Fluvial Geomorphology Report. Appendix. Teston Road Class Environmental Assessment Pine Valley Drive to Weston Road Environmental Study Report

Transcription

1 Teston Road Class Environmental Assessment Pine Valley Drive to Weston Road Environmental Study Report Appendix J Fluvial Geomorphology Report Accessible formats are available upon request.

2 TESTON ROAD CLASS ENVIRONMENTAL ASSESSMENT FLUVIAL GEOMORPHIC ASSESSMENT VAUGHAN, ONTARIO Report Prepared for: HDR Prepared by: PARISH AQUATIC SERVICES November 2016 Mississauga, Ontario Suite 200, 2500 Meadowpine Boulevard Mississauga, Ontario, Canada L5N 6C4 Phone: Fax:

3 TESTON ROAD CLASS ENVIRONMENTAL ASSESSMENT FLUVIAL GEOMORPHIC ASSESSMENT Report prepared for HDR, November 2016 Mark Wojda, M.ScE., E.I.T. Water Resources EIT reviewed by John Parish, P.Geo. Principal Geomorphologist DISCLAIMER We certify that this report is accurate and complete and accords with the information available during the site investigation. Information obtained during the site investigation or provided by third parties is believed to be accurate but is not guaranteed. We have exercised reasonable skill, care and diligence in assessing the information obtained during the preparation of this report. This report was prepared for HDR. The report may not be relied upon by any other person or entity without our written consent and that of HDR. Any uses of this report by a third party, or any reliance on decisions made based on it, are the responsibility of that party. We are not responsible for damages or injuries incurred by any third party, as a result of decisions made or actions taken based on this report Teston Rd EA - Geomorphic Assessment final v3 ii

4 TABLE OF CONTENTS 1 INTRODUCTION Study Area Objectives Approach BACKGROUND REVIEW Physiography and Soils Historical Land Use Historical Planform Changes Previous Studies Widening and Reconstruction of Teston Road Class EA (2003) Detailed Design at C2 (2011) Meander Belt Analysis for Redside Dace Habitat Setbacks Blocks 40/47 (2011) REACH DELINEATION FIELD ASSESSMENTS Rapid Assessment Protocols Rapid Assessment Results C C C C C C Detailed Survey MEANDER BELT WIDTH ASSESSMENT C2 Meander Belt Planform Analysis Empirical Analysis C6-a/b and C6-c Meander Belt Planform and Topographical Analysis Redside Dace Setback CROSSING RECOMMENDATIONS AND ENHANCEMENT OPPORTUNITIES C C C3 and C C5 and C CONCEPTUAL DESIGNS REFERENCES Teston Rd EA - Geomorphic Assessment final v3 iii

5 LIST OF FIGURES Figure 1. Study area of Teston Road between Pine Valley Drive and Weston Road... 2 Figure 2. West study area of Teston Road with 1978 and 2011 planforms... 5 Figure 3. East study area of Teston Road with 1978 and 2011 planforms... 6 Figure 4. Reach breaks for tributaries at crossings C1-C Figure 5. Reach breaks for tributaries at crossings C3-C Figure 6. Detailed survey map with long profile shown in orange and the cross-sections shown in red.. 16 Figure 7. Long profile of detailed survey downstream of Teston Road LIST OF TABLES Table 1. Proposed structure upgrades (Giffels, 2003)... 8 Table 2. RGA Classification Table 3. RGA & RSAT Summary Table 4. Detailed Survey Results Table 5. Meander Belt Width Analysis Results for C Table 6. Empirical Meander Belt Results for C APPENDICES Appendix A - Site Investigation Photos Appendix B - Meander Belt Width Figures Appendix C - General Arrangement Drawing Purpleville Creek Bridge Teston Rd EA - Geomorphic Assessment final v3 iv

6 1 INTRODUCTION HDR is conducting a Class Environmental Assessment (EA) Study of road improvements to Teston Road between Pine Valley Drive and Weston Road, in the City of Vaughan. As the proposed improvements will affect crossings of tributaries to Purpleville Creek (also known as Cold Creek),, a Division of Matrix Solutions Inc. (PARISH), has been retained to provide fluvial geomorphic input. Throughout the assessment process and during the development of alternatives for the crossing structures and roadway design, PARISH has provided interim background reports and design recommendation memos. This report represents the consolidation of these previously submitted deliverables. Further, comment is provided on recently revised roadway and bridge design elements. 1.1 Study Area The six watercourses within the study area are tributaries to Purpleville Creek, a permanent coldwater tributary of the East Humber River. The Purpleville Creek watershed drains an area of less than 10 km 2. To maintain consistency, nomenclature has been adopted from the Class Environmental Assessment and Preliminary Design report (Giffels, 2003) when referring to the tributary crossings along the roadway; from west to east, the tributaries are denoted as C1 to C6 (Figure 1). 1.2 Objectives The primary objective of this study is to ensure that fluvial geomorphic considerations are appropriately addressed in the EA process and during the development of crossing designs. As part of the East Humber River system which supports the provincially endangered Redside Dace, a permit under the Endangered Species Act (ESA) is required to replace culverts along Teston Road. As such, consideration of impacts to Redside Dace habitat is required. In order to achieve the project objectives, the following work plan was undertaken: Review of background information and historic analysis of channel form; site reconnaissance - rapid assessments and detailed surveys; delineation of meander belt widths and identification of erosion hazards; integration of desktop assessment results and field data; develop recommendations on crossing structure sizing and configuration; and, design conceptual channel treatments, as necessary. A number of previous studies have been completed regarding the watercourses in the study area; the recommendations and preliminary designs included in the previously completed studies (summarized in Section 2.4) provided a foundation for the development of the updated recommendations presented in this study (Section 6). Teston Road EA Fluival Geomorphic Assessment 1

