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Somass Watershed Flood Management Plan
Rivers, lakes, and the inlet form the landscape of our region. We are studying flood management for the Somass River System so we can plan effectively for its future.
WHAT'S NEW?Since November, the Study team has been capturing data about the Somass Watershed:
- Water sensors installed at five locations in the Study area have been capturing water level measurements, including during the high water event that occurred in mid-December. This information will help track how water levels change through different times and conditions.
- A survey team has been out on the rivers completing a bathymetric river survey to chart the form of the river bed. This data is being compared to surveys from 1997 to understand how the rivers have changed in the past 20+ years.
- Hydrology analysis has been started to estimate 200-year flood levels and assess the effects of climate change on the system.
- Geomorphic assessment is underway to chart how the river channels have changed over time as sediment accumulates in different areas.
ABOUT THE STUDYThis project will prepare up-to-date flood mapping for the Somass watershed - including portions of shoreline along Great Central and Sproat Lakes; the Ash, Sproat, Stamp and Somass Rivers; the Somass River estuary; and, the tip of the Alberni Inlet.
This mapping will provide important information about how the river system works today and how it could be affected by changing climate, extreme storm events, and sea level rise. This will provide more certainty around potential flooding events and impacts.
Why is updated flood mapping important?Flood mapping for this area was last completed in the mid-1990s. Since that time, there have been many changes including new development, changes in the landscape, changes in climate, as well as improved methods and accuracy for predicting potential flood hazard. Recent flood events have impacted both private properties and public resources - including a partial closure of Highway 4 in 2017. Public input has indicated a strong interest in better understanding potential flood impacts and mitigation options.
How Flood Mapping Helps Communities:
TIMELINEThe Study was initiated in November 2018 and is anticipated to continue to early 2020. During 2019, the focus will be on gathering technical data and developing a hydraulic model for the watershed. Once data analysis and updated floodplain mapping is complete, community members will be invited to review the results and initiate discussions on potential mitigation options.
Alberni-Clayoquot Regional District
Planning and Development