential impacts of the restoration project on flood potential and channel stability should be the primary objective of the geomorphic review. Hence, the review of the project design focused on identifying design elements that would be most likely to affect flooding and channel stability. Study Area and Geomorphic Setting Watershed Characteristics The restoration project area (see maps in Appendix) is the entire length of Selby Creek between its confluence with the Napa River and the road crossing at Silverado Trail. Just above this road crossing is the confluence of two major tributaries comprising the watershed: Biter Creek and Dutch Henry Canyon. These tributaries drain steep mountainous terrain with forest and brush cover underlain by volcanic rocks of the Tertiary age Sonoma Volcanics. Mean annual precipitation for the watershed is about 41 inches. As can be seen in the topographic maps (Appendix), the tributaries in the upper watershed are relatively steep and confined and cross a major break in slope at the transition between the mountain slopes and the valley floor about 1,000 to 2,000 ft upstream from Silverado Trail. Sediment transported in the more energetic channels in the steep mountain valleys will tend to be deposited, at least temporarily, in the flatter valley reaches. Dutch Henry Canyon contains several thousand feet of moderately confined, moderately steep channel upstream of the valley floor, and considerable dynamic sediment storage is likely to exist in that area. Nevertheless, based on the

4 Selby Creek Restoration Plan Geomorphic Review 2 caliber (boulders and cobbles) of sediment deposited upstream of Silverado Trail, sediment transport capacity at the upper end of Selby Creek is high. Although the more abrupt transitions of channel slope and valley width in the watershed occur upstream of Selby Creek, changes in channel slope extend into Selby Creek as channel gradient continues to decline between Silverado Trail and the Napa River confluence. The gradual decline in channel slope is characteristic of the alluvial fan that occupies the portion of the Napa Valley crossed by Selby Creek. The surface of the fan is completely developed in vineyard fields, with a few residential properties fronting Selby Creek near Silverado Trail and near the confluence with the Napa River (see maps in Appendix). Alluvial Fan Characteristics and Current Conditions Typical characteristics of alluvial fan geomorphology include relatively high rates of sediment transport and deposition, concomitant channel instability manifested by bank erosion, channel avulsion and channel migration, shifting and localized occurrence of overbank flow, and declining sediment size and channel slope in the downstream (distal) portions of the fan. Alluvial fan processes are modulated by rates of tectonic uplift, base level change, climate and watershed erosion processes, and land management. Alluvial fan conditions and channel conditions in the study area in the era immediately prior to European settlement are not known with certainty for the project area. It is possible that multiple small channels, or no distinct channel, may have occupied the distal portions of the fan, and that watershed runoff reached the Napa River by a variety of shifting flow paths. Channel morphology is determined primarily by channel gradient and substrate. Channel gradient is variable locally, but is about 0.01 (1%) on average. This suggests that plane bed morphology (a flat-bottomed, rectangular channel) might be expected in steeper locations with pool development most likely to occur where gradient is in the lower end of this range at stream bends or where local flow resistance elements (e.g. woody debris) are present to for channel scour and pool development (Montgomery and Buffington 1997). Gravel dominated substrate is also more likely to develop pool morphology in response to scour caused by resistance elements. Riparian vegetation, particularly tree stems emerging from channel banks, would contribute to the development of pools. Under existing conditions that have evolved over more than 100 years of agricultural development, the position of Selby Creek appears to have been actively maintained by excavation of coarse sediment and placement of this material along the banks in crude levees. This is evident in reaches of Selby Creek upstream of Larkmead Lane (Reaches 1 through 5 in the Restoration Project). Artificial channel enlargement of this type may have affected geomorphic processes in downstream portions of Selby Creek by changing flow and sediment transport conditions. Bank protection measures, including locally extensive rip-rap, are common in the reaches downstream of Larkmead Lane (Restoration

