Bowmanville Creek Geomorphological Investigation and Meander Belt Width Assessment

Bowmanville Creek Bridge, and Taunton Road (Regional Road 4) and Regional Road 57 Intersection Municipal Class Environmental Assessment

Prepared for: The Regional Municipality of Durham c/o The Municipal Infrastructure Group Ltd. 110 Scotia Court, Unit 27 Whitby, Ontario L1N 8Y7

October 11, 2017 GEO Morphix Project No. 17008

Report Prepared by: GEO Morphix Ltd. 2800 High Point Drive Suite 100A Milton, ON L9T 6P4

Report Title: Bowmanville Creek, Geomorphological Investigation and Meander Belt Width Assessment Project Number: 17008 Status: Draft Version: 1.0 First Submission Date: October 11, 2017 Revision Date

Prepared by: Kevin Tabata, M.Sc. Approved by: Approval Date:

Table of Contents

1 Introduction ...... 1 2 Site History ...... 1 3 Subwatershed Characteristics ...... 2 4 Watercourse Characteristics ...... 2 4.1 Reach Delineation ...... 3 4.2 Reach Observations ...... 4 4.2.1 Haydon Branch Reach HB-1 ...... 4 4.2.2 Haydon Branch Reach HB-2 ...... 4 4.2.3 Main Branch Tributary Reach MB-1 ...... 5 4.3 Rapid Geomorphic Assessments ...... 5 4.4 Detailed Geomorphological Assessment ...... 6 5 Erosion Hazard Assessment ...... 7 5.1 Meander Belt Width ...... 7 5.2 Channel Migration ...... 8 6 Discussion and Recommendations ...... 8 7 References ...... 11

List of Figures

Figure 1: Bowmanville Creek reaches in study area ...... 3

List of Tables

Table 1: Reach delineation of the Haydon and Main Branches ...... 3 Table 2: Bankfull parameters of the reference channel ...... 7

Appendices

Appendix A: Photographic Record of Site Conditions ...... A Appendix B: Rapid Geomorphic Assessment Field Sheets ...... B Appendix C: Meander Belt Width Assessment ...... C

1 Introduction

The Regional Municipality of Durham identified the need to reconstruct the Taunton Road (Regional road 4) and Regional Road 57 intersection, and to replace the Bowmanville Creek Bridge over Taunton Road. A Municipal Class Environmental Assessment (EA) study was therefore initiated to confirm the need and justification for reconstructing the intersection and bridge. The Regional Municipality of Durham retained a consulting team led by The Municipal Infrastructure Group Ltd. to complete the Class EA. As part of the consulting team, GEO Morphix Ltd. fulfills the requirement for a fluvial geomorphology study of Bowmanville Creek.

A geomorphological investigation and meander belt width assessment were completed for Bowmanville Creek, which crosses Taunton Road 100 m west of Regional Road 57. The intent of the study was to document existing conditions, identify potential creek-related hazards, recommend a span for the replacement bridge, and offer mitigation measures. Based on the results of the investigation, GEO Morphix Ltd. will prepare a design during the design stage to restore a channel locally at the bridge.

2 Site History

A series of historical aerial imagery were reviewed to determine changes to the channel and surrounding land use/cover. This information, in part, provides an understanding of the historical factors that have contributed to current channel morphodynamics. An aerial photograph from 1974 (scale 1:24,000) and satellite imagery from 2005 and 2017 (Google Earth Pro) were reviewed to complete the historical assessment. Pre-1974 historical aerial photographs were not available.

In 1974, the land surrounding Bowmanville Creek in the vicinity of the study area was used primarily for agriculture. North of Taunton Road, several residential properties were located along the west side of Regional Road 57: a series of five on the north side of Taunton Road and one on the south side about 270 m south of Taunton Road.

