Merton Tertiary Planning Study: Geomorphic Assessment Fourteen Mile Creek and Associated Tributaries - Final Report V-1

Transcription

1 Merton Tertiary Planning Study: Geomorphic Assessment Fourteen Mile Creek and Associated Tributaries - Final Report V-1 December 2013 Ref:

2 2500, MeadowpineBlvd.Suite 200 Address Mississauga, Ontario, L5N 6C4 Canada (905) Telephone (905) Fax Internet Document Title: Merton Tertiary Planning Study: Geomorphic Assessment Fourteen Mile Creek and Associated Tributaries Status: Final Report Version: 01 Date: December 2013 Project name: DSEL-Bronte Green Project number: Client: David Schaeffer Engineering Ltd. Reference: Originally drafted by: Tatiana Hrytsak, M.Sc. Approved by: John Parish P.Geo. Date of approval: December 13, 2013 D. Schaeffer Engineering Ltd. Fourteen Mile Creek and Tributaries Assessment (Ref: ) i

3 Contents 1. Introduction Study Area Aims and Objectives Background Review Overview of Physical Characteristics and Historic Assessment Fourteen Mile Creek Main and West Branches Subwatershed Plan (2002, Phillips Engineering) Oakville Erosion Assessment Study (2008, PGL) Oakville Erosion Study (2010, AECOM) Functional Servicing Study Third Line and North Service Road (2012, UEM) Existing Conditions Reach Delineation Rapid Assessment Methodology Rapid Assessment Results Meander Belt Width Assessment Meander Belt Width Delineation Preliminary Meander Belt Width Factor of Safety Detailed Geomorphological Analysis Bankfull Geometry Bankfull Channel Hydraulics Sediment Distribution Erosion Threshold Analysis Conclusions References Appendix A : Reach Photos Appendix B: Detailed Geomorphological Field Data Summaries Appendix C: Historic Geomorphic Reach Descriptions D. Schaeffer Engineering Ltd. Fourteen Mile Creek and Tributaries Assessment (Ref: ) ii

4 Appendix D: Historic Aerial Photos Appendix E: Geomorphic Reach Description Tables D. Schaeffer Engineering Ltd. Fourteen Mile Creek and Tributaries Assessment (Ref: ) iii

5 1. Introduction The Merton Tertiary Planning Study area is identified as an area for potential future development in Livable Oakville policy 26.5 a). As such, on October 16, 2012, Town Council approved the development of a Tertiary Plan that will identify land usedesignations and policies for the entire Study Area. A number of technical studies arerequired to be completed as set out in Livable Oakville policy A terms of referencefor the Merton Tertiary Planning Study was developed in response to the Town srequirement for comprehensive studies to be completed prior to development proceeding.the subject study responds to the Town s Terms of Reference. 1.1 Study Area The Study Area consists of approximately 234 gross hectares and is located north of thequeen Elizabeth Way (north of the North Service Road), east of Bronte Road (andincludes some parcels of land located on the west side of Bronte Road), south of UpperMiddle Road and west of existing residentially developed lands west of Third Line.Maps of the study area are provided in Figure 1.1 and 1.2. Currently, the Saw Whet and the Deerfield Golf Courses, existing rural residential, anontario Hydro right-of-way, the Mid- Halton Pollution Control Plant, an existingdesignated heritage cemetery, and the Region of Halton Offices and Halton RegionalPolicy Headquarters occupy the subject lands. Fourteen Mile Creek and natural heritagefeatures associated with Bronte Creek traverses through the Study Area 1.2 Aims and Objectives The aim of the Fluvial Geomorphologic Assessment is to characterize the existing function of the channels within the study area, thereby developing an understanding for the potential for functional change following the construction of the proposed development. The fluvial geomorphologic assessment includes the following components: 1. Review of relevant background information 2. Delineation of channel reaches within the study area 3. Field reconnaissance of the water course within and adjacent to the subject property 4. Detailed field data collection at selected locations to gauge relative stability and further characterize site conditions. 5. Determination of erosion thresholds (critical discharges) for the three detailed sites. D. Schaeffer Engineering Ltd. Fourteen Mile Creek and Tributaries Assessment (Ref: ) 4

6 Figure 1.1: Merton tertiary study area D. Schaeffer Engineering Ltd. Fourteen Mile Creek and Tributaries Assessment (Ref: ) 5

7 Figure 1.2: Study area showing watercourses included in geomorphic assessment D. Schaeffer Engineering Ltd. Fourteen Mile Creek and Tributaries Assessment (Ref: ) 6

8 2. Background Review A background review of previous reports and mapping was undertaken in order to build on current understanding of watershed and site characteristics that may influence the subject waterways. The review also aims to identify any disturbances to the watershed or waterways that may have, or may be, impacting channel dynamics. 2.1 Overview of Physical Characteristics and Historic Assessment The Quaternary geology of the study area consists of Halton Till overlying Queenston and Georgian Bay Formations. The clayey, silty till is infrequently found in the channel as small ledges at the base of the banks. In most sections, the overlying till has been eroded away and the channel flows through shale bedrock. Large exposures of the red shale are seen in the valley walls and bed of the channel. The shale is easily eroded into smaller pieces which become part of the channel s bedload. Historic aerial photos were obtained for 1954 and 1978 to assess historic land use and planform. Due to photo quality and dense vegetation it was difficult to identify the channel location in the photos; however the channel was traced where visible to compare with the current planform (Appendix D). The channel in 1954 was difficult to identify, from what could be seen it appears to be in a similar location within the valley. The channel planform trace for 1954 does not properly relate to the current planform indicating there is likely error in the photo and the georeferencing. In 1978 the channel was slightly more visible, particularly in the larger bends where the channel approaches the valley wall. It appears as though some erosion and downstream translation has occurred between 1978 and There does not appear to be any more substantial changes in planform such as cutoffs or oxbows. Some of the smaller tributaries (SW-3, SWS-1, SW-4, and SWN-1) are easily visible in the 1978 photo and may have been more wellestablished during this time period, prior to the establishment of the golf course. SWN-1 flows across what appears to be bare soil which may mean it was maintained for drainage of the surrounding area by landowners. Land use in the study area was sparse in both 1954 and 1978 with minimal agricultural and residential use. Overall the landscape was only slightly altered during this time period. The current major land use in the area is the Saw Whet Golf Course which was developed in 1982 and encompasses the associated tributaries. The golf course has made an effort to maintain a natural vegetation buffer around each of the watercourses consisting of small woodlots and meadow vegetation. In some areas the surrounding vegetation is very dense and beginning to populate the bed of the channel. 14-Mile Creek flows through a large natural forested valley, flanked by residential development. Mature trees provide shading to the channel. The valley walls often lack vegetation due to erosion creating steep, unstable slopes. Upstream of the study area, north of Upper Middle Road, land use was historically agricultural until During the period, the area was fully developed into residences. D. Schaeffer Engineering Ltd. Fourteen Mile Creek and Tributaries Assessment (Ref: ) 7

