2. Background/Overview of Conditions

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1 2. Background/Overview of Conditions This section provides background information on the relevant conditions within the Town of Oakville that impact the formation and evolution of watercourses, including those assessed in this study. The background begins with the high level, universal controlling factor of geology, and becomes progressively more specific, describing land use change in the Town, past creek works, channel evolution concepts, before characterizing the individual creeks that were evaluated in this study. 2.1 Geology Geology is one of the dominant controls of channel form and function. Characteristics of surficial geology deposits within a drainage basin influence the rate of channel migration and evolution, the rate of incision, the volume of sediment delivered to the watercourse, channel dimensions and characteristics of the bed morphology. Physical properties of watercourses adjust to the sediment and flow regimes that are conveyed to it from the watershed. Therefore, a general understanding of the geology that the Town is situated on provides a context for the evaluation of field assessment data. The Quaternary geology of the Town consists of three deposits (see Figure 2-1): lacustrine and outwash sands along the Lake shoreline; shale and dolomite bedrock running approximately along the Queen Elizabeth Way (QEW) and many of the creek beds; and Halton Till deposits in the upland areas north of the QEW. The bedrock consists of interbedded layers of shale and limestone or dolomite, largely from the Queenston and Georgian Bay Formations. The shale is characteristically thinly bedded and friable, while the dolomite is more robust and resistant to erosion. Tectonic deformation of the shale and harder layers has occurred within the Town, as evidenced in the exposed valley walls of Joshua s. To the west of Sixteen Mile, the sequence of surficial geology varies from that observed to the east. Shale and dolomite bedrock materials become exposed closer to Lake Ontario near Rebecca Street. A large deposit of Halton Till is situated on the bedrock materials, bounded by Rebecca Street, Speers Road, Sixteen Mile and Fourteen Mile. Halton Till covers the bedrock materials north of the QEW. The watercourses are situated on geologic deposits composed of bedrock materials, and many have incised and exposed the bedrock materials within the lacustrine sands or Halton Till. Shannon s, Munn s and the lower sections of Wedgewood are exceptions to this. Several characteristics of the Town s surficial geology are noteworthy: Queenston shale tends to be easily eroded into small sized materials that subsequently break down into the parent clays; Limestone and dolomite tend to be eroded as large platy cobbles which then break down through abrasion; The dominant erosion process for watercourses situated in bedrock materials, as many creeks in the Town are, is typically incision. These characteristics will be considered in the evaluation of erosion risk, and in the recommendation of appropriate rehabilitation alternatives for priority reaches. 2

2 Falgarwood Morrison Mile Avonhead Winston Churchill Blvd. Lakeshore Rd. Wedgewood Joshua s 5 Wedgewood Morrison Morrison Munn s Shannon s West Sixteen Mile Glen Taplow McCraney Fourteen 2 Lake Ontario Upper Middle Rd. E. Burnamthorpe Rd. Channel Trafalgar Rd. Dundas St. Wedgewood Diversion Morrison Oak Rebecca St. Speers Rd. QEW Upper Middle Rd. W. 25 Figure 1 Quaternary geology of Oakville and surrounding area. 403 QEW PARISH geomorphic Legend Shale and Dolomite Halton Till Lacustrine and Outwash Sand Alluvium: Gravel, sand, silt and clay Abandoned Shoreline Feature (Iroquois Shoreline) Bedrock Pressure Release Ridge Glacial Fluting * From Karrow, 1987