5 Selby Creek Restoration Plan Geomorphic Review 3 Project Reaches 6 and 7). The relative scarcity of mature riparian vegetation limits potential development of pools, and plane bed channel morphology is most typical of the current channel condition. Judging from the high frequency of bare, near-vertical banks and the widespread absence of substantial riparian vegetation, bank erosion is relatively widespread and uncontrolled. Upstream of Larkmead Lane, bank material typically includes coarse and/or cohesive sediment that has relatively high resistance to erosion. Nevertheless, even where erosion resistant bank materials are present, persistent erosion is expected to continue under current conditions. Three major geomorphic discontinuities exist in Selby Creek. First, the Silverado Trail bridge is a major grade control structure that induces some downstream scour and deposition upstream. Conditions at this crossing, particularly fish passage issues, have been investigated recently (Koehler and Blank 2006). Second, the Larkmead Road Bridge creates a backwater effect during periods of bankfull flow under current conditions, inducing deposition of sediment upstream. The channel approaches the bridge at an angle, and under current conditions, the stream energy is focused on the right (southwest) bank. A large gravel bar has formed on the left bank, reducing the crosssection area of one of the bridge archways. The combined effect of turbulence against the bank and reduction of cross-section area by the gravel bar is reduced flow capacity and development of a backwater extending upstream, inducing additional sediment deposition upstream. Finally, at the transition from Restoration Project Reach 7 and 8 (located a short distance downstream of Cross Section 6 as shown in the map, Appendix B), the channel enlarges and gradient increases as the channel steepens in its approach to the Napa River. This suggests that Selby Creek has incised the valley floor in response to declining channel elevation in the Napa River. This grade adjustment can be expected to continue in the future, however, it is modulated to a large degree by flood flows in the Napa River that create a backwater extending well upstream in Reach 8. High rates of channel incision by Selby Creek do not appear to be occurring under present conditions. The continuity of surface flow in Selby Creek is seasonal, with most of the reach going completely dry at the surface during the summer. The water table intersects the channel bed downstream of Larkmead Bridge as the channel gradually dewaters in the spring and summer. The water table appears to reach a stable elevation approximately at the transition from Restoration Project Reach 7 and 8. One of the objectives of the project is to improve aquatic and riparian habitat conditions for steelhead, if possible including extending the seasonal duration of surface flows by deepening the channel thalweg to better maintain contact with the seasonal water table. Influence of Restoration Objectives on Geomorphic Processes The Restoration Project proposes a variety of treatment to stabilize stream banks, create lateral scour forces to encourage development of pools, and to develop stands of native riparian vegetation. Bank stabilization with boulder structures and riparian vegetation will tend to produce roughness elements that will induce lateral scour and initiate

6 Selby Creek Restoration Plan Geomorphic Review 4 development and deepening of a channel thalweg (a distinct continuous thread of high velocity flow in a relatively deep portion of the channel), hopefully progressing to development of sequences of alternating pools and gravel bars. These treatments are also predicted to reduce long-term delivery of sediment by bank erosion to the channel; the Restoration Project predicts that bank erosion will be reduced by about 6,200 yards over an unspecified time period. If this volume of material were spread over the channel bottom over the length of Selby Creek, it would represent approximately 1 ft of deposition. The introduction of riparian vegetation and boulder structures to the channel will also tend to increase channel roughness. The increased flow resistance (channel roughness) of vegetation and boulders is essential to the restoration project, and is expected to produce most of the benefits to aquatic habitat. The increased flow resistance, however, will also tend to increase overall channel roughness, potentially reducing the capacity of the channel and potentially increasing the frequency of overbank flow. The hoped-for shift of channel morphology from plane bed to development of at least some sequences of pools and gravel bars also implies a somewhat higher overall channel roughness. The field component of this investigation, discussed in the following section, was thus designed to investigate the spatial distribution of overbank flow under current conditions and to estimate the spatial variation in sediment transport capacity in Selby Creek. The results of this investigation are then used to develop design and monitoring recommendations for the Restoration Project. Field Investigation The field investigation was conducted in three days, including an initial site reconnaissance with Evan Engber of the Bioengineering Institute. The field reconnaissance familiarized us with the project area and the proposed restoration treatments, and enabled us to identify the aforementioned channel discontinuities. The reconnaissance also allowed for observation of evidence of overbank flow and sediment deposition patterns in Selby Creek. Data and observations regarding channel conditions contained in the Restoration Project proposal were also used for reconnaissance purposes and to confirm preliminary interpretations of geomorphic condition. The reaches where sediment deposition is most significant coincides with reaches that appear to be prone to overbank flow: Restoration Project Reaches 5, 6 and 7, beginning about 1,000 ft upstream of the bridge at Larkmead Lane. We surveyed six cross sections, with concurrent surveys of the channel thalweg gradient and channel surface sediment size distribution. These data were used to estimate channel flow capacity at bankfull and to estimate bed load sediment transport capacity at bankfull flow. Cross section locations were chosen to represent conditions where channel capacity was low and the potential for overbank flow was relatively high.