7 Figure 1. Study area of Teston Road between Pine Valley Drive and Weston Road C4 C5 C6 C3 C2 C1 1.3 Approach Watercourses are dynamic features that change their configuration and position within a floodplain by means of meander evolution, development, and migration processes. Watercourse form and function and stream corridor continuity must be considered in crossing design in order to avoid disruption of natural channel processes and to prevent increased risk to the infrastructure. The objective of the current assignment is to provide fluvial geomorphic input towards the road improvements and crossing structure upgrades/replacements in order to mitigate this risk and improve geomorphic conditions. A second objective is to minimize ecological impact, particularly in relation to Redside Dace habitat. In general, the two primary factors that must be considered from a geomorphic perspective at a channel crossing are the potential for channel migration and channel incision. The structural parameters affected by channel migration/erosion (lateral instability) are length, span, and skew, while channel incision (vertical instability) affects footing or bed inverts and length. In order to evaluate a channel with respect to these parameters, the following factors are considered: Channel Size: The potential for lateral channel movement and erosion tends to increase with stream size. Headwater streams tend to exhibit low rates of lateral migration due to the stabilizing influence of Teston Road EA Fluival Geomorphic Assessment 2

8 vegetation on the channel bed and banks. Erosive forces in larger watercourses tend to exceed the stabilizing properties of vegetation and result in higher migration rates. Valley Setting: Watercourses with wide, flat floodplains and with low valley and channel slopes tend to migrate laterally across the floodplain over time. Watercourses that are confined in narrow, well drained valleys are less likely to erode laterally but are more susceptible to down-cutting and channel widening, particularly where there are changes to upstream land use. Typically the classification of the valley will fall into one of three categories: confined, partially confined, and unconfined. Meander Belt Width: The meander belt width represents the maximum expression of the meander pattern within a channel reach. Therefore, this width/corridor covers the lateral area that the channel could potentially occupy over time. This value has been used by regulatory agencies for corridor delineation associated with natural hazards and the meander belt width is typically of a similar dimension to the regulatory floodplain. Meander Amplitude: The meander amplitude and wavelength are important parameters to ensure that channel processes and functions can be maintained within the crossing. The number of wavelengths upstream of the structure to be considered is dependent on the scale of the watercourse, rates of migration, and the degree of valley confinement. 100-year Migration Rates: Using historical aerial photographs, migration rates may be quantified (where possible) for each crossing location. A higher migration rate indicates a higher geomorphic risk. Rapid Geomorphic Assessment (RGA) Score: An RGA score provides a measure of the stability and health of the channel. Channels that are unstable tend to be actively adjusting and thus are sensitive to the possible effects of the proposed crossing. Accordingly, there is more risk associated with unstable channels. Where a new crossing is proposed or an existing crossing is being replaced, a collective evaluation of all these factors is used to direct the development of new structural design parameters (span, length, and skew) that are appropriate from a fluvial geomorphic perspective. For the current assignment, this is the case at C2; however, for the other crossings, other established constraints or design requirements associated with the roadway improvements have largely governed the crossing upgrades. For example, at C5 and C6, the replacement of the CSPs is not considered an option due to the recent costly construction of a retaining wall along the north side of Teston Road. Crossings C1, C3, and C4 are largely be governed by other design requirements (e.g. hydrology and hydraulics). However, the evaluation of the above-noted factors can be used to guide other aspects of roadway improvement design (i.e. embankment grading), and the identification and development of restoration opportunities. Teston Road EA Fluival Geomorphic Assessment 3

9 2 BACKGROUND REVIEW A desktop examination of the study area via topographic mapping, aerial imagery, and watercourse data allowed for the completion of a historic assessment. A background review of relevant studies and reports within the study area was conducted and summarized below. 2.1 Physiography and Soils The study area is located within the South Slope physiographic region, which extends south of the Oak Ridges Moraine to Lake Ontario. Topography across the study area consists of gently-rolling, drumlinized terrain, sloping south towards Lake Ontario. This region consists of till plains comprised primarily of clayto silt-textured material with inclusions of sand and gravel (Chapman and Putnam, 1984). Soils within the study area consist of clay, clay loams and silt loams of the Monoghan, King Clay and Peel Clay soils (Hoffman and Richards, 1953). The high clay content of the soils in combination with the shale and limestone tills and lacustrine deposits produce an arable environment with good drainage and groundwater connectivity (Giffels, 2003). Bedrock geology consists of shale, limestone, dolostone and siltstone from the Georgian Bay and Blue Mountain formations. 2.2 Historical Land Use From the 1800 s, land use was predominantly farming and logging in the greater York region. Records indicate that over 70% of York County was occupied by farm land in 1951 (Hoffman and Richards, 1953). No aerial photography from 1954 is available from the Archives of Ontario for the study area, however photographs from 1978 were obtained. By 1978, some residential development was observed, mostly in the form of acreage properties and farm houses, however the predominant land use remained farmland, natural woodlots, and vegetated stream valleys. Aerial imagery from 2011 and 2015 was used to document current conditions. A significant increase in residential land use, particularly south of the Teston Road and Weston Road intersection is observed. Land use north of Teston Road remained relatively unchanged. 2.3 Historical Planform Changes Watercourse planforms were traced using aerial imagery from 1978 and The overlaid planforms are presented in Figures 2 and 3. Where channel form is discernible, little planform change is observed, apart from any anthropogenic adjustments such as channel straightening for agricultural or drainage purposes. For reaches where the channel is poorly-formed or is not discernable from the air photo, it is difficult to assess the degree of planform adjustment. This is the case for tributaries associated with C1, C3, and C4. For C2, C5, and C6, the high degree of riparian vegetation and poor image resolution in the 1978 photograph prohibits any reliable migration/erosion rate calculation. Teston Road EA Fluival Geomorphic Assessment 4

10 Figure 2. West study area of Teston Road with 1978 and 2011 planforms C5 C6 C3 C2 C3 C1 Legend 2011 CX-x Planform 1978 Planform Crossing name and location Teston Road EA Fluival Geomorphic Assessment 5