3 2.2 Land Use Changes The physical form and function of watercourses adjust primarily in response to changes in the flow and sediment regimes. When the flow and sediment regimes of a watercourse remain stable for a prolonged period on the order of decades or centuries the form of the watercourse exists in a state of quasi-equilibrium. In this state, the watercourse is able to absorb minor changes to its controlling factors (i.e., hydrology and sediment) by adjusting one of its degrees of freedom, such as channel width, depth or gradient. However, when the change in controlling factors is greater than the ability of the channel to absorb the change, larger-scale adjustments occur, creating a period of instability that may last for decades. The Town has experienced substantial changes in land use since the early nineteenth century. The review of a historic sequence of aerial photographs (completed in prior erosion assessment studies) provides insight into the sequence of urbanization that occurred up to the present day: In 1954 agriculture was the dominant land use in the area, although several residential areas had been constructed extending to the east of McCraney ; Between 1954 and 1979 residential developments began to occupy the area between Lake Ontario and Speers Road; industrial and commercial buildings were constructed in the area south of the QEW; By the mid 1980s, the area east of Sixteen Mile was urbanized to Upper Middle Road; further development extended north to Dundas Street by 1989; The rate of urbanization in the area west of Sixteen Mile has proceeded at a slower pace; some urbanization had occurred by 1983 and increased to such an extent that by 1989 the area between the QEW and Upper Middle Road had been entirely developed; Since 1989 urbanization has extended towards Dundas Street and, more recently, beyond. Most of the urbanization within the Town consists of low- to medium-density residential housing and commercial establishments, with industrial and commercial complexes concentrated parallel to and south of the QEW. Channel instability in the Town has largely been associated with these land use changes. Urbanization reduces the volume of water that infiltrates while increasing the volume of water that drains as runoff. These hydrologic changes result in lower baseflows and increases to volumes of runoff, resulting in higher peak flows and shorter watershed response times, incurring potentially significant changes to channel form (i.e., planform, cross-section, and profile). The length of the relaxation time (i.e., the time required for the creek to adopt a new stable regime) varies depending on the magnitude of the channel adjustments and the rate at which these changes occur. The channel adjustment will vary depending on factors such as riparian vegetation and bank material. Typically, the relaxation time will be on the order of decades. However, the extent and rate of adjustment due to land use changes can be mitigated through appropriate use of stormwater management (SWM) in upland drainage areas, which reduces the hydrological effects of development. Unfortunately, most urban development that occurred prior to the 1980s had few or inadequate SWM controls, designed only to control peak flows rather than consider runoff volumes and energy in the receiving creeks. 2.3 Past Works/Flood Control There have been significant changes in drainage patterns and land use within the Town over the past 30 years, consisting primarily of channel alterations including channel diversions and watercourse channelization. The objective of this work has been primarily for flood and erosion control purposes. Flooding has historically occurred in the older development areas south of the QEW. This development preceded flood protection regulations and many homes and other buildings were constructed in the floodplains of the watercourses. Flood control studies have been performed to identify mitigation measures, consisting of the 4

4 diversions and channel works that now exist. The most significant of these includes the Morrison-Wedgewood Diversion. Located north of the QEW, this diversion conveys the runoff from five branches of the Morrison and Wedgewood creek systems to Sixteen Mile, diverting the headwater drainage of these creeks. The evaluation of flood potential is beyond the scope of this study; however, other reports have documented these conditions. This study has identified channel works in need of repair or remediation, including them in the erosion assessment. In recent years the Town has undertaken several creek restoration projects, including: Fourteen Mile, Reach 1 (completed); Fourteen Mile, Reach 2 (Localized retaining wall repair, completed) Fourteen Mile, Reach 2 (Environmental Assessment underway); Falgarwood, Reach 54 (Construction underway); Glen Oak, Reach 97 (Localized retaining wall repair, completed); Joshua s, Reach 66 (Restoration adjacent to Canning Court, completed); Wedgewood, Reaches 59 to 61 (Restoration completed). The two reaches currently undergoing restoration efforts (Fourteen Mile Reach 2 and Falgarwood Reach 54) were not included in the assessment. 2.4 Channel Evolution During the geomorphic assessment of the watercourses within the Town, evidence of channel evolution was observed, which affected the ratings and rankings of the reaches. To provide a context for the observations and discussion provided in Section 4, the following describes channel evolution processes that typically occur in channels of the type found in the Town. The form of a channel (i.e., cross-section, plan form, and profile) adjusts over time in response to several dominant controls and modifying influences, including: Hydrologic regime; Sediment supply; Floodplain materials; Floodplain vegetation; and Land forms (i.e., valley grade). This continual adjustment to a consistent regime of controls and influences is considered to be a quasi-equilibrium. Over time, a channel responds to these controls to improve the efficiency of its processes (i.e., flow, sediment transport) and to reduce the overall energy in the system, frequently creating a concave profile from the headwaters to the outlet. When one of the factors that influence channel form is altered, the channel typically responds by adjusting one or more of its characteristics to regain a new quasi-equilibrium. While some of these changes may be localized (i.e., a change in bank vegetation) and cause a local channel response, other alterations to controls, such as in hydrology, may cause a more significant response throughout the channel. Depending on the nature of the alteration to the dominant controls and influences, the channel may respond by incising into its bed, widening between its banks, increasing or decreasing in slope by changing its sinuosity, and/or by moving laterally across its floodplain. Evidence of each of these types of adjustment was observed within the Town s channels. 5