9 2.2 Fourteen Mile Creek Main and West Branches Subwatershed Plan (2002, Phillips Engineering) The Town of Oakville initiated a subwatershed plan of a 14-Mile Creek to provide direction for environmental and stormwater management associated with proposed land use change in the area. The study area was between Upper Middle Road and Regional Road 5, to the east and west of Bronte Road. This is upstream of the study area for the Merton Tertiary Planning Study. The stream morphology component documented the morphologic properties of 14-Mile Creek in the study area; the results were used to rank the watercourses according to a low, medium, or high, constraint rating. General constraints for the watershed were also identified along with opportunities for enhancement and restoration. Characterization was done using five detailed field sites in addition to desktop analysis (mapping and air photo interpretation). Most of the watercourses in the study area were headwater streams. The main influences on these streams were the agricultural land use and the presence of on-line ponds. Live-stock on the agricultural properties had free access to the watercourses resulting in trampling of banks. The on-line ponds affect the storm hydrograph by retaining water during large rainfall events, reducing the impacts of these events on channel morphology. The ponds also reduce connectivity of sediment supply as the sediments from upstream settle to the bottom of the ponds. Many of these streams have also been straightened which can lead to increased bed and bank erosion. The main branches were influenced by the surrounding bedrock geology. The soft, platey shale is easily eroded and resulted in local increases in sediment supply when the channel was in close proximity to valley walls. Based on the characterization the channels were thought to be in equilibrium with the flow regime and the erosion seen in the headwater streams was not attributed to channel processes but to poor land-use practices. Erosion in the larger reaches was attributed to natural migration tendencies within a confined valley and was not considered a serious concern. 2.3 Oakville Erosion Assessment Study (2008, PGL) The Town of Oakville undertook erosion assessments of watercourses within the Town in 2006 and The watercourses were reassessed in 2008 to update stability rankings and prioritize remediation and bank stabilization needs. Reaches were assessed in the field using the Rapid Geomorphic Assessment (RGA) and Rapid Stream Assessment Technique (RSAT) methods (see Section 3.3). Rapid assessment scores for the 131 reaches comprising the study were ranked from most to least sensitive to identify the 20 worst reaches. Reaches of Fourteen Mile Creek included in the 2008 study correspond with those in the current study. Both R-74a and R-74b in the current study are contained within the R reach and 2008 s R-75 was split into R-75a and R-75b in the current study. The rapid assessment scores are presented in the Table 2.1 and 2.2. According to the RGA scores, all three reaches of 14-Mile Creek (R-74 to R-76) were actively widening, although widening was slightly less in R-76 than in the other two reaches. Widening was leading to degradation as a secondary process in R- 74, and aggradation in R-75. R-76 was the most stable of the reaches, classified as transitional/stressed, D. Schaeffer Engineering Ltd. Fourteen Mile Creek and Tributaries Assessment (Ref: ) 8

10 but received the highest score in planimetric adjustment. Planimetric adjustment was indicated by the presence of high flow chutes and island formation. These modes of adjustment are likely resultant from increased woody debris found in R-76, associated with widening, which subsequently reduces transport of sediment, increasing aggradation, leading to island formation. Woody debris jams also encourage chute formation during high flow events. Therefore while R-76 was less active compared to the other two reaches it showed increased planimetric adjustment due to the increased woody debris. The assessments also noted that logs placed against the banks for protection were failing to reduce erosion and structurally failing. The logs were outflanked and beginning to fall into the channel, which added to the presence of woody debris. The RSAT scores indicated that the reaches are relatively similar in terms of overall stream health. The reaches received low scores in the channel stability and scour/deposition categories due to their highly active nature. Additional reach description information can be found in Appendix C. Table 2.1: Summary of RGA Results (2008) Channel 14 Mile Creek Reach Factor Value Aggradation Degradation Widening Planimetric Adjustment Stability Index Condition R In Adjustment R In Adjustment R Transitional/Stressed Table 2.2: Summary of RSAT Results (2008) Factor Value Channel Reach Channel stability Scour / deposition Instream Habitat Water Quality Riparian Condition Biological Indicators Overall Score Condition 14 Mile Creek Max. Score R Moderate R Moderate R Moderate 2.4 Oakville Erosion Study (2010, AECOM) The Oakville Erosion Assessment was updated again in 2010 using the same methodology. RSAT/RGA scores could not be obtained for the 2010 study, but erosion descriptions are provided in Appendix C. The reaches were described as similar in dimension and process to their 2008 state. Evidence of widening and bank erosion remained the primary mode of adjustment with a strong presence of fallen trees within the channel. The descriptions indicated that increased amount of woody debris within the channel is causing increased planimetric adjustment. In addition to jams, it was noted that backwatering, chutes and bypass channels were present in all three reaches. The increased woody debris could also be attributed to the failing log structures put in place for bank protection. Photos showed sections of D. Schaeffer Engineering Ltd. Fourteen Mile Creek and Tributaries Assessment (Ref: ) 9

11 thechannel where the logs have been completely removed from the bank protection structure with only stakes remaining (Appendix A: Photo 35). At the time of the assessment the upstream portion of R-76 was under construction to create a natural channel design for planned road widening. 2.5 Functional Servicing Study Third Line and North Service Road (2012, UEM) Urban and Environmental Management Inc. (UEM) completed a functional servicing and preliminary stormwater management report for the Third Line lands that included reaches 9a and 9b of the current study. A geomorphic assessment was undertaken as part of the study, the results of which are integrated into the current study. D. Schaeffer Engineering Ltd. Fourteen Mile Creek and Tributaries Assessment (Ref: ) 10