11 Figure 3. East study area of Teston Road with 1978 and 2011 planforms C5 C6 C4 C3 Legend 2011 Planform 1978 Planform Crossing name and location Teston Road EA Fluival Geomorphic Assessment 6

12 2.4 Previous Studies Widening and Reconstruction of Teston Road Class EA (2003) In 2003, Giffels Associates Limited completed a Schedule C Municipal Class Environmental Assessment for the widening and reconstruction of Teston Road from Pine Valley Drive to Bathurst Street. The study recommended the reconstruction of Teston Road to Regional arterial road standards. This assessment included an investigation of crossings C1-C6. Information for each of the crossings is summarized below. C1 Giffels (2003) described the tributary at this crossing to be an intermittent coldwater tributary which originates in the northwest quadrant of the Pine Valley Drive and Teston Road intersection. This tributary is connected to two pond/wetland features, one of which is a part of the East Humber Wetland Complex and has been classified as a Provincially Significant Wetland (PSW). The drainage area at C1 is 13.8 ha and the current culvert is a 450 mm corrugated steel pipe (CSP). C2 This tributary is a permanent watercourse situated in a wooded, confined/partially confined valley setting whose confluence with Purpleville Creek is 0.9 km downstream of Teston Road. The watercourse contains a non-sport fish community and Redside Dace have also been known to occur in this watercourse. Due to several observed groundwater seepages that contribute baseflow, this watercourse is considered permanent coldwater habitat. The drainage area at this crossing is 643 ha and the current structure is a 5.9 m by 5.0 m open footing concrete box culvert. C3 and C4 The tributaries at these crossing represent drainage swales originating north of Teston Road and are not expected to provide fisheries habitat. At C3 and C4, the drainage areas are 26.7 ha and 21.6 ha, respectively. There is a 450 mm diameter and 600mm CSP at C3 and a 450 mm CSP at C4. C5 Giffels (2003) classified this unnamed tributary to Cold Creek as intermittent and described it as originating in the wooded ravine immediately north of Teston Road. The drainage area at the crossing is 10.8 ha and there is a 600 mm CSP in place. The outlet from the CSP outlet represents a 0.3 m vertical drop barrier to upstream fish movement during periods of low flow. C6 The tributary associated with this crossing originates 1 km north of Teston Road and is categorized as permanent/intermittent coldwater habitat as it may periodically experience intermittent conditions during extended dry periods. The drainage area to the crossing is 99.0 ha and there is a 1050 mm CSP in Teston Road EA Fluival Geomorphic Assessment 7

13 place. The CSP culvert outlet exhibits a 0.75 m vertical drop which represents a complete barrier to fish passage. The Giffels report included recommendations for crossing structure upgrades or replacements, summarized in Table 1. These recommendations were not implemented but were considered for the current study. Table 1. Proposed structure upgrades (Giffels, 2003) Crossing Existing Proposed C1 14 m mm diam. CSP Replace with 24 m mm diam. CSP C2 20 m x 5.0 m OFB Extend U/S 7 m, D/S 14 m to 41 m x 5.0 m OFB C3 12 m mm diam. CSP 12 m mm diam. CSP Replace with 22 m mm diam. CSP C4 14 m mm diam. CSP Replace with 24 m mm diam. CSP C5 48 m mm diam. CSP No upgrades C6 42 m mm diam. CSP Extend U/S 3 m to 45 m mm diam. CSP Detailed Design at C2 (2011) The existing structure at C2 is an open frame structure 5.8 m wide, 5.0 m high, and approximately 20 m long, with wingwalls on both ends. The preferred design outlined in the 2003 EA (Giffels, 2003) entailed construction of up and downstream extensions on the existing structure; given the skew of the channel upstream of the culvert, realignment of the channel would be required to align with the culvert extension and would potentially disturb the steep sandy slope upstream. In consultation with Toronto and Region Conservation Authority (TRCA), the preferred EA design alternative was re-visited to consider a bridge crossing rather than culvert extension to minimize impact to the watercourse and fish habitat. In 2011, McCormick Rankin Corporation (MRC) and Ecoplans Limited submitted a detailed design to York Region for the replacement of the culvert at C2 and associated road approach upgrades. The proposed replacement involved the removal of the existing culvert and construction of a new 45 m single span concrete girder structure, shifted approximately 3 m downstream of the existing culvert. Associated with these works was the reconfiguration of a naturalized channel section under the new bridge. The overall benefit resulting from the proposed channel work was deemed considerable given the nature of the highly disturbed channel and habitat conditions through the existing culvert. The crossing design and channel works prepared by MRC and Ecoplans Ltd. was not implemented; however, it is being considered for the current study Meander Belt Analysis for Redside Dace Habitat Setbacks Blocks 40/47 (2011) Meander belt analyses were completed by Aqualogic in 2011 to support the setback requirements for Redside Dace habitat on three tributaries to Purpleville Creek in the Blocks 40/47 development areas in the City of Vaughan. The meander belt for the tributary at C2 was delineated downstream of Teston Road. The meander belt limits are defined by the largest meander footprint of the compound meander Teston Road EA Fluival Geomorphic Assessment 8