The Haydon Branch of Bowmanville Creek travelled in a southerly direction crossing Regional Road 57, from east to west, about 770 m north of Taunton Road. To the east of the Haydon Branch, the Tyrone Branch travelled south to cross Regional Road 57 approximately 400 m north of Taunton Road. The Tyrone Branch joined the Haydon Branch 330 north of Taunton Road, and continued as the Haydon Branch along the rear of the residential properties on Regional Road 57 to the bridge 100 m west of the Taunton Road and Regional Road 57 intersection. The channel continued south and crossed Old Scugog Road approximately 870 m south of Taunton Road. The Haydon Branch joined the Hampton Branch of Bowmanville Creek about 800 m downstream of Old Scugog Road.

Most of the Haydon Branch, which is the focus of this study, was situated in a largely forested corridor. North of Taunton Road, the corridor had a moderate tree density, which allowed the channel to be clearly viewed in the 1974 aerial photograph. It was also evident that the residential property owners utilized most of that land along the east side of the channel, as there were fewer trees and lawns were frequently maintained to the edge of channel. The channel had a sinuous planform, but was straight immediate upstream of Taunton Road.

On the south side of Taunton Road, the Haydon Branch channel travelled 150 m along the east side of a clearing, possibly used for farming. The east side of the channel was densely forested. With the exception of about 200 m of channel, located farther downstream towards Old Scugog

Road, the riparian area was well-forested. Although the forest obscured the view of the channel, there was a sinuous channel; however, in contrast to the channel upstream of Taunton Road, meander wavelength, amplitude and radius appeared greater.

Land use remained generally unchanged through 2005. The only notable change was on the immediate south side of Taunton Road where the apparent farmland along the west side of the channel was allowed to naturally evolve to a forest. A riparian buffer was therefore restored, although a portion of the farmland was converted to a manicured lawn. There were no apparent changes to the meandering planform. Moreover, land use, cover and channel pattern remained generally unchanged through 2017.

The apparently lack of changes to the Haydon Branch channel over the period covered by historical aerial imagery indicates that there have been no significant perturbations to the system, such as changes in hydrology or land use, that would trigger channel adjustment. According to the Durham Regional Official Plan (RMD, 2015), there will be a marginal increase in the rural population between 2016 and 2031; hence, there will likely be no significant changes to the factors that govern channel form and function.

3 Subwatershed Characteristics

The Bowmanville Creek Bridge lies in the Haydon Branch subwatershed, which is bounded by the Tyrone Branch (and tributary) to the east and Hampton Branch to the west. The Haydon Branch has a total area of 23.9 km2 with 52.6% of the area comprised of agricultural land and 32.8% forest (CLOCA et al., 2007).

The Haydon Branch is located in the upper Bowmanville Creek watershed. As such, the majority (58%) of the total stream length are first order streams. Second (18%), third (11%) and fourth (13%) order streams make up less than half of the total length of streams (CLOCA et al., 2007).

The upper subwatershed lies in the Oak Ridges Moraine physiographic region, while the lower and majority of the subwatershed is in the South Slope physiographic region (Chapman and Putnam, 2007). The Oak Ridges Moraine generally has sand and gravel deposits, which promote precipitation infiltration. The South Slope has a lower gradient and sandy till, which also provide for conditions that promote infiltration.

With respect to surficial geology, the Haydon Branch channel corridor contains modern alluvial deposits comprised of clay, silt, sand and gravel. Beyond the alluvial deposits, surficial materials are largely composed of coarse-textured glaciolacustrine deposits (sand, gravel, minor silt and clay).

The subject site is located in the South Slope physiographic region with sandy till. In isolation, this would result in a geomorphologically dynamic channel as the high proportion of sand is readily entrained. Reworking and sorting of this material, as the surficial geology indicates, serves as a modifying factor by providing channel stability. Stability is further enhanced by the largely forested setting.

4 Watercourse Characteristics

The limits of the study area were largely defined by tributary inputs and surrounding land use characteristics. The south limit of the continuous forest cover (approximately 740 m downstream of Taunton Road) served as the downstream end of the study area, and confluence with the Tyrone Branch channel (approximately 650 m upstream of Taunton Road) defined the upstream limit. It

is noted that, although the Haydon Branch channel is a tributary of the Main Branch channel, there is a small tributary within the upper Main Branch subwatershed that discharges to the Haydon Branch channel, according to CLOCA et al. (2007). While this small tributary should technically have its own subwatershed, we have also considered it to be part of the Main Branch subwatershed for consistency.