12 3. Existing Conditions This section characterizes each of the reaches within the study area based on field reconnaissance and rapid assessment work. The identified reaches are illustrated in Figure 3.1. Typical photographs of each reach are provided in Appendix A to facilitate visualization of the existing geomorphic conditions. 3.1 Reach Delineation The amount and size of sediment inputs, valley shape, land use or vegetation cover, and other parameters that influence channel form often change as you move downstream along a waterway. In order to account for these changes, channels are often separated into reaches. Reaches can be defined as stretches of channel that flow through a nearly constant valley setting and incorporate similar physical characteristics along their lengths. Thus, reaches experience similar controlling and modifying influences, which are reflected in similar geomorphological form, function, and process. The delineation of a reach considers tributary inputs, sinuosity, gradient, hydrology, local geology, degree of valley confinement, and vegetative control using methods outlined in Parish Geomorphic Ltd. (2001). Reaches specific to this study area were previously delineated for the earlier geomorphic assessment work (Parish Geomorphic, 2008; AECOM, 2010) and these delineations were reapplied for this study (Figure 3.1) in order to compare site conditions over time. As mentioned, 14-mile Creek reaches R-74 and R-75 were split for the current study, primarily based on tributary junctions and a change in sinuosity. D. Schaeffer Engineering Ltd. Fourteen Mile Creek and Tributaries Assessment (Ref: ) 11

13 Figure 3.1: Geomorphological reaches and location of detailed field investigation sites. D. Schaeffer Engineering Ltd. Fourteen Mile Creek and Tributaries Assessment (Ref: ) 12

14 3.2 Rapid Assessment Methodology While desktop analysis provides a general description of channel characteristics and some insight into the controls and modifying influences affecting channel form, it does not solely define the overall condition of the channel (e.g., stable, stressed). Prior to detailed geomorphological survey work, provisional assessment of channel stability and health were undertaken using two established reconnaissance techniques, the Rapid Geomorphic Assessment (RGA) and the Rapid Stream Assessment Technique (RSAT) Rapid Geomorphic Assessment The Rapid Geomorphic Assessment (RGA) was designed by the Ontario Ministry of Environment (1999) to assess rural and urban stream channels. It is a qualitative technique based on the presence and (or) absence of key indicators of channel instability such as exposed tree roots, bank failure, excessive deposition, etc. The various indicators are grouped into four categories representing specific geomorphic process: 1) Aggradation, 2) Degradation, 3) Channel Widening, and 3) Planimetric Form Adjustment. Over the course of the survey, the existing geomorphic conditions of each reach are noted and the specific geomorphic indicators are documented. Upon completion of the field inspection, the indicators are tallied within each category and the subsequent results are used to calculate an overall reach stability index. This index value corresponds to one of three stability classes representing the relative degree of channel adjustment and (or) sensitivity to altered sediment and flow regimes) (Table 3.1). Table 3.1: RGA Classification Factor Value Classification Interpretation 0.20 In Regime or Stable (Least Sensitive) The channel morphology is within a range of variance for streams of similar hydrographic characteristics evidence of instability is isolated or associated with normal river meander propagation processes Transitional or Stressed (Moderately Sensitive) 0.41 In Adjustment (Most Sensitive) Channel morphology is within the range of variance for streams of similar hydrographic characteristics but the evidence of instability is frequent Channel morphology is not within the range of variance and evidence of instability is wide spread D. Schaeffer Engineering Ltd. Fourteen Mile Creek and Tributaries Assessment (Ref: ) 13

15 3.2.2 Rapid Stream Assessment Technique The Rapid Stream Assessment Technique (RSAT;Galli, 1996) provides a more qualitative and broader assessment of the overall health and functions of a reach compared to the RGA. This system integrates visual estimates of channel conditions and numerical scoring of stream parameters using six categories: Channel Stability Erosion and Deposition In-stream Habitat Water Quality Riparian Conditions Biological Indicators Once a condition has been assigned a score, these scores are totaled to produce an overall rating that is based on a 50 point scoring system, divided into three classes: <20 Low Moderate >35 High Although the RSAT grades streams from a more biological and water quality perspective than the RGA, this information is still relevant within a geomorphic context. In general, the types of physical features that generate good habitat for aquatic organisms tend to represent healthy geomorphic systems as well (e.g., native fish may prefer a well-established riffle-pool sequence with little fine material on the riffles, quality riparian conditions provide food and shade to streams, woody debris and overhanging banks provide habitat structure, etc). 3.3 Rapid Assessment Results As illustrated in Table 3.2 the results of the RGA survey indicate that tributary reaches are either Transitional/Stressed or In Regime with values ranging from 0.07 to The In Regime reaches are all located on the golf course itself and show minimal definition. The reaches were dry suggesting flow only occurs during larger rainfall events. Specifically, reach SWN-1 was a small depression hardly distinguishable from the surrounding landscape that crossed one of the golf course greens. While it is considered as a channel on Ontario Base Mapping, field assessments reveal that SWN-1 is an undefined depression which does not need to be considered as a formal drainage feature and can be classified as a swale.the remaining In Regime reaches had sections where channel dimensions were well-defined by more substantial flows and should therefore be included as drainage D. Schaeffer Engineering Ltd. Fourteen Mile Creek and Tributaries Assessment (Ref: ) 14

16 features. The two reaches classified as Transitional/Stressed are located further downstream, which provides more flow for transport and erosion. SW-1 and SW-2 are also located in a more natural area of the property flowing through woodlot and meadow vegetation. Both reaches show evidence of widening in the form of fallen/leaning trees, scouring, and steep bank angles. They also show some evidence of aggradation with mid-channel bars, siltation in pools and embedded material. This pairing suggests that the channel has sufficient energy to erode its boundaries, increasing sediment supply which the channel cannot fully transport, resulting in increased deposition in the form of bars. The Fourteen Mile Creek reaches were classified either as Transitional/Stressed or In Adjustment with values ranging from 0.29 to Widening was the most prevalent form of adjustment with aggradation as a secondary process. The exception is R-74a where aggradation is the primary process of adjustment. Indications of widening included fallen/leaning trees, exposed tree roots, large organic debris in the channel, and bank scouring resulting in steep bank angles. Most reaches have remnants of bank protection structures composed of large metal stakes with logs placed between the stake and the bank. In most cases only the stakes remain and the protection has failed (Appendix A: Photo 19). R-74b was the most stable of the reaches. It did not show evidence of planimetric adjustment indicating the widening and aggradation is less severe. Progressing upstream, R-75a and R-75b show increased aggradation as well as evidence that the high amount of activity within the channel is beginning to effect planimetric form. Both reaches have chute formation suggesting the channel is adjusting its form under high flow conditions. R-75b has poorly formed bars which result from an excess sediment supply that the channel cannot properly transport. R-74a and R-76 received the highest scores (0.55 and 0.44) and are therefore the least stable. These two reaches are highly active, both receiving a score of 0.43 in planimetric adjustment. Additionally, R-74a received a particularly high score in aggradation (0.88) as a result of the effects of a beaver dam and several log jams. A large section of the reach was backwatered due to the beaver dam. The heavy presence of woody debris creates obstacles which impede flow reducing sediment transport which then increases aggradation. These obstacles often result in the creation of cutoff channels and chutes during high flow events when the channel has the energy necessary to force flow around the obstacles. R-76 is characterized by similar issues of heavy woody debris effecting deposition and channel planform. Aggradation was less severe in R-76 as jams were more loosely formed from debris as opposed to the larger beaver dam in R-74a. Islands were common in R-76 as well as high flow chutes. Significant evidence of widening and erosion was again seen in this reach. The upstream end of R-76 appeared to be recently restored through use of a natural channel design and was in good condition. Reaches 72 and 73 differed from the other reaches by receiving high scores in degradation. For reach 73 it surpassed widening as the primary process. The main indicator of degradation was large areas D. Schaeffer Engineering Ltd. Fourteen Mile Creek and Tributaries Assessment (Ref: ) 15

