GEOG 642 May 2005 Project Partners: Shoshana Risman, Rich McNelis. Sausal Creek: Dimond Canyon Watershed Assessment

Transcription

1 GEOG 642 May 2005 Project Partners: Shoshana Risman, Rich McNelis Sausal Creek: Dimond Canyon Watershed Assessment

2 I: Table of Contents List of Figures List of Tables 1.0 Introduction 2.0 Site Characterization 3.0 Methods 3.1 Long Profile 3.2 Cross-sections 3.3 Discharge, Velocity, and Mannings n 3.4 Pebble Count 3.5 Compass Traverse 3.6 Plan-view Sketch 4.0 Results and Discussion 4.1 Slope, Cross-sections, and Discharge 4.2 Erosion and Sedimentation 4.3 Plan-view 4.4 General Observations 5.0 Conclusions 6.0 References 7.0 Appendices ii iii i

3 List of Figures Fig. 1: Sausal Creek watershed: GIS inset in East Oakland DOQ 3 Fig. 2: Sediment erosion model 3 Fig. 3: El Centro Bridge photo (Chanse and Herron, 2003) 4 Fig. 4: Dimond Canyon trail map 4 Fig. 5: Concrete spillway removal: before and after (OPW 2001) 5 Fig. 6: Brush-layering 5 Fig. 7 Constructed step pool at x-section 1 5 Fig. 8 Easterly view of south side hiking path (stream along right side, out of view) 6 Fig. 9 Measuring thalweg profile on north side of stream 6 Fig. 10 Ivy-covered north side path vestige at cross-section 2 6 Fig. 11 Measuring cross-section 1 at constructed step pool 6 Fig. 12 Thalweg profile 11 Fig. 13 Cross-section 1 12 Fig. 14 Cross-section 2 12 Fig. 15 Field book plan view sketch 15 Fig. 16 Compass Traverse 16 ii

4 List of Tables Table 1. Wolman Pebble Count, Dimond Canyon, Sausal Creek, Oakland, CA. 21 Table 2. Long Profile 22 Table 3. Compass Traverse Data and Calculations, Dimond Canyon, Sausal Creek, Oakland, CA. 23 Table 4. Flow Data, Discharge and Mannings n Computations, Dimond Canyon, Sausal Creek, Oakland, CA. 24 iii

5 1.0 Introduction In January 2000, the Sausal Creek Watershed Action Plan (SCWAP) was finalized. This 25-year watershed restoration and enhancement program was formulated by the Friends of Sausal Creek (FOSC), a community-based organization dedicated to comprehensively improving the quality of the watershed. The Plan s long-range goals address six areas: natural resources, education, water quality, recreation, advocacy, and organizational development. With regards to natural resource and water quality enhancement, the Plan s priority actions focus immediately on the Dimond Canyon reach of Sausal Creek. These continuing actions include: the monitoring and enhancement of water quality and biodiversity; stream channel restoration; and erosion control. Sausal Creek s history is laced with the stereotypical late 19 th and early 20 th century human activities associated with watershed exploitation, namely: logging, water diversion, and reservoir-building for recreational usage. From the latter half of the last century onward, intensive urbanization has impacted the basin. The effects associated with these activities, and the focus of the FOSC restoration efforts, have been the usual litany of declining biodiversity, increasing hillside erosion and stream sedimentation, flooding, and declining water quality. The Dimond Canyon reach of the stream is not only a focus point for these causes and effects but is also a conduit for the transfer of these impacts from the upstream locations of the Palo Seco and Shepherd Canyon creeks to the downstream outlet into the Oakland Estuary along the San Francisco Bay. The goals of our project are threefold: to characterize the present stream morphology of a reach of Sausal Creek in Dimond Canyon and add to the database for further studies; to compare our data to previous contributions to the morphological database in an effort to 1

6 assess restoration success; and to practice and critique our application of field techniques to further our own future capabilities. While the SCWAP focuses on several restorationrelated goals, our study deals primarily with stream morphology, accented by general field observations of hillside erosion patterns, biodiversity, and community awareness. With restoration efforts less than a decade in-the-making, and the final SCWAP barely five years old, the implications of our work will be more suitable as baselines for future assessments than for an evaluation of the Plan s successes or failures. 2