7 Selby Creek Restoration Plan Geomorphic Review 5 Field Methods Cross section and channel gradient surveys were conducted with a tripod-mounted auto level with elevation measured to the nearest 0.01 ft. Cross sections are graphically displayed in Appendix B; bankfull depth was determined from the cross section graphs as the elevation difference between the lowest point in the channel and the lowest of the two channel banks. Channel gradients were measured over a distance of several channel widths, ranging from 190 ft to 300 ft. Channel gradient was estimate as the slope of a linear regression line passing through the channel elevation data from downstream to upstream. Sediment size distribution was measured with a systematic pebble count, with a count of approximately 150 per cross section site. Results Field data from channel surveys are summarized in Table 1 below. Table 1. Summary of channel survey data. Cross Section Channel slope (ft/ft) Bankfull depth (ft) Median surface sediment diameter (mm) Project Reach As can be seen in Table 1, there is relatively consistent pattern of declining channel gradient in the downstream direction, with a notable deviation at Cross Section 3 located just upstream of the Larkmead Lane bridge. This abrupt slope decline is interpreted to result from locally abundant sediment deposition in the backwater caused by the bridge during times of peak flow. Bankfull depth is lowest in the area upstream of Larkmead Lane (Cross Sections 2 and 3), and the median sediment size at these sections is lower than might be expected relative to areas upstream and downstream considering the overall slope trend. Sediment size distributions are shown in Figure 1. The apparent discontinuity in size distribution, hypothetically resulting from backwater effects at the bridge, is suggested by size distributions at Cross Sections 1 and 4 relative to Cross Sections 2 and 3. Excluding the size distributions at Cross Sections 2 and 3, the size distributions become steadily finer from upstream to downstream. This suggests accelerated depositional processes at Cross Sections 2 and 3, and supports the assessment that the Larkmead Lane bridge causes a discontinuity in the channel.

8 Selby Creek Restoration Plan Geomorphic Review 6 Percent Finer 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Sediment Diameter (mm) XS 1 (Reach 3) XS 2 (Reach 5) XS 3 (Reach 5) XS 4 (Reach 6) XS 5 (Reach 6) XS 6 (Reach 7) Whole Reach Figure 1. Surface sediment size distributions Hydraulic Analysis and Bed Load Transport Rates The survey data, summarized in Table 1, and the cross section surveys (see Appendix), provided the requisite data to estimate bankfull channel flow capacity using WinXSPro computer software developed by the USDA Forest Service (Hardy, Panja et al. 2005). Given the sediment size distributions (Figure 1), WinXSPro can also produce estimates of bed load sediment transport rate according to a widely-used formula developed for gravel bed streams. Bed load is the coarse sediment, primarily gravel, that is transported during period of peak flow by rolling or skipping along the stream bed. Bankfull Flow Estimates In addition to the survey data described above, an estimate of flow resistance (channel roughness-in this case, Mannings n ) is required to estimate discharge for bankfull flow. Flow resistance is rarely measured directly, and is usually estimated. WinXSPro contains well-known algorithms for estimating roughness; Jarrett (1984) is an appropriate algorithm for Selby Creek based on channel gradient and sediment size. For each of the six cross sections, we computed a range of bankfull flows, with the estimate based on Jarrett s roughness representing the most likely value. The range of flows was extended by evaluating bankfull discharge for the likely potential range of n. The results from this procedure are summarized in Table 2. The estimates in Table 2 provide a means to compare channel capacity at different crosssections, but does not provide any direct perspective on the frequency of flow events that would generate bankfull flows estimated in Table 2. We used the US Geological Survey s flood frequency software, NFF v3.0 (available via the internet from the USGS Water Resources Division web site), to provide flood frequency estimates for Selby Creek (Table 3). Inputs to NFF are watershed drainage area (5.8 sq. mi.), annual