4.1 Reach Delineation

Rivers and streams are frequently segmented into reaches to provide meaningful lengths of channel for study. Reaches are delineated based on changes such as hydrology, channel gradient, confinement, planform (i.e., channel pattern), geology, surrounding land use and anthropogenic disturbances (e.g., crossing structures, dams, straightening/channelization, armouring). Each reach can then be studied as a unit that is expected to function in generally uniform manner throughout its length.

The Haydon Branch of Bowmanville Creek was segmented into reaches, from downstream to upstream, following scientifically-defensible methodology proposed by Montgomery and Buffington (1997), Richards et al. (1997) and the Toronto and Region Conservation Authority (2004). The reaches are shown graphically in Figure 1. Table 1 provides the primary characteristics that define and distinguish each reach.

Figure 1: Bowmanville Creek reaches in study area Table 1: Reach delineation of the Haydon and Main Branches

Reach Start & End Locations Length Characteristics Haydon Branch Reach HB-1 South limit of 740 m Moderate channel sinuosity; dense, continuous forest cover continuous forest cover; modern alluvial to Taunton Road deposits (surficial geology)

Reach HB-2 Taunton Road to 650 m Moderate channel sinuosity; forest cover confluence with Tyrone limited along east side of channel; Branch channel maintained grass up to east bank; modern alluvial deposits (surficial geology) Main Branch Tributary Reach MB-1 Confluence with Haydon 120 m Generally straight channel; dense forest Branch to RR 57 cover; fine-textured glaciolacustrine deposits (surficial geology)

4.2 Reach Observations

Site observations for each reach were collected on May 17, 2017. Photographs are provided in Appendix A.

4.2.1 Haydon Branch Reach HB-1

Reach HB-1 is a forested corridor with a moderately sinuous channel. The forested corridor is roughly 100 m wide, but the channel largely travels near the margins except for where it crosses over from one side to the other. Notably, approximately 70 m of channel travels along the west side of the corridor with manicured grass up to the bank.

Riffles and runs sections are wide and shallow and have a rectangular cross section. Pools are not particularly deep; this is partly due to flows encountering the relatively erosion-resistant glaciolacustrine deposit under the natural substrate. The substrate in riffles and runs is comprised of sand, gravel and mostly cobble, while pool substrate is dominated by sand and gravel.

Channel banks are frequently vertical or undercut as a result of erosion. Vertical banks are typically found where tree roots have become exposed and provide erosion control. Undercut banks are associated with shallow-rooting grasses and herbaceous vegetation, and sometimes trees.

Woody debris jams were observed in the channel towards the downstream end of the reach. While none fully span the channel width, they do redirect flows and help to locally increase complexity by through bed scouring and sedimentation. Approximately 170 m downstream of Taunton Road and adjacent to the manicured grass, there is a concrete weir across the channel. On the day of visit, the weir had a 0.1 m fall, measured as the difference in water surface elevations upstream and downstream of the weir. There was also a 0.9 m deep scour pool immediately below the weir.

Located approximately 80 m downstream of Taunton Road, there is a tributary (Reach MB-1) that joins Reach HB-1 from the east. This tributary is part of the Main Branch of Bowmanville Creek.

4.2.2 Haydon Branch Reach HB-2

The channel corridor of Reach HB-2 has a lower tree density than Reach HB-1. The east side of the channel, in particular, has relatively few trees as the creek travels through the rear of several residential properties, which are maintained.

The channel is noticeably more sinuous than Reach HB-1, but still considered moderately sinuous. This may be due to the relative ease at which the channel can adjust due to the low tree density and manicured grass along the east side of channel. In fact, the most significant bank erosion occurs along the outside east bank of meander bends as there is limited woody vegetation to

retard erosion and channel migration. Where there are trees along the channel bank, they are frequently leaning, suggesting that the channel is either widening or migrating. In this case, the channel is both widening and migrating.