17 of exposed bedrock within the two reaches. In upstream reaches exposed bedrock was only found in pool areas, whereas in 72 and 73 it was exposed throughout the reaches. Small knickpoints were also found in each of the reaches indicating erosion of the substrate. Reach 5b was a short, straight stretch of channel which did not differ very significantly from the two reaches upstream. It s classification as In Regime is likely related to the short length in which there is not much room for feature development or changes. The channel was also wider than upstream reaches which results in less energy making the reach more stable. The RGA characterization of reaches 9b and 9c was completed by UEM (2012). These reaches were subdivided into six reaches (Figure 3.2). The eastern half of the tributary was relatively stable with the exception of reach 1 located at the upstream end. Reach 1 is adjusting through degradation as a result of two knickpoints slowly migrating upstream through the shale bedrock. The knickpoints are thought to be related to a previous realignment of the channel. The western reaches (4&5) were both in a transitional state due to aggradation encouraging planform adjustment. Woody debris in the channel led to siltation, chutes, and cutoffs. D. Schaeffer Engineering Ltd. Fourteen Mile Creek and Tributaries Assessment (Ref: ) 16

18 Figure 3.2: Sub-Reach delineation of 9b and 9c (UEM 2012) Table 3.2: Summary of RGA results Channel 14 Mile Creek Reach Factor Value Aggradation Degradation Widening Planimetric Adjustment Stability Index Condition R-74a In Adjustment R-74b Transitional/Stressed R-75a Transitional/Stressed R-75b Transitional/Stressed R In Adjustment D. Schaeffer Engineering Ltd. Fourteen Mile Creek and Tributaries Assessment (Ref: ) 17

19 14 Mile Creek Tributaries 14 Mile Creek Eastern Tributary (9b & 9c)* Transitional/Stressed Transitional/Stressed 5b In Regime SW Transitional/Stressed SW Transitional/Stressed SW In Regime SW In Regime SWN In Regime SWS In Regime Transitional/Stressed In Regime In Regime Transitional/Stressed Transitional/Stressed In Regime *rapid assessment work on these branches completed by UEM (2012) Table 3.3: Summary of RSAT results Factor Value Channel Reach Channel stability Scour / deposition Instream Habitat Water Quality Riparian Condition Biological Indicators Overall Score Condition 14 Mile Creek 14 Mile Creek Tributaries Max. Score R-74a Moderate R-74b Moderate R-75a Moderate R-75b Moderate R Moderate Moderate Moderate 5b Moderate SW Moderate SW Moderate SW Moderate SW Moderate SWN Moderate SWS Moderate D. Schaeffer Engineering Ltd. Fourteen Mile Creek and Tributaries Assessment (Ref: ) 18

20 The RSAT scores (Table 3.3) were consistent throughout the study area. All reaches were classified as having Moderate health conditions, with scores falling in a small range of 24.5 to The tributaries on the golf course (SW-3, SW-4, SWS-1) received high scores in channel stability and riparian conditions because they lack consistent flow with which to modify boundaries. The banks and surrounding area was frequently covered with well-established vegetation. Lower scores were received in water quality, habitat, and biological indicators because the reaches were mostly dry and lacked geomorphic features which would provide habitat. The other two tributaries (SW-1 and SW-2) and the main channel reaches received lower scores in channel stability and scour/deposition due to the high amount of activity. Scores were higher for instream habitat and biological indicators because the frequent scour/deposition created diverse geomorphic features within the channel which serve as good, albeit transient, habitat areas. D. Schaeffer Engineering Ltd. Fourteen Mile Creek and Tributaries Assessment (Ref: ) 19

21 4. Meander Belt Width Assessment 4.1 Meander Belt Width Delineation Streams and rivers are dynamic features on the landscape. Changes in configuration and position occur through the development and evolution of meanders, and migration processes. Erosion and deposition of sediment is a key component of channel migration, enabling changes in shape and shifts in the position of a watercourse. These changes may cause loss or damage to private property and/or structures located too close to the transitioning watercourse. It is for this reason that, when infrastructure, development or other activities are proposed near a watercourse, it is desirable to designate a corridor intended to contain all of the existing and expected meander development and migration processes. Outside of this corridor, it is assumed that private property and structures will be safe from the erosion potential of the watercourse. The space that a meandering watercourse occupies on its floodplain, and in which all of the natural channel processes occur, is commonly referred to as the meander belt. Due to the spatial variability of modifying and controlling influences on channel form, two reaches situated immediately up/downstream of each other could show marked differences in planform configuration. It is for this reason that meander belt width delineation occurs on a reach-by-reach basis. Throughout the study area several reaches of the 14-mile creek are confined by valley walls. In accordance with Provincial Policy, when a channel is within a confined system the erosion hazard limit is delineated based on the stable slope allowance method. This consists of three allowance components: toe erosion, stable slope, and access. This method was applied to the governing meander of R73 to determine the hazard limit. This value was compared with the limit delineated based on the channel planform and additional setback for Redside Dace habitat (as most of the reaches are classified as habitat). The meander belt width and Redside Dace setback yielded a larger hazard limit than the stable slope allowance method (Figure 4.1) D. Schaeffer Engineering Ltd. Fourteen Mile Creek and Tributaries Assessment (Ref: ) 20