9 Selby Creek Restoration Plan Geomorphic Review 7 precipitation (41 ) and an index number relating to mean watershed elevation (1 for the upper watershsed indicating mean elevation of approximately 1000 ft to the nearest 1000 ft). Table 2. Estimated bankfull discharge for six cross sections over a range of estimated channel roughness values. Bankfull discharge (cfs) Cross Section n from Jarrett Jarrett roughness n =.04 n =.05 n =.06 N =.07 n =.08 n = Table 3. Estimated flood frequency and magnitude from USGS NFF 3.0 for Selby Creek. Recurrence Interval (yrs) Peak Discharge (cfs) Standard Error of Estimate (%) Interval Estimate (Mean +/- 1 std. er.) cfs not determined not determined not determined It is apparent from Table 2 that Cross Sections 3, 4 and 5 have substantially lower bankfull flow capacity than locations further upstream and further downstream. These sections extend from just upstream of Larkmead Lane through Project Reach 6. The best estimate of channel capacity (Jarrett s roughness, third column in Table 2) for these locations is about 330 cfs. Assuming relatively low roughness (n=0.04, fourth column in Table 2), bankfull capacity in this area might be as high as about 440 to 520 cfs. Compared to the mean estimate of peak flow magnitude and frequency summarized in Table 3, stream flow exceeds channel capacity at these three sections more frequently than the one year in two (2 yr recurrence interval, annual probability > 0.5). Considering the low range of peak flow magnitudes, it is possible that stream flow exceeds channel capacity only about once in ten years (10 yr recurrence interval, annual probability about 0.1). It should be noted the in the aforementioned study of fish passage at Silverado Trail, the Napa RCD estimated peak flows for these recurrence intervals to be much higher than predicted by the USGS NFF program. We observed evidence of overbank flow along the left bank (northeast bank) upstream of Larkmead Lane and along the right bank (southwest bank) downstream of Larkmead

10 Selby Creek Restoration Plan Geomorphic Review 8 Lane. Overbank flow channels were evident downstream of Larkmead Lane in spring 2007; overbank sand deposits were observed and sampled in spring of 2006 upstream and downstream of Larkmead Lane. We are certain that overbank flow occurred in these areas during the winter of 2005/2006, and there was a low frequency, high magnitude flood event (approximately 25 yr recurrence interval or greater) in the region on January 1, 2006, but are uncertain regarding the occurrence of overbank flow during the winter of 2006/2007. There was a flow event approaching the 2 year recurrence interval in the region during late December, Based on the hydraulic analysis, flood frequency analysis, and field observations, it is evident that the portion of Selby Creek extending from the vicinity of Larkmead Lane downstream through Project Reach 6 is relatively likely to experience overbank flow (flood) events. Insufficient data are available to determine the frequency of flooding in this reach, but available estimates of flood frequency suggest that the frequency is probably relatively high (annual probability of about 0.5). Bed Load Transport Rate Estimates WinXSPro was used to estimate bed load transport rates for flows ranging up to bankfull. Figure 2 summarizes the bed load transport estimates. It must be emphasized here that bed load transport estimates have high uncertainty, and that the primary value in this application is the relative magnitude of bed load transport among the six surveyed cross sections. Sediment Discharge (lb/s) XS 1, Reach 3 XS 2, Reach 5 XS 3, Reach 5 XS 4, Reach 6 XS 5, Reach 6 XS 6, Reach Water Discharge (cfs) Figure 2. Estimated bed load transport rates as a function of discharge. The bed load transport analysis indicates that transport capacity is greatest at the upstream-most cross sections, with a sharp decline at Cross Section 3 immediately upstream of Larkmead Lane. This localized decline in bed load transport is consistent

