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: i 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 ii 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 1 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