14 pattern based on historical comparison to current conditions. Immediately downstream of the road, the meander belt limit was determined to be 36 m. It is noted that the watercourse is located in a partiallyconfined setting and development setback limits are set per Provincial Technical Guidelines based on the 100-year erosion setback as determined by historical analysis or by application of guideline criteria, which are then used to add the stable slope limits determined by geotechnical analysis. For the Blocks 40/47 study, it was required that the historic meander belt corridor be demarcated in order to add the 30 m horizontal setback required for Redside Dace. 3 REACH DELINEATION Preliminary reaches for the six watercourses within the study area were identified using available aerial photography, topographic mapping, watercourse planform, and surficial geology. Reaches are lengths of channel (typically 200 m to 2 km) that display similarity with respect to valley setting, planform, floodplain materials, and land use/cover. Reach length will vary with channel scale since the morphology of low-order watercourses will vary over a smaller distance that those of higher-order watercourses. At the reach scale, characteristics of the watercourse corridor exert a direct influence on channel form, function, and processes. Final reach delineations were refined during the field investigation. Figures 4 and 5 display the location of reach breaks. The watercourse at C1 was delineated into three reaches: C1-a upstream and two reaches downstream of Teston Road, C1-b and C1-c. The channel is poorly defined and is not always discernable in the air photos, particularly the upstream reach of C1-a where there is a wetland. Reach C1-b appears to be an agricultural drainage swale before transitioning into a wooded ravine in reach C1-c. At C2, minor sinuosity is noted on the channel form on both and up- and down-stream reaches, herein referred to a C2-a and C2-b, respectively. Although outside of the general study area along Teston Road, two additional reaches (C2-a1 and C2-a2) have been delineated upstream of C2-a. The tributaries at C3 and C4 were each delineated into two reaches, with Teston Road acting as the reach break; C3-a and C3-b, and C4-a and C4-b. The tributary at C5 was delineated into two reaches, with Teston Road acting as the reach break, C5-a upstream and C5-b downstream. Upstream of C5-a, two additional reaches were identified, C5-a1 and C5-a2. C6-a and C6-b are two branches that join immediately upstream of crossing C6. Downstream of the crossing, the tributary is considered reach C6-a/b. Downstream of the confluence of C6-a/b with C5-b, the reach becomes C6-c. Teston Road EA Fluival Geomorphic Assessment 9

15 Figure 4. Reach breaks for tributaries at crossings C1-C3 C2-a2 C2-a1 C3-a C2-a C3 C2 C3-b C1-a C2-b C1 C1-b C1-c Legend Watercourse Reach break Crossing name and location CX-x Reach name Teston Road EA Fluival Geomorphic Assessment 10

16 Figure 5. Reach breaks for tributaries at crossings C3-C6 ld C5-a2 C5-a1 C6-a C6-b C3-a C4-a C5-a C5 C5-b C6 C6-a/b C4 C6-c C3 C3-b C4-b Legend Watercourse Reach break Crossing name and location CX-x Reach name Teston Road EA Fluival Geomorphic Assessment 11

17 4 FIELD ASSESSMENTS 4.1 Rapid Assessment Protocols The Rapid Geomorphic Assessment (RGA) was designed by the Ontario Ministry of the Environment (2003) to assess reaches in rural and urban channels. This qualitative technique documents indicators of channel instability. Observations are quantified using an index that identifies channel sensitivity based on the presence or absence of evidence of aggradation, degradation, channel widening, and planimetric adjustment. Overall, the index produces values that indicates whether a channel is in a stable/in regime (score 0.20), stressed/transitional (score ), or in an adjustment (score 0.40) condition (see Table 2 for detailed descriptions). Table 2. RGA Classification Factor Classification Value In Regime or Stable (Least Sensitive) Transitional or Stressed (Moderately Sensitive) In Adjustment (Most Sensitive) Interpretation 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 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 The Rapid Stream Assessment Technique (RSAT; Galli, 1996) provides a more qualitative and broader assessment of the overall health and function of a reach. This system integrates visual estimates of channel conditions and numerical scoring of stream parameters using six categories: channel stability, erosion and deposition, instream habitat, water quality, riparian conditions, and biological indicators. Scores are divided into three classes of stream health: low (<20), moderate (20-35), and high (>35). While the RSAT scores stream from a more biological and water quality perspective than the RGA, this information is also of relevance within a geomorphic context. This is based on the concept that, in general, the types of physical features that generate quality fish habitat tend to represent stable geomorphology as well (i.e., fish prefer a variety of physical conditions pools provide resting areas while riffles provide feeding areas and contribute oxygen to the water good riparian conditions provide shade and food woody debris and overhanging banks provide shade). Additionally, the RSAT approach includes semi-quantitative measures of bankfull dimensions, type of substrate, vegetative cover, and channel disturbance. Teston Road EA Fluival Geomorphic Assessment 12

18 4.2 Rapid Assessment Results Field reconnaissance was completed to confirm site reaches and perform Rapid Geomorphic Assessments (RGA) and the Rapid Stream Assessment Technique (RSAT) in May Site photographs are provided in Appendix A C1 During the rapid assessment, a small ill-defined outlet channel from the existing wetland was observed. Minor slumping was observed along the embankment and tall grasses and bulrushes near the entrance to the culvert created flat and saturated ground conditions. Where flow was observed in a channel, the wetted depth was measured to be 25 cm with 10 cm depth at low-flow conditions. No estimation of bankfull channel measurements could be obtained minimal definition and due to broad/ unconfined floodplain. Downstream of the Teston Road crossing, along C1-b, backwatering was observed where the outlet is obstructed with tall reeds, grasses and bulrushes. Approximately 20m downstream, the watercourse crosses southeast under Pine Valley Drive via a CSP that outlets and is then redirected via piped flow through a residential manicured grassed residential property. Due to absence of observable channel features, no RGA/RSAT scores were determined C2 Upstream of crossing C2, the watercourse was observed to flow from a wooded, confined valley setting with an average bankfull width and depth of 5 m and 1 m, respectively, in the vicinity of the crossing. Minor sinuosity is observed upstream of the valley where flows are less confined. Widening was the dominant geomorphic process observed with evidence of erosion such as undercutting, fallen trees, bank slumping and debris jams. C2-a received an RGA score of 0.18 (in regime) and was determined to be of moderate health with an RSAT score of 23. Damage within the culvert was prevalent with cracks, exposed re-bar, and broken slabs of concrete observed. Downstream of crossing C2, reach C2-b exits the culvert and continues through a wooded, confined valley setting. Immediately downstream of the road crossing, a fallen fence crosses the watercourse, which collects debris and likely creates backwatering during higher flows, as evidenced by overbank sedimentation and sand deposits. Large organic debris was observed in the channel, with minor undercutting along banks. Bankfull width and depth was observed to be 5 m and 0.75 m, respectively. Widening and aggradation were determined to be the dominant geomorphic processes with the reach being assessed an RGA score of 0.213, classifying it as being in a transitional state. An RSAT score of 23 indicates moderate stream health C3 At C3, flow is diffuse and unconfined through agricultural fields, with roadside-drainage ditches augmenting flow both the upstream and downstream watercourses during high runoff events. Due to absence of channel features, no RGA/RSAT scores were determined. Teston Road EA Fluival Geomorphic Assessment 13

