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Staff Report
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Report To: Planning and Development Committee
Date of Meeting: April 6, 2021 Report Number: PDS-022-21
Submitted By: Ryan Windle, Director of Planning and Development Services
Reviewed By: Andrew C. Allison, CAO By-law Number:
File Number: PLN17.3 Resolution#:
Report Subject: Graham and Wilmot Creek Flood Plain Mapping Update Study
Recommendations:
1. That Report PDS-022-21 be received;
2. That Council approve the Municipal contribution of $30,000 from the Tax Rate
Stabilization Reserve Fund to undertake the Graham and Wilmot Creek Flood Plain
Mapping Update Study, in partnership with the Ganaraska Region Conservation
Authority, the Region of Durham, and the National Disaster Mitigation Program ;
3. That the Mayor and Clerk be authorized to execute the necessary agreements; and
4. That all interested parties listed in Report PDS-022-21 and any delegations be advised
of Council’s decision.
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Report Overview
Flood plain mapping helps to identify areas that may be at risk of flooding during severe
storms and is an important tool for land use planning and emergency preparedness.
Ganaraska Region Conservation Authority’s flood plain mapping for the Graham and Wilmot
Creek watersheds is nearly 45 years old and is the oldest of the flood plain data sets used
for Clarington.
The National Disaster Mitigation Program provides funding support for flood mitigation
projects, with focus on those that inform future mitigation investments. In late 2020,
Planning and Development Services, in partnership with Ganaraska Region Conservation
Authority and the Region of Durham, applied to the National Disaster Mitigation Program for
grant support for the Graham and Wilmot Creek Flood Plain Update Study. Approval of the
Municipality’s portion of the project costs is being recommended.
1. Background
1.1 On November 10, 2020, the Federal Government announced a new intake (intake 6) of
the National Disaster Mitigation Program (NDMP). This intake invited eligible
organizations to submit proposals for funding support of up to 50% to a maximum of
$1.5 million per eligible project.
1.2 The Ganaraska Region Conservation Authority (GRCA) approached the Municipality
and the Region of Durham to collaborate on a funding application to update the flood
plain mapping for the Graham and Wilmot Creek watersheds. GRCA’s exi sting flood
plain mapping for these two watersheds dates back to 1977.
1.3 On November 30, 2020, Planning and Development Services submitted a proposal to
the NDMP for the Graham and Wilmot Creek Flood Plain Mapping Update Study
(Study). Notice of provincial support of the application was received on February 1,
2021. An update was received on March 23, 2021, indicating a delay in Federal
decision making. However, projects that may be compromised by a delayed start date
were authorized to proceed as of April 1, and project costs incurred from this date would
be recognized if federal approval is granted.
1.4 The purpose of this report is to seek approval of the Municipal funding contribution for
the Study in advance of the Federal decision. These funds will allow for the field /
survey work to proceed this spring, which is necessary for the project to be completed
within the prescribed NDMP project completion timeframe.
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2. Overview
Study Area
2.1 The Graham and Wilmot Creek watersheds are shown in Attachment 1. The Grah am
Creek watershed drains an area of 78 square kilometers. Mulligan Creek is the largest
tributary of Graham Creek; however, other tributaries such as Crooked Creek and Lytle
Creek are also part of the watershed. The Wilmot Creek watershed drains an area of
98 square kilometers. The main branch of Wilmot Creek is joined by four other
tributaries - Orono Creek, Hunter Creek, Stalker Creek and Foster Creek.
2.2 The urban areas of Newcastle Village and Orono, along with the hamlets of Brownsville,
Leskard and Newtonville fall within these watersheds. The total population of these
watersheds is approximately 13,400 people, with 73% in the urban areas, 3% in the
hamlets and 24% in the rural areas.
2.3 Of the approximately 13,400 people living in the watersheds, 11% live within the existing
mapped flood plain. There are three senior (assisted living) residences, three childcare
facilities and six schools within 100 m to 500 m of the existing mapped flood plain area.
In addition, 25 commercial and industrial businesses and 531 municipal infrastructure
assets are located in the existing mapped flood plain.
Study Purpose
2.4 The original flood hazard mapping for Graham and Wilmot Creeks was completed by
Dillion Consulting for the GRCA in 1977. The Study will update flood plain mapping for
the Graham and Wilmot Creek watershed areas to accurately identify the areas
currently subject to flooding, factoring in changes that have occurred over time that can
affect the size and location of the f lood plain area. These include updated topographical
information, improved modelling techniques and software, and new development and
infrastructure construction. The scope will exclude Foster Creek, which was recently
updated as part of new development in the area.
2.5 Knowing the extent of a flood plain is an important tool for land use planning and
emergency management. It informs the Official Plan, zoning by-law and the review of
development applications, helping to direct future development outside of f lood-prone
areas, to avoid injury, loss of life and property damage. It is also used to identify where
flooding may impact access to roads, and emergency routes, and can help property
owners to understand their potential risk of and to prepare for a flooding event. In
addition, flood plain mapping can be used to support assessments of the vulnerability of
roads and culverts to riverine flooding across Clarington.
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2.6 The Study will use the 2016 provincial LiDAR data and additional structure survey
information to update the hydrologic and hydraulic models for Graham and Wilmot
Creeks to modernize the flood mapping for the vulnerable areas of Newcastle and
Orono.