7 2.0 Site Characterization The 2,656 acre Sausal Creek watershed extends from the hills of the East Bay Regional Park down to the Oakland Estuary. Sausal and its tributaries, the Shepherd s Canyon and Palo Seco creeks, originate in the open spaces of the Park but then join to flow primarily through highly urbanized Oakland, CA until reaching San Francisco Bay. Fig. 1: Sausal Creek watershed: GIS inset in East Oakland DOQ Fig. 2: Sausal Creek Watershed In the late 19 th and early 20 th centuries, the watershed was logged and dammed, and water was diverted from the stream as well. Since then, intense urbanization has taken place in much of the watershed: the stream has been channeled and culverted, broken sewer lines drain into the creek, and its morphology has been affected by increased runoff and sedimentation. 3

8 Fig. 3: El Centro Bridge photo (Chanse and Herron, 2003) Our study area is the Dimond Canyon reach of Sausal Creek, the area targeted by the SCWAP. This section of the stream is located between the El Centro and Leimert bridges and has been subjected to intense restoration efforts. A much-used hiking trail runs along the south side of the stream from El Centro to Liemert. Fig. 4: Dimond Canyon trail map 4

9 Restoration efforts involved: dam removal, reshaping the meander of the stream, and constructing new banks out of erosion control materials. Step pools were created to inhibit further down-cutting of the stream bed. Native species were planted to both help control erosion and increase biodiversity. Fig. 5: Concrete spillway removal: before and after (OPW 2001) Fig. 6: Brush-layering (OPW 2004) Fig. 7 Constructed step pool at x-section 1 Currently, the stream through Dimond Canyon is highly incised and still flowing through the restoration-created channel. The hiking path lies between the southern valley walls and the stream. On the north side, former location of the hiking path, very dense 5

10 vegetation, mainly ivy, covers the valley wall. At times the valley slopes directly abut the north side of the stream; at others, a flat trail-remnant plain allowed access for crosssection measurements. The stream cuts perpendicularly through massive bedded, highly folded and fractured sandstone. Fig. 8 Easterly view of south side hiking path (stream along right side, out of view) Fig. 9 Measuring thalweg profile on north side of stream Fig. 10 Ivy-covered north side path vestige at cross-section 2 Fig. 11 Measuring crosssection 1 at constructed step pool 6

11 3.0 Methods 3.1 Longitudinal Profile We used standard methods as outlined by Harrelson We chose to measure the long profile of the Sausal Creek thalweg starting from the upstream end-point of the Jackson et al study. We initiated our measurements by establishing a benchmark at the El Centro sewer manhole, extrapolating its elevation from the El Centro bridge culvert benchmark established by Jackson et al. We used a tape, rod, and level to establish elevation at approximately the instream point where Jackson et al ended their long profile. Our instream thalweg and water surface profiles, using the same tools, extended approximately one meander. Measurements were taken over two separate days due to our slow progress the first day. Height of water measurements differed over the two days due to a change in stream flow as the result of intervening rainfall, with the second day having higher flows. Slope was calculated through linear equation applied to fit the thalweg pts for the two separate days of surveying. 3.2 Cross-sections We chose to measure cross-sections at two points along the stream, near the beginning and end of our profile length. These points were chosen due to accessibility concerns, as steep valley walls, tree cover, and streamside vegetation density limited our ability to make accurate cross-section measurements elsewhere. We again used the horizontal tape, rod, and level approach to measure ground and water surface elevations. The crosssections were measured on separate days and reflected the different stream flow conditions described above. 7

12 3.3 Discharge, Velocity, and Mannings n We estimated discharge in the El Centro bridge culvert downstream from our study site using the orange peel method. This site was chosen due to its unobstructed confines. We divided the culvert stream width into six 6-inch sections and measured their depths. Orange peels were placed in each width interval and a stopwatch-timing was used to determine surface velocity along a predetermined stretch. Surface velocities were multiplied by a factor of 0.8 and the result was multiplied by the width and depth for each section. The totals for depth, width, area, and velocity were calculated and discharge was calculated using standard methods as outlined by Harrelson and Prof. Davis. Mannings n was calculated using slope from line of best-fit in longitudinal profile. This measure was compared to standard values literature values and comparing our visual observation of our selected stream reach characteristics with the photos and descriptions from USGS Water-Supply Paper Pebble Count The sediment size was characterized by a Wolman pebble-count as described by Harrelson et al. D 50 grain-size was estimated from two 100 pebble samples taken at our cross-section. The blind-reach method was used to attempt to randomize the samples, and the b-axis was measured using a ruler. Random walk-abouts within a 9m2 area were used rather than grid or transect sampling. 3.5 Compass Traverse We measured a plan view of our stream reach using the compass traverse method. Equipment used consisted of a Suunto compass, Suunto clinometer, tape, and red-white 8