19 4.2.4 C4 The channel at C4 was observed to be dry during the rapid assessments. Recent improvements to the upstream entrance to the CSP were observed with addition of new culvert opening (450mm) and rip-rap lined embankment at the entrance. Downstream of the crossing, minor erosion was observed along the short channelized portion of the watercourse before it enters a section of shrubs with exposed clay under the consolidated bed. The watercourse was observed to exit the shrub patch downstream and flow becomes diffuse as an agricultural swale. Due to absence of defined channel features, no RGA/RSAT scores were determined C5 During the rapid assessment, C5-a was observed to enter the culvert from a wooded, confined valley. Permit to Enter was not granted for properties north of Teston Road, therefore only a short segment of the channel immediately upstream of Teston Road was examined. Minimal flow was observed and the entrance to the culvert was blocked with material/debris, forming a 0.2m drop from the blockage to the bottom of the culvert opening. Bankfull width and depth was estimated to be 1.5m and 0.5m, respectively. Widening was observed, with fallen trees, large organic debris exposed tree roots being observed. At the downstream exit of the culvert south of Teston Road, along C5-b, the outlet was observed to be perched approximately 0.6m above the ground, located above a large scour hole. The receiving channel showed signs of severe degradation with channel incision, increase in bank heights, and elevated tree roots. The scour hole at the outlet measured 2.1m wide by 1.1m deep, with soft unconsolidated material at the bed of the channel, which was largely dry at the time. The channel continues for approximately 20m until it confluences with reach C6-a/b. Overall, reaches C5-a and C5-b were assessed together and were scored an RSAT value of 12, indicating low health, and an RGA score of 0.278, indicating a state of transition C6 C6-a flows along a confined wooded valley parallel to Teston Road and is joined by C6-b. Permit to Enter was not granted for properties north of Teston Road, therefore only the combined channel immediately upstream of Teston Road within the right of way was examined. The left bank of the channel has been hardened with sheet metal before the watercourse enters the constructed crossing at C6. Heavy organic debris jams are observed upstream of the crossing, with some bank scour, exposed roots and undercutting observed. Bankfull width and depth was measured to be 5m and 1.5m, respectively. Downstream of Teston Road, reach C6-a/b begins at the culvert which is perched approximately m above the water surface, entering a large plunge pool, estimated to be 1.3m deep. The pool is located within a steep valley setting and severe bank failure and slumping were noted. Bank slumping and exposed tree roots were noted during the assessment, with this stretch of channel receiving an RSAT score of 23 and an RGA score of 0.244, indicating the watercourse is of moderate health and Teston Road EA Fluival Geomorphic Assessment 14

20 transitional in terms of stream stability. Approximately 25m downstream, the watercourse is joined by the C5-b tributary, demarcating the upstream extent of reach C6-c. Reach C6-c begins at the confluence of reaches C5-b and C6-a/b and continues downstream to the confluence with Purpleville Creek. The upstream portion of reach C6-c was walked, with increased sinuosity, bank erosion and significant woody debris noted throughout. Bankfull width was observed to be approximately 4m and bankfull depths 1-1.5m. The channel comes into contact with both valley walls in the confined setting. Widening was the dominant geomorphic process identified, and the reach scored an RSAT value of 25 and an RGA value of 0.213, indicating that the reach is of moderate health and is transitional in terms of stream stability. Table 3. RGA & RSAT Summary Reach C2-a C2-b C5-a & b (US and DS of Teston Rd) C6-a/b (DS of Teston Rd) C6-c Factor Value Aggradation Degradation Widening Planimetric Adjustment *Reaches for tributaries at C1, C3, and C4 were not assessed RGA or RSAT scores Stability Index (Condition) 0.18 (In Regime) (Transitional) (Transitional) (Transitional) (Transitional) RSAT Score Detailed Survey In November 2015, a detailed survey was conducted encompassing reaches C6 a/b through a part of C6- c. The upstream survey extent is the culvert outlet at Teston Road crossing C6, continuing to the confluence with C5-b, and then continuing downstream from the confluence for a total survey distance of 226m (Figure 6). Five cross-sections through the channel were surveyed, and a summary of the channel metrics and profile is provided below. Note that the elevations shown in the profiles and crosssections are relative to the specific ground elevation of the total station and are not geodetic. The detailed survey revealed a greater amount of sinuosity than was visible from the aerial imagery. The channel was confined along both banks as it exited the culvert at C6 and flowed perpendicular to Teston Road, with the left bank (looking downstream) exhibiting significant erosion due to the steep bank angles and valley wall contact. Following the confluence with C5-b, the channel takes a 90 degree bend where it enters a larger confined valley system. However, the floodplain within this confined valley Teston Road EA Fluival Geomorphic Assessment 15

21 widens out and the channel demonstrated a greater degree of sinuosity with increased bankfull widths as it flows downstream. The average bankfull width and depth was determined to be 5.60m and 0.92m, respectively (Table 4). The average wetted width of the channel at the time of survey was 2.04m, with a water depth range of 0.15m at a riffle to 0.65m in a pool. The long profile bed gradient at the site was determined to be 1.27%, and the bed material consisted primarily of medium to very coarse sand. Table 4. Detailed Survey Results Parameter Average Range Bankfull Width (m) 5.6m 4.08m-8.05m Bankfull Depth (m) 0.92m 0.56m-1.45m Gradient (%) 1.27% n/a Figure 6. Detailed survey map with long profile shown in orange and the cross-sections shown in red. XS2 XS1 XS4 XS3 XS5 Teston Road EA Fluival Geomorphic Assessment 16