Funding
2.7 The NDMP is administered by Public Safety Canada. The program invests in projects
that support building a body of knowledge on flood risks and foundational flood
mitigation programs. The original program period from 2015 to 2020 was renewed to
provide two additional years.
2.8 Intake 6 of the NDMP Program was opened for project proposals which included flood
risk assessments, flood mapping, flood mitigation plans and non -structural flood
mitigation projects, to be undertaken between April 1, 2021 and March 31, 2022.
2.9 The Study was submitted as a Stream 2: Flood Mapping proposal. It is estimated that
the full 12-month project period will be required to complete the Study and grant
reporting requirements and involves both field work and computer modelling. The work
would be carried out by the GRCA as they have LiDAR expertise.
2.10 The total budgeted cost to undertake the Study was $141,000. The breakdown of cost
contribution to the project, as proposed, is outlined in Table 1.
Table 1: NDMP Project Proposal Cost Contribution Breakdown
Contributor Type Contribution
Amount
National Disaster Mitigation Program Grant $70,500
Region of Durham Funding $30,000
Ganaraska Region Conservation Authority In Kind $10,500
Municipality of Clarington Funding $30,000
$141,000
Linkages to Other Projects
2.11 The Study builds on previous work done within the Municipality that was supported by
the NDMP, such as the Emergency Flood Access Risk Assessment and Mitigation
Study (Aquafor Beech Limited, March 31, 2020), which indicated the following:
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Models for Wilmot and Graham Creeks are not georeferenced (crossings could not
be located within the watersheds based on their IDs) and were flagged by the study
team as potentially not being accurate from a vertical datum and results perspective.
Therefore, the results from the existing HEC-RAS models for Wilmot and Graham
Creeks were not used in the analysis in this study (except for one crossing which
could be located in Wilmot Creek).
By producing updated models and mapping for Graham and Wilmot Creeks, elements
of the previous Emergency Flood Access Risk Assessment and Mitigation Study
(Aquafor Beech Limited, March 31, 2020) and other Flood Risk Assessment work
undertaken by GRCA for Clarington can be updated to provide better quality information
for emergency planning and flood mitigation purposes.
2.12 The Study aligns with Action 3.3 of the Clarington Corporate Climate Action Plan - work
with the Conservation Authorities to update flood mapping based on the most up -to-date
climate projections. It also supports implementation of several other CCCAP actions,
including:
Action 2.21 - Identify roadways that are the least likely to be impacted by flooding
and incorporate them into community emergency evacuation plans.
Action 3.6 - Assess the municipal trail system to determine areas that are most
vulnerable to flooding based on climate projections.
Action 3.8 - Utilize climate projections to identify areas of roads that are
vulnerable to flooding. Create a plan to upgrade road areas that are at high risk.
Action 4.17 - Assess bridges and embankments to determine areas that are most
vulnerable to flooding based on climate projections.
2.13 The Study is also linked to an NDMP (Intake 6) application that was submitted by the
Region of Durham to assess vulnerable roads and culverts to riverine flooding across
Durham Region and confirm their ability to meet intended design standards under
current and future climate change scenarios. The updated models and mapping
produced through the Study would be used to inform the Region of Durham's risk
assessment work.
3. Concurrence
3.1 This report has been reviewed by the Director of Financial Services/Treasurer who
concurs with the recommendation.
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4. Conclusion
4.1 Flood plain mapping is an important tool for land use planning and emergency
management. GRCA’s flood plain mapping for the Graham and Wilmot Creek
watersheds is nearly 45 years old. The information updated through this study will be
used to update the flood hazard mapping for Graham and Wilmot Creeks as
administered by the GRCA, will inform the updated Municipality of Clarington Official
Plan and zoning mapping, will support the creation of future inundation mapping, and
will be used in future risk analyses by the Region of Durham and others.
4.2 The NDMP provides an opportunity to offset 50% of the $141,000 required to update the
flood plain mapping with the majority of the remaining funds offset by partner
contributions from GRCA and the Region. It is respectfully recommended that the
Municipality’s financial contribution of $30,000 (21% of project costs) be approved in
order to proceed with the necessary field / survey work this spring to avoid negatively
impacting the project schedule. Should NDMP funding be denied, other funding
opportunities will be pursued, and the updated field / survey data will be needed for
future use.
Staff Contact: Amy Burke, Senior Planner, 905-623-3379 ext. 2423 or aburke@clarington.net
and Faye Langmaid, Manager of Special Projects, 905-623-3379 ext. 2407 or
flangmaid@clarington.net
Attachments:
Attachment 1 – Graham and Wilmot Creek Watersheds Map
Interested Parties:
The following interested parties will be notified of Council's decision:
Linda J. Laliberte, CAO, Ganaraska Region Conservation Authority
Elaine Baxter-Trahair, CAO, Regional Municipality of Durham
Wilmot Creek
Graham Creek
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This map is for information purposes only and the Ganaraska Region Conservation Authority takes noresponsibility for, nor guarantees, the accuracy of the information contained within the map.Prepared by Ganaraska Region Conservation Authority: Nov 2020.Produced using information provided by the Ministry of Natural Resources, GRCA and other municipal sources.Copyright (c) Queen's Printer, 2020.
Wilmot Creek and Graham Creek WatershedFloodplain and Wetlands
Floodplain
Watershed Boundary
Local Municipalities
Wetland
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Watercourse
Highway
Arterial
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