5 Most watercourses work to reduce their energy grade and to develop a concave profile from its headwaters to its outlet through a gradual degradation of the channel invert and by making alterations in sinuosity. As watercourses incise (i.e., degrade), areas of the floodplain can become disconnected from the channel, and as the watercourse moves laterally through the floodplain these areas become abandoned, creating terraces in the valley profile. Many such terraces were observed in the watercourses throughout the Town, particularly north of the QEW. As the slope of the watercourse changes through incision, the hydraulic characteristic of the channel changes and the form of the channel adjusts to maintain its flow and sediment transport processes. These adjustments can include meander cut-offs or development/extension, deposition of materials and shifting of floodplain position. Each of these alterations was observed in the Town s watercourses. While the channel works to regain a new quasi-equilibrium, it appears to be sensitive and in a state of adjustment or transition during field reconnaissance. The term adjustment refers to large-scale plan form changes where the channel is adjusting many aspects of its physical form. Watercourses situated on bedrock tend to incise, especially when the bedrock characteristics includes bedding planes, such as in limestone, dolomite and/or shale. The process of bed incision contributes sediment to the watercourse. Although incision is a long-term process, the rate of incision decreases as the grade of the watercourse flattens, usually through the process of headcutting and knick point migration. Throughout the study area, creeks were observed to be experiencing substantial rates of incision and adjustment. This is exacerbated in areas where the creeks have incised into narrow valleys, preventing the dissipation of energy on the floodplains during high flows. Over time, these incised creeks increase the width of their valley, reduce their slope and develop a stable configuration that is characterized by knick points and accumulations of sediment. Non-natural alteration of a watercourse, such as channelization, impairs the natural form and function of a creek. However, if the dominant controls and influences within the creek are not likewise altered, the creek will attempt to regain a natural form over time. Human alterations of a watercourse tend to reduce channel length, resulting in an increase in slope. Loss of sinuosity and of bed morphology (i.e., through paving the channel with concrete) causes a reduction in the natural mechanisms of energy dissipation, and in conjunction with the increases slope of the altered channel the flow energy in the watercourse will increase, creating potential issues with bed and bank erosion in downstream areas. The tendency of a straightened watercourse is to regain a natural configuration. The flow energy contained in the bankfull and larger flows are used to develop this natural configuration through bed incision and bank erosion. As a result, bank protection works can begin to fail. A channel evolution model developed by Simon (1989, Figure 2-2) illustrates some of the dominant processes that occur within an altered channel (i.e., incision, widening and aggradation) as it works to regain a natural form that is connected to its floodplain. The need for a watercourse to alter its form is exacerbated if the hydrologic regime of the channel is also altered, as is the case in many urban areas such as the Town. 6