13 segmented rods. Tape distances, azimuth foresights and backsights, and angles of inclination were fed into an Excel spreadsheet to graph a plan view. 3.6 Plan-View Sketch We sketched a very rough plan view of the stream reach and surrounding banks and slopes while in the field, and augmented it afterwards from our field book notes and compass traverse results. 9

14 4.0 Results and Discussion 4.1 Slope, Cross-sections, and Discharge To characterize the stream, we studied the slope, cross-section morphology, grain-size distribution, meander characteristics, pool/riffle/bar characteristics, and bank/hillside characteristics. We used these to classify the stream using the Rosgen approach. It is important to note that our inexperience at field research led to several significant errors that taint our results. These will be discussed specifically below. However, our results are in-line with the results of previous studies of the stream and contribute to the Sausal Creek database. The longitudinal profile and cross-sections show the mixed-characteristics of an urbanized stream which has seen some meander pattern restoration but is deeply incised. The longitudinal profile has a pattern of deeper and shallower areas which suggests a step, pool and riffle pattern. However, this apparent pattern is has not been statistically analyzed and our team is not agreed on the labeling of these features. With regards to slope, our measurements along the 416 ft. study reach determined a range of for the thalweg and water surface. This is in-line with the Jackson et al estimate of 0.017, and slightly steeper than the Chanse and Herron estimate of (both estimates calculated by us using change-in-elevation/linear-distance from long profile graphs). 10

15 202 Longitudinal profile ( , ) (all measurements in feet) Location of x- section Location of x- section 1 and upstream pool Location of stop/start point for two-day measurement (noticeable change in discharge) Bankfull (estimated from x-sections) y = x y = 0.016x y = x Thalweg Elevation Water surface elevation Water surface elevation Linear ( Water surface elevation) Linear ( Water surface elevation) Linear (Thalweg Elevation) Fig. 12 Thalweg profile Our two cross-sections show a deeply incised stream channel. We estimated bankfull from visual observation of a trash-line along the banks, slight bank-erosion features, and an ivy growth line. We question whether any significance can be associated between these features and the concept of bankfull (with all its implications), as the major restoration project was completed only five years previous, hardly leaving enough time for long-term flood patterns to establish a meaningful bankfull level. Other than a slightly sagging horizontal tape and foliage-complications with level readings, the only serious caveat here is that cross-section 2 fails to adequately describe the bank-side hiking trail located on the south side between tape distance 15 and ft. 11

16 We measured a smaller cross-section of the pool immediately upstream of cross-section 1 to show changing thalweg conditions at this step-pool restoration feature. X-section South (all measurements in feet) North Ground surface elevation 204 Water surface elevation Pool upstream of x-section 1 South North Pool bed elevation Pool water surface elevation Fig. 13 Cross-section South X-section 2 ( ) (all meaurements in feet) North Ground surface elevation 212 Water surface elevation ( ) Fig. 14 Cross-section 2 12

17 Velocity and discharge at the El Centro bridge culvert were determined to be 4.59 feet per second and the 4.29 cubic feet per second, respectively. The derived Mannings n is which represents an extremely low roughness which represents the smoothness of the cement pipe culvert. This value of is representative of the smoothness of the culvert and not the roughness of our reach of Sausal Creek in Dimond Canyon as it compares to Mannings n for the smoothest natural-earthen streams (Davis, 2005). Rather than take measurements in the culvert we should have taken them in the study reach itself in order to use slope to calculate a Mannings n and to have calculations representative of our reach. Mannings n as determined from comparisons to photos from USGS Water Supply Paper 1849 seemed to be in the.45 to.55 range. Also, as our field days took place in several stream flow conditions, our calculations cannot be tied to our cross-section flow depths in any useful way. The deep incision observed in both cross-sections, slope of less than 2%, and historic anthropogenic alterations lead makes this stream resemble a G type stream accouding to Rosgen classifications. 4.2 Pebble Count To attempt to characterize the stream with regards to erosion and sedimentation we combined pebble count samples at our cross-section sites with general bed surface structure observation. Total median grain-size was determined to be 20 mm (18 and 21 at each sample site respectively). This value characterizes surface sediments in the stream to be generally course gravel (Harrelson et al, 1994). For comparison, a study in 2004 and of Dimond Canyon characterized the bed material as medium (13mm) and course gravel (30mm) (Jackson et al, 2004). A previous study characterized this stretch as having 13