11 Selby Creek Restoration Plan Geomorphic Review 9 with field observations, however, it is not likely that the bed load transport rate is near zero at bankfull flow as indicated in Figure 2. The upper end of the curves shown in Figure 2 indicate the approximate relative magnitude of bed load transport rates at bankfull flow, which is physically near the maximum possible rate. Figure 2 shows that the maximum bed load capacity transport capacity occurs at Cross Section 1 and is near 3,000 lbs/sec. Moving downstream, the bed load capacity at Cross Section 2 is about 1,700 lbs/sec, falls to near zero at Cross Section 3, then increases to between about 600 to 900 lbs/sec at Cross Sections 4 to 6. Similarly, at the hypothesized bankfull flow of about 330 cfs in the middle and lower reaches of Selby Creek, bed load transport rates at Cross Sections 1 and 2 would be about 1200 and 800 lbs/sec, respectively, compared to a maximum rate of 500 lbs/sec at Cross Sections 3-5. This indicates that sediment deposition would tend to occur in the lower reaches of Selby Creek, particularly at Larkmead Lane, as the upper reaches may transport more sediment downstream than can be transported in the downstream reaches. The reduction in sediment transport capacity in the middle and lower reaches of Selby Creek could be manifested a decline in surface sediment size distribution. Surface sizes are substantially lower at Cross Sections 2, 3, 5 and 6 relative to 1 and 4. The relatively coarse sediment distribution at Cross Section 4, a short distance downstream of Larkmead Lane, might be in part the result or high deposition rates upstream of Larkmead Lane that effectively lower the sediment supply immediately downstream. Regardless, relative to the upper portion of Selby Creek (Project Reaches 1-4), the lower portion of Selby Creek beginning at Project Reach 5 is likely to be subject to bed load sedimentation. Potential Project Impacts on Geomorphic Processes As described above, Project Reaches 5 and 6 appear to be relatively prone to both sedimentation and overbank flow, and the influence of the Restoration Project on geomorphic processes in this area are a potential concern. The sedimentation process would be expected to be progressive, and create positive feedback: increased deposition reduces channel flow capacity, further reducing bed load transport capacity, increasing sediment deposition, and reducing channel flow capacity. This cycle would also suggest progressively increasing frequency of overbank flow. Although there is evidence suggesting that geomorphic processes alone may be responsible for the hypothesized cycle of sedimentation and reduced channel capacity, there is also evidence that management influences contribute to or cause this cycle. First, channel enlargement in the upper portions of Selby Creek may have increased the efficiency of transport of bed load sediment to the lower reaches of Selby Creek. Second, the large gravel bar formed upstream of Larkmead Lane appears to be a direct result of the hydraulic effects of the bridge that create backwater conditions upstream. Third, channel banks extending about 1,000 ft downstream from Larkmead Lane appear to have been impacted by chain link fence installations that protrude into the channel, and may have increased turbulence near the bank, potentially accelerating erosion. In addition,