The lower portion of exposed banks frequently reveal former bed substrate (gravel and cobble), parent material (glaciolacustrine deposits), or former bed substrate atop glaciolacustrine deposits. The upper portion is comprised of fine-grained soils as well as the roots of grasses and herbaceous vegetation. The exposure of former bed substrate and/or glaciolacustrine deposits indicates that the channel had degraded.

Bed morphology is also more spatially variable. Riffles and pools are better defined as there are greater differences in depth and therefore function. Bed materials are, however, similar with sand, gravel and cobbles in riffles, and sand and gravel in pools.

At Taunton Road, gabion baskets were previously installed at the interface between the channel and the northwest approach embankment. The gabion baskets are in poor condition with deteriorated gabion wire and missing gabion stone.

4.2.3 Main Branch Tributary Reach MB-1

Reach MB-1 is under the same forest cover as Reach HB-1. The channel has a generally straight planform and travels from Regional Road 57 to the Reach HB-1 channel at its confluence 80 m downstream of Taunton Road.

The Reach MB-1 channel does not have well-defined banks, although there is a clear low-flow path similar to a swale. The width of the channel varies longitudinally, but this variability appears to be more a function of surrounding floodplain relief than a channel that has developed a geomorphologically stable cross section.

Substrate is comprised of fines (clay and silt), sand, gravel and small cobble. The bed material is poorly sorted, likely due to the low energy of flows, and its distribution appears to be largely controlled by the woody debris frequently found on the bed.

Leaning and j-shaped trees are found along the channel. These are not the result of channel widening or meander bend migration, as roots have not been exposed. Instead, the tree leaning appears to be the result of soil instability along the channel.

At Regional Road 57, flows are conveyed across the road through a CSP culvert. At the downstream (west) end of the culvert, there is a 0.2 m fall from the culvert invert to the water surface of the scour pool. Under low-flow conditions, this culvert may be a barrier to fish passage in two ways. First, the perched condition can prevent fish from entering the culvert. Second, the perched condition ensures that the flow depth through the culvert is minimized, thereby potentially inhibiting passage by larger fish species.

There is a second crossing structure within a couple of metres of the west end of the CSP culvert. This is an abandoned concrete structure with a deteriorating concrete apron/bed that extends about 2 m downstream. On the day of the site visit, flow was split around the concrete apron.

4.3 Rapid Geomorphic Assessments

Channel instability for Reaches HB-1 and HB-2 was semi-quantified through the application of the Ontario Ministry of the Environment’s (2003) Rapid Geomorphic Assessment (RGA). Observations were quantified using an index that identifies channel sensitivity based on evidence of aggradation, degradation, channel widening, and planimetric form adjustment. The index

produces values that indicate whether the channel is stable/in regime (score <0.20), stressed/transitional (score 0.21-0.40) or adjusting (score >0.41). Completed field sheets are provided in Appendix B.

Reach HB-1 was assessed to be in transition (score = 0.23). Channel degradation is the primary form of adjustment with observations of suspended armour layer along the banks and exposed parent material (glaciolacustrine deposits) on the bed. Channel widening is also evident as there are exposed tree roots along the banks and fallen and leaning trees.

Reach HB-2 was also in transition (score = 0.34), but exhibited greater signs of instability. Instability is mainly expressed in the form of channel widening with indicators such as leaning trees, exposed tree roots, extensive scouring along the toe of banks, and bank slumping. Degradation is a significant as suggested by the suspended armour layer along the banks and exposed glaciolacustrine deposits on the bed.

4.4 Detailed Geomorphological Assessment

A detailed geomorphological assessment was completed for the study reach to determine average bankfull channel characteristics. This information not only characterizes the channel, but can also be used as a basis for in-water design work, such as bank protection and natural channel designs.

The detailed assessment first involved determining an appropriate length of channel to survey based on the width of the channel (typically 20 times the bankfull width) and distribution of geomorphic units (riffles, runs, pools). An equilibrated section of the reach is then selected for this length of channel to survey to ensure that the results represent normal conditions.