22 Figure 4.1: Comparison of the confined setback and meanderbelt width. 4.2 Preliminary Meander Belt Width A preliminary meander belt width was delineated for the reaches. First, a meander belt axis was identified, following the general down-valley orientation of the meander pattern. The meander belt is essentially centered along the meander axis. Second, the preliminary meander belt is established by drawing lines parallel to the governing outermost meanders of the existing channel planform, following the meander axis. The step also takes surrounding topography from contour lines into consideration. The distance between the two lines is measured and used to represent the width of the preliminary meander belt. Preliminary meander belt widths for reaches 9b and 9c were delineated by UEM (2012) based on their sub-reaches (Figure 4.2). The values from the UEM study were used to delineate the meander belt widths of these reaches for this study (Figure 4.3) D. Schaeffer Engineering Ltd. Fourteen Mile Creek and Tributaries Assessment (Ref: ) 21

23 4.3 Factor of Safety From a geomorphic perspective, the 100-year migration rate quantifies the lateral and downstream movement of meander features. This value typically represents the erosion setback to be applied to either side of the meander belt width in order to account for bank erosion and channel migration over time. The large extent of the study area made proper georeferencing of the historic aerial photographs difficult. The error was too significant to allow for accurate, pragmatic migration rates. A qualitative review of the historic aerial photographs was provided in the background section and the photos/selected traces can be found in Appendix D. In lieu of accurate 100-year migration rates, a 10% setback was instead applied on either bank as a factor of safety for future erosion. Additionally the 7.5m regulated setback was applied as per Conservation Halton s Policy. Finally, the main reaches of 14-Mile Creek and the larger tributaries (SW-1, SW-3, 9a, 9b, and 9c) are classified as occupied or contributing Redside Dace habitat. This requires a separate 30m setback applied to each bank from the preliminary setback. This is the furthest setback and is thus governs the final meander belt width (Figure 4.3).A summary of the preliminary belt widths, erosion setback and final belt widths determined for each study reach is provided in Table 4.1. Figure 4.2: Map of meander belt widths for reaches 9b and 9c (UEM, 2012) D. Schaeffer Engineering Ltd. Fourteen Mile Creek and Tributaries Assessment (Ref: ) 22

24 Figure 4.3: Map of meander belt widths D. Schaeffer Engineering Ltd.- Fourteen Mile Creek and Tributaries Assessment (Ref: ) 23

25 Figure 4.4: Map of study area with topographic contours D. Schaeffer Engineering Ltd.- Fourteen Mile Creek and Tributaries Assessment (Ref: ) 24

26 Table 4.1: Summary of Meander Belt Width Parameters Reach Condition based on RGA results Preliminary Meander Belt Width (m) Factor of Safety (10% on each bank) (m) FOS + Preliminary Belt Width + 7.5m regulated setback Preliminary Belt Width + Redside Dace Setback (m) R-74a In Adjustment R-74b Transitional/Stressed R-75a Transitional/Stressed R-75b Transitional/Stressed R-76 In Adjustment SW-1 Transitional/Stressed SW-2 Transitional/Stressed SW-3 In Regime N/A SW-4 In Regime N/A SWS-1 In Regime N/A 73 Transitional/Stressed Transitional/Stressed b In Regime a N/A (9b) Transitional/Stressed (9b) In Regime (9b) In Regime (9c) Transitional/Stressed (9c) Transitional/Stressed (9c) In Regime D. Schaeffer Engineering Ltd.- Fourteen Mile Creek and Tributaries Assessment (Ref: ) 25

27 5. Detailed Geomorphological Analysis In addition to rapid assessment, detailed geomorphological field data were collected along reaches R- 75a, SW-2, and 73 as identified in Figure 3.1. Selection of these sites was based on degree of channel instability and representative spatial coverage of the site. A summary of the data collected for each site are provided in Appendix B. For the purposes of the detailed field investigation, the following tasks were undertaken: Measurements of bankfull cross-sections at 5 locations per site. Bank characterization (i.e., height, angle, composition, degree of vegetative cover). Bed substrate characterization using a modified Wolman pebble count to evaluate grain size and distribution. A long profile survey of the channel bottom and bankfull elevations to determine local energy gradients, including top-of-riffle, bottom-of-riffle, maximum pool depth and any obstructions to flow. Digital photography showing each of the 5 cross-sections per site, for a total of 10 crosssections. D. Schaeffer Engineering Ltd.- Fourteen Mile Creek and Tributaries Assessment (Ref: ) 26

28 5.1 Bankfull Geometry As part of the detailed field assessment, standard protocols and known field indicators were used to quantify bankfull cross-sectional dimensions (e.g. bankfull depth and width). The bankfull channel area generally represents the maximum capacity of the channel before flow spills into the floodplain, and is usually identified by obvious breaks, or inflections, in the cross section profile and changes in vegetation. Bankfull dimensions for SW-2 are found in Table 5.1. Bankfull width varies from 2.3m to 3.5m with an average of 3.01m. Average bankfull depths are fairly consistent, ranging from 0.2m to 0.29m with a mean depth of 0.24m and an average maximum depth of 0.37m. These dimensions resulted in an average cross-sectional area of 0.73m 2. Bank height averaged between 0.35m and 0.28m with the left bank being slightly higher. The average bank angle was approximately 27 degrees. Bankfull dimensions for R-75a are found in Table 5.2. Bankfull dimensions of the main stem of 14- Mile Creek are roughly triple the size of its tributary. Width varies from 6.44m to 9.96m with an average of 8.18m. R-75a is quite sinuous with several bends in which the channel narrows. Selection of cross-section locations was difficult as there were few straight sections with consistent widths. This explains the larger variation of cross-section widths found in R-75a. While widths varied, average bankfull depths were very consistent with a range of 0.43m to 0.49m and an average maximum depth of 0.62m. These dimensions produced an average cross-sectional area of 3.31m 2. Average bank height was 0.55m; both banks were similar in height. The left bank was steeper with an average angle of 26 degrees; the right bank was on average 18 degrees. Bankfull dimensions for reach 73 are found in Table 5.3. Bankfull dimensions in reach 73 are relatively similar to those found upstream in R-75a. Width varies from 6.18m to 8.70m, with an average of 7.01m. Bankfull depths are very consistent within the 5 cross sections, and when compared to R-75a. Average depth ranged from 0.42m to 0.47m. Maximum bankfull depth ranged from 0.59m to 0.73m with an average of 0.66m. These dimensions produced an average crosssectional area of 3.19m 2. Average bank height was 0.54m. Bank angles varied between gentle slopes around and steeper banks around Table 5.1: Bankfull geometry results for representative cross-sections for SW-2 Cross-section Name: XS-1 XS-2 XS-3 XS-4 XS-5 Average Bankfull Width (m) Average Bankfull Depth (m) Maximum Bankfull Depth (m) Bankfull Width:Depth Cross-sectional Area (m 2 ) Wetted Perimeter (m) Hydraulic Radius (m) D. Schaeffer Engineering Ltd.- Fourteen Mile Creek and Tributaries Assessment (Ref: ) 27