22 Figure 7. Long profile of detailed survey downstream of Teston Road. 5 MEANDER BELT WIDTH ASSESSMENT When meanders change shape and position, the associated erosion and depositional processes that occur can cause loss or damage to property and infrastructure. For this reason, when development or other activities are contemplated near a watercourse, it is desirable to designate a corridor that is projected to contain all of the natural meander and migration tendencies of the channel. Outside of this corridor, it is assumed that private property and structures will be safe from the erosion potential of the watercourse. The extent that a meandering watercourse occupies on its floodplain is commonly referred to as the meander belt. Meander belt assessments were completed for crossings C2 and C5/C6. At C2, the meander assessment is used to direct the development of new bridge structural design parameters. At C5/C6, the meander belt assessment is used to assist in the evaluation of impacts to Redside Dace habitat. There are two approaches presented by the Ministry of Natural Resources (2002) in support of the Natural Hazards Policies (3.1) of the Provincial Policy Statement of the Planning Act for determining the erosion hazard limit for watercourses. The approaches are distinguished based on the relationship between the watercourse and its valley: one approach is for unconfined systems and a second approach for confined systems. For unconfined systems, the hazard develops from channel erosion and migration, and therefore requires the delineation of a meander belt width and associated erosion allowance. Confined systems contain watercourses that may be restricted from occupying its potential meander belt by the valley walls, requiring both channel migration and slope processes to be considered with the establishment of both a toe erosion allowance and a stable slope allowance. Teston Road EA Fluival Geomorphic Assessment 17

23 Because the tributary at C2 and tributaries at C5 and C6 are located within confined/partially-confined valley systems, the method for defining development setbacks as a constraint limit requires the use of the Provincial Policy Statement 3.1.1(b); however, while this approach is most appropriate for establishing development limits for a property at a reach scale, geomorphic hazards at a crossing location can also be examined through the delineation of a belt width within the unconfined portions of the valley floor. Therefore, the plotting of the meander belt limits was done across the unconfined portions of the valley floor with occasional points of coincident valley toe contact. The Belt Width Delineation Procedures document (Parish Geomorphic Limited, 2004) was used to guide the meander belt assessment. The procedures are applicable to a range of systems and follow a processbased methodology for determining the meander belt width based on background information, historic data, degree of valley confinement, planform and channel metrics (Parish Geomorphic Ltd., 2004). 5.1 C2 Meander Belt Planform Analysis Using historical and current aerial imagery, preliminary meander belt widths were determined for tributary reaches at crossing C2 (C2-a, C2-a1, C2-a2, and C2-b). The values ranged from 24 m to 34 m and are presented in Table 5. Typically, historical migration/erosion rates are measured and a 100-year erosion setback is applied in order to account for potential future widening of the meander belt. As described in Section 2.3, watercourse planforms were traced using aerial imagery from 1978 and 2011, however the high degree of riparian vegetation and poor image resolution in the 1978 photograph prohibits any reliable migration/erosion rate calculation at C2. In cases where a lateral migration rate cannot be accurately quantified, a factor of safety equivalent to 10% of the preliminary meander belt width can be applied to both sides of the belt width (i.e. 20% total of the meander belt width). Due to the lack of an accurate migration analysis, the 10% factor of safety was applied to each reach. The final meander belt widths ranged from 28.8 m to 40.9 m and are presented in Table 5. A figure showing the extent of the meander belt widths is included in Appendix B. Note that the meander belt width displayed in the figure for reaches C2-a and C2-b are based on the width determined for the upstream reach C2-a2, which displayed the greatest meander extent (34 m). Table 5. Meander Belt Width Analysis Results for C2 Reach Preliminary Meander Belt Width Final Meander Belt Width C2-a 28 m 33.6 m C2-a1 24 m 28.8 m C2-a2 34 m 40.9 m C2-b 28 m 33.6 m Teston Road EA Fluival Geomorphic Assessment 18

24 5.1.2 Empirical Analysis Meander belt widths can be further verified using empirical relations based on measured channel parameters, such as bankfull width. Relationships established by Williams (1986), Ward (2002), and Lorenz et al. (1985) were used to estimate meander belt widths for the tributary at C2. Bankfull channel width (5 m) measured during the RGAs were used as input parameters for the empirical analyses. The equations and results are presented in Table 6. The resulting empirical belt width estimates range from 26.1 m to 38.3 m, with an average of 32.0 m. These values corroborate the results for preliminary belt widths obtained from planform-delineation. Table 6. Empirical Meander Belt Results for C2 Source Equation Meander Belt Width (m) Williams (1986) - width (m) 4.3W 1.12 = 26.1 Ward (2002) - width (ft) 6W 1.12 = 31.7 Lorenz et al. (1985) - width (m) 7.53W 1.01 = 38.3 Average = C6-a/b and C6-c Meander Belt Planform and Topographical Analysis At this site, a high degree of vegetative cover did not allow for delineation of the meander belt via aerial imagery, and therefore a detailed survey was undertaken to capture the extent of the existing planform. This analysis was supported by available topographic information and observations made during the field assessments. Immediately downstream of crossing C6, the stream along reach C6-a/b displayed widening and some characteristics of downcutting processes. As a channel adjusts by widening and incising rather than lateral migration, it will often have a narrow or non-existent floodplain and is typically in a ravine or valley. Per PARISH (2004), in the case where a reach has incised into its floodplain, as evident by the contour pattern on topographic mapping, the meander belt can be defined as the area between laterally extreme meander bends in the planform pattern. Bed degradation at locations may also cause the erosion of erodible valley walls and subsequently create a wider floodplain. In this situation, bank erosion and widening were noted, however for the current setting there is a limit to the amount of potential floodplain width that can be created as one valley wall is the existing built-up road embankment that would require intervention prior to any major erosion. The preliminary belt width for this reach was set by the laterally extreme meander bends, as measured during the detailed survey. The belt width for C6-a/b measures 19.6m. Downstream of the confluence with C5-b, the channel continues to be contained within a confined system, although the floodplain becomes wider. There are valley wall contacts along both sides of the valley. As per Parish (2004), a belt width boundary would be set from top of valley to begin with, and Teston Road EA Fluival Geomorphic Assessment 19

