High-Resolution Assessment of Changes in Shoreline

Water shortages are leading communities to coax more value out of their reservoirs. Raising a weir or dam can raise the overall reservoir level and increase the available storage. When the water level is raised beyond the natural range and impacts the reservoir’s shoreline or natural boundary (image 1), new areas become submerged, and waves affect them.

Another approach is to adjust the average weir height but keep the maximum height the same for a seasonal increase in storage; however, even if the maximum water level doesn’t increase, this approach might still impact the location of the natural boundary and the shoreline shape. For example, modified inundation during the growing season might mean different plants thrive along the shoreline. Alternately, modified water levels coinciding with different seasonal wind-wave energy variations will lead to different forces on the shoreline.

For decades, the Cowichan Lake Weir has controlled the water levels of the second-largest lake on Vancouver Island. With climate change, steady declines in lake inflows have been observed, and further declines are expected. The Cowichan Water Use Plan proposed to raise the weir by 0.7 m to increase water storage for dry summer seasons. Compared to the 3 m annual range in lake levels, 0.7 m is relatively small and didn’t impact the maximum lake level. A new tool was needed to estimate the shoreline impacts of this change.

KWL accepted the challenge by building this new tool: our innovative Shoreline Impacts Calculator for Changing Climates (SICCC, image 2). A combination of field surveying and computational models was used to map the natural boundary location and to estimate the existing range of water levels and wave energy. We devised a hypothesis around which variables would most impact the natural boundary and tested it against field observations and alternate modelling approaches.??For more, check out our recent publication in the journal “Water.”

The map (image 3) shows how much our calculator predicts the natural boundary will change due to this 0.7 m increase in weir height, even though the maximum water level isn’t changing. Guess what the maximum change in natural boundary was in the comments, and we will reveal our findings later in the week!??

The SICCC model is the latest in KWL’s portfolio of tools to assess shoreline impacts; over the coming month, keep an eye on our social media for more project highlights.? ?

#Innovation #KWL #Engineering #ClimateAction #SICCC #CowichanLake #KWLInnovationMonth?

Our core team: Crystal Campbell,?Clayton Hiles,?Craig Sutherland,?Eric Morris,?Ryan Taylor; Chad Davey??