18 medium gravel sized bed material (13mm) (Chanse and Herron, 2003). These sediment size groupings are close but it is possible that bed material size has increased over these three years. Although change is possible due to changes in upstream erosion and effects of the restoration project difference in methodology must be considered. These results cannot be perfectly aligned for comparison, and so apparent change can be overwhelmed by effects of methodology difference bias and error in production. New to this type of research, and with time a factor, we did not employ rigorous sampling techniques, such as gridding or transect-walks. This certainly resulted in a sampling bias toward easily accessible bed sites. The use of Wolman pebble count did not allow us to take armoring or sub-surface samples (with the exception of imbedded cobble estimates). We used manual ruler measurements rather than any pebble-box or sieve. Additionally, we did a simple median calculation, with no statistical transformations. 4.3 Planimetric view We addressed the plan-view characterization of our study reach in two ways: with a rough field notebook sketch and with a compass traverse. The former was used to get an overall view of several characteristics of the reach: surrounding vegetation, location of the hiking trail, the meander shape, and stream features such as riffles and step pools. The latter was used to determine the boundaries of stream flow on the date of observations. Site Sketch: 14

19 Fig. 15 Field book plan view sketch The compass traverse yielded poor results as the two of us working together could not come up with azimuth foresights and backsights that were in conjunction. Although this plot shows the result of some data correction to an error of +/-2 per azimuth, it still 15

20 appears inaccurate. It is important to note that the starting pts of X,Y and Z are wrong because historic GIS pt measurements were not available. The plot shown below does not seem to adequately represent the stream shape. The compass traverse figure is too narrow at the downstream side and seems to exaggerate the meander shape in comparison to visual observations in the field and on the trail map Dimond Cnyn Compass Traverse Fig. 16 Compass Traverse Compass Traverse Dimond Canyon, Sausal Crk, Oakland. X and Y values are in meters, UTM coordinates are not descriptive of this site. 16

21 4.4 General Observations During the course of our field days, we were approached many times by hikers asking about our activities. Some were members of FOSC, others just seemed to be folks who took a great interest in the history and future of the watershed. Several of the passersby related stories of the park s history or their observations of the flora and fauna. While the information they gave us could not be categorized as data, it was a clear indication of the passion for and likelihood of success of the SCWAP. One member of our team spotted an eight inch fish in the stream on one of the days of field work. Speculation and corroborative reports lead us to believe it that it was a rainbow trout juvenile. We observed several erosional gullies leading to the stream as well as a trickle of what smelled like discharge from a leaking sewage line. The stream water clarity ranged from clear to silty-brown, varying with rain events. 17

22 5.0 Conclusion Sausal Creek is an urbanized stream who s watershed starts in near 1300 feet elevation in regional parklands of the Berkeley Hills, drains 2565 acres through the riparian mainstem of the stream through Dimond Canyon and empties through a highly channelized and culverted Urban Oakland area into the Oakland Estuary. The stream is currently in a restoration process led by the stewardship group Friends of Sausal Creek which has published a 25 year watershed plan and impelled the November 2001 physical meander restoration and continued replanting of a riparian reach in Dimond Canyon. Our study took a morphological snapshot of a 416 ft reach of this restoration area. The study characterized the present stream morphology of a reach of Sausal Creek in Dimond Canyon, added information to the database for further studies and compared our data to previous contributions to the morphological database in an effort to assess restoration success. The study was also conducted as an educational exercise to practice and critique watershed assessments students application of field techniques to build our skills. The longitudinal profile and cross-sections show the mixed-characteristics of an urbanized stream which has seen some meander pattern restoration but is deeply entrenched. The longitudinal profile shows an apparent pattern of deeper and shallower areas which suggests a step, pool and riffle pattern. With regards to slope, our measurements along the 416 ft. study reach determined a range of for the thalweg and water surface. This is in-line with the Jackson et al estimate of 0.017, and slightly steeper than the Chanse and Herron estimate of This mild slope of slightly less than 2% is possibly influenced by historic check dams, current presence of large 18