12 Selby Creek Restoration Plan Geomorphic Review 10 coarse gravel and cobble removed from vineyard fields appears to be placed along the banks, often in the space between the bank and the chain link fence. In addition, heavy bank rip-rap has been used to armor the banks in several locations, and this may have induced accelerated bank erosion downstream. The combined impact of these uncoordinated, and in some cases, inappropriate, efforts to increase channel capacity or stabilize channel banks may have been to reduce channel flow capacity and increased sedimentation in the lower reaches of Selby Creek. The Restoration Project is a coordinated and comprehensive plan that will provide widely distributed treatments to stabilize stream banks. Proposed plantings and bank protection structures along stream banks will tend to maintain the high velocity thalweg nearer the center of the channel, reducing potential bank erosion and potentially increasing channel depth and pool frequency. This will substantially reduce the potential for accelerated bank erosion in response to uncoordinated bank protection. Ideally, a potential decline in channel capacity associated with increased roughness will be compensated by increased channel depth. The Restoration Project is also expected to reduce bank erosion rates in Selby Creek, reducing the supply of coarse sediment and reducing the potential for sedimentation. Finally, anticipated development of a vegetated riparian corridor could promote formation of natural levees (sand deposits near the top of bank) that tend to occur as high velocity flows in the channel slow and deposit entrained suspended sediment along the edge of the channel. When this material is colonized by vegetation, it can be stabilized and, over periods of decades, increase the height of the stream bank. Conclusions and Recommendations Given the extent and value of vineyard planting that border most of Selby Creek, there is limited opportunity for lateral channel adjustment in the Restoration Project. Consequently, restoration objectives must be met primarily through lateral channel stabilization techniques intended to increase channel depth while maximizing ecological values in the aquatic and riparian environments. Control of erosion processes that contribute to the sediment load of Selby Creek is necessary to optimize the benefits of the Restoration Project. Flooding along Selby Creek appears to occur frequently, particularly in the reach immediately above and below Larkmead Lane. Introduction of roughness elements to the channel to promote desirable aquatic habitat might be expected to induce more frequent flooding, however, the intended long-term effect of the project is to create a deeper channel and reduce sedimentation rates. It should be acknowledged that existing conditions and processes will likely lead to increased flood frequency in the absence of the Restoration Plan. The following recommendations pertain to potential modifications of the Restoration Project design plan, as well as channel and watershed management objectives that would support the Restoration Project s objectives.

13 Selby Creek Restoration Plan Geomorphic Review Reduce or eliminate the proposed use of cross-channel structures that could restrict vertical channel adjustment. Channel adjustment must be accommodated primarily through vertical channel adjustment, which is intended to be manifest by channel deepening. 2. Maximize channel enlargement and avoid channel encroachment in construction of bank stabilization structures. Attempt to increase the cross-sectional area of the channel wherever possible. 3. Encourage the development of a routine channel maintenance procedure in the area immediately upstream of the Larkmead Lane bridge. Excavation of gravel accumulations that obstruct flow through the bridge archways should occur with enough regularity to mitigate the depositional, flood inducing effects of backwater upstream of the bridge. Without such a maintenance program, the geomorphic discontinuity at this location will persist, and the potential for a damaging channel avulsion upstream of the bridge that would route flood flow parallel to Larkmead Lane toward the Napa River. 4. Promote watershed-wide erosion control programs targeting anthropogenic sediment sources in Dutch Henry Canyon and Biter Creek, and along Selby Creek, to reduce long-term sedimentation potential in Selby Creek. Encourage vineyard managers to avoid placing rock and other materials from vineyard along the channel banks that may ultimately enter the channel. 5. Develop a monitoring plan capable of measuring changes in channel geometry that would document the long-term effect of the Restoration Project on channel depth and bankfull capacity.

14 Selby Creek Restoration Plan Geomorphic Review 12 References Cited Hardy, T., P. Panja, et al. (2005). WinXSPRO, A channel cross section analyzer, user's manual, version 3.0, USDA Forest Service Rocky Mountain Research Station. Jarrett, R. (1984). Flow resistance in gravel-bed rivers. Journal of Hydraulic Engineering 105(HY4): Koehler, J. and P. Blank (2006). Selby Creek-Silverado Trail Culvert Fish Passage Assessment. Napa, Napa County Resource Conservation District: 14. Montgomery, D. R. and J. M. Buffington (1997). Channel-reach morphology in mountain drainage basins. Geological Society of America Bulletin 109(5):

15 Selby Creek Restoration Plan Geomorphic Review 13 APPENDIX (Three maps on two 11 x 17 sheets)

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