6 Figure Overview of channel adjustment processes 2.5 Reach-Based Assessment The physical characteristics and form of a watercourse typically vary from upstream to downstream. This change in characteristics tends to be directly related to the amount of flow, which increases from upstream to downstream as a larger drainage area contributes to the channel. For example, a channel will tend to become wider and deeper as it flows downstream. However, this general rule does not always apply when the characteristics of the drainage area or riparian corridor change along the length of the watercourse. Sections of a channel that support a forested riparian corridor tend to be wider and shallower than a section of the same watercourse surrounded by scrub or grasses. Bed sediment composition and size also varies along the length of the channel. The larger bed materials will be found in the upstream section of the reach, as they are too heavy to be entrained within channel flows. Sediment size in the creek bed is related to the velocity of flows (i.e., the energy available to transport sediment). Channel bed material is also influenced by local geology. Coarse sediments in streams often originate in-situ rather than from upstream, and may be too large for the channel forming discharge to mobilize. The topography and geology of the study area was assessed prior to the completion of the 2001 Erosion Inventory and (TSH, 2001). The variability in channel forms, surrounding land use, geology and valley wall confinement suggested that the creeks should be divided into sections to facilitate evaluation. For that reason, the watercourses were divided into reaches of length between 200m and 2,000m. Reaches are sections of 7

7 channel that are similar with respect to plan form, gradient and surrounding land use. Given the similarity in dominant controls and influences within each reach, it can be assumed that channel form and function within a reach will also be similar. The 2001 assessment identified 60 reaches, and these were expanded in the 2006 assessment to the current total of 130 reaches. The evaluation of erosion risk issues within the watercourses is structured around this reach-based approach, and priority sites will be identified by their reach. 2.6 Overview of s Assessed The creeks assessed include all of those completed as part of the 2008 Erosion Inventory and Assessment study. The creeks are characterized in the following sections, listed in order from west to east through the Town. The creeks and reaches are displayed in Figure 2-3 (west area) and Figure 2-4 (east area) on the following pages. In summary, the following creeks and reaches were assessed in this study: Table Summary of s and Reaches Assessed Reaches Sheldon 3 69, 70 and 71 Fourteen Mile and its Tributaries35 1, 1a, 2, 3, 4, 5, 5a, 5b, 6, 6a, 7, 8, 9, 10, 11, 12, 13, 14, 14a, 14b, 15, 16, 75, 75a, 75b, 75c, 75d, 76, 76a, 76aa, 76ab, 76b, 76c, 76d, 76e McCraney 13 17, 18, 19, 19a, 19b, 20, 21, 22, 23, 30, 31, 32, 32a Taplow 5 24, 25, 26, 27, 28 Glen Oak 5 29, 29a, 29b, 96, 97 Shannon s 3 92, 93, 94 Munn s 8 33, 34, 35, 77, 78, 79, 80, 81 Morrison West8 36, 37, 38, 82, 83, 84, 85, 86 Morrison Main Branch10 46, 47, 48, 49, 50, 51, 52, 52a, 53, 53a Morrison East 7 39, 40, 41, 42, 43, 44, 45 Falgarwood 1 54 (not assessed during current study) Wedgewood 9 55, 55a, 56, 57, 58, 59, 60, 61, 95 Joshua s 19 62, 63, 64, 65, 66, 67, 68, 68a, 68b, 87, 87a, 87b, 88, 88a, 88b, 89, 89a, 89b, 89aa Clearview 3 90, 91, 91a 8

8 81 75c 75 b d b 19b c 76 Legend 39 b Reach Breaks 76e 76 Reach Numbers 93 Lake Ontario 76 aa Surveyed Watercourses 92 19a 14a 75b a 76 76a b Major Roads Property Fabric 75a Public Land a a b a 5b 5a Kilometers and Assessment Erosion Inventory 30 3 Oakville West 21 2 Datum: NAD 83, Zone 17 Source: Town of Oakville a 71 1:28, Lake Ontario May 2011 Figure 2-3

9 81 89b aa Legend a 94 Reach Breaks Major Roads Surveyed Watercourses 88b Public Land 88 # 41 a b !"" 35 Property Fabric Lake Ontario 88a Reach Numbers a a 68b 91 a a Erosion Inventory and Assessment Oakville East Datum: NAD 83, Zone 17 Source: Town of Oakville :27, May a 47 Lake Ontario 2 Kilometers 52a 52 1 Figure 2-4

