Hantsport Stormwater Management Study
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MUNICIPALITY OF WEST HANTS Hantsport Stormwater Management Study July 2018 – 17-6276 July 3, 2018 Hantsport Municipal Public Works Office 137 Chain Lake Drive 20 Main Street Suite 100 Hantsport, NS Halifax, Nova Scotia B0N 2T0 Canada B3S 1B3 Municipality of West Hants Telephone Hantsport Stormwater Management Study 902.450.4000 Fax Aenon: Mr. Brad Carrigan, Director of Public Works 902.450.2008 Dear Mr. Carrigan, Dillon Consulng Limited (Dillon) is pleased to present the following report entled Hantsport Stormwater Management Study. The aached report provides the methodology and hydrologic and hydraulic simulaon results for the drainage network in Hantsport. The report assesses the current drainage network under exisng and future development condions. The effects of climate change have also been invesgated as part of the study. Preliminary recommendaons have been developed for areas of concern with respect to the need for stormwater conveyance improvements. Sincerely, DILLON CONSULTING LIMITED Sarah Devereaux, M.Eng., P.Eng., FEC Partner, Project Manager SLD:jgc Our file: 17-6276 Dillon Consulting Limited i Table of Contents Executive Summary 1.0 Introduction 1 2.0 Background 1 3.0 Existing Drainage Network 4 3.1 Site Reconnaissance and Survey .......................................................................................... 4 3.1.1 September 5th – 8th, 2017 .................................................................................................... 4 3.1.2 October 4th, 2017................................................................................................................. 5 3.1.3 November 22nd, 2017 .......................................................................................................... 6 3.2 Hydrometric Observations ................................................................................................... 6 3.2.1 Halfway River (September 5th – October 4th) ........................................................................ 6 3.2.2 Willow Brook (October 4th – November 22nd) ....................................................................... 8 3.2.3 Flood Frequency Analysis .................................................................................................. 10 4.0 Hydrologic and Hydraulic Analysis 12 4.1 Hydrologic Characteristics ................................................................................................. 12 4.1.1 Catchment Parameters ...................................................................................................... 12 4.1.2 Meteorological Inputs ....................................................................................................... 13 4.1.3 Water Level Data ............................................................................................................... 15 4.2 Hydraulic Model Development .......................................................................................... 16 4.3 Hydraulic Model Calibration .............................................................................................. 18 4.3.1 Willow Brook ..................................................................................................................... 18 5.0 Simulation Results 21 5.1 Existing Performance ......................................................................................................... 22 5.1.1 Downtown – Chittick Avenue, Main Street & School Street................................................ 22 5.1.2 Riverview Road, Maple Avenue & Birch Street ................................................................... 22 5.1.3 Foundry Road .................................................................................................................... 25 5.1.4 William Street, Prince Street & Main Street ....................................................................... 25 5.1.5 Willow Street..................................................................................................................... 26 Municipality of West Hants Hantsport Stormwater Management Study July 2018 – 17-6276 ii 5.1.6 Holmes Hill Road, Maple Avenue & Chestnut Avenue ........................................................ 26 5.1.7 Rand Street, Bog Road & Evangeline Drive ......................................................................... 27 5.1.8 Rand Street, Bishopville Road & Riverview Road ................................................................ 27 5.2 Future Performance .......................................................................................................... 28 5.2.1 Downtown – Chittick Avenue, Main Street & School Street – Future Land Use Conditions ......................................................................................................................... 29 5.2.2 Riverview Road, Maple Avenue & Birch Street – Future Land Use Conditions .................... 29 5.2.3 Foundry Lane – Future Land Use Conditions ...................................................................... 29 5.2.4 William Street, Prince Street & Main Street – Future Land Use Conditions ......................... 31 5.2.5 Willow Street – Future Land Use Conditions ...................................................................... 31 5.2.6 Holmes Hill Road, Maple Avenue & Chestnut Avenue – Future Land Use Conditions .......... 31 5.2.7 Rand Street, Bog Road & Evangeline Drive – Future Land Use Conditions .......................... 32 5.2.8 Rand Street, Bishopville Road & Riverview Road – Future Land Use Conditions ................. 32 5.3 Future Performance with Climate Change Conditions ........................................................ 33 5.3.1 Downtown – Chittick Avenue, Main Street & School Street – Future Land Use Conditions with Climate Change ........................................................................................ 33 5.3.2 Riverview Road, Maple Avenue & Birch Street – Future Land Use Conditions with Climate Change ................................................................................................................. 34 5.3.3 Foundry Lane – Future Land Use Conditions with Climate Change ..................................... 34 5.3.4 William Street, Prince Street & Main Street – Future Land Use Conditions with Climate Change ................................................................................................................. 35 5.3.5 Willow Street – Future Land Use Conditions with Climate Change ..................................... 36 5.3.6 Holmes Hill Road, Maple Avenue & Chestnut Avenue – Future Land Use Conditions with Climate Change ......................................................................................................... 36 5.3.7 Rand Street, Bog Road & Evangeline Drive – Future Land Use Conditions with Climate Change .............................................................................................................................. 37 5.3.8 Rand Street, Bishopville Road & Riverview Road – Future Land Use Conditions with Climate Change ................................................................................................................. 37 6.0 Assessment of Future Flood Risk Vulnerability 38 6.1 Urban Drainage Flood Risk................................................................................................. 38 6.2 Halfway River Flood Risk .................................................................................................... 40 7.0 Preliminary Drainage Improvement Options 42 8.0 Conclusion 45 Municipality of West Hants Hantsport Stormwater Management Study July 2018 – 17-6276 iii Figures Figure 2-1: Study Location .................................................................................................................... 2 Figure 2-2: Photograph of Post-Failure Aboiteau near Hantsport (taken November 22, 2017) .............. 3 Figure 2-3: Photos of Recently Upgrade Roadway on Chittick Avenue (left) and typical Road section (right) ...................................................................................................................... 4 Figure 3-1: Halfway River Water Level Observations ............................................................................. 7 Figure 3-2: 24-Hour Water Level Observation Summary ....................................................................... 8 Figure 3-3: Level Logger Deployment in Willow Brook (left), and Downstream Open Bottom Pre- Cast Structure Facing Downstream (right)............................................................................ 9 Figure 3-4: Willow Brook Water Level Observations (Geodetic Elevation) ........................................... 10 Figure 3-5: Regional Frequency Analysis Theoretical Peak Flow Plot ................................................... 11 Figure 4-1: Map of Sub-Catchment Delineation .................................................................................. 14 Figure 4-2: 24-Hour Alternating Block Method Distribution for 100-year Historical Event ................... 15 Figure 4-3: Existing Drainage Network ................................................................................................ 19 Figure 4-4: Comparison of Willow Brook Simulated and Observed Hydrograph for October 30th, 2017 Event ........................................................................................................................ 20 Figure 5-1: Simulation Results – Catchment Areas .............................................................................