29 Left Bank Angle (bankfull) ( o ) Right Bank Angle (bankfull) ( o ) Table 5.2: Bankfull geometry results for representative cross-sections for R-75a Cross-section Name: XS-1 XS-2 XS-3 XS-4 XS-5 Average Bankfull Width (m) Average Bankfull Depth (m) Maximum Bankfull Depth (m) Bankfull Width:Depth Cross-sectional Area (m 2 ) Wetted Perimeter (m) Hydraulic Radius (m) Left Bank Angle (bankfull) ( o ) Right Bank Angle (bankfull) ( o ) Table 5.3: Bankfull geometry results for representative cross-sections for reach 73. Cross-section Name: XS-1 XS-2 XS-3 XS-4 XS-5 Average Bankfull Width (m) Average Bankfull Depth (m) Maximum Bankfull Depth (m) Bankfull Width:Depth Cross-sectional Area (m 2 ) Wetted Perimeter (m) Hydraulic Radius (m) Left Bank Angle (bankfull) ( o ) Right Bank Angle (bankfull) ( o ) Bankfull Channel Hydraulics Channel form is generally thought to be a response to the water and sediment supplied to the system, coupled with valley constraints, such as bedrock and vegetation. The bankfull channel dimensions presented in Section 5.1 likely formed to carry a certain discharge. Using the gradients and bankfull channel cross-sections measured in the field, bankfull discharge can be estimated for SW-2, R-75a, and 73, along with other important flow characteristics, including the main driver of sediment entrainment, shear stress (Table ). Bankfull discharge for SW-2 is estimated to be 1.0m 3 /s. At this discharge, the water in the channel moves at an average rate of 1.14m/s, resulting in an average shear stress of 26.29N/m 2. The mean maximum velocity and maximum shear stress are 1.83m/s and 42.84N/m 2, respectively (Table 5.4). D. Schaeffer Engineering Ltd.- Fourteen Mile Creek and Tributaries Assessment (Ref: ) 28

30 For R-75a the average bankfull discharge is 3.68m 3 /s. The accompanying velocity is 1.03m/s, resulting in an average shear stress of 15.48N/m 2. The mean maximum velocity and maximum shear stress are 1.39m/s and 24.13N/m 2, respectively(table 5.5). While R-75a has a higher discharge than SW-2, its resultant shear stress and velocities are lower due to a gentler gradient than SW-2. In reach 73, the average bankfull discharge is approximately 3.33m 3 /s. The velocity at this discharge is 0.87m/s, resulting in an average shear stress of 12.68N/m 2. The mean maximum velocity and maximum shear stress are 1.29m/s and 19.14N/m 2, respectively (Table 5.6). Table 5.4: Bankfull hydraulics for representative cross-sections in SW-2. Cross-section Name: XS-1 XS-2 XS-3 XS-4 XS-5 Average Bankfull Discharge (m 3 /s) Average Bankfull Velocity (m/s) Maximum Bankfull Velocity (m/s) Average Shear Velocity [u*] (m/s) Stream Power (W/m) Average Shear Stress (N/m 2 ) Maximum Shear Stress (N/m 2 ) Left Bank Shear Stress (N/m 2 ) Right Bank Shear Stress (N/m 2 ) Critical Particle Diameter for Analysis (m) Table 5.5: Bankfull hydraulics for representative cross-sections in R-75a. Cross-section Name: XS-1 XS-2 XS-3 XS-4 XS-5 Average Bankfull Discharge (m 3 /s) Average Bankfull Velocity (m/s) Maximum Bankfull Velocity (m/s) Average Shear Velocity [u*] (m/s) Stream Power (W/m) Average Shear Stress (N/m 2 ) Maximum Shear Stress (N/m 2 ) Left Bank Shear Stress (N/m 2 ) Right Bank Shear Stress (N/m 2 ) Critical Particle Diameter for Analysis (m) Table 5.6: Bankfull hydraulics for representative cross-sections in reach 73. Cross-section Name: XS-1 XS-2 XS-3 XS-4 XS-5 Average Bankfull Discharge (m 3 /s) D. Schaeffer Engineering Ltd.- Fourteen Mile Creek and Tributaries Assessment (Ref: ) 29

31 Average Bankfull Velocity (m/s) Maximum Bankfull Velocity (m/s) Average Shear Velocity [u*] (m/s) Stream Power (W/m) Average Shear Stress (N/m 2 ) Maximum Shear Stress (N/m 2 ) Left Bank Shear Stress (N/m 2 ) Right Bank Shear Stress (N/m 2 ) Critical Particle Diameter for Analysis (m) Sediment Distribution A modified Wolman pebble count was used to quantify channel bed substrate distributions. Bank material was characterized at each cross section for each surveyed reach, as part of the detailed survey. The average sediment characteristics for each reach are summarized in Table 5.7. Detailed sediment distributions for both reaches can be found in Appendix B. Reach SW-2 has a median grain size (D 50 ) of 41.03mm and a D 90 (ie., size where 90% of the samples are finer) of 125.4mm. These values indicate that most of the bed material is classified as very coarse gravel and the largest sizes are small cobbles. Reach R-75a has a median grain size of 62.67mm and a D 90 of 140.7mm. These values indicate that the bed material in the main channel is mostly small cobbles with the largest material being composed of large cobbles. The range of material in R-75a is more consistent and less variable than SW-2. Reach 73 has a median grain size of 57.19mm and a D 90 of 184.4mm. Most of the bed material is classified as very coarse gravel with the largest material being large cobbles, comparable to R-75a. 5.4 Erosion Threshold Analysis In essence, an erosion threshold analysis determines the hydraulics, such as discharge, channel depth, or average channel velocity, at which the channel produces enough shear stress to initiate the mobilization of sediment of a given size, usually the D 50. The analysis alsohelps evaluate a reach s erosion sensitivity by comparing theboundary shear stress associated with modeled flowsto the critical shear stress required to entrain sediment. Erosion threshold analysis was undertaken for SW-2, R- 75a, and 73based on measured cross-sections and consideration of the median bed substrate size (D 50 ), as well as bank materials. Nine different models were used to calculate erosion thresholds, including models based on critical shear stress and permissible velocity, in order to consider a range of results. The model results were examined for convergence and compatibility with field observations. Selection of appropriate thresholds was also based on an understanding of site conditions and the assumptions and ranges of conditions under which the models are applicable. D. Schaeffer Engineering Ltd.- Fourteen Mile Creek and Tributaries Assessment (Ref: ) 30