25 then adjusted to reasonable locations, dependent on site-specific conditions and constraints. For the current study area, the detailed survey planform was overlain onto topographic mapping. Historic toe erosion and channel migration rates were not measurable from aerial imagery due to extensive vegetative cover. While it is expected that the erosion at valley toe contacts will continue, the expansion of the meander belt through continuous slope failures or valley form widening is less likely to occur. The preliminary belt width for this reach was therefore set by the laterally extreme meander bends, as measured during the detailed survey and equals 25.7m for C6-c Redside Dace Setback The meander belt extents were completed to support the evaluation of roadway design alternatives (i.e. embankment design) with respect to impact on Redside Dace habitat. A 30 m setback is applied to each side of the preliminary belt width. Therefore, the overall Redside Dace corridor for C6-a/b is 79.6m wide. The 30m was applied to both sides of the channel even though the north valley wall is primarily road embankment and the 30m extends across the existing Teston roadway - area that may be questionable in terms of being considered riparian habitat and should be taken into consideration when comparing alternatives. With the 30 m setback applied to the preliminary with for C6-c, the overall Redside Dace corridor width is 85.7m wide and is largely located at or above mid-valley. Note that the results of this assessment are not intended for hazard delineation purposes; however, the meander belt assessment is considered appropriate for consideration of the 30m Redside Dace setback in the evaluation of embankment design alternatives. If the delineation of hazard limit is necessary, the approach for confined systems (PPS) should be applied to the watercourses or a suitable geotechnical investigation can be undertaken. A figure of the meander belt extents with the applied 30m Redside Dace setbacks is included in Appendix B. 6 CROSSING RECOMMENDATIONS AND ENHANCEMENT OPPORTUNITIES Fluvial geomorphic recommendations regarding roadway improvements and crossing structure upgrades/replacements have been developed based the results of the desktop assessment, field investigation results, and geomorphic analyses, allowing for a collective evaluation of the factors outlined in Section 1.3, where applicable. 6.1 C1 Due to the lack of channel definition upstream of the existing crossing, the primary consideration for the crossing design at this location is hydraulically-driven by wetland function. The existing 450mm culvert is undersized with evidence of embankment failure at the opening of the crossing. HDR has recommended the installation of twin 500mm CSPs is not expected to negatively alter the hydrologic regime at this crossing. Teston Road EA Fluival Geomorphic Assessment 20

26 6.2 C2 HDR has proposed to replace the existing culvert at crossing C2 with a 45 m bridge (General Arrangement Drawing presented in Appendix C). This span is equivalent to the bridge proposed by MRC/Ecoplans Ltd. in The information presented in the 2011 report (direct/indirect impacts, mitigation measures, etc.) largely remain applicable. A span of 45 m is considered appropriate from a fluvial geomorphic perspective. The meander belt width assessment resulted in a belt width of 40.9 m at the crossing, however that value is based on a governing meander amplitude in an upstream reach (C2- a2) that is located a relatively far distance from the crossing. More immediately upstream of the crossing (<200 m), the meander amplitudes are dampened by the confined setting (topographic constraints) of the system. As such, the meander belt extent is narrower, and the measured belt width for C2-a was determined to be 33.6 m, which includes a safety setback. Historic migration analysis was not possible due to vegetative cover and photo quality, however during the field assessments, the RGA score (0.18) for the reach upstream of the crossing location classifies the channel as is in-regime and therefore stable. With removal of the culvert, there will be temporary disturbance of the channel, however there is significant opportunity to improve long term overall corridor conditions. The bankfull channel width is 5 m; with removal of the culvert walls, road embankments will be sloped down to the floodplain at approximately 2:1, thereby allowing for the development of an overbank and floodplain through the structure that is 32.5m wide. This width matches well with valley conditions in the vicinity of the crossing and presents a connection of the valley up and downstream of the structure. Following culvert removal, the channel can be rehabilitated with significant improvements in regards to planform alignment, natural geomorphic processes (e.g. sediment transport, minor adjustments) and aquatic habitat opportunities. Design elements that suit the aquatic habitat preferences of Redside Dace can be incorporated into the design (e.g. large woody debris, deep pools, appropriate substrate gradation, etc.). 6.3 C3 and C4 The intermittent agricultural swales at C3 and C4 were dry at the time of the assessment and displayed little evidence of geomorphic processes. Channel erosion and migration was not discernible from aerial imagery. At C3, HDR has proposed the removal of the twin CSPs to provide flow conveyance via an 1800 mm by 900mm concrete box culvert, consistent with the Block 40 proposed design downstream of the crossing. Given the absence of erosion concerns at this location, it is not anticipated that the proposed larger structure will impact flow or channel processes at this location. It is recommended that the structure be oriented on a 30 skew in order to align with the existing channel orientation both upstream and downstream of the crossing. Teston Road EA Fluival Geomorphic Assessment 21