Eight representative cross sections were surveyed in the study reach for the purpose of determining average bankfull channel dimensions (e.g., width, average bankfull depth, maximum depth, and bank angles). The bankfull level was determined based on accepted field indicators. A survey of the bed profile was also completed to determine slope and compute bankfull hydraulics. A modified Wolman (1954) pebble count was completed to characterize the bed materials. The channel measurements are then used to calculate bankfull flow characteristics such as discharge, average velocity, and erosion or sediment transport sensitivity. A summary of measured and computed values is presented in Table 2.

Table 2: Bankfull parameters of the reference channel

Channel parameter Results Measured Average bankfull channel width (m) 9.5 Average bankfull channel depth (m) 1.02 Average cross-sectional area (m2) 6.2 Average width-to-depth ratio 15.7 Bankfull channel gradient (%) 0.43

D50 (mm) 9

D84 (mm) 43 Manning’s n roughness coefficient 0.036 Computed Bankfull discharge (m3/s)a 8.30 Average bankfull velocity (m/s) 1.36 Unit stream power at bankfull discharge (W/m2) 36.7 Tractive force at bankfull (N/m2) 27.1 Critical shear stress (N/m2)b 6.7 c Flow competency for D50 (m/s) 0.55 c Flow competency for D84 (m/s) 1.12 a Based on Manning’s equation b Based on Shields diagram from Miller et al. (1997) c Based on Komar (1987)

The computed results in Table 2 suggest that D84 (43 mm grain size) is below the threshold of entrainment during bankfull flows, while D50 (9 mm grain size) is fully entrained. This is inconsistent with the notion that bankfull discharge is equivalent to the channel-forming (dominant) discharge, which is defined as a theoretical discharge that if maintained indefinitely would produce the same channel geometry as the natural long-term hydrograph. However, channel degradation may have resulted in bed armouring and therefore greater resistance to entrainment.

Reach HB-1 has a mixed-grain-size bed and small grains can be trapped in pockets between large grains. This can cause "equal mobility", in which small grains can be transported just as easily as large ones (Wilcock and Crowe, 2003). Hence, the low entrainment threshold of D50 may not accurately reflect its mobility.

5 Erosion Hazard Assessment

5.1 Meander Belt Width

Most watercourses in southern Ontario have a natural tendency to develop and maintain a meandering planform, provided there are no spatial constraints. A meander belt width assessment estimates the lateral extent that a sinuous channel has historically occupied and will likely occupy

in the future. This assessment is therefore useful for determining the potential hazard to the proposed Bowmanville Creek Bridge as well as the road. In this case, the meander belt of Reach HB-1 is of interest as only upstream channel planform adjustments can have an impact on the bridge or road.

When defining the meander belt width for a creek system, unconfined and confined systems are assessed differently (TRCA, 2004). Unconfined systems are those with poorly-defined valleys or those with valley walls positioned where a sinuous channel would not realistically contact. Confined systems are those where a watercourse is contained within a defined valley, where meander bend development may be constrained by valley walls.

In unconfined systems, the meander belt width can be graphically defined using orthorectified aerial imagery. The channel’s meander belt axis is initially determined for each reach, and the lateral limits of the meander belt, as defined by the channel’s maximum meander amplitude, is then used to measure the meander belt width.

According to available topographic information, which was confirmed in the field, Reach HB-2 is an unconfined system. The meander belt width was determined to be 54.5 m, which includes a 20% factor of safety. The results are presented graphically in Appendix C. It should be reiterated that the meander belt width assessment is completed on a reach basis and, although the meander belt in Appendix C is shown to extend through the private properties upstream of Taunton Road, it is intended strictly for the depiction of the potential hazard to Taunton Road and the Bowmanville Creek Bridge.

5.2 Channel Migration

By overlaying historical aerial imagery (orthorectified and georeferenced), individual meander bends can potentially be tracked in the lateral and downstream directions over time to determine the 100-year migration rate. The results are then used to assess potential erosion hazards to Taunton Road.

Although tree cover was relatively low in Reach HB-2, the position of individual meander bends on successive historical aerial photographs could not be determined. As such, migration rates and associated potential risks to infrastructure could not be assessed. The generally straight portion of channel immediately upstream of Bowmanville Creek Bridge, however, was determined to be planimetrically stable over the 43-year period covered by historical aerial imagery.