32 Results of the erosion threshold analyses are presented in Table 5.7. The critical discharge in SW-2 was estimated at 0.43m 3 /s. This indicates that bed load transport is initiated at 43% of the bankfull discharge. In reach R-75a, critical discharge is estimated at 4.02m 3 /s, and transport is, therefore, initiated at 111% of the bankfull discharge. The higher threshold in R-75a is attributed to the larger material found there. It is also attributed to the lower gradient in R-75a. This is also true for reach 73 in which the material is comparable to that in R-75a and there is a slightly lower gradient, resulting in a slightly higher critical discharge (4.26m 3 /s). Due to this increase in critical discharge and a slightly lower average bankfull discharge, transport in reach 73 is not likely to occur unless the discharge reaches 128% of the bankfull. While R-75a experiences higher discharges than SW-2 the difference in gradient results in comparable shear stresses. Essentially, the flow in reach R-75a is attempting to mobilize material that is larger than that found in SW-2 with the same amount of energy. This results in needing a higher critical discharge to compensate for the lack of gradient. As the channel is not fully competent to transport bedload at bankfull stage, the energy is dissipated by eroding the finer bank material. Bank erosion and scour, in conjunction with bed aggradation, are prevalent in all of the Fourteen Mile Creek reaches, supporting this conclusion. In addition to this the large areas of bedrock exposure, which are not assessed as part of the erosion threshold analysis, are very difficult to erode. This reinforces the notion that most of the energy is expended through widening the channel boundary. Erosion threshold analysis was also done for the banks because widening was identified as the primary form of adjustment in the study area (Table 5.7). The critical discharge calculated for the banks was significantly lower than those calculated for the bed. For SW-2 and R-75a, transport would occur at approximately 7% of bankfull, at discharges of 0.07 and 0.27m 3 /s. In reach 73 the critical discharge is slightly higher (0.63m 3 /s) indicating that transport would occur at approximately 19% of bankfull. The bank material in the three reaches was similar, composed of fine, cohesive sediments which can be eroded relatively easily along the bank toe at sustained flows. This type of erosion is slow and will only lead to small bank failures over the long-term depending on the geotechnical strength of the bank. The more important process is that which occurs during high flow events. Through the duration of a high flow event bank material becomes saturated which weakens the cohesive strength allowing substantial erosion and collapse to occur more readily. The widening is more likely attributed to a hydrological regime that is characterized by frequent, flashy flood events. It is recommended that any future development in the Merton Tertiary Planning area maintains or improves upon the current flow regime. An increase in high flow events would be detrimental to the state of the watercourses as they are already experiencing widening and erosion which could be exacerbated. D. Schaeffer Engineering Ltd.- Fourteen Mile Creek and Tributaries Assessment (Ref: ) 31

33 Table 5.7: Average bankfull characteristics and erosion thresholds using bed material. Parameter R-75a 73 SW-2 Bankfull Geometry Average Bankfull Width (m) Average Bankfull Depth (m) Bankfull Gradient (%) Bed Material Bed Material D 50 (mm) Bed Material D 84 (mm) Bankfull Hydraulics Manning s n (estimate) Average Bankfull Velocity (m/s) Average Bankfull Discharge (m 3 /s) Thresholds Method of analysis Bed threshold Komar (2001) Critical particle size (mm) Bank threshold (Chow, 1959) Fine/cohesive sediment Bed threshold Komar (2001) Bank Threshold (Chow, 1959) Fine/cohesive sediment Bed threshold Komar (2001) Bank threshold (Chow, 1959) Fine/cohesive sediment Critical Discharge (m 3 /s) Critical: Bankfull Discharge (%) 111% 7.34% 128% 18.9% 43% 7% Critical Velocity (m/s) Critical Shear Stress (N/m 2 ) No of cross-sections analyzed D. Schaeffer Engineering Ltd.- Fourteen Mile Creek and Tributaries Assessment (Ref: ) 32

34 6. Conclusions This report presents the findings of geomorphological reach characterization, erosion threshold analysis at selected detailed fieldwork sites, and meander belt width assessment for Fourteen Mile Creek and its associated tributaries flowing through the Merton Tertiary Planning area. The report is intended to provide a characterization of existing conditions within the watercourses and an indication of how they may change with future development. Based on the report findings the following key conclusions can be drawn: Meander belt widths Meander belt widths have been delineated for all reaches of sufficient size. Erosion setbacks used for meander belt widths were based on the current state of the channel as historical migration rates could not be determined. Final belt widths ranged from a minimum of 24m to a maximum of 170m. Larger belt widths were determined for reaches exhibiting higher activity to allow a larger area for adjustment. Any future development should occur outside of the meander belt widths to ensure stability. Reach characterization and erosion thresholds Eleven reaches have been delineated within the study area. Results of rapid field assessment indicate that the majority of reaches are in a state of transition or adjustment. Only four reaches were characterized as stable which were located within the Saw Whet golf course itself. These reaches were small channels with little definition that only experience flow during rainfall events. The main method of adjustment was widening with aggradation as a secondary process. This pairing indicates that the stream power of the channel is not high enough to fully mobilize the bed load and therefore energy is focused on the lateral boundaries resulting in widening. Larger material eroded out of the banks is deposited often at the base of the banks with little to no subsequent transport. This characterization of channel processes is supported by erosion threshold calculations which show that in order to mobilize the bed load in the main channel (ie. R-75a) bankfull discharge must be exceeded. A channel that is unable to mobilize its bed will instead dissipate its energy through bank erosion and planimetric adjustments. Bank thresholds were also calculated based on the indications that widening is the primary mode of adjustment. These thresholds were significantly lower than the bed thresholds, based on the difference in grain size composition. The bank material is fine, cohesive sediment as opposed to the large shale fragments which populate the bed. The threshold discharge for the banks is quite low and would likely only result in toe erosion which is only a threat to bank stability over a long-term sustained period. The widening is more likely attributed to frequent, flashy flows which saturate and destabilize the banks by reducing the cohesive strength. These conclusions are in agreement with historical data from the Oakville Erosion Studies (2008 and 2010) which have characterized the channel as widening resulting in increased woody debris forming jams within the channel. These jams exacerbate channel adjustment by encouraging the development D. Schaeffer Engineering Ltd.- Fourteen Mile Creek and Tributaries Assessment (Ref: ) 33

