Upper Squamish Valley Flood Plain Mapping

Apr 7, 2017
Electoral Area D

 

Project Summary:

In March 2017, the SLRD was awarded a grant of $150,000 from the Emergency Management B.C. Disaster Mitigation Program to be used for the development of floodplain mapping, risk assessment and flood mitigation planning. The funds were used to complete Flood Hazard Mapping and Risk Assessment of the Upper Squamish Valley area, located in SLRD Electoral Area D. 

The Squamish River is one of two river systems in the SLRD that are subject to frequent flooding, and that hold the highest consequences in terms of potential impacts. The District of Squamish (DOS) has recently completed a comprehensive flood plain assessment.

Download the District of Squamish Integrated Flood Hazard Management Plan Background Report

This project completes the assessment of the Squamish River system flood plain from the extent of habitation in the Upper Squamish Valley to the DOS boundary. The project results will inform both emergency management plans and development criteria, such as the Flood Control Level (FCL), in an area that is subject to recurrent flooding as well as increased development. The information derived from the SLRD study, in combination with the DOS study already completed, gives a complete flood risk profile to the entire Squamish River system, which will assist both the SLRD and DOS in moving forward with applications for future flood mitigation funding, where available. 

Project Updates:

January 2, 2019 - Residents and stakeholders are invited to attend a presentation of the report's findings, followed by a Q&A with project engineers and SLRD Emergency Management staff on Saturday, January 12, 2019 from 2:30 - 4:30 p.m. at the Queen of Peace Monastery (1021 Cloudburst Crescent, Squamish - first right turn after the Pilchuck Bridge, Squamish Valley Road). Learn more here. 

November 26, 2018 - The Upper Squamish River Flood Hazard Mapping and Risk Assessment report is now complete and available for download. The study shows that: 

  • Almost all of the valley is subject to geomorphic hazards. 
  • A potential outbreak flood from an upstream landslide blocked river could reach populated areas within a few hours and raise the water surface by several meters. 
  • At the 50-year flood event and above, most of the valley floor is flooded, with typical depths of 1 to 2 m within the inundated area. 
  • When areas are inundated, much of it has a high hazard rating and classified as dangerous for most to all people. 
  • Flood inundation affects all four receptors evaluated; people, the economy, the environment, and culture within the Upper Squamish River Valley. 
  • Natural geomorphic changes at the Squamish-Cheakamus confluence could potentially cause an increased water surface extending upstream nearly to populated areas at river kilometer 30. 

The study recommends:

  • Sharing the results with key authorities, stakeholders and the public in order to reduce potential loss-of-life and flood damages during future extreme flood events through education and awareness.
  • Planning new development away from high hazard areas and implementation of the Squamish River FCLs in order to create more flood resilient development. 
  • Access and egress routes requiring improvement be identified and the location of temporary evacuation areas be determined. 
  • Consideration also be given to relocating or flood-proofing existing housing and other development in extreme flood hazard areas. 
  • Considering that the Squamish River channel is highly dynamic and considering the ongoing aggradation, the river channel should be monitored and re-surveyed every 5 to 10 years and the hydraulic model updated as required.
  • During future flood events, high water marks should be obtained to allow for future model calibration.

A community meeting will be held in January 2019 where NHC will present the results of the study and provide an opportunity for a question and answer session with SLRD Emergency Program staff also attending.

December 01, 2017 - The project schedule has moved significantly due to delays in surveying the project area of the Squamish River as a result of water levels at first too low, and then too high for effective survey in the fall of 2017. Survey work is now scheduled for completed in the summer of 2018, with the final report due in November 2018. 

September 18, 2017 - The Request for Proposals was issued and is available for download in the SLRD Contracting Directory. The deadline to submit proposals is 4:30 p.m. on Friday, September 29, 2017.

Project Schedule:

Anticipated DateAction
September 18, 2017Issue Request for Proposals (RFP)
September 29, 2017RFP Closes (4:30 p.m.)
October 16, 2017Proposal Acceptance and Project Commencement
October 24, 2017 (no later than)Initial project methodology meeting with Project Steering Committee
February 1, 2018Final report due
February 28, 2018 (no later than)Public presentation to stakeholders

Project Background:

At the April 19, 2017 meeting, the SLRD Board authorized the SLRD to allocate $150,000 in grant funding from Emergency Management BC to undertake floodplain mapping and flood risk assessment for the Upper Squamish Valley.

The funding was part of a $750,000 investment in flood protection in the SLRD made by the Province on March 31.

Floodplain mapping and flood risk assessment in the Upper Squamish Valley will allow for better and more accurate emergency management response plans, as well as informing work done by the SLRD Planning Department related to property development in the area.

A flood map identifies the boundaries of a potential flood event based on type and likelihood and can be used to help identify the specific impacts of a flood event on, for example, structures, people and assets.

Floodplain mapping in the province of British Columbia was formerly the responsibility of the Ministry of the Environment. However, during the late 1990’s, the provincial government drew back from the programs that provided flood mitigation and assessment data which was useful to local governments. 

Though the Squamish-Lillooet Regional District (SLRD) receives updated flood inundation maps from BC Hydro for river systems downstream of power generating facilities as a requirement of the Dam Safety Act (Bridge River and Cheakamus), other river systems have not been assessed since 1993 – 94.

The Province of BC, through Emergency Management BC, has provided this one-time grant of $150,000 to the SLRD for the purposes of flood mitigation, including floodplain mapping and flood risk assessment.

The Squamish River is one of two river systems in the SLRD that are subject to frequent flooding, and that hold the highest consequences in terms of potential impacts. (Through another provincial funding stream, the Pemberton Valley Dyking District has received grant funding for floodplain mapping and flood risk assessment on the other high-consequence river, the Lillooet River system.)

The District of Squamish (DoS) has recently completed a comprehensive floodplain assessment. By using the $150,000 grant to complete the assessment of the Squamish River system floodplain from the extent of habitation in the Upper Squamish Valley to the DoS boundary, the SLRD will gain important information on flood risk that will inform both emergency management plans and development criteria, such as the Flood Control Level (FCL), in an area that is subject to recurrent flooding as well as an increase in development. The information derived from the SLRD study, in combination with the DoS study already completed, will give a complete flood risk profile to the entire Squamish River system. That complete picture will benefit the SLRD and the DoS in moving forwards with applications for future flood mitigation funding where available.

 

Inside the SLRD > Current Projects & Initiatives > Upper Squamish Valley Flood Plain Mapping