10 2.6.1 Sheldon Sheldon from Lake Ontario to the Oakville/Burlington border (Reaches 69, 70 and 71) was assessed on October 22, The creek is situated in a residential area from Lake Ontario to Lakeshore Road and again from Burloak Road to its upstream limits within the Town of Oakville. From Lakeshore Road to Burloak Road the creek runs through an open space/park area characterized by wide floodplain and gentle bank slopes. Some erosion protection measures have been implemented from Lake Ontario to Lakeshore Road, including a concrete bed and banks along portions of the creek. Upstream of Lakeshore Road, the creek flows through Shell Park and Shell owned private property Fourteen Mile and Tributaries The lower reaches of Fourteen Mile, from the mouth of Lake Ontario to South Service Road East (Reaches 1a to 5b), were assessed on October 13, The primary land use around this portion of the creek consists of residential areas and parks/open space, with an area of industrial land beginning approximately 200m downstream of Speeres Road. Much of this creek has been altered with development. Vegetation within the floodplain varies from grass to forest depending on the surrounding land use. The upper reaches of Fourteen Mile upstream of the QEW to Dundas Street (Reaches 72 to 76) were assessed on October 18, 20, 21 and 22. This portion of Fourteen Mile is located primarily within open space, although there has been increased development north of Upper Middle Road in recent years. Many of the reaches in this area are characterized by steep valley walls; however, risk is mitigated by the relatively sparse private property and public infrastructure. As development increases the risk from erosion in these areas may increase. Tributaries of Fourteen Mile north of the QEW were evaluated on October 8, 12, 18 and 20, Moderate to steep forested valleys surrounding wide forested floodplains characterize this portion of the creek. The valley slopes become gentle to the north near Upper Middle Road. The portion of creek from Bray s Lane to Bowman Drive is naturalized with gentle to moderate slopes. It should be noted that the creek is piped underground upstream of Glenn Abbey Gate at Glen Abbey Park (Reach 16, upstream of Reach 15) McCraney McCraney was evaluated on October 5, 7 and 8, The section of McCraney upstream of the QEW (i.e., Reaches 17-19) is located within residential areas with some open spaces and an extensive trail network adjacent to the creek. The creek banks are forested with relatively wide floodplains adjacent to the valley slopes. McCraney from Lake Ontario to Speers Road is primarily located in residential areas; however, Appleby College is located on the left bank south of Lakeshore Road. In some areas the creek flows on private property. Banks are gentle to moderately sloping and vegetated with grass or trees and shrubs. There are incidences of bank protection features that have been constructed by local residents, particularly in the locations where the creek is on private property Taplow Taplow from North Service Road West to Upper Middle Road (i.e., Reaches 24-28) was evaluated on September 30, This creek has a relatively wide forested floodplain area surrounded by steep to moderate valley walls, though they are more prevalent in the downstream portions. The creek is surrounded by residential development along its length, and becomes particularly well vegetated as it flows through the Glen Abbey Woods. 11