35 of chutes and cut-offs. Based on the current state of the channel, it is recommended that any new development of the Merton Tertiary Planning area must mitigate stormwater runoff to maintain current discharge levels in Fourteen Mile Creek and its associated tributaries. Any increase in flow to the tributaries and consequently Fourteen Mile Creek will increase activity in a channel that is already highly active within its floodplain. In some areas the channel abuts the valley wall and therefore slope stability should be considered, ensuring any development is placed a sufficient distance from valley walls. Opportunities for Enhancement The watercourses within the Tertiary Planning Area present a good opportunity to preserve and maintain a natural system and undertake minor works to improve a few problem areas. The length of 14-Mile Creek that is contained within the valley is highly active due to natural processes; this area may be left as is without any enhancement. The small tributaries that are contained within the golf course (SW-3, SW-4, and SWS-1) may benefit from the redevelopment of the golf course. Historic aerial photographs showed these reaches to be more well-established prior to the golf course development, water-taking measures such as ponds has likely lead to reduced flows and poor channel definition. Re-development of the area provides the opportunity for the tributaries to become more permanent, established features, as they currently only carry water during high rainfall events. Finally, the tributaries contained in the Third Line Lands (9a, 9b, and 9c) are the only reaches that could benefit from select channel modification. The upstream section of 9b was previously modified as noted in UEM (2012) and currently has two knickpoints. It was also characterized as having rip-rap, concrete rubble, and a small concrete weir. Head-cutting was also noted on 9c at the upstream end, leading to failing concrete lining at an outfall. These reaches, particularly 9b and 9c, could benefit from small spot treatments and channel design work to repair previously modified areas. D. Schaeffer Engineering Ltd.- Fourteen Mile Creek and Tributaries Assessment (Ref: ) 34

36 7. References AECOM. (2010). Creek Erosion Inventory andassessment Study Report Submitted to: Town of Oakville Chow, V.T. (1959). Open Channel Hydraulics. New York, NY: McGraw-Hill Book Co. Galli, J. (1996). Rapid stream assessment technique, field methods. Metropolitan Washington Council ofgovernments. 36pp. Parish Geomorphic Ltd. (2001).Geomorphological protocols for subwatershed studies. Submitted to: Regional Municipality of Ottawa-Carleton. Parish Geomorphic Ltd. (2008). Oakville Erosion Assessment 2008 Appendix A: Reach Summaries. Phillips Engineering. (2002). Fourteen Mile Creek Main and West Branches Subwatershed Plan. Submitted to: Town of Oakville. UEM.(2012). Functional Servicing Study Third Line and North Service Road. Submitted to: GSP Group Inc. D. Schaeffer Engineering Ltd.- Fourteen Mile Creek and Tributaries Assessment (Ref: ) 35

37 Appendix A: Reach Photos Photo 1: SW-1 scour in meander bend and point bar deposition. Photo 2: SW-1 Narrowed, dry section of channel through meadow area.

38 Photo 3: SW-2 Bend scour and large gravel deposition in channel. Photo 4: SW-2 Channel entering meadow section, narrowing.

39 Photo 5: SW-2 Cross-section 1 facing downstream Photo 6: SW-3 facing upstream where channel flows through golf-course.

40 Photo 7: SW-4 Culvert at Bronte Road where reach begins and forms large pool Photo 8: SW-4 Channel flowing through wooded area in upstream section of reach.

41 Photo 9: SW-4 Channel crosses open meadow area and loses definition completely, photo facing upstream Photo 10: SW-4 Downstream section of channel through meadow area, channel is significantly narrower.

42 Photo 11: SWN-1 Upstream limit of reach where channel crosses golf course and is undefined. Photo 12: SWN-1 Downstream section where channel again crosses golf course as a small undefined depression.

43 Photo 13: SWN-1 Section near the downstream end where channel has incised. Photo 14: SWS-1 Area where channel shows definition through woodlot.

44 Photo 15: SWS-1 Downstream end where channel flows through meadow, and shows less definition. Photo 16: R-74a Large beaver dam located at downstream end where outfall flows into channel from right bank, photo facing upstream.

45 Photo 17: R-74a Backwatering upstream of beaver dam. Photo 18: R-74a Woody debris jam.

46 Photo 19: R-74a Bank scour where placed log bank protection has been completely removed by flow. Photo 20: R-74b Deposition along right side of channel and erosion along left bank.

47 Photo 21: R-74b Vegetated point bar and erosion along valley wall contact. Photo 22: R-75a Large riffle composed of angular shale fragments.

48 Photo 23: R-75a Tree roots exposed by bank erosion. Photo 24: R-75a High flow chute (top of photo) located on the outside of a meander bend which could eventually cut off a second meander bend located downstream of the photo. Arrow indicates direction of flow.

49 Photo 25: R-75b Small boulders in channel. Photo 26: R-75b Valley wall composed of Queenston Shale Formation.

50 Photo 27: R-75b Eroding valley wall and large area of shale deposition.] Photo 28: R-75b Large point bar composed of shale fragments.

51 Photo 29: R-76 Formation of vegetated island within channel. Photo 30: R-76 Valley wall erosion causing root exposure and leaning trees.

52 Photo 31: R-76 Vegetated debris jam, flow is diverted to left of obstacle, large areas of deposition are seen on the right of obstacle (flow direction indicated by arrow). Photo 32: R-76 Close-up of area of gravel deposition seen at bottom right of previous photo.

53 Photo 33: R-76a Woody debris in channel creating jam. Photo 34: R-76 Natural channel design section located at upstream end of reach.

54 Photo 35: R-74 in 2010 area where bank protection has been completely removed and only metal stakes remain. Photo 36: R-73 small knickpoint

55 Photo 37: Typical channel conditions in R-73, eroding bank in bend, shale fragment deposition Photo 38: Valley contact in channel bend, R-73.