6 Discussion and Recommendations

It is understood that the Regional Municipality of Durham intends to reconstruct the Taunton Road and Regional Road 57 intersection. To accommodate the proposed intersection reconstruction, the Bowmanville Creek Bridge at Taunton Road would need to be removed and replaced with a wider structure. The bridge, which was constructed in 1957, was also identified to be in need of repairs and the intersection reconstruction therefore offers an opportune time to replace the deteriorating structure.

Reach HB-2 – the portion of Bowmanville Creek Haydon Branch between Taunton Road and the upstream confluence with the Tyrone Branch – was investigated to determine the potential erosion hazard to Taunton Road and the Bowmanville Creek Bridge. The meander belt width of Reach HB-2 was determined to be 54.5 m, which represents the maximum lateral limits that the channel can potentially occupy. Moreover, although migration rates of Reach HB-2 meander bends could not be assessed, the generally straight section of channel that approaches the bridge was

determined to be stable with respect to planform. As such, the span of the replacement bridge should be, at minimum, greater than the channel width.

The average channel width of Reach HB-2 was determined to be 9.5 m; however, the channel width immediately upstream and downstream of the Bowmanville Creek Bridge was approximately the same as the bridge span (7.8 m). The higher average width can be explained in large part by the inclusion of pools at meander bends, which are not only typically wider than riffles at crossover sections between bends, but also wider in this case due to the lack of woody vegetation (i.e., natural erosion control).

A 12-m span bridge is recommended for the replacement structure. A restored bankfull channel is also recommended under the bridge. The 12-m span would accommodate the approximately 7.8-m wide channel and any need to adjust the channel width to ensure seamless transitions with the existing channel banks upstream and downstream of the proposed bridge.

The proposed channel under the bridge should be designed based on principles of fluvial geomorphology and natural channel design, with consideration to the anticipated lack of direct sunlight exposure. A restored channel with banks would improve instream hydraulics as well as partially replicate flood hydraulics with the ability of flows to access the overbank area under the bridge. Overbank areas, between the channel and the bridge abutments, would also facilitate terrestrial wildlife passage.

The proposed channel will likely receive little direct sunlight under the bridge, and the likelihood of vegetation establishment will therefore be limited. To ensure long-term stability of the restored channel without the soil-stabilizing benefit of vegetation, materials used to construct the channel should be hydraulically-sized to resist entrainment under a range of flows, which can be determined through a review of the hydraulic model after being updated with the proposed bridge dimensions. Riverstone (i.e., rounded or subrounded stone) is recommended as this would locally improve aquatic habitat. The bed can also be designed to be morphologically complex, e.g., with the riffles and pools to further enhance aquatic habitat. Surficial bed materials can be comprised of natural substrate, similar to that upstream, to encourage sediment transport through the bridge. Subsurface bed materials not exposed to flow, in combination with bank and overbank materials, can be sized for stability to protect the bridge footings from exposure due to scouring.

Although the channel immediately upstream of the bridge was assessed to be laterally stable, it is recommended that woody plantings be installed along the banks beyond the proposed bridge footprint. Trees and shrubs will enhance bank stability and provide added insurance that there will be no channel-migration-related risks to the proposed bridge or road. Depending on the size of the proposed bridge footprint, there may be little land remaining within the right-of-way for plantings, in which case it is recommended that permission to sought to plant along the west bank. Field observations indicate that the west bank may be more susceptible to erosion due to the upstream channel alignment. Furthermore, the west overbank area is not in use by the property owners and therefore may be considered more acceptable as an area for plantings.