11 Erosion is occurring along the length of the creek; however, it is most prevalent in the downstream reaches where the steeper valley walls are affected Glen Oak Glen Oak was evaluated on October 4, This assessment was taken from the McCraney / Glen Oak confluence near Fourth Line and Weldon Avenue up to Upper Middle Road. The banks are well vegetated and the floodplains are relatively wide. Land use surrounding the creek is primarily residential Shannon s Shannon s upstream of its confluence with Sixteen Mile was evaluated on October 27, 2010 from Neyagawa Boulevard to River Glen Boulevard. The creek from Neyagawa Boulevard to just downstream of River Oaks Boulevard is contained within a valley system characterized by steep slopes which were noted as unstable in many areas. This portion of creek has been noted in previous assessments for continued monitoring to gauge potential impacts from the extensive erosion and downcutting, and has been recommended in this assessment as a priority area for restoration. Upstream of River Oaks Boulevard the creek is intermittent and poorly defined Munn s Munn s travels through several residential neighbourhoods and is adjacent to numerous properties. Although this creek is located north of the QEW, it is not characterized by the steep valley slopes that are typical of the majority of other creeks upstream of the QEW. There are however, erosion issues along the length of the creek. Munn s was evaluated on October 27, New development has occurred in the upstream sections of the creek near Upper Middle Road. Downstream of Munn s Avenue, the creek is contained within a fairly wide and forested floodplain, contained within treed valley walls. At various locations the creek flows directly adjacent to the valley walls, which is creating potential erosion risk issues, approaching residential fence lines and prompting some homeowners to construct their own erosion control measures. Erosion is also occurring where the creek is located in the floodplain. Upstream of Munn s Avenue the floodplain widens. Upstream of the pedestrian trail at River Oaks Park the creek is not well defined and does not appear to have a consistent baseflow. There are no erosion concerns upstream of the pedestrian trail in River Oaks Park as creek modifications and wetland/pond areas are relatively new and flows appear to be low Morrison West Morrison West was evaluated from the Morrison-Wedgewood Diversion Channel to Dundas Street East (Reaches 36 to 38 and 82 to 86) on October 27 and 29, The steep forested valley slopes are surrounded mainly by residential and open space land uses. The Sheridan College campus runs along the east side of Reaches 36 to 38. The floodplain within the valley walls is generally wider and gentler than the other creeks with valley systems north of the QEW. Morrison West upstream of Upper Middle Road to Glenashton Boulevard travels through residential area. The creek is contained within wide floodplains. Upstream towards Glenashton Boulevard the creek is an engineered channel consisting of a rip-rap bed and banks with regular meanders and a wide grassed floodplain. Upstream of Glenashton Boulevard, the development is serviced by a series of SWM ponds which discharge to the creek. 12

12 2.6.9 Morrison Main The Main branch of Morrison was evaluated on November 1, 2010, from Lake Ontario to South Service Road (Reaches 46 to 53a). The creek is situated in park areas and residences with gently sloping grassed and treed floodplains. Upstream of Lakeshore Road, the residences are immediately adjacent to the creek in several locations and the floodplains are flat and vegetated by trees and grasses. Erosion mitigation measures are present along several reaches of the creek, and in some cases have been implemented by the residents. These measures include gabion baskets, heavy rip rap, concrete retaining walls, and concrete blocks Morrison East Morrison East, from the Morrison-Wedgewood Diversion Channel to south of Postridge Drive (i.e., Reaches 39 to 45), was assessed on November 2, Adjacent land use to the park is primarily parks and open space, with residential areas beyond. The creek consists of a shale bed with forested floodplains and, for the bulk of the reaches, steep valley slopes. Some erosion control work has occurred in the past which generally appears to be gabion baskets stacked two to three levels high in problem locations. In some of the locations where gabion baskets are not present there is erosion, most notably along valley walls adjacent to the creek Falgarwood Falgarwood (Reach 54) from the diversion channel to Gainsborough Drive was undergoing restoration works and was not assessed as part of this study. Previous assessments had noted extensive erosion and downcutting, resulting in impacts to adjacent property and storm outfalls Wedgewood Wedgewood was evaluated on October 29 and November 1, The creek upstream of the QEW, from the Morrison-Wedgewood Diversion Channel to Upper Middle Road, is typical of creeks north of the QEW in that the creek is contained within steep valley walls on a bed of shale. The surrounding land use is primarily residential; however, there is open space towards the downstream end. Erosion was noted along the length of the creek, as well as incision and deposition. Where Wedgewood flows into the diversion channel, material deposition from upstream areas is evident. Wedgewood downstream of the QEW consists of gentle to moderately sloping banks. Residential areas and open space surround the creek along its length. Vegetation along the creek is generally grass and forest type vegetation Joshua s Joshua s was evaluated on November 3, 4, 5 and 8, The lands surrounding Joshua are primarily open space, sports fields and residences. Floodplains along the creek are often wide and well vegetated with forestlike vegetation. Banks are generally moderately sloping; however, some locations have steep slopes Clearview Clearview between Winston Churchill Boulevard and its upstream limit was evaluated on November 8, The is situated among industrial and agricultural land uses. Portions of the creek have been lined with gabion baskets or concrete blocks/curbs. Some industrial areas are encroaching on the creek. 13