27 HDR has proposed twin 600m CSPs at C4. As erosion risk is also low for the channel at C4, the proposed replacements is acceptable from a geomorphic perspective. The perpendicular orientation of the crossing to the road is also acceptable given it is in alignment with the existing channel orientation. 6.4 C5 and C6 Preliminary recommendations for C5 and C6 were provided to HDR during the early stages of the current assessment process. At C5, indicators of erosion, particularly at the outlet of the existing crossing and an accumulation of organic material at the upstream entrance to the culvert were observed. It was posited that the grade of the existing CSP may be too great, creating higher velocities within the culvert and causing erosion and scour at the outlet. Therefore, the preliminary recommendation provided by PARISH for C5 entailed culvert replacement. At C6, the accumulation of organic debris in the channel upstream of the crossing suggests that degradation and erosion are occurring. This is particularly evident downstream of the crossing where a large scour pool has formed beneath the perched outlet. Preliminary recommendations provided by PARISH included extending the culvert downstream and rehabilitating the channel such that fish passage is re-established and erosion hazards are mitigated. Bank stability measures and energy dissipation features were proposed given the existing erosion hazards observed in the downstream channel. As the assessment process progressed, HDR indicated that the culvert entrance and retaining wall along the north side of Teston Road at crossings C5 and C6 is not being considered for replacement and that a culvert extension on the south side of Teston Road is likely to be necessary to accommodate road improvements. As such, the assessment at these crossings did not warrant an evaluation of ideal crossing structure parameters, as culvert replacement is not an option. However, to support an evaluation of embankment alternatives in the vicinity of crossings C5 and C6 on the south side of Teston Road, the meander belt and Redside Dace setback limits were provided to HDR. The evaluation considered permanent impacts of the grading footprint on Redside Dace habitat, which consists of two elements: the first element includes bankfull stream width within the aquatic resource area; the second element includes the meander belt width of the stream and associated riparian habitat that is a minimum 30m from the meander belt (measured horizontally). A cost is then applied to each alternative and a relative score is determined for each alternative. As such, the meander belt zone and the meander belt zone + 30m zone were delineated in the vicinity of crossings C5 and C6. As a result of this evaluation, HDR is proposing a retaining wall on the south side, west of Weston Road in the vicinity of C5 and C6. From a geomorphic perspective, this is considered the most appropriate option, as it limits encroachment onto the existing tributary valley. Bioengineering treatments along the north valley wall and banks of C6 can be implemented to provide stability and improve riparian conditions. The widening of Teston Road at this location also presents an opportunity to improve the geomorphic conditions downstream of the culvert outlets at C5 and C6, as noted in the preliminary Teston Road EA Fluival Geomorphic Assessment 22

28 recommendations provided by PARISH. Stabilization works (e.g. at perched outlets) can enhance channel form and function and incorporate aquatic habitat elements, thereby providing overall benefit to aquatic species. During a field investigation in June 2015 of the channel downstream of the current study area, LGL reported the presence of a concrete-log weir with a decrepit bridge. This structure presents a barrier to fish passage and inhibits connectivity of the study channel with the main branch Purpleville Creek, attributing the lack of fish in the large scour pool downstream of C6 to this structure. There is opportunity for removal of the structure, improving connectivity and allowing for the establishment of aquatic habitat elements that suit the preference of Redside Dace and other fish species. 7 CONCEPTUAL DESIGNS Conceptual designs for channel realignments and rehabilitation works will be provided at the next stage of the assessment process and will be refined during the detailed design stage. The designs will incorporate natural channel design principles to create dynamically stable systems which mitigate erosion and long-term maintenance while enhancing aquatic and terrestrial habitat. Teston Road EA Fluival Geomorphic Assessment 23

29 REFERENCES Aqualogic Meander Belt Analysis for Redside Dace Habitat Setbacks. Appendix J of Master Environmental/ Servicing Plan, Block 40/47, City of Vaughan. Prepared for: Block 40/47 Developers Group Inc. Chapman, L.J. and Putnam, D.F The Physiography of Southern Ontario; Ontario Geological Survey. Ecoplans Ltd. and McCormick Rankin Corporation Teston Road Culvert Replacement on Tributary C2 of Cold Creek, 300m East of Pine Valley Drive in the City of Vaughan. MNR File No. AU-C Galli, J Rapid stream assessment technique, field methods. Metropolitan Washington Council of Governments. 36pp. Giffels Associates Limited Class Environmental Assessment: Widening and Reconstruction of Teston Road from Pine Valley Drive to Bathurst Street. Hoffman D. W. and N. R. Richards, Soil Survey of York County. Report No. 19 of the Ontario Soil Survey. Experimental Farm Service, Canada Department of Agriculture and Ontario Agricultural College. Lorenz, J.C., Heinze, D.M Determination of Widths of Meander-Belt Sandstone Reservoirs from Vertical Downhole Data, Mesaverde Group, Piceance Creek Basin, Colorado. AAPG Bulletin, Volume 69. Ministry of Natural Resources Technical Guide - River and Stream Systems: Erosion Hazard Limit. Ministry of the Environment Stormwater Management Planning and Design Manual, Ontario Ministry of Environment, March Parish Geomorphic Ltd Belt Width Delineation Procedures. Submitted to: Toronto and Region Conservation Authority. Ward, A. D. Mecklenberg, J. Mathews, and D. Farver Sizing Stream Setbacks to Help Maintain Stream Stability. Paper Number: ASAE Annual International Meeting. Chicago, IL, USA. July 28-July 31, 2002 Williams, G.W., River meanders and channel size. Journal of Hydrology 88: Teston Road EA Fluival Geomorphic Assessment 24

30 APPENDIX A - SITE INVESTIGATION PHOTOS Photo 1: View of culvert at C1 Photo 2: View of culvert at C2

31 Photo 3: View of large woody debris in tributary channel at C2 Photo 4: View of CSPs at C3

32 Photo 5: View of CSP at C4 Photo 5: View upstream of culvert outfall at crossing C5

33 Photo 7: View downstream towards culvert at crossing C6 with sheet pile wall along LB Photo 8: View of perched culvert downstream of Teston Road at crossing C6 with deep scour pool

34 Photo 9: View downstream towards detailed survey XS-4 along reach C6-c Photo 10: View upstream towards detailed survey XS-5 along reach C6-c

35 APPENDIX B - MEANDER BELT WIDTH FIGURES C2

36 C5/C6