With respect to design implementation (i.e., construction), we recommend the following mitigation measures:

• Restrict in-water work to the coldwater timing window (July 1 to September 15) (CLOCA et al., 2007); • Restrict vegetation removals to outside the key breeding bird period identified by Environment Canada for migratory birds to ensure compliance with the Migratory Birds Convention Act, 1994;

• Delineate the limits of construction to prevent unanticipated impacts to natural surroundings, including trees and the watercourse; • Isolate any in-water work areas to prevent the release of sediment to the receiving watercourse; • Remove any stranded fish and wildlife from the isolated work area and transfer them to a safe and appropriate location (to be performed by a qualified technician with approvals from the Ontario Ministry of Natural Resources and Forestry); • Complete works within an isolated area in the dry by pumping water to an area (with appropriate sediment controls) that allows discharge to travel over a well-vegetated area and return to the watercourse downstream of the work area; • Store materials and operate equipment such that deleterious substances do not enter the water; and • Prepare a storm contingency plan.

7 References

Central Lake Ontario Conservation Authority (CLOCA), Fisheries and Oceans Canada, and Ontario Ministry of Natural Resources. 2007. Central Lake Ontario Fisheries Management Plan – Draft.

Chapman, L.J. and Putnam, D.F. 2007. Physiography of southern Ontario. Ontario Geological Survey, Miscellaneous Release--Data 228.

Montgomery, D.R. and Buffington, J.M. 1997. Channel-reach morphology in mountain drainage basins. Geological Society of America Bulletin, (109) 5: 596-611.

Ontario Geological Survey (OGS). 2010. Surficial geology of Southern Ontario. Ontario Geological Survey, Miscellaneous Release--Data 128-REV.

Ontario Ministry of the Environment. 2003. Stormwater Management Planning and Design Manual. March 2003.

Regional Municipality of Durham (RMD). 2015. Durham Regional Official Plan: Consolidation June 26th, 2015. Prepared by Corporate Services Department, Legislative Services Division.

Richards, K.S., Brooks, S., Clifford, N.J., Harris, T. and Lane, S.N. 1997. Real geomorphology: theory, observation and testing. In Stoddard, D.R. (ed.), Process and Form in Geomorphology. London, Routledge, pp. 265-292.

Toronto and Region Conservation Authority (TRCA). 2004. Belt Width Delineation Procedures.

Wilcock, P.R. and Crowe, J.C. 2003. Surface-based transport model for mixed-size sediment. Journal of Hydraulic Engineering, 129 (2): 120-128.

Williams, G.P. 1986. River meanders and channel size. Journal of Hydrology, 88: 147-164.

Wolman, M.G. 1954. A Method of Sampling Coarse River-Bed Material. Transactions, American Geophysical Union, 35: 951-956.

Appendix A: Photographic Record of Site Conditions

Photo 1 Photo Reach HB Reach

Meander bend towards downstream end of reach, viewed downstream. J-shape trees

along outside bank indicate slow meander bend migration.

Photo 2 Photo Reach HB Reach

Bank erosion with exposed tree roots.

Photo 3 Photo Reach HB Reach

Meander bend viewed downstream.

Photo 4 Photo Reach HB Reach

Woody debris jam viewed upstream. Note the flow diversion around the jam (centre right), and bar development in foreground downstream of jam.

5 5

Photo Photo Reach HB Reach

Valley wall contact approximately 200 m downstream of Taunton Road. Flow is from right

to left.

6 6

Photo Photo Reach HB Reach

Meander bend viewed downstream. Note fallen tree on outside (right) bank due to bend migration.

7 7

Photo Photo Reach HB Reach

Weir located 170 m downstream of Taunton Road, viewed upstream. Note manicured

lawn along west (left) bank at 2423 Taunton Road.

8 8

Photo Photo Reach HB Reach

Concrete weir and 0.9 m deep scour pool. Bedload transport is impeded at weir.

9 9

Photo Photo Reach HB Reach

Bar along bank and run viewed downstream. Leaning trees along both banks indicate

channel widening.

10 10

Photo Photo Reach HB Reach

Channel located 80 m downstream of Taunton Road, viewed downstream. Tributary (Reach MB-1) enters from east (left) bank (see arrow).

Photo 11 11 Photo Reach HB Reach

Exposed tree roots along bank, viewed downstream.

2 2

Photo 1 Photo Reach HB Reach

Undercut east outer bank of meander bend with leaning trees and exposed roots, 40 m downstream of Taunton Road. Flow is from bottom-left to centre-right.

