Flood Projects in the Thompson River Watershed

Background

Flood hazard mapping completed in 2019-20 was intended to fill basic information gaps identified in the Thompson Watershed risk assessment. It was done at a base (screening) level, covering 478 square km across 11 floodplain sites in the Thompson-Nicola Regional District and one site in the Cariboo Regional District.

In 2020-21, the base level flood hazard mapping was updated to use the LIDAR data collected in 2019-20 for similar areas in the Thompson and Cariboo, and detailed flood mapping was completed within the City of Merritt on the Nicola and Coldwater Rivers.

The outcomes include hydrologic analysis results and screening-level flood hazard maps at a level of detail suitable for:

• Identification of sites that may be subject to flood hazards,
• Prioritization of sites for detailed study,
• Conversations at the community and regional level that centre around flood risk, including mitigation strategies to reduce existing or future flood risk,
• Emergency preparedness and response.

The outcomes of the detailed flood mapping on the Nicola and Coldwater Rivers within the City of Merritt are flood hazard scenario maps and Flood Construction Level maps within the city boundary, including the following:

• Flood depth, velocity and intensity maps for the 20-, 50-, 100,- 200-, 500-year and 200- and 500-year climate change adjusted return period events,
• Designated floodplain maps depicting the 200-year return period flood levels including a freeboard allowance of 0.6 m (i.e., flood construction levels).

The flood hazard mapping project in 2019-20 and the 2020-21 projects were funded by the Union of BC Municipalities Community Emergency Preparedness Fund program.

2021-2022 Project Work

FBC Detailed Flood Mapping Study:

Frequency-Magnitude Relationship for the Coldwater River

Following the November 15, 2021 flood in the Coldwater River, an urgent need emerged to estimate the peak flow of the Coldwater River to inform long-term reconstruction and mitigation efforts. The primary objective of this work was to provide a baseline estimate of the frequency-magnitude relationship for the Coldwater River at Merritt. The analysis is based on current data and methods.

Read the draft report

Connect & Learn Event (June 2022)

Frequency-Magnitude Relationship for the Coldwater River

• Event recording on YouTube
• Presentation Slides

Other Materials

• Frequency-Magnitude Relationship for the Coldwater River (Draft - May 20, 2022)
• Thompson River Watershed Flood Mapping work plan extract (June 2021)
• Bathymetric surveys field schedule

Also see Advisory Committee for meeting summaries and related materials

2020-2021 Project Work

The following flood projects were completed in the Thompson River Watershed and other areas of the Cariboo Regional District in 2020-21, and the final products are available:

• Thompson-Nicola Regional District Flood Hazard Assessment (2021)
• Merritt Detailed Flood Mapping Study: Nicola and Coldwater Rivers (2021): Download from Sharepoint (large file)
• Cariboo Regional District Flood Hazard Assessment (2021)

GIS and database files from the 2020 and 2021 flood mapping work are available on request for flood projects. Requests can be made to the .

Base Level Flood Mapping Sites

The above map (updated to 2021) shows the sites chosen for base-level flood hazard mapping in the Thompson-Nicola and Cariboo Regional Districts.

VIEW LARGE MAP

2019-2020 Project Work

The following flood projects were completed in Thompson River Watershed in 2019-2020, and the final project deliverables are available. 

• Base-Level Flood Hazard Mapping (Thompson & Cariboo)
• Flood Hazard Maps
• LIDAR Acquisition

Base-Level Flood Hazard Mapping - Final Report Available

The final report from 2020 is available for base-level flood hazard mapping in the Thompson watershed.

READ THE REPORT

Flood Hazard Maps

Flood hazard map layers from this project can be accessed through an online, interactive mapping website.

Also on the site are layers from the 2018-2019 Thompson Watershed risk assessment.

LEARN MORE ABOUT THE MAPS

LIDAR Acquisition

Raw topographical data was collected in the Fall of 2019 using light detection and ranging (Lidar) technology, and imagery captured in almost 5000 km² of valley bottom throughout the Thompson River Watershed.

The project data allowed for detailed, up-to-date topographic maps and will support future detailed floodplain mapping. The deliverables of the project are intended to be shared with all orders of government in the watershed.

This data can be accessed by any order of government through the BC Ministry of Forests, Lands, Natural Resource Operations and Rural Development.  to initiate a data sharing agreement and outline your geographic area of interest

This project is funded by the National Disaster Mitigation Program, funded equally by Public Safety Canada and Emergency Management BC.

Advisory Committee

A project Advisory Committee — with representation from elected officials and staff from local government, First Nations and the Province of BC — has provided guidance on this project. Information on the work of the Advisory Committee, and materials related to this work, are available: see Advisory Committee & Resources.

Learn More

For more information, contact:

Terry Robert
Director, Special Projects
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