23 paved cement and embedded boulders in the stream bed and post-restoration structures acting as gradient controls. The bed material was characterized as coarse gravel with through a Wolman pebble-count as described by Harrelson et al. The D 50 grain-size was estimated from a 100 pebble sample taken at each cross-section. The D 50 grain-size for the entire stream was 20 mm, with medians of 18 and 21 mm at the two cross-sections. The current effect of upstream erosion on sediment size is interesting but as no significant difference is apparent between data from 2003, 2004, and 2005, we can neither make conclusions as to recent fluctuations in sediment-size nor point to sources. Hopefully future studies will be able to use these data sets as a baseline for further study. We conclude that the deep incision observed in both cross-sections, slope of less than 2%, course gravel bed-material and historic anthropogenic alterations lead this stream to resemble an urbanized G type gravel lined stream with according to Rosgen classifications. General observations of native plant growth and local stewardship commitments led by the Friends of Sausal Creek in partnership with educational and municipal institutions are fairly encouraging for the continued restoration of the physical natural-stream structures, riparian community, water quality and overall watershed health. 19

24 6.0 References Ash, S.L.?. Monitoring the Water Quality of Sausel Creek. Environmental Sciences, University of California, Berkeley. Barnes, Harry Jr Roughness Characteristics of Natural Channels, USGS Water Supply Paper US Govt Printing Office, Wash. DC. Chanse, Vikki Along Sausal Creek: an assessment of vegetation, habitat and morphology of an adopted urban creek. Berkeley, CA: Water Resources Archive (last viewed on-line 5/18/04). FOSC (Friends of Sausal Creek) Promoting Watershed Awareness (last viewed on-line 5/18/05). Graymer, R.W.?. Geologic map and database of the Oakland Metroploitan area, Alameda, Contra Costa, and San Francisco Counties. USGS; MF-2342 Harrelson, Cheryl, C. L. Rawlins, and John C. Potyondy (1994). Stream channel reference sites: an illustrated guide to field technique. USDA Forest Service General Technical Report RM-245. Jackson, et al Sausul Creek Watershed Assessment. San Francisco State University, Geography (last viewed on-line 5/18/05). Owens-Viani, Lisa Sausal Creek Watershed: A Cultural and Natural History. Richmond: Aquatic Outreach Institute. OPW (Oakland Public Works) Sausal Creek Restoration Project. (last viewed on-line 5/18/04). OPW (Oakland Public Works. Date unknown (likely 2000). Initial Environmental Review Sausal Creek Restoration in Dimond Canyon. Courtesy of Ali Schwarz, OPW. Rosgen, David A classification of natural rivers. Catena 22:

25 7.0 Appendices Table 1. Wolman Pebble Count, Dimond Canyon, Sausal Creek, Oakland, CA. X-section 1 Pebble Count (cm) X-section 2 Pebble Count (cm) Median grain size (D50)= cm

26 Table 2. Long Profile 20-Mar-05 March 20, 2005 and March 25, Mar-05 Thalweg tape distance (ft'in) 20-Mar-05 Thalweg tape distance (decimal ft) Thalweg tape distance (ft'in) 25-Mar-05 Thalweg tape distance (decimal ft) Absolute Thalweg Backsight( distance (ft) ft) Height of Instrument( ft) March 20, 2005 Foresight (ft) March 25, 2005 Absolute Foresight Elevation (ft) (ft) March 20, 2005 Depth (ft) March 25, 2005 Depth (ft) Absolute elevation water surface (ft) Station ID BM TP BM CP TP Tie-in(2004) 2' Tie-in(a)(2004) 3' ' ' ' ' ' ' ' ' ' ' ' ' Absolute elevation water surface (ft) ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' BM3 251' Data corrected from field book to correct for measurement error. 22

27 Table 3 : Compass Traverse Data and Calculations, Dimond Canyon, Sausal Creek, Oakland, CA. Closed Compass Traverse Geog/Geol 642: Watershed Assessment & Restoration total traverse hd: Cells in red are derived, should not be modified traverse closure error: Cells in green should be set mag decl D factor traverse closure direction: uncorrected corrected sta tape (tape i sd az (fs) bscorrectedcorrected vert bsrev err addtoaz corr Az hd dx dy dz x' y' z' travhd closhd x y BM

28 Table 4 Flow Data, Discharge and Mannings n Computations, Dimond Canyon, Sausal Creek, Oakland, CA. Sausal Creek El Centro Ave Culvert Computations Field Data ###### Orange peel method trial # Length of run time (sec) sfc vel avg 0.8 x sfc W( Q (org (ft) (ft/sec) vel ft) D (ft) Dinches A=W*D peel) ave sum edge of channel ft cfs m cms s N derivation from Q: N derived from Q Q S (long profilea WP R N These use 1.48 multipl cfs ft cms m Q m