Photo 13 13 Photo Reach HB Reach

Low-radius bend viewed towards Bowmanville Creek Bridge, 40 m downstream of Taunton

Road.

Photo 1 Photo Reach HB Reach

Channel viewed downstream from Bowmanville Creek Bridge.

Photo 1 Photo Reach HB Reach

Downstream side of Bowmanville Creek Bridge. Flow occupies the full bridge span.

Photo Photo Reach MB Reach

Tributary at confluence with Reach HB-1, 80 m downstream of Taunton Road.

Photo 1 Photo Reach MB Reach

Channel with poorly defined banks, 25 m upstream of confluence with Reach HB-1.

Limited flow on day of field investigation. Flow is from top-right to bottom-left.

Photo 1 Photo Reach MB Reach

Tributary approximately 50 m of confluence, viewed upstream. Note lack of bank definition, leaning trees and woody debris jam.

Photo 1 Photo Reach MB Reach

Abandoned crossing structure adjacent to Regional Road 57, viewed upstream. Note

outflanked concrete apron.

Photo Photo Reach MB Reach

West (downstream) end of Regional Road 57 CSP culvert and abandoned crossing structure, viewed downstream.

Photo Photo Reach MB Reach

West (downstream) end of Regional Road 57 CSP culvert and scour pool, viewed

upstream. Note 0.2 m fall from culvert invert to downstream water surface.

Photo Photo Reach MB Reach

East (upstream) end of Regional Road 57 CSP culvert.

Photo 2 Photo Reach HB Reach

Bowmanville Creek Bridge, viewed downstream.

Photo 2 Photo Reach HB Reach

West approach embankment with gabion toe erosion protection in poor condition. Flow is from right to left.

Photo 2 Photo Reach HB Reach

Channel viewed upstream, 40 m upstream of Bowmanville Creek Bridge.

Photo 2 Photo Reach HB Reach

Meander bend viewed downstream towards 5034 RR 57, 100 m upstream of Taunton Road. Note the lack of woody vegetation along outside bank.

Photo 2 Photo Reach HB Reach

Outside bank of meander bend at 5060 RR 57, 150 m upstream of Taunton Road. Note

exposed glaciolacustrine deposit along to of bank, and manicured grass along bank.

Photo 2 Photo Reach HB Reach

Undermined fence and exposed tree roots along bank.

Photo 2 Photo Reach HB Reach

Exposed glaciolacustrine deposit along lower portion of bank indicates channel

degradation. Manicured grass to top of bank results in decreased bank stability.

Photo Photo Reach HB Reach

Meander bends viewed downstream. Note point bar in foreground and erosion along outside banks, which suggest meander bend migration.

Photo Photo Reach HB Reach

Sand, gravel and cobble point bar located 200 m upstream of Taunton Road, at 2440

Taunton Road, viewed upstream.

Photo Photo Reach HB Reach

Wide and shallow channel, viewed downstream. Note leaning trees in background.

Photo Photo Reach HB Reach

Near-vertical bank at 5080 RR 57, 250 m upstream of Taunton Road. Note concrete

debris used for erosion control, exposed tree roots and glaciolacustrine deposit on bed.

Photo Photo Reach HB Reach

Slumping bank along inside bank of bend at 5096 RR 57, 325 m upstream of Taunton Road. Slumping is likely due to lack of woody vegetation along bank.

Photo Photo Reach HB Reach

Heavily leaning trees and exposed roots along bank.

Photo Photo Reach HB Reach

Leaning and fallen trees along outside bank of meander bend, viewed downstream.

Appendix B: Rapid Geomorphic Assessment Field Sheets

Appendix C: Meander Belt Width Assessment

E G

I O

5 7

54.5 m

D OA N R NTO TAU

Legend Meander Belt Width Delineation 9 Reach break ± Bowmanville Creek Watercourse banks in 2017 Crossing at Taunton Road, Bowmanville 0 50 Meander belt width (54.5 m) Metres

Imagery: Google Earth Pro, 2017. Reach break, Watercourse banks, and Meander belt width: GEO Morphix Ltd., 2017.